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Structure and Evolution of a Sauropod Tooth Battery
Abstract
This chapter addresses the tooth-bearing bones and dental battery of Nigersaurus taqueti and provides an initial cranial reconstruction. It also reviews the feeding specializations common to diplodocoids and how these were modified within rebbachisaurids. The skull and neck of the holotypic specimen of N. taqueti were found in close association. The premaxillary, maxillary, and dentary teeth are explained. The tooth battery of Nigersaurus is quite different from that in ornithischians. In Nigersaurus, the teeth are restricted to the transverse portion of the anterior end of the skull, and at least the lower tooth row extends lateral to the parasagittal plane of the lower jaw. Unlike the parasagittal dental batteries of ornithischians, the dental battery in Nigersaurus is oriented transversely and may have been used for cropping rather than prolonged oral processing. Dental batteries evolved three times independently within Dinosauria—in euornithopod and neoceratopsian ornithischians and in rebbachisaurid sauropods.
... Moreover, rapid rates of growth (e.g., Curry, 1999;Lehman and Woodward, 2008;Sander et al., 2011) and unique morphologies often linked to specific niches and novel modes of food procurement (e.g., Christian et al., 2013;Hummel et al., 2008;Stevens and Parrish, 2005;Whitlock, 2011) may have driven their success as ecological titans. Dental complexes of sauropod dinosaurs have been studied in Diplodocidae, Rebbachisauridae, and Camarasauridae (D'Emic et al., 2013;Schwarz et al., 2015;Sereno et al., 2005;Stevens and Parrish, 2005) demonstrating that dental morphology and physiology (i.e., tooth and alveolar arrangement and tooth replacement strategies) directly impact feeding, digestion, and even food procurement. As such, these dental systems can provide considerable insight into sauropod paleobiology and paleoecology (e.g., Barrett and Upchurch, 1995;Fiorillo, 1998;Gee, 2011;McHugh, 2018;Tütken, 2011). ...
... Dietary habits and adaptations in sauropods have dominantly been studied through the lenses of rates of tooth replacement, neck biomechanics, tooth microwear, snout shapes, species richness, and estimates of population densities (e.g., Barrett and Upchurch, 1995;D'Emic et al., 2013;Fiorillo, 1998;Gee, 2011;McHugh, 2018;Schwarz et al., 2015;Sereno et al., 2005;Stevens and Parrish, 2005;Tütken, 2011;Whitlock, 2011;Whitlock et al., 2018). These studies reveal a wide range of diet-linked morphologies among different taxa; however, variance in the number of replacement teeth observed in the premaxilla, maxilla, and dentary among apatosaurine sauropods has yet to be fully investigated. ...
... Among neosauropods, tooth replacement in the premaxillae, maxillae, and/or dentaries have been described in a variety of taxa, including the flagellicaudatan genera Dicraeosaurus, Diplodocus, and Apatosaurus, the macronarian genera Brachiosaurus and Camarasaurus, and the rebbachisaurid genus Nigersaurus (Table 1) (D'Emic et al., 2013(D'Emic et al., , 2019McHugh, 2018;Schwarz et al., 2015;Sereno and Wilson, 2005). Of these taxa, macronarians are measurably disparate from those of the clades Flagellicaudata (including TATE-099) and Rebbachisauridae in tooth volume, shape, replacement rate, as well as fewer numbers of replacement teeth (D'Emic et al., 2013(D'Emic et al., , 2019. ...
Dental complexes of sauropod dinosaurs have been studied in members of Diplodocoidea and Macronaria. However, the disparity among the number of replacement teeth between the premaxilla, maxilla, and dentary of apatosaurine sauropods has yet to be fully investigated. TATE-099, a nearly complete and associated apatosaurine skull and dental complexes from the upper Morrison Formation (Upper Jurassic) at Como Bluff, Wyoming, contains cranial characters consistent with Apatosaurus sp. Unerupted dental complexes of the right premaxilla, maxilla, and dentary were imaged and digitally reconstructed using computed tomography (CT). Results indicate four premaxillary alveolar positions each with 5-7 unerupted replacement teeth, 10 maxillary alveolar positions each with 3-5 unerupted replacement teeth, and 10 dentary alveolar positions each with only 1-2 unerupted replacement teeth. The capacity of replacement teeth in TATE-099 is higher than reported in the genus Diplodocus and consistent with data from previous studies on niche partitioning among coeval Morrison Formation sauropods. Disparity among the capacity of dental complexes of TATE-099 further suggests novel feeding mechanics in apatosaurines. CT data also support a new hypothesis of tooth replacement in diplodocids, where entire rows of teeth are replaced as a single unit, rather than individually. The high-capacity of replacement teeth in the premaxilla is only known to be succeeded by one taxon (Nigersaurus) and suggests frequent wear of the premaxillary teeth. However, considerably fewer replacement teeth in the dentary of TATE-099 suggests less-frequent. These results offer insight into the feeding mechanisms and disparity of sauropods within Flagellicaudata.
... However, the structure of some of these teeth is also consistent with that in Rebbachisauridae. Very similar isolated sauropod teeth from the Upper Cretaceous Bauru Group of Brazil, initially referred to Titanosauria [56], were reinterpreted by Sereno and Wilson [30] as belonging to Rebbachisauridae. Similar teeth are also known from the Lower Cretaceous (Barremian) Wessex Formation of the Isle of Wight, United Kingdom [57] and in Nigersaurus [30,31]. ...
... Very similar isolated sauropod teeth from the Upper Cretaceous Bauru Group of Brazil, initially referred to Titanosauria [56], were reinterpreted by Sereno and Wilson [30] as belonging to Rebbachisauridae. Similar teeth are also known from the Lower Cretaceous (Barremian) Wessex Formation of the Isle of Wight, United Kingdom [57] and in Nigersaurus [30,31]. However, an isolated rebbachisaurid tooth from the Barremian La Amarga Formation of Argentina, illustrated in fig. ...
... Most sauropod teeth from Dzharakuduk lack these crests but they are present on ZIN PH 2416/16 [3]. Rebbachisaurid teeth are also characterized by asymmetrical enamel thickness, being thicker on the labial side than on the lingual side [27, 30,35], a condition also found on some sauropod teeth from Dzharakuduk. One of the notable characters of the sauropod teeth from Dzharakuduk is the reduction of the wrinkled enamel texture [3]. ...
Dzharatitanis kingi gen. et sp. nov. is based on an isolated anterior caudal vertebra (USNM 538127) from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. Phylogenetic analysis places the new taxon within the diplodocoid clade Rebbachisauridae. This is the first rebbachisaurid reported from Asia and one of the youngest rebbachisaurids in the known fossil record. The caudal is characterized by a slightly opisthocoelous centrum, ‘wing-like’ transverse processes with large but shallow PRCDF and POCDF, and the absence of a hyposphenal ridge and of TPRL and TPOL. The neural spine has high SPRL, SPDL, SPOL, and POSL and is pneumatized. The apex of neural spine is transversely expanded and bears triangular lateral processes. The new taxon shares with Demandasaurus and the Wessex rebbachisaurid a high SPDL on the lateral side of the neural spine, separated from SPRL and SPOL. This possibly suggests derivation of Dzharatitanis from European rebbachisaurids. This is the second sauropod group identified in the assemblage of non-avian dinosaurs from the Bissekty Formation, in addition to a previously identified indeterminate titanosaurian.
... Lavocat figured and described only a few bones. The unusual morphology of the vertebrae and skull and the diplodocoid affinity of Rebbachisaurus was only revealed later on the basis of better preserved skulls and skeletons of Limaysaurus in Argentina Salgado 1995, Salgado et al. 2004) and Nigersaurus in Niger (Sereno et al. 1999, 2007, Sereno and Wilson 2005. ...
... This tooth form, on the other hand, may pertain to a narrow-crowned titanosaurian sauropod, the remains of which have been found in situ in the Douira Formation. The enamel on the potential rebbachisaurid crown is present on both sides and is lightly textured (Fig. 107), unlike crowns in the derived rebbachisaurid Nigersaurus (Sereno and Wilson 2005). There are no grooves on mesial and distal crown edges for adjacent crowns, and the crown tip is truncated by a single low-angle wear facet (Fig. 107B), rather than a pair of wear facets as in Nigersaurus (Sereno and Wilson 2005). ...
... The enamel on the potential rebbachisaurid crown is present on both sides and is lightly textured (Fig. 107), unlike crowns in the derived rebbachisaurid Nigersaurus (Sereno and Wilson 2005). There are no grooves on mesial and distal crown edges for adjacent crowns, and the crown tip is truncated by a single low-angle wear facet (Fig. 107B), rather than a pair of wear facets as in Nigersaurus (Sereno and Wilson 2005). If these slender subcylindrical crowns pertain to R. garasbae, the Kem Kem rebbachisaurid may not have had the derived self-supporting tooth batteries present in Nigersaurus. ...
The geological and paleoenvironmental setting and the vertebrate taxonomy of the fossiliferous, Cenomanian-age deltaic sediments in eastern Morocco, generally referred to as the “Kem Kem beds”, are reviewed. These strata are recognized here as the Kem Kem Group, which is composed of the lower Gara Sbaa and upper Douira formations. Both formations have yielded a similar fossil vertebrate assemblage of predominantly isolated elements pertaining to cartilaginous and bony fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs, as well as invertebrate, plant, and trace fossils. These fossils, now in collections around the world, are reviewed and tabulated. The Kem Kem vertebrate fauna is biased toward largebodied carnivores including at least four large-bodied non-avian theropods (an abelisaurid, Spinosaurus, Carcharodontosaurus, and Deltadromeus), several large-bodied pterosaurs, and several large crocodyliforms.
No comparable modern terrestrial ecosystem exists with similar bias toward large-bodied carnivores. The Kem Kem vertebrate assemblage, currently the best documented association just prior to the onset of the Cenomanian-Turonian marine transgression, captures the taxonomic diversity of a widespread northern African fauna better than any other contemporary assemblage from elsewhere in Africa.
Keywords
Africa, Cretaceous, dinosaur, Gara Sbaa Formation, Douira Formation, paleoenvironment, vertebrate
... The discovery of a superbly preserved new African rebbachisaurid in the Aptian -Albian sediments of Niger by the Sereno's team increased the importance of the clade (Sereno et al. 1999(Sereno et al. , 2007Sereno and Wilson 2005). The material, despite still awaiting a detailed postcranial description, permitted an evaluation of the quite peculiar rebbachisaurid skull and lower jaws, demonstrating to be highly distinctive from those of any other clade, especially titanosaurs. ...
... These, especially with the squared jaws of Antarctosaurus wichmannianus (Huene 1929), were misunderstood by several authors as belonging to diplodocoids (Jacobs et al. 1993;Upchurch 1998;Wilson and Sereno 1998). The finding of new and well-preserved lower jaws of both rebbachisaurid (Sereno et al. 1999;Sereno and Wilson 2005;Sereno et al. 2007) and titanosaur (Apesteguía 2004) permitted a clear differentiation and the definitive status of titanosaurs for squared-jawed forms such as Antarctosaurus (Huene 1929), Bonitasaura (Apesteguía 2004) and materials from Brazil (MPM125R), as already stated by Huene (1929), Powell (2003Powell ( , written in 1986 and Salgado (2000). Furthermore, although both clades share slender crowned teeth, the detailed descriptions allowed the recognition of much more slender and partially striated crowns in rebbachisaurids (Sereno et al. 1999;Sereno and Wilson 2005;Apesteguía 2007) than in derived titanosaurs. ...
... The finding of new and well-preserved lower jaws of both rebbachisaurid (Sereno et al. 1999;Sereno and Wilson 2005;Sereno et al. 2007) and titanosaur (Apesteguía 2004) permitted a clear differentiation and the definitive status of titanosaurs for squared-jawed forms such as Antarctosaurus (Huene 1929), Bonitasaura (Apesteguía 2004) and materials from Brazil (MPM125R), as already stated by Huene (1929), Powell (2003Powell ( , written in 1986 and Salgado (2000). Furthermore, although both clades share slender crowned teeth, the detailed descriptions allowed the recognition of much more slender and partially striated crowns in rebbachisaurids (Sereno et al. 1999;Sereno and Wilson 2005;Apesteguía 2007) than in derived titanosaurs. ...
Rebbachisauridae are poorly known 'bizarre' sauropods with two nearly complete skeletons collected: Limaysaurus tessonei and Nigersaurus taqueti. Whereas the latter taxon allowed the understanding of their cranial novelties, other species show some peculiarities in the postcranium. L. tessonei, Rebbachisaurus garasbae and a new form (MMCH-Pv-49) from Villa El Chocón, Patagonia, exhibit peculiar pectoral girdles and the loss of the hyposphene-hypantrum accessory articulations in their amphiplathyan dorsal vertebrae. Actually, the postzygapophyses are not only devoid of hyposphenal locks but also additionally show a curved postzygapophyseal eave that allows a sliding over the corresponding structure of the anterior side of the neural arch, a curved concave and elongated platform continuous along both prezygapophyses: the prezygapophyseal shelf. As the 'ball and socket' opisthocoelous centra in macronarians optimised mobility, the 'U-eaves and shelf complex' of rebbachisaurids permitted wider movements between successive vertebrae. While in titanosaurs the increased mobility occurred related to the centrum shape, in rebbachisaurids it is related to a complex system in the neural arch. Furthermore, whereas macronarians show large centra, rebbachisaurids underwent a minimisation of the centrum. These changes in both sauropod lineages probably had an outstanding relevance in the diversity and ecological roles that sauropods experienced in Cretaceous terrestrial ecosystems.
... However, the age range could span over the Albian-Cenomanian (C Underwood, pers. comm., 2018), which is closer to the age given to the Algerian Cretaceous Continental Intercalaire (Lefranc & Guiraud, 1990;Le Loeuff et al., 2012) and to the fossil-rich Cretaceous 'Continental Intercalaire' beds of Tunisia (Fanti et al., 2016) as well as sauropod bonebeds from Niger (Sereno & Wilson, 2005). The Kem Kem beds are considered to be made up of two formations (see Fig. 1): the fossil-rich lower Ifezouane Formation and the upper Aoufous Formation, rich in ichnofossils (Cavin et al., 2010;Belvedere et al., 2013); also named the lower sandy unit (a braided fluvial system) and the upper marly unit (a coastal lagoon), respectively (Cavin et al., 2010;Belvedere et al., 2013;Mannion & Barrett, 2013;Ibrahim et al., 2014). ...
... It consists of teeth with high SI (2,(2)(3)(4)9) and CI (0,6-0,9), rugose enamel wrinkling (but see discussion on this), prominent mesial and distal carinae, together with a labial convexity, and a slightly distal inclination of the apex, and a subcylindrical to lemon-shaped cross-section. There are many intra-group specific morphological differences within this morphotype, however as teeth both differ morphologically within one toothrow, as well as between upper and lower toothrows (Sereno & Wilson, 2005;Wilson, 2005;Zaher et al., 2011;Holwerda, Pol & Rauhut, 2015;Martínez et al., 2016;Mocho et al., 2016;Wiersma & Sander, 2016), enamel wrinkling as well as the presence of carinae are taken as the main drivers for comparisons (see Carballido & Pol, 2010;Holwerda, Pol & Rauhut, 2015). Moreover, enamel wrinkling can be demonstrated to change over ontogeny, with indications that juveniles have smooth, or smoother enamel wrinkling in comparison with adult animals (Fiorillo, 1991;Fiorillo, 1998;Díez Díaz et al., 2012;Díez Díaz, Pereda Suberbiola & Sanz, 2012;Díez Díaz, Ortega & Sanz, 2014;Holwerda, Pol & Rauhut, 2015). ...
