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A new dinosaur with theropod affinities from the Late Triassic Santa Maria Formation, South Brazil
Journal of Verterbrate Paleontology
Abstract
The Late Triassic (Carnian) upper Santa Maria Formation of south Brazil has yielded some of the oldest unequivocal records of dinosaurs. Here, we describe a new saurischian dinosaur from this formation, Nhandumirim waldsangae, gen. et sp. nov., based on a semiarticulated skeleton, including trunk, sacral, and caudal vertebrae, one chevron, right ilium, femur, partial tibia, fibula, and metatarsals II and IV, as well as ungual and non-ungual phalanges. The new taxon differs from all other Carnian dinosauromorphs through a unique combination of characters, some of which are autapomorphic: caudal centra with sharp longitudinal ventral keels; brevis fossa extending for less than three-quarters of the ventral surface of the postacetabular ala of the ilium; dorsolateral trochanter ending well distal to the level of the femoral head; distal part of the tibia with a mediolaterally extending tuberosity on its cranial surface and a tabular caudolateral flange; conspicuous, craniomedially oriented semicircular articular facet on the distal fibula; and a straight metatarsal IV. This clearly distinguishes Nhandumirim waldsangae from both Saturnalia tupiniquim and Staurikosaurus pricei, which were collected nearby and at a similar stratigraphic level. Despite not being fully grown, the differences between Nhandumirim waldsangae and those saurischians cannot be attributed to ontogeny. The phylogenetic position of Nhandumirim waldsangae suggests that it represents one of the earliest members of Theropoda. Nhandumirim waldsangae shows that some typical theropod characters were already present early in dinosaur evolution, and it represents possibly the oldest record of the group known in Brazil. http://zoobank.org/urn:lsid:zoobank.
Supplementary resource (1)
Data
February 2019
... The specimens described here were unearthed from deposits of the Alemoa Member of the Santa Maria Formation, at the locality known as Waldsanga ( Fig. 1; Huene, 1942;Langer, 2005b;Langer et al., 2007) or Cerro da Alemoa (Da Rosa, 2004, 2015. This site also yielded the type-specimens of the early sauropodomorph Saturnalia tupiniquim (Langer et al., 1999), the cynodonts Gomphodontosuchus brasiliensis (Huene, 1928;Langer, 2005a) and Alemoatherium huebneri (Martinelli et al., 2017), and the possible theropod dinosaur Nhandumirim waldsangae (Marsola et al., 2019a). Yet, the most abundant fossils from this locality are referred to the rhynchosaur Hyperodapedon . ...
... The main lithology of the site is composed of massive, reddish mudstones of the Alemoa Member, overlayed by the yellowish to orange stratified sandstones of the Caturrita Formation ( Fig. 1E; Marsola et al., 2019aMarsola et al., , 2019b. The lower and intermediate levels of the Alemoa Member in the site represent distal floodplain deposits, whereas the upper level represents more proximal settings (Da Rosa 2005, 2015Marsola et al., 2019a). ...
... The main lithology of the site is composed of massive, reddish mudstones of the Alemoa Member, overlayed by the yellowish to orange stratified sandstones of the Caturrita Formation ( Fig. 1E; Marsola et al., 2019aMarsola et al., , 2019b. The lower and intermediate levels of the Alemoa Member in the site represent distal floodplain deposits, whereas the upper level represents more proximal settings (Da Rosa 2005, 2015Marsola et al., 2019a). According to previous stratigraphy studies (Horn et al., 2014), the strata exposed at Waldsanga belong to the Candelária Sequence, Santa Maria Supersequence (Santa Maria 2 Sequence of Zerfass et al., 2003), including the upper part of the Santa Maria Formation (Gordon, 1947) and the lower part of the Caturrita Formation (Andreis et al., 1980). ...
New specimens and the reassessment of many silesaurids have recently shed light on the origin and early evolution of dinosaurs and their close relatives. Yet, the group is relatively poorly represented in South America, an area that likely played an important role in dinosaurian origins. Since the discovery of Sacisaurus agudoensis from the Norian Caturrita Formation, only the fragmentary Gamatavus antiquus and Amanasaurus nesbitti have been reported from the Triassic of south Brazil. Here we describe disarticulated silesaurid remains from Waldsanga, one of the most important tetrapod-bearing localities of the Santa Maria Formation, which represent the second Carnian occurrence of the group in Brazil. The postcranial elements exhibit a combination of dinosauromorph symplesiomorphies and silesaurid diagnostic traits, showing that a conservative anatomy is pervasive among early dinosauromorphs. We also conducted a set of exploratory analyses to infer the phylogenetic relations of the new occurrence and the robustness of some of the most recent phylogenetic hypotheses in face of the increasing diversity of Silesauridae. This revealed a rather uncertain evolutionary scenario not only for Silesauridae, but for early dinosauromorphs in general. SUPPLEMENTARY FILES-Supplementary files are available for this article for free at www.tandfonline.com/UJVP. Citation for this article: Mestriner, G., Marsola, J. C. A., Nesbitt, S. J., Da-Rosa, A. A. S., & Langer, M. (2023) Anatomy and phylogenetic affinities of a new silesaurid assemblage from the Carnian beds of south Brazil. Journal of Vertebrate Paleontology. https://doi.
... A broader sample of saurischians are required to properly evaluate that possibility, which is beyond the scope of this work. For the same reasons, the recent proposals that (1) most Carnian 'sauropodomorphs' nest outside of Eusaurischia , (2) the putative theropod Nh. waldsangae (Marsola et al. 2018) may belong to Saturnaliidae (Pacheco et al. 2019), and (3) the still often suggested non-sauropodomorph affinity of E. lunensis will not be tested here. ...
... When early sauropodomorph phylogeny is arranged in a more pectinate fashion, Sat. tupiniquim most frequently nests closer to bagualosaurs than to other Carnian forms (Martínez and Alcober 2009;Alcober and Martínez 2010;Cabreira et al. 2011Cabreira et al. , 2016Martínez et al. 2012b;Bittencourt et al. 2015;McPhee et al. 2015;Müller et al. 2016aMüller et al. , b, 2017aMüller et al. , b, 2018aWang et al. 2017;Agnolín and Rozadilla 2018;Pretto et al. 2017;Bronzati et al. 2017Bronzati et al. , 2019aZhang et al. 2018;Marsola et al. 2018 Pretto et al. (2019) was the only so far not to find Sat. tupiniquim as a sauropodomorph, but instead forming a Guaibasauridae clade outside Eusaurischia. ...
... barberenai is also found outside Saturnaliidae, as sister to the clade formed by that group and bagualosaurs (Martínez et al. 2012b(Martínez et al. , 2015Pretto et al. 2019;Müller and Garcia 2020), which frequently also includes Pan. protos in a polytomy (Cabreira et al. 2016;Müller et al. 2017bMüller et al. , 2018aBaron and Williams 2018;Garcia et al. 2019;Marsola et al. 2018). Other hypotheses place Pam. ...
Carnian (Late Triassic) deposits of South America provide the oldest unequivocal dinosaur records worldwide, most of which has been assigned to the sauropodomorph lineage. This includes Eoraptor lunensis, Panphagia protos, and Chromogisaurus novasi, from the Ischigualasto Formation, Argentina, and Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi, and Bagualosaurus agudoensis, from the Santa Maria Formation, Brazil. Here, we demonstrate that their holotypes anatomically differ from one another, supporting the taxonomic validity of the species. In addition, a morphological disparity analysis, with significant statistical support, clustered some of the better-known specimens of E. lunensis, Sat. tupiniquim, and Bu. schultzi, with the respective holotypes. For the latter two taxa, this was corroborated by a specimen-level phylogenetic analysis that also found Ba. agudoensis as the sister taxon to post-Carnian sauropodomorphs. Our results also suggest that Bu. schultzi and E. lunensis are the earliest branching sauropodomorphs and that Sa. tupiniquim and Pam. barberenai are closer to Bagualosauria. A species-level phylogenetic analysis further suggests that Bu. schultzi and E. lunensis form a clade, that Sa. tupiniquim is the sister taxon to Bagualosauria, and that Pan. protos and Ch. novasi are also more highly nested, forming a clade with Pam. barberenai.
... The Upper Triassic beds from Brazil provide evidences of the origin and initial radiation of dinosaurs (Colbert 1970;Langer et al., 1999;Bonaparte et al., 1999;Cabreira et al., 2016;Marsola et al., 2018a;Pacheco et al., 2019). Distinct Assemblage Zones (AZs) mark different evolutionary stages of the group (Schultz et al., 2020). ...
... On the other hand, there is no evidence of a trochanteric shelf associated with the anterior trochanter, which could be result of taphonomic biases. The trochanteric shelf is seen in almost all other known dinosaurs from Carnian, except by Staurikosaurus pricei (MCZ 1669, Bittencourt andKellner 2009;Garcia et al., 2019), Nhandumirim waldsangae (Marsola et al., 2018a(Marsola et al., , 2018b, and juvenile specimens of Pampadromaeus barberenai (CAPPA/UFSM 0028, Müller et al., 2019) and Buriolestes schultzi (ULBRA-PVT056). ...
... Actually, depending on the phylogenetic framework, the group lacks representatives from Carnian (Cabreira et al., 2016;Pacheco et al., 2019). From Brazil, the only putative theropod from Carnian is Nhandumirim waldsangae (Marsola et al., 2018a(Marsola et al., , 2018b. However, the taxon was regarded as a sauropodomorph by some authors (e.g. ...
The early evolution of theropod dinosaurs is poorly understood. Whereas sauropodomorphs are well-known from the oldest dinosaur bearing outcrops, the record of theropods is fragmentary and ambiguous. The Triassic deposits from Brazil yielded some of the oldest dinosaurs worldwide. These dinosaurs came from two distinct Assemblage Zones (AZ): the Hyperodapedon AZ (Carnian) and the Riograndia AZ (early Norian). Here, a specimen previously assigned to cf. Dinosauromorpha is reassessed. CAPPA/UFSM 0157 comes from an enigmatic assemblage with predominance of the traversodotind cynodont Siriusgnathus. This assemblage has been tentatively assigned to the Riograndia AZ. However, the absence of index fossils still hampers a reliable assignation. The specimen, which comprises a proximal portion of a left femur, belongs to a new theropod taxon erected here as Erythrovenator jacuiensis gen. et sp. nov. The new dinosaur differs from all other known Triassic dinosaurs based on the absence of a raised dorsolateral trochanter of the femur. Erythrovenator jacuiensis gen. et sp. nov. is regarded as a thero-pod on the basis of the pyramidal shape of the anterior trochanter in anterior view. The results of a phylogenetic analysis corroborate this assignation. Therefore, the new dinosaur represents one of the oldest theropod dinosaurs worldwide, shedding lights on some of the earliest theropod features. Finally, the new specimen also represents the first carnivorous dinosaur from the assemblage dominated by the traversodontid cynodont Siriusgnathus, increasing our knowledge of the faunal content of this enigmatic assemblage.
... The phylogenetic relationships of the three Early Jurassic neotheropod specimens from central England were tested using the phylogenetic dataset originally published by Nesbitt et al. (2009) and iteratively modified by Ezcurra & Brusatte (2011), You et al. (2014), Nesbitt & Ezcurra (2015), Martill et al. (2016), Ezcurra (2017), Martínez & Apaldetti (2017), Marsola et al. (2019), Marsh et al. (2019b) and Griffin (2019) (Supporting Information, File S1). Here, WARMS G667-690 and the holotypes and only known specimens of Sarcosaurus andrewsi and Sarcosaurus woodi were added to the dataset. ...
... The analysis of the data matrix using the three neotheropod specimens from central England as different terminals found 27 most parsimonious trees (MPTs) of 1267 steps with a consistency index (CI) of 0.3631 and a retention index (RI) of 0.7052 (best score hit 73 times of the 100 replicates). The overall topology of these MPTs is mostly congruent with those recovered in the analyses of the most recent iterations of this matrix (Ezcurra, 2017;Marsh et al., 2019b;Marsola et al., 2019), but with some differences related to unstable terminals within Neotheropoda (see Discussion). Resembling previous analyses, we found a major dichotomy at the base of Neotheropoda between Coelophysoidea and a lineage leading to Averostra. ...
... The discussion of the early evolution of Neotheropoda in an explicit phylogenetic context is complicated because of the relatively unstable placement of several Late Triassic and Early Jurassic species (e.g. Dracoraptor hanigani, Lepidus praecisio, Liliensternus liliensterni, Sarcosaurus woodi, Sinosaurus triassicus and Zupaysaurus rougieri; Carrano et al., 2012;Martill et al., 2016;Ezcurra, 2017;Wang et al., 2017b), even in different iterative analyses of the same phylogenetic matrix (Martill et al., 2016;Ezcurra, 2017;Marsh et al., 2019b;Marsola et al., 2019). Here, Lepidus praecisio is recovered deeply nested within Coelophysidae as the sister-taxon of Coelophysis bauri, as in Ezcurra (2017) and similar to Marsola et al. (2019), but contrasting with its position as the earliest member of the branch leading to Averostra in Marsh et al. (2019b). ...