... It consists of teeth with high SI (2,(2)(3)(4)9) and CI (0,6-0,9), rugose enamel wrinkling (but see discussion on this), prominent mesial and distal carinae, together with a labial convexity, and a slightly distal inclination of the apex, and a subcylindrical to lemon-shaped cross-section. There are many intra-group specific morphological differences within this morphotype, however as teeth both differ morphologically within one toothrow, as well as between upper and lower toothrows (Sereno & Wilson, 2005;Wilson, 2005;Zaher et al., 2011;Holwerda, Pol & Rauhut, 2015;Martínez et al., 2016;Mocho et al., 2016;Wiersma & Sander, 2016), enamel wrinkling as well as the presence of carinae are taken as the main drivers for comparisons (see Carballido & Pol, 2010;Holwerda, Pol & Rauhut, 2015). Moreover, enamel wrinkling can be demonstrated to change over ontogeny, with indications that juveniles have smooth, or smoother enamel wrinkling in comparison with adult animals (Fiorillo, 1991;Fiorillo, 1998;Díez Díaz et al., 2012;Díez Díaz, Pereda Suberbiola & Sanz, 2012;Díez Díaz, Ortega & Sanz, 2014;Holwerda, Pol & Rauhut, 2015). ...
The Cretaceous Kem Kem beds of Morocco and equivalent beds in Algeria have produced a rich fossil assemblage, yielding, amongst others, isolated sauropod teeth, which can be used in species diversity studies. These Albian-Cenomanian (∼113–93.9 Ma) strata rarely yield sauropod body fossils, therefore, isolated teeth can help to elucidate the faunal assemblages from North Africa, and their relations with those of contemporaneous beds and geographically close assemblages. Eighteen isolated sauropod teeth from three localities (Erfoud and Taouz, Morocco, and Algeria) are studied here, to assess whether the teeth can be ascribed to a specific clade, and whether different tooth morphotypes can be found in the samples. Two general morphotypes are found, based on enamel wrinkling and general tooth morphology. Morphotype I, with mainly rugose enamel wrinkling, pronounced carinae, lemon-shaped to (sub)cylindrical cross-section and mesiodistal tapering towards an apical tip, shows affinities to titanosauriforms and titanosaurs. Morphotype II, characterized by more smooth enamel, cylindrical cross-section, rectangular teeth with no apical tapering and both labial and lingual wear facets, shows similarities to rebbachisaurids. Moreover, similarities are found between these northwest African tooth morphotypes, and tooth morphotypes from titanosaurs and rebbachisaurids from both contemporaneous finds from north and central Africa, as well as from the latest Cretaceous (Campanian–Maastrichtian, 83.6 Ma–66.0 Ma) of the Ibero-Armorican Island. These results support previous hypotheses from earlier studies on faunal exchange and continental connections between North Africa and Southern Europe in the Cretaceous.
... As noted above, a similarly placed and apparently equally large fenestra was first identified as the antorbital fenestra in Nigersaurus (Sereno et al. 1999: fig. 2D; Sereno and Wilson 2005: fig. 5.5). ...
... 5.5). To judge by the published images (Sereno et al. 1999;Sereno and Wilson 2005) and personal observation of the preserved Nigersaurus maxilla (MNN GDF512), the latter fenestra corresponds more probably to the preantorbital fenestra. Indeed, the anterior margin of the preantorbital fenestra is at the height of the subnarial foramen in Nigersaurus (Sereno et al. 1999: fig. ...
... Indeed, the anterior margin of the preantorbital fenestra is at the height of the subnarial foramen in Nigersaurus (Sereno et al. 1999: fig. 2D), whereas the antorbital fenestra, as reconstructed (Sereno and Wilson 2005;Sereno et al. 2007), is well above the foramen. Therefore, Lavocatisaurus and Nigersaurus share the presence of a large preantorbital fenestra, which occupies around half of the maxillary body. ...
Rebbachisaurids are a group of basal diplodocimorph sauropods that diversified in Gondwana at the end of the Early Cretaceous and the beginning of the Late Cretaceous. It is a group of great palaeobiogeographical interest, for it clearly illustrates various processes of dispersal throughout Gondwana and to Laurasia prior to the breakup of Africa and South America. However, the relationships within the group are still under discussion owing to the scarcity of cranial material that would help clarify them. In the present paper we describe the new rebbachisaurid Lavocatisaurus agrioensis gen. et sp. nov. from the Aptian-Albian (Lower Cretaceous) of Neuquén (Argentina). Remains have been recovered belonging to an adult specimen (holotype) and two immature specimens (paratypes). Taken together, almost all the bones of the taxon are represented, including most of the cranium. Lavocatisaurus agrioensis gen. et sp. nov. is the first rebbachisaurid from Argentina with an almost complete cranium, making it possible to recognize differences with respect to other rebbachisaurids, such as the highly derived Nigersaurus. Among its most notable characters are the presences of a large preantorbital fenestra and maxillary teeth that are significantly larger than those of the dentary. Our phylogenetic study places Lavocatisaurus amongst basal rebbachisaurids, as the sister lineage to Khebbashia (the clade formed by Limaysaurinae + Rebbachisaurinae). This position, which is somewhat more derived than that previously suggested for Comahuesaurus and Zapalasaurus (the Argentinean rebbachisaurids closest in geographical and geological terms), reaffirms the presence of different basal rebbachisaurid lineages in the Early Cretaceous of Patagonia.
... However, the age range could span over the Albian-Cenomanian (C Underwood, pers. comm., 2018), which is closer to the age given to the Algerian Cretaceous Continental Intercalaire (Lefranc & Guiraud, 1990;Le Loeuff et al., 2012) and to the fossil-rich Cretaceous 'Continental Intercalaire' beds of Tunisia (Fanti et al., 2016) as well as sauropod bonebeds from Niger (Sereno & Wilson, 2005). The Kem Kem beds are considered to be made up of two formations (see Fig. 1): the fossil-rich lower Ifezouane Formation and the upper Aoufous Formation, rich in ichnofossils (Cavin et al., 2010;Belvedere et al., 2013); also named the lower sandy unit (a braided fluvial system) and the upper marly unit (a coastal lagoon), respectively (Cavin et al., 2010;Belvedere et al., 2013;Mannion & Barrett, 2013;Ibrahim et al., 2014). ...
... It consists of teeth with high SI (2,(2)(3)(4)9) and CI (0,6-0,9), rugose enamel wrinkling (but see discussion on this), prominent mesial and distal carinae, together with a labial convexity, and a slightly distal inclination of the apex, and a subcylindrical to lemon-shaped cross-section. There are many intra-group specific morphological differences within this morphotype, however as teeth both differ morphologically within one toothrow, as well as between upper and lower toothrows (Sereno & Wilson, 2005;Wilson, 2005;Zaher et al., 2011;Holwerda, Pol & Rauhut, 2015;Martínez et al., 2016;Mocho et al., 2016;Wiersma & Sander, 2016), enamel wrinkling as well as the presence of carinae are taken as the main drivers for comparisons (see Carballido & Pol, 2010;Holwerda, Pol & Rauhut, 2015). Moreover, enamel wrinkling can be demonstrated to change over ontogeny, with indications that juveniles have smooth, or smoother enamel wrinkling in comparison with adult animals (Fiorillo, 1991;Fiorillo, 1998;Díez Díaz et al., 2012;Díez Díaz, Pereda Suberbiola & Sanz, 2012;Díez Díaz, Ortega & Sanz, 2014;Holwerda, Pol & Rauhut, 2015). ...
... It consists of teeth with high SI (2,(2)(3)(4)9) and CI (0,6-0,9), rugose enamel wrinkling (but see discussion on this), prominent mesial and distal carinae, together with a labial convexity, and a slightly distal inclination of the apex, and a subcylindrical to lemon-shaped cross-section. There are many intra-group specific morphological differences within this morphotype, however as teeth both differ morphologically within one toothrow, as well as between upper and lower toothrows (Sereno & Wilson, 2005;Wilson, 2005;Zaher et al., 2011;Holwerda, Pol & Rauhut, 2015;Martínez et al., 2016;Mocho et al., 2016;Wiersma & Sander, 2016), enamel wrinkling as well as the presence of carinae are taken as the main drivers for comparisons (see Carballido & Pol, 2010;Holwerda, Pol & Rauhut, 2015). Moreover, enamel wrinkling can be demonstrated to change over ontogeny, with indications that juveniles have smooth, or smoother enamel wrinkling in comparison with adult animals (Fiorillo, 1991;Fiorillo, 1998;Díez Díaz et al., 2012;Díez Díaz, Pereda Suberbiola & Sanz, 2012;Díez Díaz, Ortega & Sanz, 2014;Holwerda, Pol & Rauhut, 2015). ...
The Cretaceous Kem Kem beds of Morocco and equivalent beds in Algeria have produced a rich fossil assemblage, yielding, amongst others, isolated sauropod teeth, which can be used in species diversity studies. These Albian-Cenomanian (~113 – 93.9 Ma) strata rarely yield sauropod body fossils, therefore, isolated teeth can help to elucidate the faunal assemblages from North Africa, and their relations with those of contemporaneous beds and geographically close assemblages. Eighteen isolated sauropod teeth from three localities (Erfoud and Taouz, Morocco, and Algeria) are studied here, to assess whether the teeth can be ascribed to a specific clade, and whether different tooth morphotypes can be found in the samples. Two general morphotypes are found, based on enamel wrinkling and general tooth morphology. Morphotype I, with mainly rugose enamel wrinkling, pronounced carinae, lemon-shaped to (sub)cylindrical cross-section and mesiodistal tapering towards an apical tip, shows affinities to titanosauriforms and titanosaurs. Morphotype II, characterized by more smooth enamel, cylindrical cross-section, rectangular teeth with no apical tapering and both labial and lingual wear facets, shows similarities to rebbachisaurids. Moreover, similarities are found between these northwest African tooth morphotypes, and tooth morphotypes from titanosaurs and rebbachisaurids from both contemporaneous finds from north and central Africa, as well as from the latest Cretaceous (Campanian-Maastrichtian, 83.6Ma – 66.0Ma) of the Ibero-Armorican Island. These results support previous hypotheses from earlier studies on faunal exchange and continental connections between North Africa and Southern Europe in the Cretaceous.
... All develop high tooth-replacement rates (Chure et al. 2010;D'Emic et al. 2013), probably in response to a highly abrasive/gritty diet (Chure et al. 2010;Whitlock 2011;D'Emic et al. 2013). Also, on the basis of both craniodental and postcranial evidence, rebbachisaurids Sereno and Wilson 2005;Sereno et al. 2007;Whitlock 2011) and dicraeosaurids (Upchurch and Barrett 2000;Christian 2002; Barrett and Upchurch 2005; but see Whitlock 2011) are usually considered to have been specialized low browsers, and diplodocids (Upchurch and Barrett 2000;Christian 2002; Barrett and Upchurch 2005;Dzemski and Christian 2007;Christian and Dzemski 2011;Whitlock 2011) and probably some titanosaurs would have indulged in low browsing for at least parts of the foraging cycle. However, diplodocids occupy a region of biomechanical morphospace separated from that of titanosaur taxa. ...
... The same is generally true for rebbachisaurids (Table 1), with the exception of Nigersaurus. Nigersaurus is unique among sauropodomorphs in possessing teeth with asymmetrical enamel distribution (Sereno and Wilson 2005;Sereno et al. 2007;D'Emic et al. 2013) arranged in a complex, self-supporting and sharpening "tooth battery" (Sereno and Wilson 2005;Sereno et al. 2007) and in apparently having closed the supratemporal fenestra, necessitating a dramatic rearrangement of the adductor musculature (Sereno et al. 2007). The poor sampling of rebbachisaurid and dicraeosaurid crania means that the taxonomic distribution of specific functional complexes remains unknown, and the disparity present within these forms may be underestimated. ...
... The same is generally true for rebbachisaurids (Table 1), with the exception of Nigersaurus. Nigersaurus is unique among sauropodomorphs in possessing teeth with asymmetrical enamel distribution (Sereno and Wilson 2005;Sereno et al. 2007;D'Emic et al. 2013) arranged in a complex, self-supporting and sharpening "tooth battery" (Sereno and Wilson 2005;Sereno et al. 2007) and in apparently having closed the supratemporal fenestra, necessitating a dramatic rearrangement of the adductor musculature (Sereno et al. 2007). The poor sampling of rebbachisaurid and dicraeosaurid crania means that the taxonomic distribution of specific functional complexes remains unknown, and the disparity present within these forms may be underestimated. ...
Sauropodomorpha included the largest known terrestrial vertebrates and was the first dinosaur clade to achieve a global distribution. This success is associated with their early adoption of herbivory, and sauropod gigantism has been hypothesized to be a specialization for bulk feeding and obligate high-fiber herbivory. Here, we apply a combination of biomechanical character analysis and comparative phylogenetic methods with the aim of quantifying the evolutionary mechanics of the sauropodomorph feeding apparatus. We test for the role of convergence to common feeding function and divergence toward functional optima across sauropodomorph evolution, quantify the rate of evolution for functional characters, and test for coincident evolutionary rate shifts in craniodental functional characters and body mass. Results identify a functional shift toward increased cranial robustness, increased bite force, and the onset of static occlusion at the base of the Sauropoda, consistent with a shift toward bulk feeding. Trends toward similarity in functional characters are observed in Diplodocoidea and Titanosauriformes. However, diplodocids and titanosaurs retain significant craniodental functional differences, and evidence for convergent adoption of a common “adaptive zone” between them is weak. Modeling of craniodental character and body-mass evolution demonstrates that these functional shifts were not correlated with evolutionary rate shifts. Instead, a significant correlation between body mass and characters related to bite force and cranial robustness suggests a correlated-progression evolutionary mode, with positive-feedback loops between body mass and dietary specializations fueling sauropod gigantism.
... This wear pattern resembles a distinctive type of wear present in Diplodocus spp., which also has apical wear facets on the labial sides of the upper and lower tooth crowns (Barrett & Upchurch 1994). Double apical wear facets are present in the rebbachisaurid Nigersaurus taqueti, which set this taxon apart from most other sauropods (Sereno & Wilson 2005;Sereno et al. 2007). The secondary wear facet, which cannot have been formed by contact with an opposing tooth, is generally considered the result of non-occlusal abrasion (Holland 1924;Barrett & Upchurch 1994;Upchurch & Barrett 2000;Sereno & Wilson 2005). ...