Neotheropoda represents the main evolutionary radiation of predatory dinosaurs and its oldest records come from Upper Triassic rocks (c. 219 Mya). The Early Jurassic record of Neotheropoda is taxonomically richer and geographically more widespread than that of the Late Triassic. The Lower Jurassic (upper Hettangian–lower Sinemurian) rocks of central England have yielded three neotheropod specimens that have been assigned to two species within the genus Sarcosaurus, S. woodi (type species) and S. andrewsi. These species have received little attention in discussions of the early evolution of Neotheropoda and recently have been considered as nomina dubia. Here, we provide a detailed redescription of one of these specimens (WARMS G667–690) and reassess the taxonomy and phylogenetic relationships of the genus Sarcosaurus. We propose that the three neotheropod specimens from the Early Jurassic of central England represent a single valid species, S. woodi. The second species of the genus, ‘S. andrewsi’, is a subjective junior synonym of the former. A quantitative phylogenetic analysis of early theropods recovered S. woodi as one of the closest sister-taxa to Averostra and provides new information on the sequence of character state transformations in the lead up to the phylogenetic split between Ceratosauria and Tetanurae.
... Conversely, Saturnalia tupiniquim (MCP-3845 PV) presents a dorsal vertebra incorporated to the sacral series (i.e. dorsosacral) (see Marsola et al. 2019), similar to Riojasaurus incertus. the postacetabular ala of CAPPA/UFSM 0200 is slightly more robust than that of coeval basal saurischian dinosaurs (e.g. ...
... the discovery of CAPPA/UFSM 0200 increases the record of Carnian dinosauromorphs in southern Brazil, comprising the first dinosaur collected at Piche outcrop, quantitatively improving the distribution of dinosaurian remains within the Hyperodapedon Assemblage Zone of the Candelária Sequence. Outcrops of this fossiliferous unit and their correlates in the Ischigualasto Formation (northwestern Argentina) include a dinosauromorph fauna that, so far, comprises lagerpetids ( Sereno and Arcucci 1994, Cabreira et al. 2016), silesaurids ( Martínez et al. 2013, see also Agnolin and rozadilla 2017, Baron 2017), putative ornithischians (Casamiquela 1967, but see Agnolin and rozadilla 2017, Baron 2017), putative theropods ( Martínez et al. 2011, Marsola et al. 2019, and other saurischians, especially herrerasaurids (reig 1963, Colbert 1970, Alcober and Martínez 2010 and sauropodomorphs (Eoraptor lunensis Sereno et al. 1993, Saturnalia tupiniquim Langer et al. 1999, Panphagia protos Martínez and Alcober 2009, Chromogisaurus novasi Ezcurra 2010, Pampadromaeus barberenai Cabreira et al. 2011, Buriolestes schultzi Cabreira et al. 2016, Müller et al. 2018a, Bagualosaurus agudoensis Pretto et al. 2018. ...
... Because ontogenetic data of most triassic dinosauromorphs are scarce, and many taxa are restricted to a single incomplete specimen (e.g. Colbert 1970, Martínez and Alcober 2009, Ezcurra 2010, Pretto et al. 2018, Marsola et al. 2019) the limited sample precludes the establishment of a reliable pattern to be followed as a model, whether regarding either ontogeny or individual variation. Once such traits could be related to intraspecific variation, we suggest caution when considering the faintness or roughness (i.e. the degrees of "development") of these muscle scars in phylogenetic or taxonomic evaluations. ...
Discoveries in Carnian-aged rocks are establishing a rich and diverse dinosaurian fauna at the so-called 'dawn of the age of dinosaurs' in the Late triassic of Western Gondwana. Accordingly, Brazilian strata from the Candelária Sequence have contributed extensively to this trend. here, we present a new dinosaurian specimen (CAPPA/UFSM 0200) from this geological unit. the material was collected at a fossiliferous site that had no previous record of dinosaurs. Our specimen comprises a single ilium, which we describe in detail. Its anatomy is consistent with Carnian sauropodomorph dinosaurs, but differs from coeval specimens by several features, although we do not discard the possibility of these features being the result of intraspecific variation. In part of our phylogenetic investigation, CAPPA/UFSM 0200 was recovered within Saturnaliinae, a group comprised of Carnian sauropodomorphs from South America. however, based on examination of better-sampled coeval taxa, a character (a strong rugosity in the ilium) supporting this less inclusive position might be related to intraspecific variation and so, should be carefully considered. this study increases the distribution of dinosaur remains in fossiliferous units from southern Brazil and adds to the discussion regarding intraspecific variation and its implications in the phylogeny of early dinosaurs.
... Rio Grande do Sul state, southern Brazil (Da-Rosa, 2015). This site was radioisotopically dated as 233.23 ± 0.73 Ma (Fig. 3E), mid Carnian in age , which had so far yielded several noteworthy vertebrate fossil specimens (Fig. 4), emphasizing the type-series of the sauropodomorph dinosaur Saturnalia tupiniquim (Langer et al., 1999), the saurischian dinosaur with putative theropod affinities Nhandumirim waldsangae (Marsola et al., 2019), the proterochampsid archosauriform Cerritosaurus binsfeldi (Price, 1946), the probainognathian cynodont Alemoatheruim huebneri (Martinelli et al., 2017a), and the traversodontid cynodont Gomphodontosuchus brasiliensis (Huene, 1928). Nearby outcrops belonging to the same complex yielded the type-specimens of the pseudosuchian Rauisuchus tiradentes (Zahn Sanga/Sanga do Dente - Lautenschlager and Rauhut, 2014), the proterocampsid archosauriform Rhadinosuchus gracilis (Ezcurra et al., 2015), and the herrerasaurid dinosaur Staurikosaurus pricei (Sanga Grande/Sanga de Baixo - Colbert, 1970), although nowadays most of the original complex has been buried due to urban expansion, isolating or even destroying some outcrops (Da-Rosa, 2018). ...
... Moreover, this site provided an extensive sample of rhynchosaurs and a wide variety of dinosauromorphs (Fig. 9), mainly represented by saurischian dinosaurs (Colbert, 1970;Langer et al., 1999). Even though these outcrops provided type-specimens of many dinosaurs such as Nhandumirim waldsangae (Marsola et al., 2019), Saturnalia tupiniquim and Staurikosaurus pricei, latest intensive fieldwork in this locality and reassessment of already collected material revealed a hidden diversity of dinosauromorph groups (dinosaurs, silesaurids and lagerpetids) that is only comparable to faunal assemblages in (younger) horizons from the Ischigualasto Formation of Argentina and from the Hayden Quarry of southwestern USA (see Irmis et al., 2007;Martínez et al., 2013). Overall, recent expeditions in Upper Triassic beds from southern Brazil are unearthing an outstanding diversity of dinosauromorphs, that is still relatively scarce in this area, in comparison to other vertebrate groups such as cynodonts and rhynchosaurs, with exceptionally well-preserved and reasonably complete specimens (Cabreira et al., 2011(Cabreira et al., , 2016Müller et al., 2018bMüller et al., , 2018dPretto et al., 2018). ...
... Regarding theropods, Brazilian specimens from Carnian are so far restricted to Nhandumirim waldsangae (Marsola et al., 2019), which is putatively associated to this clade. Similar to silesaurids/ornithischians, Herrerasauridae is often regarded as a basal branch of Theropoda. ...
Late Triassic deposits from south Pangea (Argentina and Brazil) bear the oldest (so far) and most informative unequivocal records of dinosaurs worldwide. Herein we describe a new lagerpetid dinosauromorph from a classic dinosaur-bearing locality (Cerro da Alemoa site) from the Candelária Sequence (Santa Maria Formation), southern Brazil, and report the oldest co-occurrence of dinosaurs, lagerpetids and silesaurids, in the same layer of a Triassic outcrop. Although tentatively regarded as an immature specimen, the new lagerpetid represents a new morphotype due to the occurrence of the following features: (1) distal condyles transversely wider than deep; (2) absence of flange in the craniomedial margin of the femur; (3) round shaped and medially deflected medial condyle; (4) round shaped crista tibiofibularis. This suit of traits differentiates the new specimen from Ixalerpeton polesinensis, (which was so far the only lagerpetid found in Brazilian strata) and from other known lagerpetids. As non-dinosaurian dinosauromorphs are still relatively scarce in Brazilian Triassic rocks, recent records from this region are gradually providing new data regarding faunal turnovers and biostratigraphy of south Pangean terrestrial deposits. Additionally, new insights on the oldest dinosauromorph-bearing sites throughout the Triassic, as well as regarding taxonomic diversity and geographic distribution of early dinosauromorphs reinforces previous hypotheses where dinosaurs and dinosaur-relatives consistently coexisted (for at least 21 Ma) before their extinction .
... The inclusiveness of Theropoda is one of those topics open to debate. Several Late Triassic panavians, like herrerasaurs, Tawa hallae, Daemonosaurus chauliodus, Eodromaeus murphii, Nhandumirim waldsangae, and Eoraptor lunensis, have been found either nested within or outside the lineage (Rauhut, 2003;Sereno et al., 2012;Langer et al., 2017;Marsola et al., 2018;Pacheco et al., 2019;Novas et al., 2021;Nesbitt and Sues, 2021). Within Neotheropoda (the least inclusive clade that includes Coelophysis bauri and Neornithes), the Coelophysoidea lineage was once thought to include forms close to Dilophosaurus wetherilli (Gauthier, 1986;Rauhut, 2003), more recently placed along the Averostra branch (Langer et al., 2017;Zahner and Brinkmann, 2019;Marsh and Rowe, 2020;Ezcurra et al., 2021). ...
... The anteromedial tuber is distinctive and anteroposteriorly long (Fig. 3a). It is more protuberant than those of Eoraptor lunensis (PVSJ 212), Thecodontosaurus antiquus (BRSUG 23615, Fig. 3l), and several coelophysids (Coelophysis bauri AMNH 2704, 7224 and MCZ 4331, Fig. 3d), in which the tuber does not project significantly from the main portion of the head, but also distinct from that of Nhandumirim waldsangae (LPRP/USP 0651, Fig. 3j), which projects much further anteromedially (Marsola et al., 2018). The projection of the tuber in Pendraig milnerae (NHMUK PV R37591, Fig. 3b) is similar to that of BRSUG 28403, but the latter shows a more angled tuber in proximal view. ...
Theropods originated in the Late Triassic and their relations and early evolution are still topics of discussion. Within Neotheropoda, coelophysoids represent their earliestworldwide radiation and include most Triassic theropods, but their internal relations remain volatile. In this paper, we discuss the significance of a coelophysoid femur from the Rhaetian Tytherington fissures near Bristol, UK. The specimen belongs to a small-sized individual and is complete, but for the fourth trochanter blade. The most distinctive aspects of the femur are a sharply pointed lateral condyle and the pentagonal distal outline. The features that supposedly correlate with ontogenetic development, in addition to several well-developed scars, indicate it probably pertains to a mature individual. Its inclusion in a taxon-character matrix recovered the specimen within Coelophysoidea, but created a polytomy encompassing all members of the group. A definitive referral of the femur to the previously recorded coelophysoid Pendraig milnerae is precluded by the lack of overlap in diagnostic
anatomical parts, the paucity of specimens from the Bristol Channel Triassic fissures, and the possible geological age difference between them.
... Erythrovenator jacuiensis Müller, 2021 belongs to a fauna tentatively assigned to the Riograndia AZ (Marsola et al., 2019;Miron et al., 2020;Müller, 2021; but see discussions in Schultz et al., 2020 andMartinelli et al., 2021). An important finding of a non-sauropodomorph dinosauromorph is the species Sacisaurus agudoensis Ferigolo & Langer, 2006, which was initially assigned to Ornithischia. ...
... The sacral vertebrae of Bagualosaurus agudoensis includes two primordial vertebrae, as in MCN-PV 10344c, but differs from our specimen by the presence of an additional caudosacral vertebra . In Nhandumirim waldsangae the sacrum is composed of three vertebrae, and their ventral surface is less concave in lateral view than in the proximal dorsal and caudal vertebrae (Marsola et al., 2019). The second sacral of N. waldsangae is longer than wide compared to the third sacral, while in MCN-PV 10344c they are shorter than the third sacral of N. waldsangae. ...
The Predebon Site, located in São João do Polêsine, Quarta Colônia region (Rio Grande do Sul, Brazil) has a Triassic fauna, including footprints and traces of small vertebrates and abundant remains of rhynchosaurs. This fauna is typical of the Hyperodapedon Assemblage Zone, which is correlated to the late Carnian Ischigualasto Formation (Ischigualasto-Villa Unión Basin) in Argentina. The present study records new fossil remains for the Predebon Site collected in 2001 that consists of two dorsal and two sacral vertebrae referred to the same individual (MCN-PV 10344), and two isolated, serrated blade-shaped teeth (MCN-PV 10425 and 10426). The trunk vertebrae were identified as between 11th and 15th. The sacral vertebrae are fully fused, with no indication of another fused vertebral element, not even signs suggestive of dorsosacral and caudosacral vertebrae, also because the ilia are not preserved. The general characteristics observed are: (i) lateral fossa in the vertebral body; (ii) concave ventral face of the vertebral body; (iii) neural spine high and wide at the top, subquadrangular in shape, in both dorsal and sacral vertebrae; (iv) infrapre- and infrapostzygapophyseal ridges on the dorsals; (v) presence of hyposphene and hypantrum; and (vi) first sacral vertebra larger than the second, with transverse processes and broad sacral ribs, triangular in shape in dorsal view. This set of features in the vertebral elements is similar to that present in Herrerasaurus ischigualastensis from the Ischigualasto Formation and allows us to consider MCN-PV 10344 as a member of the Herrerasauridae clade. It differs from Staurikosaurus pricei, which has three smaller and more slender sacral vertebrae and a low neural spine without subquadrangular platform at the top, and from Gnathovorax cabreirai, which has subrectangular platforms, slightly more elongated anteroposteriorly, suggesting the presence of a new herrerasaurid morphotype. The two isolated, serrated blade-shaped teeth were attributed to Archosauriformes indet., because this morphotype is observed in several groups within this clade. Keywords: Dinosauria, Hyperodapedon Assemblage Zone, late Carnian, Predebon Site, Rio Grande do Sul, Brazil.