... Double apical wear facets are present in the rebbachisaurid Nigersaurus taqueti, which set this taxon apart from most other sauropods (Sereno & Wilson 2005;Sereno et al. 2007). The secondary wear facet, which cannot have been formed by contact with an opposing tooth, is generally considered the result of non-occlusal abrasion (Holland 1924;Barrett & Upchurch 1994;Upchurch & Barrett 2000;Sereno & Wilson 2005). García and Cerda (2010: figure 7) explained the formation of secondary wear facets by anterior displacement of the lower tooth relative to the opposite upper tooth during ontogeny. ...
... This occlusal contact would result in secondary wear facets, a labial one on the upper tooth and a lingual one on the lower tooth (Figure 13(c)). This secondary wear is the first evolutionary step toward the formation of a tooth battery, which is extensively developed in Nigersaurus taqueti (Sereno & Wilson 2005). In the sample of 252 sauropod teeth from the Bissekty Formation, only 38 specimens (15.7%) have two apical wear facets. ...
The isolated adult teeth of titanosaurian sauropods from the Upper Cretaceous Bissekty Formation at Dzharakuduk, Uzbekistan, differ little in overall structure but show considerable variation in enamel sculpturing and wear patterns. The crown shape of unworn juvenile teeth ranges from lanceolate to conical. Most specimens have enamel texture resembling crumpled paper or completely smooth enamel. Longitudinal grooves along the mesial and distal edges are present on only a few tooth crowns and might be developed on both the labial and lingual sides. Among 252 worn tooth crowns there are eight variants of wear patterns, all possible combinations of 0–2 apical and 0–2 lateral wear facets. The most common is wear pattern A1L0 (one apical facet, no lateral facets; 62.7%). The next most common variant has two apical and no lateral facets (A2L0, 12.3%). These apical wear facets include the primary wear facets, which are produced by an opposing functional tooth, and secondary wear facets, which are produced by a replacing upper tooth coming into contact with the functional lower tooth at a late wear stage. The relative abundance of tooth crowns with two apical wear facets possibly suggests incipient development of a tooth battery in the Bissekty titanosaur.
... Apart from some early and influential papers (Janensch, 1935(Janensch, -1936Nowinski, 1971; Barrett & Upchurch, 1994;Calvo, 1994;Fiorillo, 1998), the dentition and feeding strategies of sauropods had not figured prominently in the "dinosaur renaissance" (but see bibliography in Whitlock, 2011). However, the last two decades have seen a huge interest in sauropod dental morphology, tooth replacement, and evolution of their dentition (Christiansen, 2000;Chatterjee & Zheng, 2002, 2005Sereno & Wilson, 2005;Barrett, 2006;Sereno et al., 2007;Chure et al., 2010;García & Cerda, 2010a, 2010bYoung et al., 2012;D'Emic et al., 2013;Díez Díaz, Tortosa & Le Loeuff, 2013;Díez Díaz, Ortega & Sanz, 2014;Kosch et al., 2014;Holwerda, Pol & Rauhut, 2015;Wings et al., 2015;Barrett et al., 2016;García & Zurriaguz, 2016;Mocho et al., 2016;Wilson et al., 2016;Averianov & Sues, 2017;Carballido et al., 2017;Mocho et al., 2017;Ősi, Csiki-Sava & Prondvai, 2017;Wiersma & Sander, 2017;Holwerda et al., 2018;McHugh, 2018;Moore et al., 2018;Tschopp, Mateus & Norell, 2018;Woodruff et al., 2018;D'Emic & Carrano, 2020;Bindellini & Dal Sasso, 2021;Chang et al., 2021;Price & Whitlock, 2022;Peterson et al., 2022;Torcida Fernández-Baldor et al., 2023). Our study presents a detailed morphological description of the dentition of Europasaurus holgeri. ...
... These denticles are worn off in the functional teeth. The 'en echelon' pattern of the teeth observed in Europasaurus is a synapomorphy of Eusauropods and has been described in the other sauropods detailed above as well as in others (Wilson & Sereno, 1998;Chatterjee & Zheng, 2005;Sereno & Wilson, 2005;Carballido et al., 2017). ...
The basal macronarian sauropod Europasaurus holgeri is known only from the Late Jurassic of the Langenberg Quarry near Goslar, Lower Saxony, Germany. Europasaurus has been identified as an insular dwarf and shows a clear resemblance to Camarasaurus and Giraffatitan . This study provides a detailed description of the dentition of Europasaurus based on an array of fossils outstanding in their abundance, variety of preservation, and ontogenetic range. Dental morphology for the replacement and functional dentitions, the tooth replacement pattern, and implications for food intake are described for the Europasaurus dentition, which is characterized by broad-crowned teeth. Characteristic features for Europasaurus are the presence of denticles on replacement teeth, the wrinkled enamel, and large wear facets both on the apex and on the carinae of the tooth crowns. The partially articulated skull SNHM-2207-R and isolated tooth rows DfmMh/FV 580.1 and DfmMh/FV 896.7 suggest the presence of strong connective tissue partially covering the teeth. This connective tissue would have provided stability and protection for the teeth. Evidence for this connective tissue include exposed tooth necks, in-situ teeth with strongly resorbed roots which no longer would have been connected to the jaw bone, and wrinkled enamel and its surface pattern. The same features can be observed in other sauropod taxa as well. We therefore suggest that eusauropods in general possessed this connective tissue structure, which may be an autapomorphy of the group. Possibly, this hypothetical structure is homologous to the rhamphotheca in birds and some non-avian theropods, which, however rarely, show such a close integration of keratinous tissue and teeth that we hypothesize here.
... The enamel on the labial and lingual sides is plesiomorphically consistent around the whole circumference in sauropods (Sereno and Wilson, 2005), such as in Camarasaurus (D'Emic et al., 2013). Apomorphic asymmetrical enamel has been reported in the diplodocoid Diplodocus (D'Emic et al., 2013) and Nigersaurus (Sereno and Wilson, 2005;Sereno et al., 2007), and Nigersaurus has a highly asymmetrical enamel, such that the enamel on the labial side is ten times thicker than the enamel on the lingual side (Sereno et al., 2007). ...
... The enamel on the labial and lingual sides is plesiomorphically consistent around the whole circumference in sauropods (Sereno and Wilson, 2005), such as in Camarasaurus (D'Emic et al., 2013). Apomorphic asymmetrical enamel has been reported in the diplodocoid Diplodocus (D'Emic et al., 2013) and Nigersaurus (Sereno and Wilson, 2005;Sereno et al., 2007), and Nigersaurus has a highly asymmetrical enamel, such that the enamel on the labial side is ten times thicker than the enamel on the lingual side (Sereno et al., 2007). Given that the sauropod teeth described in this work are dissimilar to Nigersaurus in that they possess a spatulate tooth crown, and can be excluded from the Diplodocoidea based on a low SI value of 2.3, this Euhelopus-like titanosauriform convergently evolved asymmetrical enamel. ...
Three eusauropod teeth (SDUST‐V1064, PMOL‐AD00176, PMOL‐ADt0005) are reported from the Lower Cretaceous Yixian Formation of Ningcheng, southeastern Inner Mongolia, China. Two of them (SDUST‐V1064, PMOL‐AD00176) are assigned to early‐diverging titanosauriforms in having slightly mesiodistal expansion at the base of the tooth crown, a slenderness index value >2.0 and <4.0, and D‐shaped cross section. Furthermore, SDUST‐V1064 and PMOL‐AD00176 are referred as an Euhelopus ‐like titanosauriform on the basis of having a sub‐circular boss on the lingual surface and an asymmetrical crown‐root margin which slants apically, respectively. CT scan data of SDUST‐V1064 reveals new dental information of early‐diverging titanosauriforms, for example, the enamel on the labial side thicker than that on the lingual side, an enamel/dentine ratio of 0.26 and a boss present on the lingual side of the dentine of the crown.
... For example, the rostral keratin cover could have functioned as ornamentation for sexual or interspecific signalling, and (or) as a protective barrier for bulk feeding on abrasive plant matter. Diplodocid sauropods, such as Camarasaurus, Diplodocus, Europasaurus, and Nigersaurus, have no or reduced bony septa that separate teeth into discrete tooth alveoli and exhibit tooth root reabsorption, like in Camarasaurus [63][64][65]. Sauropod keratin cover and thick gingival tissue might have held these teeth in place while allowing for higher tooth replacement rates [64,65]. ...
... Diplodocid sauropods, such as Camarasaurus, Diplodocus, Europasaurus, and Nigersaurus, have no or reduced bony septa that separate teeth into discrete tooth alveoli and exhibit tooth root reabsorption, like in Camarasaurus [63][64][65]. Sauropod keratin cover and thick gingival tissue might have held these teeth in place while allowing for higher tooth replacement rates [64,65]. ...
Teeth evolved early in vertebrate evolution, and their morphology reflects important specializations in diet and ecology among species. The toothless jaws (edentulism) in extant birds likely coevolved with beak keratin, which functionally replaced teeth. However, extinct dinosaurs lost teeth multiple times independently and exhibited great variation in toothrow distribution and rhamphotheca-like keratin structures. Here, we use rostral jawbone surface texture as a proxy for rostral keratin covering and phylogenetic comparative models to test for the influence of rostral keratin on toothrow distribution in Mesozoic dinosaurs. We find that the evolution of rostral keratin covering explains partial toothrow reduction but not jaw toothlessness. Toothrow reduction preceded the evolution of rostral keratin cover in theropods. Non-theropod dinosaurs evolved continuous toothrows despite evolving rostral keratin covers (e.g. some ornithischians and sauropodomorphs). We also show that rostral keratin covers did not significantly increase the evolutionary rate of tooth loss, which further delineates the antagonistic relationship between these structures. Our results suggest that the evolution of rostral keratin had a limited effect on suppressing tooth development. Independent changes in jaw development may have facilitated further tooth loss. Furthermore, the evolution of strong chemical digestion, a gizzard, and a dietary shift to omnivory or herbivory likely alleviated selective pressures for tooth development.
... These older teeth are all associated with a broad-crowned t2 replacement tooth lingually, suggesting that the t1 generation of teeth were rapidly replaced with a more adult-like tooth morphology. These t1 teeth are similar to the functional teeth of certain titanosaur and diplodocoid sauropods 1,23,24 . These teeth also lack the lingual median ridge that is present in the functional teeth of basal sauropodomorphs, the presence of which is the ancestral condition for dinosaurs 25 . ...
... Embryonic Lufengosaurus teeth are therefore implanted in a pleurodont fashion, similar to hatchling alligators (Fig. 3) 27 , and even some sauropods 32 . In neosauropods, as many as 4-8 generations of teeth are present at each tooth position within a single large trough, and there are no mineralized periodontal tissues between successive generations of teeth, except for a thin layer of cementum coating the tooth roots 1,12,23 . Recent histological studies have suggested that sauropods were truly thecodont based on the presence of the stereotypically mammalian complement of dental attachment tissues 12 , but the size discrepancy between the teeth and the jaws means that functional diplodocid teeth are implanted in a similar, pleurodont fashion to the t1 teeth of the embryonic specimens of Lufengosaurus. ...
Rare occurrences of dinosaurian embryos are punctuated by even rarer preservation of their development. Here we report on dental development in multiple embryos of the Early Jurassic Lufengosaurus from China, and compare these to patterns in a hatchling and adults. Histology and CT data show that dental formation and development occurred early in ontogeny, with several cycles of tooth development without root resorption occurring within a common crypt prior to hatching. This differs from the condition in hatchling and adult teeth of Lufengosaurus, and is reminiscent of the complex dentitions of some adult sauropods, suggesting that their derived dental systems likely evolved through paedomorphosis. Ontogenetic changes in successive generations of embryonic teeth of Lufengosaurus suggest that the pencil-like teeth in many sauropods also evolved via paedomorphosis, providing a mechanism for the convergent evolution of small, structurally simple teeth in giant diplodocoids and titanosaurids. Therefore, such developmental perturbations, more commonly associated with small vertebrates, were likely also essential events in sauropod evolution. Dinosaurs had some of the most complex dentitions known. Here, Reisz et al. characterize dental development across embryonic, hatchling and adult Lufengosaurus, an Early Jurassic sauropodomorph dinosaur, and suggest that derived sauropod dentition evolved by paedomorphosis (juvenilization).
... Different sauropod species possibly employed different feeding strategies (e.g., Dodson 1990). This assumption appears reasonable from an ecological point of view and also fits to the diversity of jaw and tooth morphology observed among sauropods (e.g., Upchurch & Barrett 2000;Sereno & Wilson 2005). For Brachiosaurus, the suggested neck posture differs between horizontal (Frey & Martin 1997;Berman & Rothschild 2005;Stevens & Parrish 2005a, 2005b and forwardly inclined or nearly vertical (Janensch 1950b;Bakker 1987;Paul 1987Paul , 1988Christian & Heinrich 1998;Christian 2002aChristian , 2002bChristian , 2004. ...
... The term "feeding strategy" is used here for the way the food is chosen from different heights and distances, e.g. by keeping the neck in a high or in a low position or by frequent changes of the height of the head. Closely related are the questions which food was chosen (e.g., Farlow 1987) and how was the food separated from the source, e.g. from a tree (e.g., Upchurch & Barrett 2000;Sereno & Wilson 2005). It can be expected that the mean feeding height and therefore the preferred neck posture of a sauropod correspond to the distribution of the food that was chosen (see e.g. ...
The neck posture of Brachiosaurus brancai Janensch, 1914 is reanalysed by employing the Preuschoft method to deduce the pattern of stress in the joints between the vertebral centra along the neck. The cogency of different methods for reconstructing the posture of a long neck, especially the Preuschoft method and approaches that are based on optimal articulation of the neck vertebrae, is discussed critically. The results corroborate the reliability of the Preuschoft method whereas the analyses of recent vertebrates with long necks show that approaches based on optimal articulation of the neck vertebrae are less suited for reconstructing habitual postures of long necks during rest. Such models are better suited for reconstructing the neck posture that was employed during locomotion. With the evidence obtained by different methods a conclusive picture of the neck posture and the feeding strategy of Brachiosaurus brancai can be drawn. The neck appears to have been slightly S-shaped with a ventrally flexed cranial section, an approximately straight middle section, and a dorsally flexed proximal part. In the habitual posture during standing, the angle between the middle section of the neck and the horizontal plane was about 60° or 70°. During locomotion the whole neck probably was kept in an lower position with the inclination reduced by approximately 20° compared with the position at rest. During feeding movements of the head relative to the neck and movements in the cranial neck section were performed without much altering the height of the centre of gravity of the neck. With slow dorsoventral movements of the whole neck pronounced changes in the feeding height were possible. Sideways movements of the whole neck were performed by lateral flexion at the base of the neck. According to these findings, the long neck of Brachiosaurus brancai was a means for browsing in great heights as well as a means for increasing the feeding volume without moving the body.
Die Halsstellung von Brachiosaurus brancai Janensch, 1914 wird mit Hilfe der Preuschoft-Methode untersucht, die auf der Ermittlung der Spannungen in den Gelenken zwischen den Wirbelkörpern entlang des Halses beruht. Verschiedene Rekonstruktionsmethoden langer Hälse werden hinsichtlich ihrer Aussagekraft kritisch betrachtet, insbesondere die Preuschoft-Methode sowie Ansätze, die auf einer optimalen Gelenkung zwischen den Wirbeln beruhen. Die Ergebnisse untermauern die Zuverlässigkeit der Preuschoft-Methode, während Analysen an langen Hälsen rezenter Wirbeltiere zeigen, dass Modelle mit optimaler Gelenkung sich weniger für die Rekonstruktion der habituellen Halsstellung während der Ruhe eignen. Stattdessen scheinen solche Modelle eher den Halsstellungen bei der Fortbewegung nahe zu kommen. Unter Einbeziehung verschiedener Methoden wird ein schlüssiges Bild der Halsstellung und der Ernährungsstrategie von Brachiosaurus brancai gezeichnet. Der Hals wurde offenbar in einer leichten S-Form gehalten, mit einem ventralflektierten vorderen Halsabschnitt, einer etwa gerade gehaltenen Halsmitte und einer dorsalflektierten Halsbasis. In der habituellen Stellung des stehenden Tieres bildete die Halsmitte einen Winkel von etwa 60° oder 70° mit der Horizontalebene. Bei der Fortbewegung wurde der Hals vermutlich um rund 20° niedriger gehalten als in der Ruheposition. Während der Nahrungsaufnahme konnte der Kopf durch Bewegungen allein des vorderen Halsabschnittes positioniert werden, ohne dass dabei der Schwerpunkt des Halses wesentliche Höhenänderungen erfahren hätte. Langsame dorsoventrale Bewegungen des gesamten Halses ermöglichten auch erhebliche Änderungen der Kopfhöhe. Seitliche Bewegungen des gesamten Halses konnten an der Halsbasis erzeugt werden. Gemäß dieser Ergebnisse war der lange Hals von Brachiosaurus brancai sowohl ein Mittel zum Erreichen von Nahrungsquellen in großer Höhe als auch zur Vergrößerung des Volumens, das bei ruhendem Körper mit dem Kopf erreicht werden konnte.
doi:10.1002/mmng.200600017
... Dental batteries have evolved independently in ornithischian (Neoceratopsia, Hadrosauridae) and saurischian (Rebbachisauridae) dinosaurs [2,[54][55][56], however, the present study is the first to examine dental battery development and evolution at the histological level. Therefore, the uniqueness of hadrosaurid dental ontogeny and histology depends on further comparisons with the dentitions of neoceratopsians and rebbachisaurid sauropods. ...
... One key prediction that can be made from this work is that future studies in the aforementioned taxa will uncover adaptations to avoiding typical amniote tooth replacement either by accelerated tooth development (as in hadrosaurids) or by some other means of spatially separating older teeth from the dental lamina [57,58]. A brief survey of descriptions of sauropod dentitions shows that they consist of numerous generations of replacement teeth that are spatially separated from one another and gradually migrate to their functional positions through ontogeny [54,55,59]. By comparison, the stacked teeth of the neoceratopsian dental battery consist of multiple generations of teeth that are closely packed, apparently more so than in hadrosaurids [56]. ...
Background
Hadrosaurid dinosaurs, dominant Late Cretaceous herbivores, possessed complex dental batteries with up to 300 teeth in each jaw ramus. Despite extensive interest in the adaptive significance of the dental battery, surprisingly little is known about how the battery evolved from the ancestral dinosaurian dentition, or how it functioned in the living organism. We undertook the first comprehensive, tissue-level study of dental ontogeny in hadrosaurids using several intact maxillary and dentary batteries and compared them to sections of other archosaurs and mammals. We used these comparisons to pinpoint shifts in the ancestral reptilian pattern of tooth ontogeny that allowed hadrosaurids to form complex dental batteries.
Results
Comparisons of hadrosaurid dental ontogeny with that of other amniotes reveals that the ability to halt normal tooth replacement and functionalize the tooth root into the occlusal surface was key to the evolution of dental batteries. The retention of older generations of teeth was driven by acceleration in the timing and rate of dental tissue formation. The hadrosaurid dental battery is a highly modified form of the typical dinosaurian gomphosis with a unique tooth-to-tooth attachment that permitted constant and perfectly timed tooth eruption along the whole battery.
Conclusions
We demonstrate that each battery was a highly dynamic, integrated matrix of living replacement and, remarkably, dead grinding teeth connected by a network of ligaments that permitted fine scale flexibility within the battery. The hadrosaurid dental battery, the most complex in vertebrate evolution, conforms to a surprisingly simple evolutionary model in which ancestral reptilian tissue types were redeployed in a unique manner. The hadrosaurid dental battery thus allows us to follow in great detail the development and extended life history of a particularly complex food processing system, providing novel insights into how tooth development can be altered to produce complex dentitions, the likes of which do not exist in any living vertebrate.
Electronic supplementary material
The online version of this article (doi:10.1186/s12862-016-0721-1) contains supplementary material, which is available to authorized users.
... By the Late Jurassic, several sauropod lineages reached even larger sizes while expanding their range of tooth breadth, including the evolution of narrow-crowned teeth in the neosauropod clade Diplodocoidea (Sereno and Wilson, 2005;Chure et al., 2010) and unusually broad-crowned teeth in the non-neosauropod clade Turiasauria (Britt et al., 2017). During the Cretaceous, sauropods independently evolved narrow-crowned teeth at least two more times, within the species-poor, anatomically stereotyped clade Brachiosauridae and the speciose, morphologically diverse Titanosauria (Chure et al., 2010). ...
Unlike most herbivores, sauropod dinosaurs evolved simple teeth that were replaced rapidly. Sauropod craniodental morphology is conserved relative to that of many archosaur clades, but tooth breadth and replacement rate vary substantially. Two neosauropod clades, Titanosauria and Diplodocoidea, independently evolved both narrow‐crowned teeth and high tooth replacement rates among a suite of other convergent features. Brachiosaurids also evolved somewhat narrower‐crowned teeth, but the two brachiosaurids whose tooth replacement rate has been examined to date have low replacement rates. Poor and uneven sampling across Sauropoda limits our understanding of the evolution of tooth replacement rate and related ecological inferences. To better understand the evolution of tooth replacement rate and tooth breadth, we integrated histological and tomographic data to nearly double the number of examined sauropod genera, focusing on improved sampling through the Cretaceous. We provide histological descriptions of the dentine and enamel of two Early Cretaceous taxa, Abydosaurus and Moabosaurus . The former has unusually thin daily increments in its dentine, indicating prolonged tooth formation times. The dentine of the latter is typical of what is observed in most sauropods, but it has enigmatic banding in its enamel. We performed ancestral state reconstruction on a time‐calibrated phylogeny to show that the earliest macronarians and brachiosaurids retain the ancestral sauropod condition of relatively low tooth replacement rates (2–3 months to replace a tooth in each alveolus), whereas diplodocoids evolved much higher rates (2–5 weeks to replace a tooth in each alveolus). Early diverging somphospondylans had a broad range of tooth replacement rates. Broad‐crowned teeth exhibit some correlation with low tooth replacement rates, whereas narrow‐crowned teeth display a more variable relationship with replacement rate.
... Narrow crowns are present in neosauropod dinosaurs, first appearing in the Late Jurassic diplodocoids and later in the late-diverging titanosaurs by homoplasy (e.g. Sereno and Wilson 2005). The morphology observed in the tooth crowns from Bahia State coincides with that observed in diplodocoids and titanosaurs as well (see Chure et al. 2010), in which all tooth crowns bear moderate-to-high SI values. ...
Supposed dinosaur remains were collected between 1859 and 1906 in the Lower Cretaceous Recôncavo Basin (Northeast Brazil). Since these materials remained undescribed, and most were considered lost. Recently, some of these historical specimens were rediscovered in the Natural History Museum of London, providing an opportunity to revisit them after 160 years. The specimens come from five different sites, corresponding to the Massacará (Berriasian-Barremian) and Ilhas (Valanginian-Barremian) groups. Identified bones comprise mainly isolated vertebral centra from ornithopods, sauropods, and theropods. Appendicular remains include a theropod pedal phalanx, humerus, and distal half of a left femur with elasmarian affinities. Despite their fragmentary nature, these specimens represent the earliest dinosaur bones discovered in South America, enhancing our understanding of the Cretaceous dinosaur faunas in Northeast Brazil. The dinosaur assemblage in the Recôncavo Basin resembles coeval units in Northeast Brazil, such as the Rio do Peixe Basin, where ornithopods coexist with sauropods and theropods. This study confirms the presence of ornithischian dinosaurs in Brazil based on osteological evidence, expanding their biogeographic and temporal range before the continental rifting between South America and Africa. Additionally, these findings reinforce the fossiliferous potential of Cretaceous deposits in Bahia State, which have been underexplored since their initial discoveries.
... Supplied with akinetic skulls that only allowed for minimal (if any) food processing, their teeth cropped, sliced, and stripped vegetation by means of a variety of morphologies that included wide-crowned, spatulate and short teeth (Vulcanodontidae, Mamenchisauridae, Turiasauridae, Euhelopodidae, "Cetiosauridae", "Omeiasauridae", Camarasauromorpha and Brachiosauridae) and narrow-crowned, pencil-like, and elongated teeth (Diplodocoidea and Titanosauria) (Upchurch and Barrett, 2000). Titanosaurs, a highly diverse group with a striking body size disparity and a worldwide distribution (Sereno and Wilson, 2005;Upchurch et al., 2011;Carballido et al., 2017), possessed mostly cylindrical teeth (although somewhat lanceolate at the cusps) with a characteristic chisel-like shape (Upchurch and Barrett, 2000). This shape resulted from the apical wear facets developed by a cusp-to-cusp occlusal position. ...
... Both the Amazonsaurus maranhensis (de et al. 2003) from the Itapecuru Formation and Itapeuasaurus cajapioensis (Lindoso et al. 2019) from the Alcântara Formation do not have any type of preserved or associated dental material. This, in addition to a dentition that is either very autapomorphic, as seen in the African taxon Nigersaurus taqueti (Sereno and Wilson 2005), or is very convergent with that seen in derived lithostrotians (Fernández-Baldor et al. 2011;Zaher et al. 2011;Wilson et al. 2016), can make it difficult to identify these isolated teeth. ...
Dinosaur fossils are commonly found in Brazilian Mesozoic strata, with teeth being frequently found in Cretaceous outcrops. Many studies have been made with the aim of reviewing the known diversity of Brazilian dinosaurs, mostly focusing solely on their palaeobiogeography. However, few tried to typify these body fossils in order to see which kinds were most prevalent in the fossil record. This study aims to count and identify all occurrences of non-avian dinosaur teeth (isolated or in situ) unearthed from Brazilian Cretaceous strata in order to objectively measure their representativity in the national fossil record. Our literature search showed that almost half of the dinosaur fossil record from the Cretaceous of Brazil is composed by teeth, those being particularly abundant in the Alcântara, Adamantina and Marília formations. Theropod teeth are more abundant in comparison to sauropod teeth, with spinosaurids, deinonychosaurs, and abelisaurids being amply found. Despite representing a large share of the Brazilian fossil record, dinosaur teeth have only recently been studied in depth, with many specimens being reassessed through the current identification methods. Other aspects besides primary taxonomic identification can also be further explored using the latest technologies on dinosaur teeth, allowing a deeper understanding of the palaeobiology of these reptiles.
... Among 'derived' titanosaurs, there is evidence for two main jaw shapes: jaws with rounded ends, like those of Ampelosaurus, Karongasaurus, Malawisaurus, Mansourasaurus, Nemegtosaurus, Quaesitosaurus, Rapetosaurus and Tapuiasaurus [17][18][19][20][21][22]115,160,168]; and squared-off jaws, like those of Antarctosaurus, Baalsaurus, Bonitasaura and Brasilotitan [141,145,[162][163][164][165]. This disparity parallels that seen in diplodocoids [105]: some have rounded jaws, such as the dicraeosaurids Suuwassea emilieae and Dicraeosaurus hansemanni [25,166]; some have squared-off jaws, such as the diplodocids Apatosaurus louisae, Diplodocus longus and Tornieria africana, and the rebbachisaurid Lavocatisaurus agrioensis [25,213,303,307]; and others have squared-off and transversely expanded jaws, namely the rebbachisaurid Nigersaurus [110,308,309]. ...
Titanosaurian sauropod dinosaurs were diverse and abundant throughout the Cretaceous, with a global distribution. However, few titanosaurian taxa are represented by multiple skeletons, let alone skulls. Diamantinasaurus matildae, from the lower Upper Cretaceous Winton Formation of Queensland, Australia, was heretofore represented by three specimens, including one that preserves a braincase and several other cranial elements. Herein, we describe a fourth specimen of Diamantinasaurus matildae that preserves a more complete skull—including numerous cranial elements not previously known for this taxon—as well as a partial postcranial skeleton. The skull of Diamantinasaurus matildae shows many similarities to that of the coeval Sarmientosaurus musacchioi from Argentina (e.g. quadratojugal with posterior tongue-like process; braincase with more than one ossified exit for cranial nerve V; compressed-cone–chisel-like teeth), providing further support for the inclusion of both taxa within the clade Diamantinasauria. The replacement teeth within the premaxilla of the new specimen are morphologically congruent with teeth previously attributed to Diamantinasaurus matildae, and Diamantinasauria more broadly, corroborating those referrals. Plesiomorphic characters of the new specimen include a sacrum comprising five vertebrae (also newly demonstrated in the holotype of Diamantinasaurus matildae), rather than the six or more that typify other titanosaurs. However, we demonstrate that there have been a number of independent acquisitions of a six-vertebrae sacrum among Somphospondyli and/or that there have been numerous reversals to a five-vertebrae sacrum, suggesting that sacral count is relatively plastic. Other newly identified plesiomorphic features include: the overall skull shape, which is more similar to brachiosaurids than ‘derived' titanosaurs; anterior caudal centra that are amphicoelous, rather than procoelous; and a pedal phalangeal formula estimated as 2-2-3-2-0. These features are consistent with either an early-branching position within Titanosauria, or a position just outside the titanosaurian radiation, for Diamantinasauria, as indicated by alternative character weighting approaches applied in our phylogenetic analyses, and help to shed light on the early assembly of titanosaurian anatomy that has until now been obscured by a poor fossil record.
... An increase in relative crown height has been observed to some extent in sauropods 75 , while an increase in the number of teeth, in terms of accelerated tooth replacement, increased numbers of replacement teeth, and increased tooth counts are known in many dinosaur groups (e.g. sauropods 59,76 ; hadrosaurids 3,63 ; ceratopsids 14,77 ). However, it appears that marked asymmetrical thickening of the dentine component of the tooth crown only occurs in some basal iguanodontians, where tooth replacement has not yet accelerated to the same high rates seen in later-branching taxa, but where continual tooth-tooth occlusion and/or less frequently replaced teeth with longer functional lives require more resistant teeth. ...