... The Arroio Cancela site is located near several classic outcrops (e.g., Cerro da Alemoa, Faixa Nova, Palotinos and Therioherpeton sites, Figure 2) in the eastern/southeastern regions of Santa Maria, where dozens of vertebrate fossils have been discovered since the beginning of the twentieth century (e.g., Da-Rosa, 2015; Marsola, Bittencourt, Butler, et al., 2018;Oliveira, 2006). The Cerro da Alemoa (or Waldsanga) is the most important of these sites, as it yielded the holotypes of the sauropodomorph dinosaur Saturnalia tupiniquim (Langer et al., 1999), the putative theropod dinosaur Nhandumirim waldsangae (Marsola, Bittencourt, Butler, et al., 2018), the loricatan rauisuchian Rauisuchus tiradentes (von Huene, 1936a(von Huene, , 1938(von Huene, , 1942, the traversodontid cynodont Gomphodontosuchus brasiliensis (von Huene, 1928), the probainognathian cynodont Alemoatherium huebneri (Martinelli, Eltink, et al., 2017), as well as abundant specimens of the rhynchosaur Hyperodapedon sp. ...
... The Arroio Cancela site is located near several classic outcrops (e.g., Cerro da Alemoa, Faixa Nova, Palotinos and Therioherpeton sites, Figure 2) in the eastern/southeastern regions of Santa Maria, where dozens of vertebrate fossils have been discovered since the beginning of the twentieth century (e.g., Da-Rosa, 2015; Marsola, Bittencourt, Butler, et al., 2018;Oliveira, 2006). The Cerro da Alemoa (or Waldsanga) is the most important of these sites, as it yielded the holotypes of the sauropodomorph dinosaur Saturnalia tupiniquim (Langer et al., 1999), the putative theropod dinosaur Nhandumirim waldsangae (Marsola, Bittencourt, Butler, et al., 2018), the loricatan rauisuchian Rauisuchus tiradentes (von Huene, 1936a(von Huene, , 1938(von Huene, , 1942, the traversodontid cynodont Gomphodontosuchus brasiliensis (von Huene, 1928), the probainognathian cynodont Alemoatherium huebneri (Martinelli, Eltink, et al., 2017), as well as abundant specimens of the rhynchosaur Hyperodapedon sp. (Da-Rosa, 2015;Langer et al., 2007), one of the index fossils for the Hyperodapedon AZ. ...
In this contribution we describe a new genus and species of gomphodontosuchine
cynodont from the Late Triassic Hyperodapedon Assemblage Zone (AZ)
of the Santa Maria Supersequence of southern Brazil, based on material collected
20 years ago. The new taxon, Santagnathus mariensis gen. et sp. nov., is
based on numerous cranial and postcranial remains, which altogether provide
data on several parts of the skeleton. Santagnathus mariensis is closely related
to Siriusgnathus niemeyerorum and Exaeretodon spp. and expands the knowledge
about gomphodontosuchine cynodonts. Morphologically, the new species
has a skull bauplan particularly similar to S. niemeyerorum and
E. riograndensis, differing from them by a unique combination of traits such as
three upper incisors, the absence of a descending process in the jugal, a more
posterior position of the postorbital bar and a preorbital region larger than the
temporal one. The new traversodontid was found associated with the rhynchosaur
Hyperodapedon sp., corroborating the assignment of the cynodont fossils
to the Hyperodapedon AZ. We also provide comments on the status of the
Argentine traversodontid cynodont Proexaeretodon vincei, typically considered
a junior synonym of Exaeretodon argentinus, and here accepted as a valid
taxon.
... The trunk vertebrae of M. raathi possess hyposphene-hypantrum accessory articulations, a saurischian synapomorphy 44 . The sacrum is composed of three vertebrae (Fig. 2a), with a dorsosacral vertebra added anterior to the primordial two sacral vertebrae, as in some Carnian 43,45 and most later 36 sauropodomorphs, early ornithischians (Eocursor, Heterodontosaurus and Lesothosaurus) and neotheropods 40 , but unlike in other Carnian sauropodomorphs, which possess an additional sacral vertebra incorporated from the caudal series 26,46 . Unlike in other Carnian sauropodomorphs 47 , but as in later-diverging taxa 47 , the sacral centra of the paratype (NHMZ 2548) are co-ossified, although those of the smaller holotype (NHMZ 2222) are not. ...
... The ilium of M. raathi is robustly built, with thick, large and wellintegrated bone scars across the blade (Fig. 2b). As in other early sauropodomorphs, but unlike in herrerasaurids and early theropods 45 , the acetabulum is anteroposteriorly shorter than it is dorsoventrally tall. The ventral edge of the iliac acetabular wall is slightly concave, forming a 'perforate' acetabulum ( Fig. 2b) that is a classic dinosaurian synapomorphy 40 , similar to the acetabular wall in later sauropodomorphs 36 and different from the ventrally straight acetabular walls in several other Carnian sauropodomorphs 26 . ...
The vertebrate lineages that would shape Mesozoic and Cenozoic terrestrial ecosystems originated across Triassic Pangaea1–11. By the Late Triassic (Carnian stage, ~235 million years ago), cosmopolitan ‘disaster faunas’ (refs. 12–14) had given way to highly endemic assemblages12,13 on the supercontinent. Testing the tempo and mode of the establishment of this endemism is challenging—there were few geographic barriers to dispersal across Pangaea during the Late Triassic. Instead, palaeolatitudinal climate belts, and not continental boundaries, are proposed to have controlled distribution15–18. During this time of high endemism, dinosaurs began to disperse and thus offer an opportunity to test the timing and drivers of this biogeographic pattern. Increased sampling can test this prediction: if dinosaurs initially dispersed under palaeolatitudinal-driven endemism, then an assemblage similar to those of South America4,19–21 and India19,22—including the earliest dinosaurs—should be present in Carnian deposits in south-central Africa. Here we report a new Carnian assemblage from Zimbabwe that includes Africa’s oldest definitive dinosaurs, including a nearly complete skeleton of the sauropodomorph Mbiresaurus raathi gen. et sp. nov. This assemblage resembles other dinosaur-bearing Carnian assemblages, suggesting that a similar vertebrate fauna ranged high-latitude austral Pangaea. The distribution of the first dinosaurs is correlated with palaeolatitude-linked climatic barriers, and dinosaurian dispersal to the rest of the supercontinent was delayed until these barriers relaxed, suggesting that climatic controls influenced the initial composition of the terrestrial faunas that persist to this day. A new Triassic dinosaur assemblage from Zimbabwe reveals that the earliest dinosaurs were confined to a temperate region in the far south of Pangaea.
... Both taxa are related to Argentinean herrerasaurids from the Ischigualasto Formation. Except for Nhandumirim waldsangae (Marsola et al., 2019), all the other dinosaurs from the Hyperodapedon AZ have been recovered as members of Sauropodomorpha (but see Pacheco et al., 2019, who recovered N. waldsangae as a sauropodomorph, sister-group to Saturnaliinae). The first sauropodomorph described for the Hyperodapedon AZ was Saturnalia tupiniquim (Langer et al., 1999), from the Alemoa site, Santa Maria. ...
... This taxon is the major component of the sampled fauna at its type locality , and other fossil vertebrates do not help to refine its biostratigraphic placement due to their fragmentary preservation and indeterminate taxonomic status. However, Siriusgnathus was recently reported outside its type-locality (Miron et al., 2020), in an outcrop which was suggested to be correlated to the Sacisaurus site (Marsola et al., 2019), of (?)Norian age (see also next section). Nonetheless, this second locality with Siriusgnathus also lacks the typical index fossils from the Brazilian Triassic AZs and other putative faunal components also found in the Sacisaurus site. ...
... The head of the femur is offset from the shaft resulting in a concave emargination just ventral to the head, common among all dinosaurs. On the anterolateral surface of the femur, a ridge extends from the ventral margin of the head then merges distally into the shaft forming a ventral emargination, such as that seen in Saturnalia tupiniquim, Nhandumirim waldsangae Marsola et al., 2018, and some coelophysoids (Kirmse et al. 2023), but unknown among core ornithischians, exclusive of silesaurids. The shaft of the femur Rethinking dinosaur origins • 9 ...
The origin of Dinosauria is thought to be deeply rooted in the high-latitude southern hemisphere (Gondwana). Nearly 6–10 million years separates Gondwanan faunas and the oldest known dinosaur occurrence in the northern hemisphere (Laurasia). However, our understanding of dinosaur origins is biased by an apparent absence of Carnian-aged (237–227 Mya) Laurasian terrestrial strata. Here we report on UWGM 1975/UWGM 7549, the oldest known Laurasian dinosaur Ahvaytum bahndooiveche gen. et sp. nov., and UWGM 7407/UWGM 7550, a silesaurid, from palaeoequatorial deposits of the lower Popo Agie Formation, Wyoming, USA. High-precision radioisotopic detrital ages [e.g. ≤229.04 ± 0.24 Mya (2σ)] from the upper Popo Agie Formation constrain an age-depth model that predicts a ~230 Mya age for UWGM 1975, making Laurasia’s first unequivocal Carnian-aged sauropodomorph dinosaur comparable in age to the oldest dinosaur faunas of Gondwana. The presence of a ~230 Mya, low-latitude, early sauropodomorph from the northern hemisphere, along with a silesaurid, challenges the hypothesis of a delayed dinosaurian dispersal out of high-latitude Gondwana. These data fill a critical gap in the early record of sauropodomorph dinosaur evolution and demonstrate widespread geographic distribution by the mid-late Carnian.
... , Bagualosaurus agudoensis(Pretto et al., 2018), Macrocollum itaquii(Muller et al., 2018), Nhandumirim waldsangae(Marsola et al., 2019), Gnathovorax cabreirai(Pacheco et al., 2019) e Erythrovenator jacuiensis(Muller, 2021). No quadro 1 consta o significado do nome de cada espécie de dinossauro, e no texto são sugeridas atividades a serem realizadas a partir desses dados. ...
A Paleontologia é a ciência que estuda os dinossauros e por isso tem imenso potencial para atrair a atenção dos estudantes; entretanto, ela é ainda mal explorada nos currículos das Escolas. Os dinossauros hollywoodianos são seres realmente fantásticos, mas desconectados da realidade dos nossos alunos, que geralmente desconhecem que o Brasil também teve seus dinossauros. Em virtude disso, o principal objetivo deste trabalho foi articular a área da Paleontologia com a Educação Básica, utilizando dinossauros brasileiros como tema central para a mediação de atividades didático pedagógicas com os alunos do Ensino Fundamental. O estudo se caracteriza como uma pesquisa bibliográfica de abordagem qualitativa, tendo sido realizado entre os anos de 2020 e 2023. O embasamento das atividades propostas utilizou a Base Nacional Comum Curricular (BNCC) e os dinossauros selecionados foram as espécies fósseis que ocorrem no Estado do Rio Grande do Sul (RS). O levantamento bibliográfico resultou na descoberta de 12 espécies de dinossauros, distribuídas em cinco cidades gaúchas, todas elas localizadas na região central do RS e pertencentes ao Período Triássico. A partir dos dados obtidos foram elaboradas e sugeridas atividades para quatro áreas da BNCC: linguagens, matemática, ciências da natureza e ciências humanas; a grande versatilidade da Paleontologia permitiu sua articulação com todas elas. Este trabalho pretende ser uma referência para professores que tenham interesse em buscar informações científicas mais aprofundadas sobre os dinossauros do RS, visando enriquecer o planejamento de suas aulas. Também espera estimular nos estudantes o interesse por ciências, a valorização do patrimônio paleontológico, e uma identidade com a Pré-história local.
... The increasing number of described early sauropodomorph specimens in recent years has expanded the understanding of the early evolution of the group as a whole, but also brought some uncertainty regarding its alpha taxonomy Müller & Garcia, 2020a). A detailed taxonomic review of early sauropodomorphs supports the hypothesis that these taxa are anatomically distinct from one another , but phylogenetic hypotheses vary among authors (Baron et al., 2017;Cabreira et al., 2016;Langer & Benton, 2006;Marsola et al., 2019;Müller, 2020;Novas et al., 2011;Pacheco et al., 2019). The description of new specimens is mandatory in order to fill anatomical gaps and produce more reliable phylogenetic inferences. ...
Buriolestes schultzi is a small sauropodomorph dinosaur from Carnian beds (ca., 233 Ma) of southern Brazil. It is one of the earliest members of that lineage and is a key taxon to investigate the initial evolution of Sauropodomorpha. Here, we attribute a new specimen to B. schultzi from Late Triassic of southern Brazil, which represents the first occurrence of the taxon outside the type locality. The new specimen comprises a disarticulated and partial skeleton, including cranial and postcranial elements. It is tentatively regarded as an additional specimen of B. schultzi according to a unique combination of traits (including autapomorphies). Conversely, the new specimen is stouter than the other specimens of B. schultzi , as shown by femoral Robustness Index . Based on femoral circumference, the estimated body mass of the new specimen is approximately 15 kg, which is far higher than the previous estimations for other specimens of B. schultzi (i.e., approximately 7 kg). In fact, the new specimen and some specimens of Eoraptor lunensis and Saturnalia tupiniquim were found to be significantly stouter than coeval sauropodomorphs. Therefore, instead of all being constructed as gracile, the earliest sauropodomorphs experienced an unappreciated intraspecific variation in robustness. This is interesting because more precise data on species body mass are crucial in order to better understand the complex terrestrial ecosystems in which dinosaurs originated.
... First, the specimen was scored in the data matrix of Müller (2021), which includes a wide range of early dinosaurs and related forms. We excluded Nhandumirim waldsangae given its immature ontogenetic status (Marsola et al., 2018). The final data matrix includes 277 characters and 63 operational taxonomic units (OTUs). ...
Whereas sauropod dinosaurs from the Jurassic and Cretaceous Periods were the largest land animals that ever lived, some of their early relatives evolved relatively large bodies during the Triassic Period. The evolutionary pathways followed by the earliest sauropodomorphs towards the acquisition of massive bodies are poorly understood. However, new finds from South America and Africa are reshaping our knowledge of this issue. Here, we describe a new early and relatively large sauropodomorph represented by a partial postcranial skeleton excavated from Carnian-aged beds (Upper Triassic) of southern Brazil. The new specimen is recovered as a sauropodomorph more closely related to bagualosaurians
than saturnaliids or other early-diverging forms in two phylogenetic analyses. The new specimen is generically indeterminate but provides important evidence of an early increase in body size in Sauropodomorpha, being significantly larger than that of coeval or older forms (except Bagualosaurus agudoensis). Furthermore, the specimen is about 3.2 times heavier than Buriolestes schultzi, the earliest-branching Sauropodomorph. The slender hind limbs and typical cursorial proportions present in the earliest sauropodomorphs are mostly maintained in the new specimen despite its larger body size.
... At 233.23 ± 0.73 Ma (U-PB zircon data, Langer et al. 2018), the Cerro da Alemoa site is the oldest known assemblage to include both dinosaurs and non-dinosaur dinosauromorphs (Garcia et al. 2019). That site and similar localities in the area from the upper part of the Santa Maria Formation (Fig. 18) have produced Ixalerpeton polesinensis Cabreira et al. (2016) and an unnamed lagerpetid (Garcia et al. 2019), an unnamed silesaurid (Langer et al. 2017b, Garcia et al. 2019, the putative theropod Nhandumirim waldsangae Marsola et al. (2019), the early sauropodomorphs Buriolestes schultzi Cabreira et al. (2016), Pampadromaeus barberenai Cabreira et al. (2011), Bagualosaurus agudoensis Pretto et al. (2018), and Saturnalia tupiniquim Langer et al. (1999), and the herrerasaurids Staurikosaurus pricei Colbert (1970) and Gnathovorax cabreirai Pacheco et al. (2019). ...
Dinosauromorph specimens from Petrified Forest National Park have been recovered from four major collecting efforts since 1982, including the most recent paleontological inventory of new park lands acquired in 2011. Additionally, an emphasis on understanding the stepwise acquisition of character traits along the dinosaurian lineage has helped identify previously collected specimens in museum collections. Here we briefly describe and use apomorphies to identify 32 additional dinosauromorph specimens found at Petrified Forest National Park, bringing the total number of dinosauromorph specimens presently known from the park to 50, a 600% increase since the year 2000. These specimens are all Norian in age and come from the Blue Mesa Member, Sonsela Member, and Petrified Forest Member of the Chinle Formation. These include the proximal end of a tibia that represents the oldest unambiguous dinosaur specimen from the Chinle Formation. We then contextualize these specimens with the dinosauromorph assemblages from the Norian of Utah, Colorado, New Mexico, and Texas, as well as the Carnian and Norian dinosauromorph assemblages from South America, Africa, and Europe. Despite increased sampling we still find no evidence for sauropodomorph and ornithischian dinosaurs in Western North America. An increase in sampling, combined with the use of apomorphies to identify collected specimens, will continue to improve the global dinosauromorph fossil record that can be used to answer questions on biochronology and the evolutionary history of the avian lineage.
... The presence of a trochanteric shelf in the described femora is also more related to the typical condition of Carnian dinosaurs, with the exception of Staurikosaurus pricei (Bittencourt & Kellner, 2009; or immature specimens (e.g. Marsola et al., 2018;. ...
The Janner site (Upper Triassic of Southern Brazil) has been intensely explored, yielding constant new findings in recent years. Among these some fragmentary dinosaur specimens still not published were sampled. In this contribution, we describe these specimens, which represent five individuals, in order to increase our understanding on the anatomy of the dinosaurs that compose the paleofauna of the Janner site. The specimen CAPPA/UFSM 0270 is comprised of a series of six articulated presacral vertebrae, plus two isolated vertebrae associated with a right femur. UFRGS-PV-1232-T comprises a sacrum and a left ilium. CAPPA/UFSM 0271 comprises a right humerus that lacks the middle portion of the diaphysis. CAPPA/UFSM 00272 and 2073 are both comprised of an isolated femur each. The fragmentary condition of the materials hampers any less inclusive assignation. However, the morphology of the elements resembles those of coeval dinosaurs. Furthermore, the new specimens increase our knowledge on the morphology of some structures poorly understood from the dinosaurs of Janner site, such as the hindlimb and axial skeleton.
... The new morphological dataset combines data from different sources, including those from Cabreira et al. [4] as well as additional operational taxonomic units (OTUs), characters and modifications from other studies [7,8,[16][17][18][19] [6,7,13,15,[19][20][21][22][23][24][25][26]. Furthermore, we scored additional characters for Dromomeron romeri, Lewisuchus admixtus, Asilisaurus kongwe and Buriolestes schultzi based on previous studies [5,6,9,12]. ...
Whereas ornithischian dinosaurs are well known from Jurassic and Cretaceous deposits, deciphering the origin and early evolution of the group remains one of the hardest challenges for palaeontologists. So far, there are no unequivocal records of ornithischians from Triassic beds. Here, we present an alternative evolutionary hypothesis that suggests consideration of traditional ‘silesaurids' as a group of low-diversity clades representing a stem group leading to core ornithischians (i.e. unambiguous ornithischians, such as Heterodontosaurus tucki ). This is particularly interesting because it fills most of the ghost lineages that emerge from the Triassic. Following the present hypothesis, the lineage that encompasses the Jurassic ornithischians evolved from ‘silesaurids' during the Middle to early Late Triassic, while typical ‘silesaurids' shared the land ecosystems with their relatives until the Late Triassic, when the group completely vanished. Therefore, Ornithischia changes from an obscure to a well-documented clade in the Triassic and is represented by records from Gondwana and Laurasia. Furthermore, according to the present hypothesis, Ornithischia was the first group of dinosaurs to adopt an omnivorous/herbivorous diet. However, this behaviour was achieved as a secondary step instead of an ancestral condition for ornithischians, as the earliest member of the clade is a faunivorous taxon. This pattern was subsequently followed by sauropodomorph dinosaurs. Indeed, the present scenario favours the independent acquisition of an herbivorous diet for ornithischians and sauropodomorphs during the Triassic, whereas the previous hypotheses suggested the independent acquisition for sauropodomorphs, ornithischians, and ‘silesaurids'.
... In addition to the new herrerasaurid, eight new operational taxonomic units (OTUs) were included. These new OTUs and their respective sources are: the lagerpetid Dromomeron gigas, following the scores of Martínez et al. (2016) andMüller, Langer & Dias-da Silva (2018a); the ornithischians Tianyulong confuciusi, Fruitadens haagarorum, and Echinodon becklesii, following scores of Agnolín & Rozadilla (2018); the saurischian Nhandumirim waldsangae, following the scores of Marsola et al. (2018); and the sauropodomorphs Bagualosaurus agudoensis, Unaysaurus tolentinoi, and Macrocollum itaquii, following the scores of Pretto, Langer & Schultz (2018) andMüller, Langer & Dias-da Silva (2018b). Finally, the modifications in scores of Pisanosaurus mertii and Silesaurus opolensis performed by Agnolín & Rozadilla (2018) were also applied. ...
Predatory dinosaurs were an important ecological component of terrestrial Mesozoic ecosystems. Though theropod dinosaurs carried this role during the Jurassic and Cretaceous Periods (and probably the post-Carnian portion of the Triassic), it is difficult to depict the Carnian scenario, due to the scarcity of fossils. Until now, knowledge on the earliest predatory dinosaurs mostly relies on herrerasaurids recorded in Carnian strata of South America. Phylogenetic investigations recovered the clade in different positions within Dinosauria, whereas fewer studies challenged its monophyly. Although herrerasaurid fossils are much better recorded in present-day Argentina than in Brazil, Argentinean strata so far yielded no fairly complete skeleton representing a single individual. Here, we describe Gnathovorax cabreirai , a new herrerasaurid based on an exquisite specimen found as part of a multitaxic association form southern Brazil. The type specimen comprises a complete and well-preserved articulated skeleton, preserved in close association (side by side) with rhynchosaur and cynodont remains. Given its superb state of preservation and completeness, the new specimen sheds light into poorly understood aspects of the herrerasaurid anatomy, including endocranial soft tissues. The specimen also reinforces the monophyletic status of the group, and provides clues on the ecomorphology of the early carnivorous dinosaurs. Indeed, an ecomorphological analysis employing dental traits indicates that herrerasaurids occupy a particular area in the morphospace of faunivorous dinosaurs, which partially overlaps the area occupied by post-Carnian theropods. This indicates that herrerasaurid dinosaurs preceded the ecological role that later would be occupied by large to medium-sized theropods.
Introdução. A variação intraespecífica refere-se às diferenças morfológicas ou comportamentais observadas entre indivíduos de uma mesma espécie, sendo determinadas por diversos fatores, como mudanças ontogenéticas; dimorfismo sexual; variação individual e condições patológicas devido a doenças ou lesões. Objetivo. O presente estudo apresenta, de forma breve, os principais fatores que geram a variação intraespecífica nos primeiros dinossauros, bem como os meios de analisá-la (e.g., investigação da morfologia externa, morfometria, histologia). Metodologia. A investigação envolveu uma revisão sistemática da literatura especializada. Resultados. No campo da Paleontologia, estudos indicam que a falha em reconhecer esse tipo de variação intraespecífica pode ser um fator responsável pela instabilidade nas inferências filogenéticas relacionadas aos dinossauros. Conclusão. Ressalta-se que o detalhamento da variação intraespecífica em dinossauros necessita de um número adequado de indivíduos com certa variabilidade no seu tamanho, forma e deposição óssea, mas há um cenário promissor para esse campo de estudos, uma vez que diferentes grupos de pesquisa têm dedicado esforços tanto à descoberta de novos materiais.
Pterosaurs, remarkable for their extensive evolutionary history and role as the first vertebrates to achieve active flight, have long intrigued paleontologists and the public alike. Spanning over 150 million years and vanishing at the end of the Mesozoic Era, pterosaurs represent a major evolutionary radiation within terrestrial ecosystems. Despite their prominence, the origins of pterosaurs have remained a complex puzzle in paleontology for over 200 years. We present a comprehensive catalog of pterosaur precursors specimens from the Upper Triassic of the Candelária Sequence within the Santa Maria Supersequence in southern Brazil and discuss their significance for understanding pterosauromorph radiation and the origins of Pterosauria. Additionally, we carried out a phylogenetic analysis to investigate the hypothesis that lagerpetids are closely related to pterosaurs, incorporating new data into the most comprehensive dataset of Triassic dinosauromorphs. Our results support the hypothesis that lagerpetids are pterosauromorphs, offering new insights into the evolutionary relationships between non-pterosaur pterosauromorphs and their better known volant relatives. This study highlights the importance of detailed anatomical and phylogenetic analyses in resolving the complex origins of pterosaurs and underscores the value of the Triassic fossil record in understanding the early evolution of pterosauromorphs.
Dinosaurs arose in the Late Triassic and diversified during the subsequent periods of the Mesozoic Era. The oldest unequivocal dinosaurs come from Carnian deposits of Brazil, Argentina, India, and Zimbabwe, with sauropodomorphs representing the bulk of this record. Saturnalia tupiniquim was described from Brazilian strata in 1999 as the first Carnian member of that group. Although several new species and specimens of coeval sauropodomorphs have been described in recent years, no new material has been formally assigned to that species. In this contribution, we describe an association of at least three partially preserved individuals of S. tupiniquim (UFSM 11660), which was excavated from the S. tupiniquim type-locality (Late Triassic of the Santa Maria Formation) and preserves cranial and postcranial elements, including the first rostrum known for the species. Assigned to S. tupiniquim according to several lines of evidence, the new specimen has a proportionally short rostrum, compared to that of coeval sauropodomorphs, providing evidence for a reduced skull in S. tupiniquim. In addition, we investigated the intraspecific variation in S. tupiniquim, highlighting the need to understand the morphological limits of such variations among the earliest dinosaurs, in order to properly explore their alpha diversity.