Dentitions of the sympatric herbivorous dinosaurs Hungarosaurus (Ankylosauria, Nodosauridae) and Mochlodon (Ornithopoda, Rhabdodontidae) (Santonian, Hungary) were analysed to investigate their dietary ecology, using several complementary methods—orientation patch count, tooth replacement rate, macrowear, tooth wear rate, traditional microwear, and dental microwear texture analysis (DMTA). Tooth formation time is similar in Hungarosaurus and Mochlodon, and traditional and DMTA microwear features suggest low-browsing habits for both taxa, consistent with their inferred stances and body sizes. However, Mochlodon possesses a novel adaptation for increasing dental durability: the dentine on the working side of the crown is double the thickness of that on the balancing side. Moreover, crown morphology, enamel thickness, macrowear orientation, and wear rate differ greatly between the two taxa. Consequently, these sympatric herbivores probably exploited plants of different toughness, implying dietary selectivity and niche partitioning. Hungarosaurus is inferred to have eaten softer vegetation, whereas Mochlodon likely fed on tougher material. Compared to the much heavier, quadrupedal Hungarosaurus, the bipedal Mochlodon wore down more than twice as much of its crown volume during the functional life of the tooth. This heavy tooth wear might correlate with more intensive food processing and, in turn, could reflect differences in the metabolic requirements of these animals.
... Paradoxically, the dinosaurs with the most significant masticatory forces applied to their cheek teeth, the ornithischians, lose mantle dentin altogether, although this has been linked to the development of a tooth battery (Wang et al., 2015). Corroborating evidence of this in sauropods comes from the rebbachisaurid Nigersaurus taqueti, previously hypothesized to have a dental array approximating a battery (Sereno and Wilson, 2005;Sereno et al., 2007). In that taxon, although mantle dentin is present, it is very thin (<5 µm; see Sereno et al., 2007: fig. ...
... In Malawi, lithostrotian titanosaurs were established as early as the Aptian [217][218][219][220][221][222], with evidence that Karongasaurus, which has narrow, chisel-like teeth, lived alongside Malawisaurus, which has broader, compressed-cone-chisel-like teeth [222]. Aptian-Albian deposits in Niger are dominated by rebbachisaurids [223][224][225][226], although titanosauriforms ( probably somphospondylans) were also present [227]. Aptian-Albian deposits in Cameroon preserve narrow-crowned sauropod teeth [228], possibly attributable to Somphospondyli [227]. ...
The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains—including teeth—remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00–2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a ‘basal’ titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1–10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early–early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.
... The alternative maximal-clade (i.e. stem-based) definitions (Upchurch 1997; better fit the most common usage of the term (Sereno et al. 2005), including such early branching Carnian taxa, and this was fixed by Fabbri et al. (2020) in Phylonyms. Indeed, as current phylogenetic studies mostly concur in placing the seven taxa that form the core of this revision closer to Saltasaurus loricatus than to either Allosaurus fragilis or Iguanodon bernissartensis, they should, by definition, be referred to as sauropodomorphs. ...
After the extinction of rebbachisaurids during the Cenomanian–Turonian interval, titanosaurs were the only group of sauropods to face the K–Pg event. This same global pattern also holds for the end-Cretaceous (Campanian–Maastrichtian) titanosaur record in South America, where their remains can be found from southern Argentina to Ecuador, with more frequent findings in Argentina and Brazil. In this chapter, we review these fossil findings and the main aspects of the taxonomy, systematics, and paleogeographic implications of this record and briefly discuss the importance of these occurrences for the understanding of titanosaur evolution. The diversity and abundance of end-Cretaceous titanosaur taxa in South America represent about 25% of the known Titanosauria species in the world, which makes them the most common group of large terrestrial herbivores of that time. Cretaceous titanosaurs from South America also vary highly in morphology and size, comprising small to large-sized taxa, for example. Their record mainly consists of appendicular and axial remains, including rare skull material, but also comprises eggs, nests, footprints, and coprolites. In South America, by the end of the Late Cretaceous, titanosaurs were generally represented by more derived titanosaurians that are mainly taxonomically assigned to more derived species within Aeolosaurini and Saltasaurinae.
... Among macronarians, Camarasaurus and the 'Río Negro titanosaur' possess three replacement teeth per alveolus (Coria & Chiappe, 2001;D'Emic et al., 2013). This condition differs from that of Diplodocoidea, which present a high tooth replacement rate and more generations of replacement teeth (e.g., five in Diplodocus; 10 in Nigersaurus) (Sereno & Wilson, 2005;D'Emic et al., 2013). Material. ...
Brachiosauridae is a lineage of titanosauriform sauropods that includes some of the most iconic non-avian dinosaurs. Undisputed brachiosaurid fossils are known from the Late Jurassic through the Early Cretaceous of North America, Africa, and Europe, but proposed occurrences outside this range have proven controversial. Despite occasional suggestions that brachiosaurids dispersed into Asia, to date no fossils have provided convincing evidence for a pan-Laurasian distribution for the clade, and the failure to discover brachiosaurid fossils in the well-sampled sauropod-bearing horizons of the Early Cretaceous of Asia has been taken to evidence their genuine absence from the continent. Here we report on an isolated sauropod maxilla from the middle Cretaceous (Albian–Cenomanian) Longjing Formation of the Yanji basin of northeast China. Although the specimen preserves limited morphological information, it exhibits axially twisted dentition, a shared derived trait otherwise known only in brachiosaurids. Referral of the specimen to the Brachiosauridae receives support from phylogenetic analysis under both equal and implied weights parsimony, providing the most convincing evidence to date that brachiosaurids dispersed into Asia at some point in their evolutionary history. Inclusion in our phylogenetic analyses of an isolated sauropod dentary from the same site, for which an association with the maxilla is possible but uncertain, does not substantively alter these results. We consider several paleobiogeographic scenarios that could account for the occurrence of a middle Cretaceous Asian brachiosaurid, including dispersal from either North America or Europe during the Early Cretaceous. The identification of a brachiosaurid in the Longshan fauna, and the paleobiogeographic histories that could account for its presence there, are hypotheses that can be tested with continued study and excavation of fossils from the Longjing Formation.
... Rebbachisaurids appear to have been the low-level feeders par excellence among sauropods. The highly derived rebbachisaurid, Nigersaurus Sereno et al., 1999, from the Aptian-Albian Elrhaz Formation of Niger has been identified as a highly specialized lowlevel feeder (Sereno & Wilson, 2005) that potentially subsisted mainly on horsetails and ferns (Sereno et al., 2007), based on its anteriorly flattened and expanded Π-shaped jaws, its 'battery' of extremely narrowcrowned teeth and the presence of labial wear facets on those teeth (implying abrasion against a flat substrate, i.e. the ground). The few cranial remains known for other rebbachisaurid taxa [notably, Lavocatisaurus agrioensis Canudo et al., 2018, Limaysaurus tessonei (Calvo & Salgado, 1995) (Paulina Carabajal & Calvo, 2015 and an indeterminate rebbachisaurid from the Candeleros Formation of Argentina, MMCh-PV 71 (Paulina Carabajal et al., 2016)] appear to be broadly similar to those of Nigersaurus, implying that the entire clade was specialized for low-level browsing. ...
The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian-lower Turonian 'upper' Winton Formation of central Queensland, northeastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian-Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their presence in both Antarctica and New Zealand during the Campanian-Maastrichtian. These later titanosaurs presumably dispersed into these landmasses from South America before the Campanian (~85 Mya), when seafloor spreading between Zealandia and Australia commenced. Although Australian mid-Cretaceous dinosaur faunas appear to be cosmopolitan at higher taxonomic levels, closer affinities with South America at finer scales are becoming better supported for sauropods, theropods and ornithopods.
... The Kem Kem is traditionally considered to be Cenomanian, as it has been found to match ammonites from the Lower Cenomanian of Bahariya, Egypt (Le Loeuff et al., 2012). However, the age probably spans over the Albian-Cenomanian (Underwood and Ward, 2018), which is closer to the age given to the Cretaceous 'Continental Intercalaire' of Algeria (Lefranc and Guiraud, 1990;Le Loeuff et al., 2012;Läng et al., 2013;Benyoucef et al., 2015;Meister et al., 2017) and to the fossil-rich Cretaceous 'Continental Intercalaire' beds of Tunisia (Fanti et al., 2016) as well as to the 'Continental Intercalaire' of Niger (Sereno and Wilson, 2005;Rauhut and López-Arbarello, 2009;Le Loeuff et al., 2012), and Libya (Le Loeuff et al., 2012). The unit named 'Continental Intercalaire', however, as mentioned, consists of several localities spread over the northern margins of the African craton, not all of which are easily dated (Le Loeuff et al., 2012), and is therefore somewhat problematic as a geological term; however, many authors still refer to it as a common name (similar to the Kem Kem being applied to the entire depositional range in southeastern Morocco, whereas the 'true' Kem Kem only applies to one specific area; Underwood and Ward (2018)). ...
... The Kem Kem is traditionally considered to be Cenomanian, as it has been found to match ammonites from the Lower Cenomanian of Bahariya, Egypt (Le Loeuff et al., 2012). However, the age probably spans over the Albian-Cenomanian (Underwood and Ward, 2018), which is closer to the age given to the Cretaceous 'Continental Intercalaire' of Algeria (Lefranc and Guiraud, 1990;Le Loeuff et al., 2012;Läng et al., 2013;Benyoucef et al., 2015;Meister et al., 2017) and to the fossil-rich Cretaceous 'Continental Intercalaire' beds of Tunisia (Fanti et al., 2016) as well as to the 'Continental Intercalaire' of Niger (Sereno and Wilson, 2005;Rauhut and López-Arbarello, 2009;Le Loeuff et al., 2012), and Libya (Le Loeuff et al., 2012). The unit named 'Continental Intercalaire', however, as mentioned, consists of several localities spread over the northern margins of the African craton, not all of which are easily dated (Le Loeuff et al., 2012), and is therefore somewhat problematic as a geological term; however, many authors still refer to it as a common name (similar to the Kem Kem being applied to the entire depositional range in southeastern Morocco, whereas the 'true' Kem Kem only applies to one specific area; Underwood and Ward (2018)). ...
... Morphospace expansion in the Aptian suggests that this was a time of diversification of dental and jaw morphologies, particularly among sauropods and early hadrosauroids (Fig. 3). This includes Nigersaurus taqueti, which is the only sauropod known to have evolved a specialized "dental battery" (Sereno and Wilson 2005), and early hadrosauroids (Altirhinus kurzanovi, Jinzhousaurus yangi) with primitive versions of dental batteries. Dental batteries would later become more advanced in hadrosaurids and were likely a key factor in the success of this group in the Late Cretaceous (Norman and Weishampel 1985;Strickson et al. 2016). ...
Understanding temporal patterns in biodiversity is an enduring question in paleontology. Compared with studies of taxonomic diversity, long-term perspectives on ecological diversity are rare, particularly in terrestrial systems. Yet ecological diversity is critical for the maintenance of biodiversity, especially during times of major perturbations. Here, we explore the ecological diversity of Cretaceous herbivorous dinosaurs leading up to the K-Pg extinction, using dental and jaw morphological disparity as a proxy. We test the hypothesis that a decline in ecological diversity could have facilitated their rapid extinction 66 Ma. We apply three disparity metrics that together capture different aspects of morphospace occupation and show how this approach is key to understanding patterns of morphological evolution. We find no evidence of declining disparity in herbivorous dinosaurs as a whole—suggesting that dinosaur ecological diversity remained high during the last 10 Myr of their existence. Clades show different disparity trends through the Cretaceous, but none except sauropods exhibits a long-term decline. Herbivorous dinosaurs show two disparity peaks characterized by different processes; in the Early Cretaceous by expansion in morphospace and in the Campanian by morphospace packing. These trends were only revealed by using a combination of disparity metrics, demonstrating how this approach can offer novel insights into macroevolutionary processes underlying patterns of disparity and ecological diversity.
... The second generation replacement tooth in a given alveolus is positioned somewhat mesiolingual to the first generation tooth in that alveolus. It is possible that the lack of a second generation of replacement teeth in more posterior alveoli reflects differential rates of tooth replacement along the tooth row, as has been noted for some other sauropods (Sereno & Wilson, 2005;Wiersma & Sander, 2016). Ontogenetic influences on tooth replacement rates and number are not known for sauropods. ...
Bellusaurus sui is an enigmatic sauropod dinosaur from the Middle-Late Jurassic Shishugou Formation of northwest China. Bellusaurus is known from a monospecific bonebed preserving elements from more than a dozen juvenile individuals, including numerous bones of the skull, providing rare insight into the cranial anatomy of juvenile sauropods. Here, we present a comprehensive description of the cranial anatomy of Bellusaurus , supplementing the holotypic cranial material with additional elements recovered from recent joint Sino-American field expeditions. Bellusaurus is diagnosed by several unique autapomorphies, including a neurovascular foramen piercing the ascending process of the maxilla at midheight, the frontal process of the nasal extending farther posteriorly onto the frontal than the prefrontal, and U-shaped medial and lateral notches in the posterior margin of the ventral process of the squamosal. Several features identified here, including a preantorbital opening in the maxilla, a stepped dorsal margin of the vomerine process of the pterygoid, and the partitioning of the dorsal midline endocranial fossae associated with the dural venous sinuses into anterior and posterior components by a transverse ridge of the parietal, are consistent with recent phylogenetic hypotheses that recover Bellusaurus as a basal macronarian or close relative of Neosauropoda. We review the current state of knowledge of sauropod cranial ontogeny, placing several aspects of the cranial anatomy of Bellusaurus in an ontogenetic context and providing explicit hypotheses of ontogenetic transformations that can be tested by future discoveries of ontogenetic variants of sauropod skulls. While scoring ontogenetically variable characters as unknown may help to alleviate the biasing effects of ontogeny on the phylogenetic position of juvenile specimens, we caution that this approach may remove phylogenetically informative character information, and argue that inference methods that are known to be less sensitive to homoplasy than equal weights parsimony (i.e., implied weights parsimony; Bayesian approaches) should also be employed.
... Rebbachisauridae is a clade of small to medium-sized, morphologically peculiar diplodocoid sauropod dinosaurs known from the Early and mid-Cretaceous of Europe, South America, and Africa. Previous works have attempted to elucidate the paleobiology of rebbachisaurids based on the skeletal anatomy of these unusual sauropods (e.g., Apesteguía 2005;Sereno and Wilson 2005;Sereno et al. 2007;Apesteguía et al. 2010;Fanti et al. 2013Fanti et al. , 2015Wilson and Allain 2015;Paulina Carabajal et al. 2016). Nevertheless, many aspects of rebbachisaurid paleobiology remain poorly understood, a circumstance that is due in large part to the highly incomplete nature of most fossils of these dinosaurs (Ibiricu et al. 2012). ...