The central region of Rio Grande do Sul State, in southern Brazil, has increasing importance due the discoveries of Triassic fossils, including some of the world’s oldest dinosaurs and their tracks. Tridactyl footprints of Carnian age, from the Santa Maria Formation, have been identified as ?Grallator isp., in addition to indeterminate tracks of dinosaurs. These footprints are attributed to basal dinosauriforms and they are considered the earliest examples of dinosaur tracks in Brazil. These discoveries hold significant implications, as they are associated with a diverse fauna whose dating aligns with the Carnian Pluvial Episode. This is a pivotal period marked by substantial environmental changes linked to global warming, leading to significant extinctions and transitions in both flora and fauna. Other tracks, dating back to the Norian or possibly Rhaetian age, were reinterpreted as “Theropod tracks indet.”, and were produced by large theropod dinosaurs. These particular occurrences are connected to the Caturrita Formation and provide valuable insights into a later episode following the climate changes and their resulting effects on faunal and floral composition. Previously registered tracks within the Caturrita Formation at the Novo Treviso site, attributed to prosauropod dinosaurs, have been reinterpreted as belonging to the Guará Formation, ranging from the Late Jurassic to the Early Cretaceous. Thus, the Santa Maria-Caturrita sequence, a sedimentary record shaped by diverse processes in ancient fluvial systems, offers an almost continuous timeline of the transition between the emergence of dinosaurs and their eventual establishment as ecologically dominant elements in continental faunas. These Brazilian Triassic dinosaur tracks, albeit limited to two strata at present, provide valuable supplementary data to the osteological record, further reinforcing these significant events in paleontological history.
Dinosauria debuted on Earth’s stage in the aftermath of the Permo-Triassic Mass Extinction Event, and survived two other Triassic extinction intervals to eventually dominate terrestrial ecosystems. More than 231 million years ago, in the Upper Triassic Ischigualasto Formation of west-central Argentina, dinosaurs were just getting warmed up. At this time, dinosaurs represented a minor fraction of ecosystem diversity. Members of other tetrapod clades, including synapsids and pseudosuchians, shared convergently evolved features related to locomotion, feeding, respiration, and metabolism and could have risen to later dominance. However, it was Dinosauria that radiated in the later Mesozoic most significantly in terms of body size, diversity, and global distribution. Elevated growth rates are one of the adaptations that set later Mesozoic dinosaurs apart, particularly from their contemporary crocodilian and mammalian compatriots. When did the elevated growth rates of dinosaurs first evolve? How did the growth strategies of the earliest known dinosaurs compare with those of other tetrapods in their ecosystems? We studied femoral bone histology of an array of early dinosaurs alongside that of non-dinosaurian contemporaries from the Ischigualasto Formation in order to test whether the oldest known dinosaurs exhibited novel growth strategies. Our results indicate that the Ischigualasto vertebrate fauna collectively exhibits relatively high growth rates. Dinosaurs are among the fastest growing taxa in the sample, but they occupied this niche alongside crocodylomorphs, archosauriformes, and large-bodied pseudosuchians. Interestingly, these dinosaurs grew at least as quickly, but more continuously than sauropodomorph and theropod dinosaurs of the later Mesozoic. These data suggest that, while elevated growth rates were ancestral for Dinosauria and likely played a significant role in dinosaurs’ ascent within Mesozoic ecosystems, they did not set them apart from their contemporaries.
The idea that birds are maniraptoran theropod dinosaurs is now considered an evolutionary consensus. An “open” (i.e., completely or substantially perforate) acetabulum is considered an important synapomorphy verifying the bird–dinosaur nexus. Here, I present anatomical evidence from the acetabulum and its important appurtenances, the supracetabular crest and the antitrochanter, that hip anatomy differs substantially between dinosaurs and birds. Given the thin bone of the acetabular walls and the varied tissue, both hard and soft, in the acetabular region and especially the lower part of the basin, it is apparent that many avian skeletons exhibit some anatomical loss of soft tissue and thin bone, some perhaps related to changes in gait, but also in part related to the dramatic trend in bone reduction associated with flight, especially in more advanced crown taxa. Many basal birds and early diverging neornithines tend to have a nearly closed or partially closed acetabula, thus rendering the current terms “open” or “closed” acetabula inaccurate; they should be modified or replaced. Given new evidence presented here, the relationship of “dinosaurs” and birds must be re-evaluated.
We describe a new small-bodied coelophysoid theropod dinosaur, Pendraig milnerae gen. et sp. nov, from the Late Triassic fissure fill deposits of Pant-y-ffynnon in southern Wales. The species is represented by the holotype, consisting of an articulated pelvic girdle, sacrum and posterior dorsal vertebrae, and an associated left femur, and by two referred specimens, comprising an isolated dorsal vertebra and a partial left ischium. Our phylogenetic analysis recovers P. milnerae as a non-coelophysid coelophysoid theropod, representing the first-named unambiguous theropod from the Triassic of the UK. Recently, it has been suggested that Pant-y-ffynnon and other nearby Late Triassic to Early Jurassic fissure fill faunas might have been subjected to insular dwarfism. To test this hypothesis for P. milnerae , we performed an ancestral state reconstruction analysis of body size in early neotheropods. Although our results indicate that a reduced body size is autapomorphic for P. milnerae , some other coelophysoid taxa show a similar size reduction, and there is, therefore, ambiguous evidence to indicate that this species was subjected to dwarfism. Our analyses further indicate that, in contrast with averostran-line neotheropods, which increased in body size during the Triassic, coelophysoids underwent a small body size decrease early in their evolution.
Triassic beds from Argentina and Brazil provide the most relevant fossil record of early dinosauriforms in terms of numerical abundance and taxonomic diversity. This record currently represents the best source to understand the origin and early evolutionary radiation of dinosaurs. In the present paper we offer an updated review focused on the available evidence of Carnian dinosaurs from this continent, but we also discuss the record of Triassic dinosaur precursors and the evolution of Triassic dinosaurs in other continents. It is clear that, aside the agreed taxonomic composition of some particular dinosaurian subclades (e.g., Herrerasauridae, Neotheropoda), there is no consensus about early dinosaur phylogeny, and our paper is not the exception. Recent years witnessed the discovery of several new early dinosaurian taxa, as well as reviews of the taxonomic allocation of several renowned forms such as Lagerpeton, Lewisuchus, Pisanosaurus, and Eoraptor. New analyses demonstrate that evidence supporting the taxonomic referrals of pre-Norian dinosaurs to Theropoda, Sauropodomorpha and Ornithischia are tenuous, at best. Here we present new anatomical observations and comparisons for each of these South American early dinosauriforms with the aim to test previous phylogenetic interpretations. Evidence from South America allows reviewing the phylogenetic relationships of taxa from other continents, including Tawa, Chindesaurus, and Daemonosaurus, which are here suggested to nest within Herrerasauria. Evidence at hand indicates that herrerasaurs were a successful clade of archaic predatory saurischians that inhabited both South and North America, and probably also India and Europe.
Upper Triassic (Carnian) strata from the Candelária Sequence of southern Brazil bear the oldest records of dinosaurs worldwide. In consequence, investigation of the specimens yielded by these fossiliferous units is crucial for a more comprehensive knowledge regarding the origin, early diversification and radiation of dinosaurs. Herein we reassess a dinosaur specimen from Brazil, informally known as the ‘Big Saturnalia’, a supposed large-sized sauropodomorph unearthed at the ‘Cerro da Alemoa’ locality in Santa Maria municipality, Rio Grande do Sul State. However, our phylogenetic analyses and comparisons of the known elements of this specimen resulted in herrerasaurid affinities instead. In fact, it is the largest specimen so far of a herrerasaurid from the Candelária Sequence. It preserves cranial and postcranial elements, with the former being unprecedented for dinosaurs from the Alemoa local fauna. The
morphology of the specimen allows new insights into the anatomy, evolution and distribution of some character states among Herrerasauridae, including but not limited to the typical craniocaudally short caudal dorsal vertebrae. Moreover, the specimen adds to the dinosauromorph diversity in the Carnian units of southern Brazil and its large size provides further support for herrerasaurids as top-tier predators during the dawn of dinosaurs in south-western Pangaea.
Embora o grupo dos dinossauros sauropodomorfos seja amplamente conhecido em virtude dos gigantescos saurópodes, sua origem ainda é pouco compreendida em virtude da escassez de esqueletos completos ou datações precisas. Entretanto, novos achados e datações realizadas em rochas Triássicas do Brasil têm trazido à tona informações valiosas no que tange essa questão. A combinação desses novos dados com técnicas mais avançadas de investigação (e.g. tomografias computadorizadas) vem possibilitando o estabelecimento dos padrões macroevolutivos que direcionaram a evolução inicial do grupo. Através das descobertas realizadas nos leitos Triássicos do Rio Grande do Sul, podemos entender de forma mais refinada como foi que os sauropodomorfos passaram de animais pequenos e pouco abundantes aos maiores animais que já andaram sobre a Terra.
Sacisaurus agudoensis is the only silesaurid known from the Triassic beds of the Santa Maria Supersequence and the correlation of its type locality to the other Triassic deposits of south Brazil has always been controversial. In an attempt to improve this, a handful of dinosaur and cynodont remains found associated to S. agudoensis are here described and compared. The anatomy of the sauropodomorph is more similar to that of Norian forms such as Pantydraco caducus and Unaysaurus tolentinoi than to that of Carnian taxa such as Saturnalia tupiniquim and Pampadromaeus barberenai. The cynodonts recovered based on isolated teeth include a brasilodontid and a Riograndia-like form. This assemblage is consistent with a Norian age, as is also suggested by local stratigraphic correlation, which positions the site in the Caturrita Formation.
The two vertebrate fossil assemblages from the ?Middle Triassic Ntawere Formation have been known since the 1960s, but little new work has been done since the description of novel taxa in the 1960s and 1970s. Three recent field seasons have increased vertebrate diversity in the upper Ntawere assemblage and expanded biostratigraphic connections between the lower and upper Ntawere assemblages and assemblages in fossiliferous basins across southern Pangea. The upper Ntawere contains hybodontoid sharks, ptychoceratodontid lungfish, large- and small-bodied stereospondyl amphibians (Cherninia, ‘Stanocephalosaurus,’ Batrachosuchus, a new taxon), stahleckeriid dicynodonts (Sangusaurus, Zambiasaurus), traversodontid and trirachodontid cynodonts (Luangwa, a new species, Cricodon), and at least four archosauromorphs, including a large loricatan pseudosuchian, a shuvosaurid poposauroid, and silesaurid dinosauriforms (Lutungutali), whereas the lower Ntawere contains the cynodonts Cynognathus and Diademodon and species of the dicynodont Kannemeyeria. The lower and upper Ntawere assemblages have been correlated with the middle and upper subzones of the Cynognathus Assemblage Zone of the Karoo Basin, South Africa, into a network of connections between assemblages in modern day Tanzania, Argentina, Brazil, Namibia, Antarctica, and India. Although lower Ntawere correlations are reinforced by the occurrence of Cynognathus, new observations from the upper Ntawere, in combination with field work in Tanzania, Namibia, and Brazil, have shifted the geographic focus of biostratigraphic connection away from the Karoo later in the Triassic. A recent radiometric date from Argentina from below the horizon correlated with both the Karoo and the lower Ntawere places these, and all higher assemblages, into the Carnian Stage of the Late Triassic.
Citation for this article: Peecook, B. R., J. S. Steyer, N. J. Tabor, and R. M. H. Smith. 2018. Updated geology and vertebrate paleontology of the Triassic Ntawere Formation of northeastern Zambia, with special emphasis on the archosauromorphs; pp. 8–38 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).
Triassic dinosaurs from South Brazil are considered as some of the oldest known worldwide, but their precise correlation to other early dinosaur occurrences have proven difficult. The problem of such long-distance faunal correlations has been exacerbated by reliance on an equivocal tetrapod biostratigraphy and the lack of palynomorphs and other age-bearing microfossils. Here, we present new high-precision U-Pb zircon geochronology (CA-ID-TIMS method) from two classical dinosaur-bearing fossil sites in south Brazil; a weighted mean ²⁰⁶Pb/²³⁸U date of 233.23 ± 0.73 Ma (2σ complete uncertainty) from the Santa Maria Formation and a single zircon ²⁰⁶Pb/²³⁸U date of 225.42 ± 0.37 Ma representing the maximum age of the Caturrita Formation. The new age results, combined with available geochronology from other Triassic dinosauromorph occurrences, allow establishing a chronostratigraphic framework for the Late Triassic appearance of dinosaurs in western Pangea. Within this context, the major macroevolutionary events associated with the rise of dinosaurs can be recognized and their possible links to coeval paleoenvironmental and biotic shifts can be examined.
Pisanosaurus mertii was originally described on the basis of an incomplete skeleton from the early Late Triassic (Carnian) of northern Argentina. It is consistently regarded by most authors as a very basal ornithischian, the sister group of remaining members of the clade. The referral to Ornithischia is based mainly on tooth-bearing bones and tooth morphology. On the other hand, the postcranium is recognized as strikingly plesiomorphic for ornithischians, and even for dinosaurs. The recent description of non-dinosaurian dinosauriforms of the clade Silesauridae having ornithischian-like dentition invites a review of the phylogenetic affinities of Pisanosaurus. In this regard, an overview of the holotype specimen allows a reanalysis of previous anatomical interpretations of this taxon. The phylogenetic analysis presented here suggests that Pisanosaurus may be better interpreted as a member of the non-dinosaurian Silesauridae. It shares with silesaurids reduced denticles on the teeth, teeth fused to maxilla and dentary bone, sacral ribs shared between two sacral vertebrae, lateral side of proximal tibia with a fibular flange, and dorsoventrally flattened pedal ungual phalanges. The present analysis indicates that Pisanosaurus should be removed from the base of the Ornithischia and should no longer be considered the oldest representative of this dinosaurian clade.
Significance
Birds—the fastest growing terrestrial vertebrates—develop unlike all other living reptiles. As part of this postnatal developmental mode, birds possess a low amount of intraspecific variation, and the timing of the origin of this low variation is poorly constrained. By studying well-sampled growth series of nonavian dinosaurs and their closest relatives, we were able to identify this transition within Mesozoic theropod dinosaurs. Surprisingly, the earliest dinosaurs and their close relatives possessed an extremely high amount of variation, higher than either crocodylians or birds. This high variation is the ancestral dinosaurian scheme and was lost in more derived nonavian theropods, including Allosaurus and Tyrannosaurus . High variation could have contributed to the rise of dinosaurian dominance during the Triassic–Jurassic mass extinction.
Surviving through the end-Permian mass extinction, stereospondyls reemerged reaching a widespread distribution during the Early Triassic. A well representative lineage of this clade, Capitosauroidea, became worldwide abundant from Early to Late Triassic, in which their first undoubtful representatives were recovered from Lower Triassic deposits. Here, we describe a new capitosauroid, Tomeia witecki gen. et sp. nov., from the Sanga do Cabral Supersequence (Paraná Basin). Although relatively incomplete, the material presents a particular combination of early and late-diverging capitosauroid characters. Supporting Tomeia witecki as a new capitosauroid, our phylogenetic analysis placed the taxon as part of a clade that comprises only Early Triassic capitosauroids, specifically as the sister-taxon of the madagascarian Edingerella madagascariensis and close to Watsonisuchus spp., from Australia, South Africa and Madagascar. The status of Tomeia witecki as a new capitosauroid from western Gondwana supports a continuous record of the Stereospondyl lineage, since their first appearance during the Middle Permian in this supercontinent. Additionally, the temporal range of the Sanga do Cabral Supersequence during the Early Triassic was specifically reinforced as Olenekian, mainly based on the overall faunal content previously reported to this unit, associated with the known temporal distribution from those taxa phylogenetically closer to Tomeia witecki.
http://zoobank.org/urn:lsid:zoobank.org:pub:7AA9F874-BED5-4A99-B098-B50656E706C1
Dinosauromorpha includes dinosaurs and other much less diverse dinosaur precursors of Triassic age, such as lagerpetids [1]. Joint occurrences of these taxa with dinosaurs are rare but more common during the latest part of that period (Norian-Rhaetian, 228-201 million years ago [mya]) [2, 3]. In contrast, the new lagerpetid and saurischian dinosaur described here were unearthed from one of the oldest rock units with dinosaur fossils worldwide, the Carnian (237-228 mya) Santa Maria Formation of south Brazil [4], a record only matched in age by much more fragmentary remains from Argentina [5]. This is the first time nearly complete dinosaur and non-dinosaur dinosauromorph remains are found together in the same excavation, clearly showing that these animals were contemporaries since the first stages of dinosaur evolution. The new lagerpetid preserves the first skull, scapular and forelimb elements, plus associated vertebrae, known for the group, revealing how dinosaurs acquired several of their typical anatomical traits. Furthermore, a novel phylogenetic analysis shows the new dinosaur as the most basal Sauropodomorpha. Its plesiomorphic teeth, strictly adapted to faunivory, provide crucial data to infer the feeding behavior of the first dinosaurs.
Sauropod dinosaurs present exceptional challenges in understanding their biology because of their exceptional body size. One of these, life history, can be inferred from the histology of their bones. For this purpose, the diverse sauropod assemblage of the Upper Jurassic Tendaguru beds was sampled with a new coring method which provided unprecented access to and insights into sauropod bone histology.
Growth series of humeri and femora as well as long growth records from single bones suggest that all four sauropod taxa are characterized by continued growth after sexual maturity but that growth was determinate. Fibrolamellär bone is dominant in the samples, indicating that the bones of the Tendaguru sauropods grew at rates comparable to those of modern large mammals. The growth pattern of these sauropods thus combines typically reptilian traits with typically mammalian traits. In the details of their bone histology, the Tendaguru sauropod taxa show considerable variation which reflects life history. In addition, Barosaurus exhibits probable sexual dimorphism in bone histology.
Das Verständnis der Biologie der sauropoden Dinosaurier wird durch ihre enorme Körpergröße außerordentlich erschwert. Allerdings kann ein Aspekt, die Lebensgeschichte, anhand der Histologie ihrer Knochen untersucht werden. Zu diesem Zweck wurde die diverse Sauropoden-Vergesellschaftung der oberjurassischen Tendaguru-Schichten beprobt, und zwar mit einer neuartigen Kernbohrmethode, die einen herausragenden Zugang und Einblick in die Knochenhistologie der Sauropoden ermöglichte.
Wachstumsserien von Humeri und Femora sowie umfassende Überlieferungen des Wachstums von Individuen anhand einzelner Knochen machen es wahrscheinlich, daß alle vier Sauropoden-Taxa der Tendaguru-Schichten durch ein auch nach der Geschlechtsreife anhaltendes Wachstum gekennzeichnet waren. Allerdings ging das Wachstum nicht bis zum Tode des Tieres weiter, sondern kam bei einer etwas variablen Maximalgröße zum Stillstand.
Fibrolamellärer Knochen ist der vorherrschende Knochentyp in den Proben, was anzeigt, daß die Tendaguru-Sauropoden mit für Säugetieren typische Raten wuchsen. Die Tendaguru-Sauropoden kombinerten also ein für Reptilien typisches Muster des Wachstums, nämlich nach der Geschlechtsreife anhaltendes Wachstum, mit für Säuger typischen Raten des Wachstums. Die verschiedenen Sauropoden-Taxa zeigen erstaunliche Unterschiede in den Details ihrer Knochenhistologie, die Unterschiede in der Lebensgeschichte belegen. Bei Barosaurus scheint außerdem ein Geschlechtsdimorphismus in der Histologie der Langknochen vorzukommen.
doi:1002/mmng.1999.4860020107
Os sítios fossilíferos de Santa Maria são conhecidos desde o início do século XX, tendo sido aí registrados fósseis de vertebrados, invertebrados e vegetais de idade Neotriássico. Este patrimônio, entretanto, carece de prote-ção por parte do Poder Público, tornando-o sujeito à depredação na maioria dos casos. Neste trabalho são apontados os sítios fossilíferos existentes na região urbana de Santa Maria, sul do Brasil, com vistas a auxiliar na sua prote-ção.
The ontogeny of early-diverging dinosauromorphs is poorly understood because few ontogenetic series from the same species-level taxon are known and what is available has not been extensively documented. The large numbers of skeletal elements of the silesaurid Asilisaurus kongwe recently recovered from Tanzania provide an opportunity to examine the ontogenetic trajectory of the earliest known member of Ornithodira and one of the closest relatives to Dinosauria. We examined the ontogeny of the femur and the histology of a series of long bone elements. We observed bone scar variation in a series of femora (n = 27) of different lengths (73.8–177.2 mm). We hypothesize that most femora follow a similar developmental trajectory; however, we observed sequence polymorphism in the order of appearance and shape of bone scars, and we quantified this polymorphism using ontogenetic sequence analysis (OSA). Additionally, five femora, three tibiae, a fibula, and a humerus were thin-sectioned to examine osteological tissues. No lines of arrested growth (LAGs) are present in any specimen, and there is little histological information about the ontogenetic stage of femora, although none have slowed or ceased growth. The woven-fibered bone present in the cortex of elements sectioned is similar to that of the earliest dinosaurs. This sequence polymorphism provides an alternate hypothesis for the robust/gracile dichotomy found in early dinosaurs often interpreted as sexual dimorphism. The shared femoral features found in Asilisaurus and early dinosaurs suggest that this ontogenetic pattern is plesiomorphic for Dinosauria, and that size is a poor predictor of maturity in early dinosauriforms.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Griffin, C. T., and S. J. Nesbitt. 2016. The femoral ontogeny and long bone histology of the Middle Triassic (?late Anisian) dinosauriform Asilisaurus kongwe and implications for the growth of early dinosaurs. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1111224.
Many recent studies of theropod relationships have been focused on the phylogeny of coelurosaurs and the question of the origin of birds, but the interrelationships and evolution of basal theropods are still poorly understood. Thus, this paper presents a phylogenetic analysis of all theropods, but focuses on the basal members of this clade. The result supports the inclusion of Eoraptor and herrerasaurids in the Theropoda, but differs from other recent studies in two main aspects: (1) The taxa usually grouped as ceratosaurs form two monophyletic clades that represent successively closer outgroups to tetanurans. The more basal of these clades, the Coelophysoidea, comprise the majority of Late Triassic and Early Jurassic theropods. The other clade of basal theropods that are usually included in the Ceratosauria comprises Ceratosaurus, Elaphrosaurus, and abelisaurids. (2) Two monophyletic groups of basal tetanurans are recognized: the Spinosauroidea and the Allosauroidea. In contrast to other recent phylogenetic hypotheses, both clades are united in a monophyletic Carnosauria. The branching pattern of the present cladogram is in general accordance with the stratigraphic occurrence of theropod taxa. Despite the differences in recent analyses, there is a significant level of consensus in theropod phylogeny. At least four different radiations of non-avian theropods can be recognized. These radiations show different patterns in Laurasia and Gondwana, and there are increasing differences between the theropod faunas of the two hemispheres from the Triassic to the Cretaceous.
Approximately 40% of a skeleton including cranial and postcranial remains representing a new genus and species of basal neotheropod dinosaur is described. It was collected from fallen blocks from a sea cliff that exposes Late Triassic and Early Jurassic marine and quasi marine strata on the south Wales coast near the city of Cardiff. Matrix comparisons indicate that the specimen is from the lithological Jurassic part of the sequence, below the first occurrence of the index ammonite Psiloceras planorbis and above the last occurrence of the Rhaetian conodont Chirodella verecunda. Associated fauna of echinoderms and bivalves indicate that the specimen had drifted out to sea, presumably from the nearby Welsh Massif and associated islands (St David’s Archipelago). Its occurrence close to the base of the Blue Lias Formation (Lower Jurassic, Hettangian) makes it the oldest known Jurassic dinosaur and it represents the first dinosaur skeleton from the Jurassic of Wales. A cladistic analysis indicates basal neotheropodan affinities, but the specimen retains plesiomorphic characters which it shares with Tawa and Daemonosaurus.
The early evolution of Ornithodira -the clade including pterosaurs and dinosaurs- is poorly known. Until a decade ago, the basal radiation of Dinosauromorpha, the clade including dinosaurs and birds, was poorly understood because of the poor fossil record restricted to specimens known from the Ladinian Chañares Formation in Argentina. Over the last years the discovery of several non-dinosaurian dinosauromorphs dramatically expanded this record and also demonstrated that this group -previously restricted to de Middle Triassic- survived at least well into the Norian. Although Norian non-dinosaurian dinosauromorphs have been reported from several regions around the world, the only known Norian non-dinosauriform dinosauromorphs -Dromomeron romeri Irmis, Nesbitt, Padian, Smith, Turner, Woody, and Downs and Dromomeron gregorii Nesbitt, Irmis, Parker, Smith, Turner, and Rowe- come from North America. We report here the first record from the Southern Hemisphere of a non-dinosauriform dinosauromorph, Dromomeron gigas sp. nov., from the Norian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovers Dromomeron gigas nested into the monophyletic group Lagerpetidae, and as the sister taxon to Dromomeron romeri. The inclusion of D. gigas within Lagerpetidae suggests that body size increased in this lineage over time, as was previously demonstrated for Dinosauriformes as a whole, and that lagerpetids reached a larger size than previously thought. Finally, the new finding provides new information on the basal radiation of Dinosauromorpha constituting the first record of a Norian association of dinosaurs with non-dinosauriform dinosauromorphs outside North America.
Nesbitt, S.J. and Ezcurra, M.D. 2015. The early fossil record of dinosaurs in North America: A new neotheropod from the base of the Upper Triassic Dockum Group of Texas. Acta Palaeontologica Polonica 60 (X): xxx–xxx. The dinosaur record from the stratigraphically-lowest portions of Upper Triassic deposits of western North America is poor and only consists of a handful of fragmentary hind limb elements. Here we present an articulated segment of the ankle region of a dinosaur that consists of the distal ends of the tibia and fibula and a complete astragalocalcaneum. Additionally, we suggest that an isolated femur and maxilla from the same locality may belong to the same taxon. Using the most comprehensive analysis of early theropod relationships currently available, we determined that the new specimen pertains to a coelophysoid neotheropod (i.e., more closely related to Coelophysis bauri than to Allosaurus fragilis). The stratigraphic position of the locality where the new specimen was discovered is equivalent to the famous Otis Chalk localities and this set of localities likely predates the rest of the Dockum Group and possibly the entirety of the fossiliferous portion of the Chinle Formation on the Colorado Plateau. Therefore, the new specimen represents one of the oldest neotheropods. Accordingly, neotheropods were present at or just after the onset of both the Chinle Formation and Dockum Group deposits.