In dinosaurs and other archosaurs, the presence of foramina connected with internal chambers in axial and appendic-ular bones is regarded as a robust indicator of postcranial skeletal pneumaticity (PSP). Here we analyze PSP and its paleobiological implications in rebbachisaurid diplodocoid sauropod dinosaurs based primarily on the dorsal vertebrae of Katepensaurus goicoecheai, a rebbachisaurid from the Cenomanian–Turonian (Upper Cretaceous) Bajo Barreal Formation of Patagonia, Argentina. We document a complex of interconnected pneumatic foramina and internal chambers within the dorsal vertebral transverse processes of Katepensaurus. Collectively, these structures constitute a form of PSP that has not previously been observed in sauropods, though it is closely comparable to morphologies seen in selected birds and non-avian theropods. Parts of the skeletons of Katepensaurus and other rebbachisaurid taxa such as Amazonsaurus maranhensis and Tataouinea hannibalis exhibit an elevated degree of pneumaticity relative to the conditions in many other sauropods. We interpret this extensive PSP as an adaptation for lowering the density of the skeleton, and tentatively propose that this reduced skeletal density may also have decreased the muscle energy required to move the body and the heat generated in so doing. Given that several rebbachisaurids inhabited tropical to subtropical paleolatitudes during the extreme warmth of the mid-Cretaceous, increased PSP may have better enabled these sauropods to cope with extraordinarily high temperatures. Extensive skeletal pneumaticity may have been an important innovation in Rebbachisauridae, and perhaps also in saltasaurine titanosaurs, which evolved an even greater degree of PSP. This may in turn have contributed to the evolutionary success of rebbachisaurids, which were the only diplodocoids to survive into the Late Cretaceous.
... This has long been the general understanding of this term, with acknowledgement that heterodontosaurids including Heterodontosaurus do not exhibit this level of dental integration (Crompton and Charig 1962). Tooth batteries are now known to occur in neoceratopsians, iguanodontians and rebbachisaurid sauropods (Sereno and Wilson 2005). Heterodontosaurid teeth, in contrast, erupt independently within separate alveoli. ...
Heterodontosaurids comprise an important early radiation of small-bodied herbivores that persisted for approximately 100 My from Late Triassic to Early Cretaceous time. Review of available fossils unequivocally establishes Echinodon as a very small-bodied, late-surviving northern heterodontosaurid similar to the other northern genera Fruitadens and Tianyulong. Tianyulong from northern China has unusual skeletal proportions, including a relatively large skull, short forelimb, and long manual digit II. The southern African heterodontosaurid genus Lycorhinus is established as valid, and a new taxon from the same formation is named Pegomastax africanus gen. n., sp. n. Tooth replacement and tooth-to-tooth wear is more common than previously thought among heterodontosaurids, and in Heterodontosaurus the angle of tooth-to-tooth shear is shown to increase markedly during maturation. Long-axis rotation of the lower jaw during occlusion is identified here as the most likely functional mechanism underlying marked tooth wear in mature specimens of Heterodontosaurus. Extensive tooth wear and other evidence suggests that all heterodontosaurids were predominantly or exclusively herbivores. Basal genera such as Echinodon, Fruitadens and Tianyulong with primitive, subtriangular crowns currently are known only from northern landmasses. All other genera except the enigmatic Pisanosaurus have deeper crown proportions and currently are known only from southern landmasses.
... 7), titanosaur teeth from the Upper Cretaceous of Uzbekistan (Sues et al., 2015: fig. 5G-I) and in teeth of Nigersaurus from Lower Cretaceous beds of Niger (Sereno & Wilson, 2005;Sereno et al., 2007). It is likely that these all represent upper teeth. ...
Although Titanosauria is the most diverse and late-surviving sauropod lineage, cranial elements are known for just over 24 of its 70+ genera - the vast majority of which are fairly fragmentary and restricted to the Late Cretaceous. Only three complete titanosaur skulls have been described to date; two of these are from the latest Cretaceous (Nemegtosaurus, Rapetosaurus), and the third, Tapuiasaurus, is from the Early Cretaceous (Aptian). In this contribution, we build on the initial treatment of the taxon by providing a complete description of the cranial elements that benefits from additional preparation and computed tomography imaging. We identify six additional features diagnosing Tapuiasaurus macedoi, including a jugal with an elongate lacrimal process forming much of the posteroventral border of the antorbital fenestra, a lateral temporal fenestra divided by a second squamosal-postorbital contact, and upper jaw teeth with labial wear facets. We directed the new morphological data in Tapuiasaurus as well as other observations towards a re-analysis of its phylogenetic position within Titanosauria. Our analysis yielded 34 most parsimonious trees, most of which recovered Tapuiasaurus in a basal position adjacent to the Early Cretaceous taxa Malawisaurus and Tangvayosaurus, but two trees recovered it within Late Cretaceous nemegtosaurids. We explored the effects of missing data and missing stratigraphic ranges on our results, concluding that (1) when missing data levels are high, resolution of even small amounts of that missing data can have dramatic effects on topology, (2) taxa that are mostly scored for characters that cannot be scored in other taxa may be topologically unstable and (3) there were several suboptimal trees that had greatly improved stratigraphic fit with relatively little compromise in terms of tree length.
The Upper Jurassic of Portugal is well known for its dinosaurian fauna, which includes five sauropod species. Although only one of these species preserves associated dental material, isolated sauropod teeth are commonly found in the Upper Jurassic units of Portugal. The morphological diversity of Portuguese sauropod teeth has already been described and attributed to four dental morphotypes. Here, we report an additional 24 heart‐shaped teeth, 9 spatulate teeth, 16 compressed chisel‐shaped teeth and 10 pencil‐shaped teeth of the hitherto unstudied collection of Museu da Lourinhã. All four morphotypes are attributed to sauropod clades known from the Portuguese Upper Jurassic fossil record, based on morphology and tooth slenderness. Although statistical tests show a clear relation between a widely used Slenderness Index (SI) and taxonomy, morphology proves to be necessary to correctly interpret any usage of the SI as a taxonomic tool. As such, when it comes to the Upper Jurassic Portuguese tooth record, we attribute the heart‐shaped teeth to Turiasauria, spatulate teeth to Camarasauridae, compressed chisel‐shaped teeth to Titanosauriformes indet., and pencil‐shaped teeth to Flagellicaudata. A reassessment of sauropod dental evolution shows a general trend of increasing tooth slenderness in all studied taxonomic groups, and a disappearance of broad‐crowned taxa with well developed tooth‐to‐tooth occlusion by the end of the Early Cretaceous. We suggest that this may be correlated with the evolution of dental batteries in ornithischians, which were more efficient in oral food processing.
The Barremian-aged Wessex Formation of the Isle of Wight, UK, offers a globally significant glimpse into the sauropod dinosaur faunas of the early Cretaceous. These deposits have yielded specimens of several neosauropod lineages, such as rebbachisaurids, titanosauriforms (including some of the earliest titanosaur remains), and possible flagellicaudatans. Here, we report an undescribed sauropod partial hindlimb from the Wessex Formation (NHMUK PV R16500) and analyse its phylogenetic affinities. This hindlimb preserves the left tibia, astragalus and pes, lacking only a few phalanges. NHMUK PV R16500 can be diagnosed based on two autapomorphies: an unusually high distal end to midshaft transverse width ratio in metatarsals III and IV, and the presence of small bump-like projections located in the centre of the proximal articular surfaces of the unguals of pedal digits I and II. The phylogenetic affinities of NHMUK PV R16500 are uncertain: although our analyses recover it as an early-branching somphospondylan, a single character change moves it to close to Flagellicaudata when extended implied weighting is applied. The possibility of flagellicaudatan affinities for NHMUK PV R16500 implies a potential ghost lineage that survived the Jurassic/Cretaceous boundary; however, we present evidence that the somphospondylan position is more probable and should be preferred.
The sauropod genus Mamenchisaurus, from the Late Jurassic–Early Cretaceous of East Asia, has a convoluted taxonomic history. Although included in the first cladistic analysis of sauropods, only recently has the monophyly of Mamenchisaurus, and the anatomical diversity of the many penecontemporaneous East Asian eusauropods, been evaluated critically. Here, we re-describe the holotype and only specimen of M. sinocanadorum. Although the original diagnosis is no longer adequate, we identify several autapomorphies that support the validity of this species, including an elongate external mandibular fenestra and distinctive pneumatic structures on the cervical centra. We incorporate new data into a phylogenetic character matrix that also includes Bellusaurus and Daanosaurus, both of which are known only from juvenile material and are often hypothesized to be neosauropods (or close relatives thereof). We recover all species of Mamenchisaurus as part of a radiation of predominantly Middle–Late Jurassic East Asian eusauropods, but the genus is non-monophyletic, underscoring the need for further systematic revision of mamenchisaurid taxonomy. Analyses that score ontogenetically variable characters ambiguously recover Bellusaurus and Daanosaurus as juvenile mamenchisaurids, a hypothesis supported by several features that are unique to mamenchisaurids or exhibit little homoplasy, including anteriorly bifurcate cervical ribs. Finally, computed-tomography reveals extensive vertebral pneumaticity in M. sinocanadorum that is comparable to that of the largest sauropods, and updated scaling analyses imply a neck over 14 m long, rivalling estimates for other exceptionally long-necked sauropods. Previous work has suggested that the elongated cervical ribs of particularly long-necked sauropods such as M. sinocanadorum stabilized the neck by limiting its mobility. Given that extent of pneumaticity responds dynamically to a bone’s habitual loading, we propose that long cervical ribs – and other structural modifications that limited flexibility – promoted the evolution of increasingly long necks by producing a more predictable biomechanical milieu amenable to increased pneumatization.
With 17 species formally identified throughout the world, Rebbachisauridae is, at present, the best-represented group of South American diplodocoids, and it has a temporal record ranging from the Barremian up to the Turonian. Defined as all diplodocoids more closely related to Rebbachisaurus garasbae than to Diplodocus carnegii, these sauropods are characterized by postcranial synapomorphies (e.g., absence of the hyposphenal ridge on anterior caudal vertebrae; presence of spinodiapophyseal lamina in caudal vertebrae). Although relatively complete skulls are known in only a few genera (Limaysaurus, Lavocatisaurus, and Nigersaurus), the whole cranial evidence indicates that they were highly specialized with respect to other diplodocoids (for instance Diplodocidae). South America counts ten genera of Rebbachisauridae, most of them from the Argentine Patagonia. They embrace a rather diverse group of basally branching forms (Amazonsaurus, Zapalasaurus, Comahuesaurus, and Lavocatisaurus), derived forms (as the limaysaurines Limaysaurus and Cathartesaura and the rebbachisaurines Katepensaurus and Itapeuasaurus), together with forms of uncertain phylogenetic filiation (Rayososaurus). Rebbachisaurids were important in South America toward the end of the Early Cretaceous, integrating, at that time, the sauropod faunas together with macronarians (Titanosauriformes) and other diplodocoids (Dicraeosauridae). They persisted up to at least the Turonian, being the last diplodocoids in becoming extinct globally.
Camarasaurus represents one of the most common dinosaurs from North America, and certainly a contender for one of the most abundantly represented dinosaur taxa worldwide. With numerous specimens ranging the gamut of completeness and maturity, Camarasaurus would theoretically represent a neosauropodian exemplar towards better understanding intra- and interspecific variation, dimorphism, and life history development and strategies. And yet, counterintuitively, its abundance is seemingly a deterrent for active research. Herein we describe a new specimen of Camarasaurus sp. which is most notably known from a nearly complete and articulated skull. While Camarasaurus cranial material is unquestionably the most common sauropod cranial material from North America, our understanding of the total cranial morphology is limited, and largely relies on more limited and historic specimens. In addition to further illuminating the morphology and variation present in Camarasaurus crania, associated post-crania also allow for the first recognition of possible cranial allometry. The identification of this perplexing cranial allometry in several specimens indicates that it is not a singular variation. Though this analysis was not able to source the causal mechanism, factors such as taxonomy, dimorphism, or extreme intra-/intraspecific variation are all possible considerations for future analyses. The recognition of this undocumented cranial allometry further emphasizes that despite being so numerous, there is still vast gaps in our knowledge about Camarasaurus; and this analysis further echoes that the genus is in desperate need of revision.
Xenoposeidon proneneukos is a sauropod dinosaur represented by a single partial dorsal vertebra, NHMUK R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with Rebbachisaurus garasbae : an “M”-shaped arrangement of laminae on the lateral face of the neural arch. Following the more complete Rebbachisaurus garasbae , these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its elevated parapophysis, the holotype vertebra is considered a posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the from the Berriasian–Valanginian (earliest Cretaceous) Ashdown Beds Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon 's true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible.
Xenoposeidon proneneukos is a sauropod dinosaur represented by a single partial dorsal vertebra, NHMUK R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with Rebbachisaurus garasbae : an “M”-shaped arrangement of laminae on the lateral face of the neural arch. Following the more complete Rebbachisaurus garasbae , these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its elevated parapophysis, the holotype vertebra is considered a posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the from the Berriasian–Valanginian (earliest Cretaceous) Ashdown Beds Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon 's true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible.
Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colorado are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominating the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.
Dental replacement in Heterodontosauridae has been debated over the last five decades primarily on indirect evidence, such as the development of wear facets and the position of erupted teeth. Direct observation of unerupted teeth provides unambiguous data for understanding tooth replacement but this has been done only for Heterodontosaurus and Fruitadens. This study addresses dental replacement in Manidens condorensis based on the positioning of functional and replacement teeth using microcomputed tomography data, differential wear along the dentition and the differences in labiolingual/apicobasal level of functional teeth. Dental replacement in Manidens condorensis was continuous in an anterior-to-posterior wave pattern, with asynchronous tooth eruption and the addition of new teeth posteriorly to the toothrow during ontogeny. Manidens shows the first evidence of dental replacement for the large dentary caniniform in Heterodontosauridae, which possibly had replacement timing distinct from the cheek dentition. Newly erupted teeth imbricate in a mesial cavity-distal crown base relationship during eruption, so that imbrication of the mid-posterior dentition remains unaltered during tooth replacement. The presence/absence of a small caniniform tooth in the D3 position of several specimens suggests possible intraspecific dimorphism in Manidens. On longitudinal sections of isolated crowns, the histological features such as Howship's lacunae and odontoclast spaces are similar in size to extant reptiles. The differential wear decreasing posteriorly and hypothetical Z-spacing below 2.3 in Manidens are similar to basal ornithischians. Tooth replacement in Heterodontosauridae (and other early ornithischians) provides key information for understanding the dynamics of jaw function and craniomandibular specialization to herbivory.
Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colorado are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominating the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the
quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.
Xenoposeidon proneneukos is a sauropod dinosaur from the Early Cretaceous Hastings Group of England. It is represented by a single partial dorsal vertebra, NHMUK PV R2095, which consists of the centrum and the base of a tall neural arch. Despite its fragmentary nature, it is recognisably distinct from all other sauropods, and is here diagnosed with five unique characters. One character previously considered unique is here recognised as shared with the rebbachisaurid diplodocoid Rebbachisaurus garasbae from the mid-Cretaceous of Morocco: an ‘M’-shaped arrangement of laminae on the lateral face of the neural arch. Following the more completely preserved R. garasbae , these laminae are now interpreted as ACPL and lateral CPRL, which intersect anteriorly; and PCDL and CPOL, which intersect posteriorly. Similar arrangements are also seen in some other rebbachisaurid specimens (though not all, possibly due to serial variation), but never in non-rebbachisaurid sauropods. Xenoposeidon is therefore referred to Rebbachisauridae. Due to its inferred elevated parapophysis, the holotype vertebra is considered a mid-posterior dorsal despite its elongate centrum. Since Xenoposeidon is from the Berriasian–Valanginian (earliest Cretaceous) Ashdown Formation of the Wealden Supergroup of southern England, it is the earliest known rebbachisaurid by some 10 million years. Electronic 3D models were invaluable in determining Xenoposeidon ’s true affinities: descriptions of complex bones such as sauropod vertebrae should always provide them where possible.