Herrerasaurids were predatory, obligatorily bipedal dinosaurs recorded in early Late Triassic rocks of South America. It has been suggested recently that the Herrerasauridae constitute a paraphyletic assemblage, but several apomorphic traits in the dorsal, sacral, and caudal vertebrae and the pectoral and pelvic girdles support the monophyly of this group. The relationships of Dinosauria with other members of Ornithodira are considered, supporting the monophyly of the newly recognized clade Dinosauriformes. The Dinosauria, including Herrerasauridae, Saurischia, and Ornithischia, is diagnosed on the basis of six synapomorphic traits. The hypothesis that the Herrerasauridae constitute the sister-group of the remaining dinosaurs is supported here on the basis of four apomorphic traits uniquely shared by Saurischia and Ornithischia. -from Author
Living crocodilians and limbed lepidosaurs have a large caudofemoralis longus muscle passing from tail to femur. Anatomical and electromyographic data support the conclusion that the caudofemoralis is the principal femoral retractor and thus serves as the primary propulsive muscle of the hind limb. Osteological evidence of both origin and insertion indicates that a substantial caudofemoralis longus was present in archosaurs primitively and was retained in the clades Dinosauria and Theropoda. Derived theropods (e.g., ornithomimids, deinonychosaurs, Archaeopteryx and birds) exhibit features that indicate a reduction in caudofemoral musculature, including fewer caudal vertebrae, diminished caudal transverse processes, distal specialization of the tail, and loss of the fourth trochanter. This trend culminates in ornithurine birds, which have greatly reduced tails and either have a minute caudofemoralis longus or lack the muscle entirely.
As derived theropod dinosaurs, birds represent the best living model for reconstructing extinct nonavian theropods. Bipedal, digitigrade locomotion on fully erect limbs is an avian feature inherited from theropod ancestors. However, the primitive saurian mechanisms of balancing the body (with a large tail) and retracting the limb (with the caudofemoralis longus) were abandoned in the course of avian evolution. This strongly suggests that details of the orientation (subhorizontal femur) and movement (primarily knee flexion) of the hind limb in extant birds are more properly viewed as derived, uniquely avian conditions, rather than as retentions of an ancestral dinosaurian pattern. Although many characters often associated with extant birds appeared much earlier in theropod evolution, reconstructing the locomotion of all theropods as completely birdlike ignores a wealth of differences that characterize birds.
Recent discoveries have shown that non-dinosaurian dinosauromorphs were morphologically diverse, glob- ally distributed, and have a stratigraphic range extending into the Upper Triassic. Silesauridae, the sister group to Dinosauria, contains at least seven species. Here we describe Lutungutali sitwensis, gen. et sp. nov., the first silesaurid from the upper portion of the Ntawere Formation of the Luangwa Basin, Zambia. The upper Ntawere Formation has been correlated with subzone C of the Cynognathus Assemblage Zone of the Karoo Basin in South Africa and the Lifua Member of the Manda beds in the Ruhuhu Basin in Tanzania, both of which are considered Anisian in age and the latter has yielded the silesaurid Asilisaurus kongwe. The results of our phylogenetic analysis, including a new pelvic character, allies Lutungutali with Upper Triassic silesaurids such as Silesaurus, Sacisaurus, and Eucoelophysis rather than with the possibly coeval Asilisaurus. The Zambian silesaurid shares a laterally oriented brevis fossa on the ilium and a transversely thin ischium in cross-section with Upper Triassic forms. Silesaurids were more diverse during their early evolution in the Anisian than previously suspected. Lutungutali and Asilisaurus are the two oldest known members of the bird-line archosaurs represented by body fossils. To- gether they show that a subclade of bird-line archosaurs was diversifying soon after its origin, building further support for the rapid diversification of Archosauria in the wake of the Permo-Triassic extinction.
Pretto, F.A., Schultz, C.L., Langer, M.C. 4.02.2015. New dinosaur remains from the Late Triassic of southern Brazil (Candelária Sequence, Hyperodapedon Assemblage Zone). Alcheringa 39, xxx–xxx. ISSN 0311-5518The oldest unequivocal dinosaurian records come from Upper Triassic strata, mostly from Argentina and Brazil. Recent fieldwork in the Brazilian deposits of Ischigualastian age (late Carnian–earliest Norian) have resulted in the collection of a new specimen (UFRGS-PV-1240-T) identified as dinosaurian by the presence of a concave emargination on the ventral surface of the femoral head and a well-developed deltopectoral crest on the humerus, which extends for ca 40% of its estimated proximodistal length. Although fragmentary, the material increases the dinosaurian record from the Late Triassic of Brazil, which is still modest when compared with coeval Argentine strata. Additionally, UFRGS-PV-1240-T augments the dinosaurian diversity at the ‘Sítio Janner’ site, which was until now restricted to the sauropodomorph Pampadromaeus barberenai. The new specimen is larger than most early dinosaurians (except for herrerasaurids), implying that members of the group were already occupying niches otherwise explored by other larger-bodied taxa in the ‘Sítio Janner’ palaeofauna, and Late Triassic palaeoenvironments in general.Flávio A. Pretto [[email protected]
/* */] and Cesar L. Schultz [[email protected]
/* */] Universidade Federal do Rio Grande do Sul, Instituto de Geociências, Setor de Paleovertebrados, Av. Bento Gonçalves, 9500—Bloco J, Prédio 43127, Campus do Vale, Agronomia−Porto Alegre, Rio Grande do Sul, Brazil, CEP 91540-000; Max C. Langer [[email protected]
/* */] Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Departamento de Biologia, Av. Bandeirantes, 3900, CEP 14040-901, Ribeirão Preto, São Paulo, Brazil.
The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic-Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic 'siltstone member' of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic.
Lewisuchus admixtus is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of Argentina, which has been recently considered a member of Silesauridae. Yet, it differs markedly from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a detailed redescription of its holotype allowed the identification of several features of the skeleton previously unrecognized amongst silesaurids. These include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital, foramina associated with cranial nerves X–XII on the caudal region of the prootic–otoccipital, and postaxial neck/trunk vertebrae with craniocaudally expanded neural spines. The presence of a single row of presacral scutes was also confirmed. Some elements previously referred to, or found associated with, the holotype, including a lower jaw, pedal elements and an astragalus, more probably correspond to proterochampsid remains. The anatomical information available for the holotype of L. admixtus was rescored into a new phylogenetic dataset for dinosauromorphs, mostly based on previous works. Lewisuchus admixtus and Pseudolagosuchus major are treated as distinct OTUs because their preserved skeletons mostly lack overlapping parts. The parsimony analysis supports the basal position of L. admixtus within dinosauriforms, prior to the silesaurid–dinosaur split, rather than at the base of Silesauridae. This suggests that a higher number of early dinosauriform clades branched in the Middle and Late Triassic than previously suggested.
Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary.
Among the few vertebrates that survived the mass extinction event documented at the Cretaceous-Paleocene boundary are dyrosaurid crocodylomorphs. Surprisingly, there is little information regarding the bone histology of dyrosaurids, despite their relatively common occurrence in the fossil record, and the potential to gain insight about their biology and lifestyle. We provide the first description of the long bone histology of the dyrosaurids. Specimens were collected from the Maria Farinha Formation, in the Paraíba Basin of northeast Brazil. Thin sections of a right femur and left tibia were made. In the left tibia, the cortex consists of lamellar-zonal bone with five lines of arrested growth (LAGs), spaced ∼300 µm apart. The tibia contains a small to medium-sized organized vascular network of both simple vascular canals and primary osteons that decrease in density periostially. The femur exhibits a similar histological pattern overall but has double-LAGs, and an EFS layer (the latter is rare in living crocodylians). Secondary osteons occur in the deep cortex near and inside the spongiosa as a result of remodeling in both bones. This tissue pattern is fairly common among slow-growing animals. These specimens were a sub-adult and a senescent. Patterns in the distribution of bone consistent with osteosclerosis suggest that these animals probably hada fast-swimming ecology. Although these results are consistent with the histology in anatomically convergent taxa, it will be necessary to make additional sections from the mid-diaphysis in order to assign their ecology.
The Santacruzodon Assemblage Zone was originally defined as a vertebrate fossil assemblage composed basically of non-mammalian cynodonts found in Santa Cruz do Sul and Venâncio Aires municipalities in southern Brazil. This assemblage zone was positioned at the top of the Sequence I, in the Triassic Santa Maria Supersequence, Paraná Basin. However, the Santacruzodon Assemblage Zone does not occur across the entire area of the Santa Maria Supersequence. Based on new paleontological, structural and sedimentological data, we propose the existence of a new third-order sequence (Santa Cruz Sequence) between Sequences I and II in the Santa Maria Supersequence. Satellite image analysis was used to identify regional, NW- and NE-oriented lineaments that limit the occurrence zone. Outcrop data allowed the identification of a regional, angular unconformity that bounds the new sequence. The faunal content allowed the correlation of the new Santa Cruz Sequence with Madagascar’s Isalo II fauna, corresponding to the Ladinian (Middle Triassic). New names were suggested for the sequences in the Santa Maria Supersequence, since the Santa Cruz Sequence was deposited between the former Sequences I and II. This unit was deposited or preserved exclusively on the hanging wall of normal faults, being absent from the adjacent structural blocks.
The beginning of dinosaur evolution is currently known based on a handful of upper Carnian–
lowermost Norian (232–225 Mya) localities situated in a paleolatitudinal belt of approximately 40–50°
S in Argentina, Brazil, Zimbabwe and India. The taxonomic diversity of the oldest known dinosaur-
bearing assemblages, included within the Hyperodapedon Assemblage Zone, is reviewed here. The Brazilian “Teyuwasu barberenarai” is reinterpreted as a nomen dubium representing an indeterminate dinosauriform, the record of cf. Saturnalia from Zimbabwe is considered a basal saurischian and only
one of the Indian specimens described by Huene can be unambiguously assigned to Dinosauria. The
highest early dinosaur species richness sampled is concentrated in southwestern Pangean assemblages
(Argentina and Brazil), with 10 to 11 different described species. By contrast, only one or two species
can be currently recognized from the approximately coeval beds of south–central Pangea (Zimbabwe
and India), which are much less well sampled. The oldest known dinosaur assemblages appear to have
been mostly restricted to subtropical to cool temperate arid areas based on recent paleoclimatological
reconstructions. This observation agrees with the hypothesis that the absence of dinosaurs in the upper
levels of the Ischigualasto Formation of Argentina is related to an increase in humidity in the basin.
Accordingly, climatic factors, with humidity as probably the most important, may have controlled
the paleobiogeographic distribution of the oldest known dinosaur assemblages. The achievement of
a worldwide dinosaur distribution during the latest Triassic may have occurred after a global climate
change, such as the end of the “Carnian Pluvial Event”, and/or the invasion of more tropical humid
climates by dinosaurs.
Bone histology has emerged as the major source of information on life history of dinosaurs, and sauropodomorphs are one of the best sampled clades. The large long bones (humerus and femur) preserve the most complete growth record, which allows inference on life history, thermometabolism, and other aspects of sauropod biology.
Basal sauropodomorphs have fibrolamellar bone interrupted by regularly spaced growth marks, and termination of growth is recorded in an external fundamental system (EFS). However, in the beststudied basal sauropodomorph, _Plateosaurus engelhardti_, growth rate deduced from growth mark counts and termination of growth are highly variable (developmental plasticity). Growth series of many taxa of sauropods also show fibrolamellar bone exclusively but differ in that growth marks appear only late in life, or in most taxa only in the EFS. Growth rate and final size are taxon specific, not variable, and genetically predetermined.
As indicated by their highly vascularized fibrolamellar bone (but also by estimates from rare growth marks and estimates from local bone tissue apposition rates), growth rates of sauropods were comparable only to those of large herbivorous mammals and birds, suggesting that sauropods were tachymetabolic endotherms.
Evolution of large body size in sauropods was brought about by an increase in growth rate and evolution of tachymetabolic endothermy, which was only incompletely developed in basal sauropodomorphs. The small- to medium-sized titanosaurs _Phuwiangosaurus_ and _Ampelosaurus_ show a reduced growth rate compared to other neosauropods. The dwarfed island forms _Europasaurus_ and _Magyarosaurus_ evolved their diminutive body size by a decrease in growth rate and, in the case of _Europasaurus_, a shortening of the active phase of growth.
Bones of the prosauropod dinosaur Plateosaurus engelhardti from the Norian localities of Trossingen (Germany) and Frick (Switzerland) were sampled for palaeohistological study. Both localities yielded rich material of adult individuals with body sizes of 4-80-10 m. Altogether 50 bones from c. 27 individuals were sampled using different methods (coring, cross-sectioning, analysis of existing fracture surfaces). The cortex of most bones consists of the laminar fibro-lamellar complex typical for dinosaurs, indicating fast growth rates. The laminar fibro-lamellar complex in Plateosaurus engelhardti is always cyclically interrupted by lines of arrested growth (LAGs). In some bones, the laminar fibro-lamellar complex changed in the exterior cortex to lamellar-zonal bone, grading peripherally into avascular lamellar bone. Thus, growth was clearly determinate in P. engelhardti, but in contrast to all other dinosaur species for which this is known, the final size of fully grown individuals covers a very broad size range (6-5-10 m). Additionally, growth in P. engelhardti may have been influenced by environmental conditions, as suggested by irregular growth cycle thickness and differences in growth rates. Both reflect a more reptilian growth pattern than is known from any other dinosaur, agreeing with the basal phylogenetic position of P. engelhardti. Nevertheless, in Plateosaurus the foundations for very fast growth and the evolution of gigantism in sauropods are already in place.