The Upper Jurassic of the Lusitanian Basin has yielded an important fossil record of sauropods, but little information is available about the tooth morphotypes represented in this region. A large sample of teeth, both unpublished and published, is described and discussed here. Four main tooth morphologies are identified: spatulate, heart-shaped, pencil-shaped, and compressed cone-chisel-shaped. Heart-shaped teeth are considered to be exclusive to a non-neosauropod eusauropod, tentatively referred to Turiasauria. The spatulate teeth can be attributed to members of the Macronaria; they have a complex cingulum, more than one lingual facet and a labial ridge. The compressed cone-chisel-shaped teeth are also attributed to macronarians and the presence of an axially twisted apex through an arc of 30°–45° suggests putative affinities with Europasaurus and basal titanosauriforms. The variability observed in the overall morphology and wrinkling pattern of the compressed cone-chisel-shaped teeth may be due to factors related to the tooth position or to the ontogeny of individuals. Finally, pencil-shaped teeth with high slenderness index values, oval and apically located wear facets, subcylindrical crowns and lacking carinae, are tentatively assigned to Diplodocoidea. The diversity of tooth morphologies is in accordance with the known palaeobiodiversity of the Portuguese Late Jurassic sauropod fauna, which is composed of non-neosauropod eusauropods (turiasaurs), diplodocoids (diplodocids) and macronarians (camarasaurids and probably brachiosaurids). The Late Jurassic sauropod fossil record of the Iberian Peninsula presents the broadest tooth morphospace range in the world from this period, suggesting a wide niche partition for sauropods, and corresponding high taxonomic diversity.
A well preserved middle caudal vertebra from middle Cretaceous (?Albian–lower Cenomanian) deposits informally known as the “Kem Kem beds” exposed in the Gara Sbaa region of Morocco is attributed to a large-bodied titanosaurian sauropod dinosaur. It represents one of the best-preserved and most complete skeletal elements reported for this sauropod group from the Kem Kem sequence. The vertebra is generally similar to middle caudals of the lithostrotian titanosaur Baurutitan britoi from the Upper Cretaceous Bauru Group of Brazil, but differs in several respects, such as: (1) a transversely compressed (as opposed to more square in posterior view) centrum; (2) a taller, anteroposteriorly longer, and more anteriorly positioned neural spine; and (3) prezygapophyses that are subtriangular in lateral view. It represents an animal that likely attained a very large body size (possibly over 25 m in total length), considerably larger than the diplodocoid Rebbachisaurus garasbae, the only named sauropod from the Kem Kem assemblage. Additional, selected specimens from the Kem Kem beds are described, with some probably referable to Titanosauria. In the Kem Kem sequence, sauropod fossils are far less common than those of predatory dinosaurs, which include several coeval, multi-ton taxa. This was likely due to an abundance of potential aquatic prey as well as complex niche partitioning among sympatric theropods, pterosaurs, and crocodyliforms. Nevertheless, some predators, such as the giant theropod Carcharodontosaurus saharicus, likely preyed on sauropods. The taxon represented by the new vertebra (and possibly other isolated remains from the Kem Kem region) and the giant Egyptian titanosaurian Paralititan stromeri rank among the largest known sauropods. Most other North African Cretaceous sauropods appear to have reached only modest adult body sizes; this could, however, be an artifact of the limited number of fossils and uncertainty in the ontogenetic stages represented by most specimens. The morphology of the Kem Kem vertebra suggests that the taxon it represents may have been more closely related to South American and/or European titanosaurians than to other members of this clade from sub-Saharan Africa.
New materials from sauropods from the Portezuelo Hill (Neuquén Province, Argentina) are described. They consist on three vertebrae and a metacarpus belonging to the Portezuelo Formation, considered as belonging to the Neuquenian Tetrapod Assemblage. They are consistent with an intermediate stage between the diplodocoid-dominated Limayan assemblages and the saltasaurines of the last endemic Coloradoan assemblage of younger beds.
Rapetosaurus krausei (Sauropoda: Titanosauria) from the Upper Cretaceous Maevarano Formation of Madagascar is the best-preserved and most complete titanosaur yet described. The skull of Rapetosaurus is particularly significant because most titanosaurs are diagnosed solely on the basis of fragmentary postcranial material, and knowledge of the titanosaur skull has remained incomplete. Material referred to Rapetosaurus includes the type skull from an adult that preserves the basicranium, rostrum, mandible, and palate. A second, juvenile skull preserves most of the braincase and cranial vault, as well as some of the palate and lower jaw. Here we provide a detailed description of Ropetosaurus cranial anatomy and highlight comparative relationships among known titanosaur and other neosauropod skulls. The Rapetosaurus skull is similar to those of diplodocoids in its overall shape, with retracted external nares and an elongated snout. However, extensive tooth distribution and bone articulations surrounding the external narial region and orbit are more similar to those of macronarians like Camarasaurus and Brachiosaurus. The maxilla, basicranium, paroccipital process, and pterygoid are among the most diagnostic elements of the Rapetosaurus skull, along with the enlarged antorbital fenestra, anteroventrally oriented braincase, and mandible. Titanosaur crania exhibit a greater diversity than previously recognized and, in light of Rapetosaurus, it is apparent that there is not a narrowly constrained bauplan for the skull of titanosaurs. Broad generalizations about evolution based on previously known, fragmentary fossils require re-evaluation. Ultimately, Rapetosaurus will be key in resolving titanosaur higher-level and ingroup phylogeny.
A study of the movement of jaw mechanics in sauropod dinosaurs.
A detailed osteological description of Tyrannosaurus rex Osborn, 1905 is presented, based primarily on the most complete specimen yet collected of this taxon (FMNH PR2081, popularly known as “Sue”) but also including observations from other specimens.Skull morphology of FMNH PR2081 is largely congruent with that described for previous specimens, but new details are added. Palatal morphology of FMNH PR2081 differs slightly from that of previously-described specimens—the internal choanae are slightly larger relative to skull size, and the anterior expansion of the fused vomers is elongate. Posteriorly, the vomers pass medially for nearly the entire length of the pterygoids.High-resolution x-ray computed tomographic (CT) analysis of the skull reveals internal details not previously observed. Complex recess systems can be traced in the jugal, lacrymal, ectopterygoid, quadrate, exoccipital, supraoccipital, prootic, and basioccipital. The exoccipital recess was perforated by a small foramen on the posterodorsal surface of the paroccipital process, and may have communicated with pneumatic chambers in the atlas-axis complex. The maxillary antra were bound medially by a thin bony wall; traces of these walls in earlier CT studies of tyrannosaurid skulls may have led to the impression that these animals had bony maxillonasal turbintes. A digital endocast was constructed from these images, confirming many previous observations based on natural endocasts, but also yielding new details, such as the presence of a large and presumably pneumatic sinus in the prootic adjacent to the pathway for the maxillary-mandibular branches of the trigeminal nerve. The olfactory bulbs were very large.The postcranium is also largely congruent with previously published descriptions. The precaudal vertebral column was heavily pneumatized, with pneumatopores penetrating the centra and neural arches of all presacral vertebrae, the cervical ribs, and the anteriormost four sacral centra. Unusual structures are tentatively identified as a proatlas arch and a rib on the last presacral vertebrae, structures previously thought absent from tyrannosaurids. The “missing chevron” partially responsible for claims that FMNH PR2081 is female was actually present.The gastralia are extensively fused anteriorly, and the morphology of the anteriormost gastral segments closely resembles the only published account of a tyrannosaurid sternum. This raises several possibilities, including the complete absence of a bony sternum in tyrannosaurids.The appendicular skeleton is congruent with those of other tyrannosaurids. A slender rodlike bone may represent a partial furcula, but this is not certain. The scapulocoracoids would probably not have met at the midline, but would nonetheless have closely approached each other in articulation.Several abnormalities in the skeleton have attracted popular attention. There is no defensible evidence for bite trauma on the skull, but the rib cage does show evidence for healed fractures. Lesions on the right scapulocoracoid and humerus coincide with fractured ribs on the right cervical-dorsal transition and may indicate a single trauma to the right side of the body. The left fibula is pathological, but may not have been fractured. Two fused tail vertebrae may preserve natural molds of the tail muscles.
Lower Cretaceous fossils from central Niger document the succession of sauropod dinosaurs on Africa as it drifted into geographic
isolation. A new broad-toothed genus of Neocomian age (∼135 million years ago) shows few of the specializations of other Cretaceous
sauropods. A new small-bodied sauropod of Aptian-Albian age (∼110 million years ago), in contrast, reveals the highly modified
cranial form of rebbachisaurid diplodocoids. Rates of skeletal change in sauropods and other major groups of dinosaurs are
estimated quantitatively and shown to be highly variable.
Fossils discovered in Lower Cretaceous (Aptian) rocks in the Ténéré Desert of central Niger provide new information about
spinosaurids, a peculiar group of piscivorous theropod dinosaurs. The remains, which represent a new genus and species, reveal
the extreme elongation and transverse compression of the spinosaurid snout. The postcranial bones include blade-shaped vertebral
spines that form a low sail over the hips. Phylogenetic analysis suggests that the enlarged thumb claw and robust forelimb
evolved during the Jurassic, before the elongated snout and other fish-eating adaptations in the skull. The close phylogenetic
relationship between the new African spinosaurid andBaryonyx from Europe provides evidence of dispersal across the Tethys seaway during the Early Cretaceous.
We describe sauropod material from the Lower Cretaceous (Aptian-Albian) Puesto Quiroga Member of the Lohan Cura Formation, exposed at the Cerro Aguada del León locality (La Picaza area, Neuquén Province, Argentina). The remains consist of disarticulated elements of at least three individuals, and are assigned to an indeterminate species of the rebbachisaurid diplodocoid Limaysaurus gen. nov. Elements from various parts of the skeleton are represented: a tooth, partial dorsal, sacral, and caudal vertebrae, a haemal arch, coracoid, humerus, ilium, pubes, ischium, femora, a tibia fragment, and an incomplete fibula. The Lohan Cura specimens are strongly reminiscent of corresponding elements in the holotype of Limaysaurus tessonei (=“Rebbachisaurus” tessonei, “Rayososaurus” tessonei) from the overlying Upper Cretaceous (lower Cenomanian) Candeleros Formation. We evaluate the phylogenetic relationships of Limaysaurus gen. nov. and other diplodocoids, and provide hypotheses regarding sauropod evolution during the Cretaceous.
Rapetosaurus krausei (Sauropoda: Titanosauria) from the Upper Cretaceous Maevarano Formation of Madagascar is the best-preserved and most complete titanosaur yet described. The skull of Rapetosaurus is particularly significant because most titanosaurs are diagnosed solely on the basis of fragmentary postcranial material, and knowledge of the titanosaur skull has remained incomplete. Material referred to Rapetosaurus includes the type skull from an adult that preserves the basicranium, rostrum, mandible, and palate. A second, juvenile skull preserves most of the braincase and cranial vault, as well as some of the palate and lower jaw. Here we provide a detailed description of Rapetosaurus cranial anatomy and highlight comparative relationships among known titanosaur and other neosauropod skulls. The Rapetosaurus skull is similar to those of diplodocoids in its overall shape, with retracted external nares and an elongated snout. However, extensive tooth distribution and bone articulations surrounding the external narial region and orbit are more similar to those of macronarians like Camarasaurus and Brachiosaurus. The maxilla, basicranium, paroccipital process, and pterygoid are among the most diagnostic elements of the Rapetosaurus skull, along with the enlarged antorbital fenestra, anteroventrally oriented braincase, and mandible. Titanosaur crania exhibit a greater diversity than previously recognized and, in light of Rapetosaurus, it is apparent that there is not a narrowly constrained bauplan for the skull of titanosaurs. Broad generalizations about evolution based on previously known, fragmentary fossils require re-evaluation. Ultimately, Rapetosaurus will be key in resolving titanosaur higher-level and ingroup phylogeny.
Des restes fossiles d’un sauropode provenant du Crétacé inférieur (Barrémien supérieur-Aptien inférieur) de Salas de los Infantes (Burgos, Espagne) sont décrits. Le matériel, qui comporte plusieurs vertèbres caudales, des chevrons, une paire d’ischions et un fémur, pourrait appartenir à un seul individu de taille moyenne. D’après la hauteur de l’arc neural et la largeur de l’épine neurale des vertèbres caudales antérieures, le spécimen est rapporté aux Diplodocoidea. De plus, il montre des affinités avec les Rebbachisauridae, un clade basal de diplodocoïdes. La forme des vertèbres caudales antérieures et de l’ischion du sauropode de Burgos est similaire à celle de ‘Rebbachisaurus’ tessonei de l’Albien-Cénomanien d’Amérique du Sud. Néanmoins, il existe des différences par rapport à celui-ci, de sorte que le sauropode de Burgos est rapporté provisoirement à un Rebbachisauridae indéterminé. Les rebbachisauridés sont connus dans l’Aptien-Cénomanien des continents gondwaniens (Afrique et Amérique du Sud), même si du matériel provenant du Coniacien-Santonien d’Argentine et de l’Hauterivien-Barrémien de Croatie leur a été rapporté. Le diplodocoïde de Burgos semble être un des plus anciens représentants des Rebbachisauridae. Cette découverte appuie l’hypothèse déjà soutenue d’une connexion terrestre entre l’Europe et l’Afrique à travers la Téthys durant le Crétacé inférieur.
Remains belonging to sauropod dinosaurs have recently been discovered in Upper Hauterivian/Lower Barremian (Lower Cretaceous) limestones of SW Istria (Croatia). The material consists of a complete cervical vertebra, a nearly complete cervical centrum, fragments of possible cervical ribs, three partial dorsal and five more or less incomplete caudal vertebrae, parts of caudal neural spines, a chevron, the distal part of a femur, the proximal portion of a tibia and other fragments of bones. The bones were collected randomly from the sea bottom, therefore despite the fact that they come from the same outcrop, the same level and probably the same bed, they cannot be assigned with certainty to the same taxon. Their vastly different sizes indicate the presence of several individuals while different morphologies suggest the probable presence of more than one taxon. The complete cervical and the anterior to mid-caudal vertebrae present a more strict affinity with Brachiosauridae, a proximal cervical centrum resembles those of “Chondrosteosaurus”, and a caudal neural spine is similar to those of the camarasaurids. The dorsal vertebrae have peculiar features (a very tall neural arch, well developed laminar complex, etc.) and characters suggesting their assignation to basal Titanosauriformes and, possibly, to Diplodocimorpha. A posterior dorsal vertebra testifies the presence of a new Diplodocimorph similar to Rebbachisaurus but more primitive.
The newly organized Long Island Natural History Museum (LINHM) has assembled a small collection of fossil vertebrates from the Cretaceous of Morocco. Among the remains in this collection are two spinosaurid (Theropoda) teeth and one sauropod tooth that we refer to either the Diplodocidae or Titanosauridae. Because of the scarcity of spinosaurid and Cretaceous sauropod teeth, a short description of the material is presented here. In addition to the dinosaurian remains, the collection includes an unidentified crocodilian tooth and a tooth identified tentatively as that of a pterosaur, which we also describe briefly. Furthermore, there are other fossil reptile teeth from the Ksar es Souk Province in the collections of the LINHM. Some of these may represent groups of reptiles other than those discussed here, but the taxonomic identity of these teeth is still being determined.
Stolokrosuchus lapparenti n.g.n.sp. from Aptian rocks exhibits clear autapomorphies and shares many features with the peirosaurid crocodyliforms from Upper Cretaceous deposits in South America. A phylogenetic analysis groups Stolokrosuchus with these taxa in a monophyletic assemblage and places the clade of peirosaurid crocodyliforms as the sister-taxon of Eusuchia. The Early Cretaceous occurrence of Stolokrosuchus suggests a greater temporal and geographic distribution for Peirosauridae. Additional Early Cretaceous crocodyliforms share a similar South American - African distribution, further supporting a faunal communication between these continents up until at least the Aptian.
The unarmored, hadrosaurian dinosaurs of the late Cretaceous of North America constitute an interesting group about which much has been written and many species described. A review of this literature showed many different angles of approach, and it was in part to reconcile these various descriptions and reduce them to certain comparable common factors that this monographic study was undertaken. Aside from the mere compilation of the literature of these dinosaurs, redescriptions were prepared, nearly always in the presence of the original types and such other associated material as had come to light since the species was named.
The authors also undertook as complete a morphological study of the animals as the circumstances permitted, learning what they could of the mechanics of the skeleton and teeth, the musculature and integument, the nervous system and sense organs, and the probable functions of these various parts in the living animal. They further endeavored to imagine the reconstructed creatures in their appropriate environment—physical, climatic, vegetal, and animate—and to picture them and their manner of life as animate beings of a vanished age. An account of their distribution both in time and space is given, as well as a discussion of their probable phylogeny and the trend of their evolution.
To date the dinosaur record in Brazil is limited to saurischians and no confirmed evidence (except probably footprints) of ornithischians is presently known. Two dinosaur taxa were described from the Triassic Santa Maria Formation: Spondylosoma absconditum and Staurikosaurus pricei. The dinosaurian affinities of Spondylosoma are questioned in the literature; Staurikosaurus is regarded by some authors as closely related to Herrerasaurus from Argentina. No Jurassic dinosaurs are known from Brazil, but there are several Cretaceous occurrences. Titanosaurid sauropods (Antarctosaurus brasiliensis, several undescribed postcranials and teeth) and theropods (teeth) are present in the Late Cretaceous strata of the Bauru Group. Spinosaurid theropods have been found in the Albian strata of northeast Brazil and are apparently closely related to some African forms. This distribution pattern may be a product of an Early Cretaceous vicariant event. Spinosaurids as regarded here are not an exclusive Gondwanan group and are also present in Europe (Baryonyx). A literal interpretation of the stratigraphic record, therefore, suggests that dinosaur faunal interchanges between Europe and Gondwana may have occurred not only from South to North as previously supposed, but in the opposite direction as well. This hypothesis is very preliminary and can be tested by new and more complete dinosaur material from Brazil and Africa.
Although herbivory probably first appeared over 300 million years ago, it only became established as a common feeding strategy during Late Permian times. Subsequently, herbivory evolved in numerous lineages of terrestrial vertebrates, and the acquisition of this mode of feeding was frequently associated with considerable evolutionary diversification in those lineages. This book, originally published in 2000, represented the first comprehensive overview of the evolution of herbivory in land-dwelling amniote tetrapods in recent years. In Evolution of Herbivory in Terrestrial Vertebrates leading experts review the structural adaptations for, and the evolutionary history of, feeding on plants in the major groups of land-dwelling vertebrates, especially dinosaurs and ungulate mammals. As such it will be the definitive reference source on this topic for evolutionary biologists and vertebrate paleontologists alike.
The isolated skulls of Nemegtosaurus mongoliensis and Quaesitosaurus orientalis from the Nemegt Basin of Mongolia are among the most complete sauropod cranial remains known from the Late Cretaceous, yet their evolutionary relationships to other neosauropods have remained uncertain. Redescription of the skull of Nemegtosaurus identifies key features that link it and its closely related counterpart Quaesitosaurus to titanosaur sauropods. These include a posterolaterally orientated quadrate fossa, ‘rocker’-like palatobasal contact, pterygoid with reduced quadrate flange and a novel basisphenoid–quadrate contact. Other features are exclusive to Nemegtosaurus and Quaesitosaurus, such as the presence of a symphyseal eminence on the external aspect of the premaxillae, a highly vascularised tooth bearing portion of the maxilla, an enclosed ‘maxillary canal’, orbital ornamentation on the postorbital, prefrontal and frontal, exclusion of the squamosal from the supratemporal fenestra and dentary teeth smaller in diameter than premaxillary and maxillary teeth.
Sauropoda is among the most diverse and widespread dinosaur lineages, having attained a near-global distribution by the Middle Jurassic that was built on throughout the Cretaceous. These gigantic herbivores are characterized by numerous skeletal specializations that accrued over a 140 million-year history. This fascinating evolutionary history has fuelled interest for more than a century, yet aspects of sauropod interrelationships remain unresolved. This paper presents a lower-level phylogenetic analysis of Sauropoda in two parts. First, the two most comprehensive analyses of Sauropoda are critiqued to identify points of agreement and difference and to create a core of character data for subsequent analyses. Second, a generic-level phylogenetic analysis of 234 characters in 27 sauropod taxa is presented that identifies well supported nodes as well as areas of poorer resolution. The analysis resolves six sauropod outgroups to Neosauropoda, which comprises the large-nostrilled clade Macronaria and the peg-toothed clade Diplodocoidea. Diplodocoidea includes Rebbachisauridae, Dicraeosauridae, and Diplodocidae, whose monophyly and interrelationships are supported largely by cranial and vertebral synapomorphies. In contrast, the arrangement of macronarians, particularly those of titanosaurs, are based on a preponderance of appendicular synapomorphies. The purported Chinese clade 'Euhelopodidae' is shown to comprise a polyphyletic array of basal sauropods and neosauropods. The synapomorphies supporting this topology allow more specific determination for the more than 50 fragmentary sauropod taxa not included in this analysis. Their distribution and phylogenetic affinities underscore the diversity of Titanosauria and the paucity of Late Triassic and Early Jurassic genera. The diversification of Titanosauria during the Cretaceous and origin of the sauropod body plan during the Late Triassic remain frontiers for future studies.
Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic and significantly predates their rise to global dominance by the end of the period. The phylogenetic history of ornithischian and saurichian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory dinosaurs were not tightly correlated with marked floral changes. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.
Sauropoda is among the most diverse and widespread dinosaur lineages, having attained a near-global distribution
by the Middle Jurassic that was built on throughout the Cretaceous. These gigantic herbivores are characterized by
numerous skeletal specializations that accrued over a 140 million-year history. This fascinating evolutionary history
has fuelled interest for more than a century, yet aspects of sauropod interrelationships remain unresolved. This
paper presents a lower-level phylogenetic analysis of Sauropoda in two parts. First, the two most comprehensive
analyses of Sauropoda are critiqued to identify points of agreement and difference and to create a core of character
data for subsequent analyses. Second, a generic-level phylogenetic analysis of 234 characters in 27 sauropod taxa is
presented that identifies well supported nodes as well as areas of poorer resolution. The analysis resolves six sauropod
outgroups to Neosauropoda, which comprises the large-nostrilled clade Macronaria and the peg-toothed clade
Diplodocoidea. Diplodocoidea includes Rebbachisauridae, Dicraeosauridae, and Diplodocidae, whose monophyly and
interrelationships are supported largely by cranial and vertebral synapomorphies. In contrast, the arrangement of
macronarians, particularly those of titanosaurs, are based on a preponderance of appendicular synapomorphies. The
purported Chinese clade ‘Euhelopodidae’ is shown to comprise a polyphyletic array of basal sauropods and neosauropods.
The synapomorphies supporting this topology allow more specific determination for the more than 50 fragmentary
sauropod taxa not included in this analysis. Their distribution and phylogenetic affinities underscore the
diversity of Titanosauria and the paucity of Late Triassic and Early Jurassic genera. The diversification of Titanosauria
during the Cretaceous and origin of the sauropod body plan during the Late Triassic remain frontiers
for future studies.
Although sauropods played a major role in terrestrial ecosystems during much of the Mesozoic Era, little effort has been directed toward diagnosing Sauropoda and establishing higher-level interrelationships among sauropods. As a consequence, the origin and evolution of major skeletal adaptations in sauropods has remained largely speculative.The cladistic analysis presented here focuses on higher-level relationships among sauropods. Based on 109 characters (32 cranial, 24 axial, 53 appendicular) for 10 sauropod taxa, the most parsimonious arrangement places four genera (Vulcanodon, Shunosaurus, Barapasaurus, and Omeisaurus) as a sequence of sister-taxa to a group of advanced sauropods, defined here as Neosauropoda. Neosauropoda, in turn, is composed of the sister-clades Diplodocoidea and Macronaria; the latter is a new taxon that includes Haplocanthosaurus, Camarasaurus, and Titanosauriformes. Titanosauriformes includes Brachiosauridae and Somphospondyli, a new taxon uniting Euhelopus and Titanosauria. Among macronarians, the position of Haplocanthosaurus is the least stable as a result of the absence of cranial remains.The basic structure of the phylogeny is resilient to various tests and establishes the evolutionary sequence of many functionally significant sauropod adaptations, such as the digitigrade posture of the manus in neosauropods. Other characteristic sauropod adaptations, such as narrow tooth crowns, increases in length and number of cervical vertebrae, and bifid neural spines, are shown to have evolved more than once. As these results underscore, the higher-level phylogeny of sauropods must be based on a broad sampling of character data.The fossil record of sauropods, although relatively limited during the early phase of the radiation (Late Triassic through Early Jurassic), nonetheless indicates that all major clades were established prior to the Late Jurassic, when substantial faunal interchange among major continental regions was still possible. The functional, temporal, and biogeographic implications of the higher-level phylogeny of sauropods are explored.
A reappraisal of current theorie suggests that the origin of flowering plants was closely correlated with the spread of big, low-browsing dinosaurs.
The structure and evolution of the mandible, suspensorium, and stapes of mammal-like reptiles and early mammals are examined in an attempt to determine how, why, and when in phylogeny the precursors of the mammalian tympanic bone, malleus, and incus (postdentary jaw elements and quadrate) came to function in the reception of air-borne sound. The following conclusions are reached.
It is possible that at no stage in mammalian phylogeny was there a middle ear similar to that of “typical” living reptiles, with a postquadrate tympanic membrane contacted by an extrastapes. The squamosal sulcus of cynodonts and other therapsids, usually thought to have housed a long external acoustic meatus, possibly held a depressor mandibulae muscle.
In therapsids an air-filled chamber (recessus mandibularis of Westoll) extended deep to the reflected lamina and into the depression (external fossa) on the outer aspect of the angular element. A similar chamber was present in sphenacodontids but pterygoideus musculature occupied the small external fossa. The thin tissues superficial to the recessus mandibularis served as eardrum. Primitively, vibrations reached the stapes mainly via the anterior hyoid cornu, but in dicynodonts therocephalians, and cynodonts, vibrations passed mainly or exclusively from mandible to quadrate to stapes and the reflected lamina was a component of the eardrum.
In the therapsid phase of mammalian phylogeny, auditory adaptation was an important aspect of jaw evolution. Auditory efficiency, and sensitivity to higher sound frequencies, were enhanced by diminution and loosening of the postdentary elements and quadrate, along with transference of musculature from postdentary elements to the dentary. These changes were made possible by associated modifications, including posterior expansion of the dentary. Establishment of a dentray-squamosal articulation permitted continuation of these trends, leading to the definitive mammalian condition, with no major change in auditory mechanism except that in most mammals (not monotremes) the angular, as tympanic, eventually became a non-vibrating structure.
Articulated digital reconstructions of two diplodocid sauropods revealed cervical poses and feeding envelopes. The necks of Diplodocus and Apatosaurus were nearly straight but gently declined such that the heads, which were themselves angled downward relative to the neck, were close to ground level in their neutral, undeflected posture. Both necks were less flexible than conventionally depicted, and Diplodocus was less capable of lateral and dorsal curvature than Apatosaurus. The results suggest that these sauropods were adapted to ground feeding or low browsing, contrary to the view that diplodocid sauropods were high browsers.
Angiosperms first appeared in northern Gondwana during the Early Cretaceous, approximately 135 million years ago. Several authors have hypothesised that the origin of angiosperms, and the tempo and pattern of their subsequent radiation, was mediated by changes in the browsing behaviour of large herbivorous dinosaurs (sauropods and ornithischians). Moreover, the taxonomic and ecological radiation of angiosperms has been associated with the evolution of complex jaw mechanisms among ornithischian dinosaurs. Here, we review critically the evidence for dinosaur-angiosperm interactions during the Cretaceous Period, providing explicit spatiotemporal comparisons between evolutionary and palaeoecological events in both the dinosaur and angiosperm fossil records and an assessment of the direct and indirect evidence for dinosaur diets. We conclude that there are no strong spatiotemporal correlations in support of the hypothesis that dinosaurs were causative agents in the origin of angiosperms; however, dinosaur-angiosperm interactions in the Late Cretaceous may have resulted in some coevolutionary interactions, although direct evidence of such interactions is scanty at present. It is likely that other animal groups (insects, arboreal mammals) had a greater impact on angiosperm diversity during the Cretaceous than herbivorous dinosaurs. Elevated levels of atmospheric CO2 might have played a critical role in the initial stages of the angiosperm radiation.
Dental microwear on the teeth of Camarasaurus and Diplodocus: implications for sauropod paleoecology
- A R Fiorillo
Fiorillo, A. R. 1991. Dental microwear on the teeth of
Camarasaurus and Diplodocus: implications for
sauropod paleoecology. In: Kielan-Jaworowska,
Z., Heintz, N., and Nakren, N. A. (eds.). Fifth
Symposium on Mesozoic Ecosystems and Biota,
Extended Abstracts. Contributions of the
Paleontological Museum, University of Oslo,
Oslo. Pp. 23-24.
Dinosaurios de America del Sur. Impreso en Artes Gráficas Sagitario Iturri
- J F Bonaparte
Bonaparte, J. F. 1996. Dinosaurios de America del
Sur. Impreso en Artes Gráficas Sagitario Iturri,
Buenos Aires.
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Gastoliths of a saurpod dinosaur from New Mexico
- D Gillette
Gillette, D. 1990. Gastoliths of a saurpod dinosaur
from New Mexico. J. Vertebr. Paleontol. 10: 24A.