Dinosaurs arose in the early Triassic in the aftermath of the greatest mass extinction ever and became hugely successful in the Mesozoic. Their initial diversification is a classic example of a large-scale macroevolutionary change. Diversifications at such deep-time scales can now be dissected, modelled and tested. New fossils suggest that dinosaurs originated early in the Middle Triassic, during the recovery of life from the devastating Permo-Triassic mass extinction. Improvements in stratigraphic dating and a new suite of morphometric and comparative evolutionary numerical methods now allow a forensic dissection of one of the greatest turnovers in the history of life. Such studies mark a move from the narrative to the analytical in macroevolutionary research, and they allow us to begin to answer the proposal of George Gaylord Simpson, to explore adaptive radiations using numerical methods.
Two recent studies have independently recovered Pisanosaurus mertii – long thought to represent the oldest known member of Ornithischia – within Silesauridae. These finds are expanded upon here, as are the implications of this hypothesis. Based upon these finds, it now appears that Ornithischia was absent in the Triassic Period entirely, which constitutes a major incongruence between the fossil record and current phylogenetic hypotheses, particularly the traditional model of dinosaur interrelationships in which Ornithischia and Saurischia are sister-taxa. It has been suggested previously that Ornithischia was simply a rare component of Late Triassic faunas, or that perhaps the clade’s ecology or geographic distribution were not conducive to producing a fossil record. Here I propose that phylogeny could hold the solution to this problem. I examine how an alternative position for Ornithischia – nested either within Theropoda or Sauropodomorpha – could be the reason behind their later appearance and relative rarity in the Early Jurassic. An Early Jurassic origin of Ornithischia would force us to consider that the anatomical similarities between ornithischians and Early Jurassic taxa might not be convergences, and to broaden the current datasets of early dinosaurs to test these ideas.
The fossil record of non-mammaliaform
probainognathian cynodonts is outstanding in the Late Triassic
rocks of Brazil and Argentina. Approximately 15 genera
are known, providing unique insights in the study of the
major skeletal transformations prior to the mammalian condition.
Globally, the diversity of probainognathians is possibly
under-represented, as the discovery of small- to very
small-sized taxa based on relatively well-preserved specimens
is rare. Several species, for example much of the Laurasian
record, are based on isolated teeth and jaw fragments. Here,
we describe a new probainognathian from the Late Carnian
Hyperodapedon Assemblage Zone of the Santa Maria Formation,
south Brazil. Alemoatherium huebneri gen. et sp. nov. is
based on a left lower jaw with almost complete dentition
that exhibits a combination of features not seen in any other
known probainognathian. Its slender lower jaw, anterodorsally
bent process of the dentary, high number of lower incisors,
reduced canine, triconodont-like postcanine teeth with
mesiolingual and distolingual cingular cusps are all features
that support the inclusion of A. huebneri as a member of the
Prozostrodontia clade. This new find highlights the conspicuous
probainognathian cynodont fossil record in southern
Brazil, with a plethora of forms near the mammalian origin.
FIGURE 9. Photographs of dorsal vertebrae 9 – 11 in right lateral view (a) and the centrum of the 12 th dorsal vertebra (b) in cranial view. Abbreviations: d 9 – d 11, dorsal vertebrae 9 to 11. Scale bar = 2.5 cm.
Lesothosaurus diagnosticus from the upper Elliot Formation of South Africa and Lesotho (?Hettangian-Sinemurian) is an important early representative of Ornithischia. In previous studies it has been recovered in several positions on the ornithischian tree including as the earliest known member of Thyreophora, the earliest known member of Neornithischia and as a member of an even a more basal ornithischian lineage, one that diverged before these major groups appeared. Given this taxon's important position as one of the few well-known early ornithischians, it is surprising that details of much of its anatomy remain unpublished. A second non-heterodontosaurid ornithischian taxon, also from the upper Elliot Formation, Stormbergia dangershoeki, has also been recovered as the earliest known member of Neornithischia; however, the validity of this taxon has been challenged. Hence, a reassessment of the taxonomic statuses and systematic positions of L. diagnosticus and S. dangershoeki within Ornithischia is required as an important step in the investigation of the early evolution of this group. A comprehensive redescription of the post-cranial material of L. diagnosticus and a re-evaluation of other 'fabrosaur' material (including the hypodigm of S. dangershoeki) was carried out to provide new information on the anatomy of these taxa and to better resolve the relationships at the base of the ornithischian tree. This study has found that the material of L. diagnosticus and S. dangershoeki almost certainly represents the same taxon and that the apparent differences between these genera is probably a product of ontogentic (rather than taxonomic) differences. A revision of the phylogenetic relationships of L. diagnosticus (when synonymized with S. dangershoeki) recovers it as the basal most member of Neornithischia.
Version 1.5 of the computer program TNT completely integrates landmark data into phylogenetic analysis. Landmark data consist of coordinates (in two or three dimensions) for the terminal taxa; TNT reconstructs shapes for the internal nodes such that the difference between ancestor and descendant shapes for all tree branches sums up to a minimum; this sum is used as tree score. Landmark data can be analysed alone or in combination with standard characters; all the applicable commands and options in TNT can be used transparently after reading a landmark data set. The program continues implementing all the types of analyses in former versions, including discrete and continuous characters (which can now be read at any scale, and automatically rescaled by TNT). Using algorithms described in this paper, searches for landmark data can be made tens to hundreds of times faster than it was possible before (from T to 3T times faster, where T is the number of taxa), thus making phylogenetic analysis of landmarks feasible even on standard personal computers.
We redescribe the holotype of the saurischian dinosaur Staurikosaurus pricei Colbert, 1970 from Late Triassic Santa Maria Formation (southern Brazil), following additional preparation that revealed new anatomical features. A revised diagnosis is proposed and the published synapomorphies for Dinosauria and less inclusive clades (e.g. Saurischia) are evaluated for this species. Some characters previously identified as present in the holotype, including the intramandibular joint, hyposphene-hypantrum articulations in dorsal vertebrae, and a cranial trochanter and trochanteric shelf on the femur, cannot be confirmed due to poor preservation or are absent in the available material. In addition, postcranial characters support a close relationship between S. pricei and Herrerasaurus ischigualastensis Reig, 1963 (Late Triassic, Argentina), forming the clade Herrerasauridae. Several pelvic and vertebral characters support the placement of S. pricei as a saurischian dinosaur. Within Saurischia, characters observed in the holotype, including the anatomy of the dentition and caudal vertebrae, support theropod affinities. However, the absence of some characters observed in the clades Theropoda and Sauropodomorpha suggests that S. pricei is not a member of Eusaurischia. Most morphological characters discussed in previous phylogenetic studies cannot be assessed for S. pricei because of the incompleteness of the holotype and only known specimen. The phylogenetic position of S. pricei is constrained by that of its sister taxon H. ischigualastensis, which is known from much more complete material.
The continental Triassic succession of southernmost Brazil comprises two second-order depositional sequences-the Sanga do Cabral (Early Triassic) and the Santa Maria (Middle to Late Triassic) supersequences. The first one includes ephemeral, low-sinuosity fluvial deposits developed on a low gradient plain. Based on fossil tetrapods, especially procolophonids, an Upper Induan age is estimated for this sequence. Facies association of the Santa Maria Supersequence indicates low-sinuosity fluvial rivers, deltas and lakes. This supersequence can be further subdivided into three third-order sequences (age provided by palaeovertebrate biostratigraphic data) as follows: Santa Maria I (Ladinian), Santa Maria 2 (Carman to Early Norian) and Santa Maria 3 (probably Raethian or Early Jurassic) sequences. The Gondwanides paroxysms I and 11 in the Sierra de la Ventana-Cape Fold Belt are directly related to the development of both supersequences. The source area of the Sanga do Cabral Supersequence was located to the south. It consisted of an uplifted peripheral bulge situated landward of the retro-foreland system, from where older sedimentary rocks were eroded. The source area of the Santa Maria Supersequence was also positioned southwards and related to the uplifted Sul-Rio-Grandense and Uruguayan shields. The Santa Maria Supersequence stratigraphic architecture is comparable to the Triassic rift basins of Western Argentina. Diagenesis, facies and palacontology of the studied succession suggest a dominantly semiarid climate during the Triassic.
Substantial differences in pelvic osteology and soft tissues separate crown group crocodylians (Crocodylia) and birds (Neornithes). A phylogenetic perspective including fossils reveals that these disparities arose in a stepwise pattern along the line to extant birds, with major changes occurring both within and outside Aves. Some character states that preceded the origin of Neornithes are only observable or inferable in extinct taxa. These transitional states are important for recognizing the derived traits of neornithines. Palaeontological and neontological data are vital for reconstructing the sequence of pelvic changes along the line to Neornithes. Soft tissue correlation with osteological structures allows changes in soft tissue anatomy to be traced along a phylogenetic framework, and adds anatomical significance to systematic characters from osteology. Explicitly addressing homologies of bone surfaces reveals many subtleties in pelvic evolution that were previously unrecognized or implicit. I advocate that many anatomical features often treated as independent characters should be interpreted as different character states of the same character. Relatively few pelvic character states are unique to Neornithes. Indeed, many features evolved quite early along the line to Neornithes, blurring the distinction between «avian» and «non-avian» anatomy.
This chapter discusses the preparation and sectioning of specimens for histological study. It covers setting up and maintaining a paleohistology lab; preparing the specimen for research; making thin-section slides; curating the slides produced; restoring the original fossil; caring for equipment and supplies; and staying safe while working with chemical and equipment hazards.
In the ponds of some regions of France, Triturus cristatus and Triturus marmoratus coexist and natural hybrids can be found. In the course of our study examining evolutionary strategies of newts, the method of individual age determination (skeletochronology) was applied. Cross-sections of femurs and phalanges were stained with Ehrlich hematoxylin. Hematoxylinophilic lines considered to be Lines of Arrested Growth (LAG) were observed and carefully counted. Our results on longevity, median age, sexual maturity and growth rate concur with the observations on life span of the two species in allopatric situations. The general morphology of the hybrids, age at sexual maturity and median life span were intermediate between those of the parental species.
ABSTRACT—A principal component analysis (PCA) performed for a set of 24 measurements on 33 femora and 15 measurements on 20 ilia of Silesaurus opolensis from the early Late Triassic of Krasiejów, southern Poland, shows that this sample is highly variable but probably monospecific. Most of the morphological variation is concentrated in the muscle attachments and proportions of bones, which significantly change in both size and position during ontogeny. Despite the small sample size, femora of smaller individuals have less flattened shafts and a more sinusoidal appearance. In many large specimens, proximal parts of muscle tendons are ossified at their attachment site on femora and remain attached to the bone in the largest specimens. The specimens with attached ossifications are interpreted as mature females that were statistically larger than proposed males. It is suggested that ossifications developed in females under calcitonin control. The intrapopulation variability of ilia is high, but less dependant on ontogeny. The population represented by a few specimens from the lower level at Krasiejów may represent a different stage in the evolution of the species than that from the upper horizon.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
A new genus and species of dinosauriform is described from the Triassic of south-west England. The description is based on isolated elements recovered from an assemblage of other dissociated tetrapod remains that include crocodylomorphs, rauisuchiforms and sphenodontians. The key elements in the new taxon are the ilium, astragalus, and the humerus, and these exhibit five synapomorphies of Dinosauria. Three of these, namely a largely to fully perforate acetabulum, the presence of a brevis fossa, and a reduced astragalus with an ascending process, are considered to be particularly relevant. The definition and diagnosis of the Dinosauria are restated and the positions of the new form, herrerasaurs and Eoraptor relative to true dinosaurs are discussed.
Recent discoveries have shown that non-dinosaurian dinosauromorphs were morphologically diverse, globally distributed, and have a stratigraphic range extending into the Upper Triassic. Silesauridae, the sister group to Dinosauria, contains at least seven species. Here we describe Lutungutali sitwensis, gen. et sp. nov., the first silesaurid from the upper portion of the Ntawere Formation of the Luangwa Basin, Zambia. The upper Ntawere Formation has been correlated with subzone C of the Cynognathus Assemblage Zone of the Karoo Basin in South Africa and the Lifua Member of the Manda beds in the Ruhuhu Basin in Tanzania, both of which are considered Anisian in age and the latter has yielded the silesaurid Asilisaurus kongwe. The results of our phylogenetic analysis, including a new pelvic character, allies Lutungutali with Upper Triassic silesaurids such as Silesaurus, Sacisaurus, and Eucoelophysis rather than with the possibly coeval Asilisaurus. The Zambian silesaurid shares a laterally oriented brevis fossa on the ilium and a transversely thin ischium in cross-section with Upper Triassic forms. Silesaurids were more diverse during their early evolution in the Anisian than previously suspected. Lutungutali and Asilisaurus are the two oldest known members of the bird-line archosaurs represented by body fossils. Together they show that a subclade of bird-line archosaurs was diversifying soon after its origin, building further support for the rapid diversification of Archosauria in the wake of the Permo-Triassic extinction.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP