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Ornithischian remains from the Chorrillo Formation (Upper Cretaceous), southern Patagonia, Argentina, and their implications on ornithischian paleobiogeography in the Southern Hemisphere
Abstract
The fossil record of ornithischians in South America is sparse, and they are clearly underrepresented when compared with sauropod dinosaurs. However, recent discoveries indicate that ornithischians were more diversified than thought. The aim of the present contribution is to describe isolated remains belonging to ankylosaurs, and ornithopods, including basal euiguanodontians and hadrosaurs coming from the Chorrillo Formation (upper Campanian–lower Maastrichtian), Santa Cruz province, southern Argentina. The fossil remains of ankylosaurs reported here are the southernmost recorded for the continent. They show a unique combination of plesiomorphic features, indicating that they may belong to a basal ankylosaur. Ankylosaurs and hadrosaurids are thought to have arrived in South America during the latest Cretaceous through Central America. However, a detailed overview of the fossil record of Gondwana indicates that both clades were present and probably diversified along southern continents. This indicates that their presence in South America may be alternatively interpreted as the result of migration from other landmasses, including Africa and Europe, or may even be the result of Jurassic–Early Cretaceous vicariance from their northern counterparts.
... As far as South America is concerned, fossil sites that have yielded hadrosaurid bone remains are currently limited to the southern Argentinian provinces of La Pampa, Rio Negro, Chubut and Santa Cruz (Casamiquela 1964;Bonaparte et al. 1984;Martinelli & Forasiepi 2004;Ju arez-Valieri et al. 2010;Apestegu ıa et al. 2012;Coria 2014Coria , 2016Coria et al. 2012;Gasparini et al. 2015;Cruzado-Caballero & Powell 2017;Ibiricu et al. 2021;Rozadilla et al. 2021) and southern Chile (Magallanes Region; Soto-Acuña et al. 2014). ...
... Distal caudals are very similar but differ in having a more elongate centrum and a shallower ventral excavation. This combination of characters is present in most hadrosaurids (Rozadilla et al. 2021). ...
... Bonapartesarus was considered a lambeosaurine in a preliminary work by Powell (1987) but later re-assessed as a saurolophinine by Cruzado-Caballero & Powell (2017). Conversely, Coria (2009) Rozadilla et al. (2021) proposed that Patagonian hadrosaurids may be representatives of an endemic Gondwanan radiation. ...
Here we describe a new hadrosaurid from the Upper Cretaceous (Campanian-Maastrichtian) Allen Formation of R ıo Negro Province, northwest Patagonia. The new taxon is based on cranial and postcranial elements from subadult and adult specimens. The new taxon may have reached 8-9 m in total body length, and it is diagnosed by a unique combination of characters, including a very low maxilla with respect to the dentary, and a dentary with a prominent and elongate anterior process with a deep groove on its anterior end, among other features. The new taxon is known from well-preserved elements and constitutes one of the most complete hadrosaurids known from South America. Features of the teeth, cranial and postcranial bones of the new taxon overlap with those of other hadrosaurid specimens previously recorded from this continent. This new evidence allows us to recognize that Secernosaurus koerneri, Bonapartesaurus rionegrensis and 'Kritosaurus' australis are valid taxa. The latter can be distinguished from the other South American taxa, as well as from Kritosaurus from North America. Thus, a new generic name is proposed for the species 'Kritosaurus' australis. Phylogenetic analysis recovers a new clade of South American hadrosaurids composed of the new taxon, 'Kritosaurus' australis, Bonapartesaurus and Secernosaurus. The new South American clade is tentatively nested among Kritosaurini and is supported by several traits, including an ilium with a subhorizontal ridge separating the preacetabular notch from the pubic pedicle, a longitudinal ridge on the dorsal surface of the postacetabular process, and a twisted distal end of the postacetabular process. The recovery of a monophyletic clade of South American hadrosaurids indicates that the history of the clade on Gondwanan landmasses is far from well understood, and new discoveries may change the current picture of the taxonomy and phylogenetic relationships of southern duck-billed dinosaurs. http://zoobank.org/urn:lsid:zoobank.org:pub:6C6F0056-9D3A-4097-A10E-2E33C9DB76B9
... The Maastrichtian Chorrillo Formation is the youngest of the units that accumulated during the period of complete continentalization of the basin at this latitude. This unit has been the focus of paleontological studies since the 1940s (Feruglio, 1945;Bonaparte, 1996;Bonaparte et al., 2002), but its paleontological content was not analyzed in some detail until recent years Chimento et al., 2020Chimento et al., , 2021Rozadilla et al., 2021). Moreover, in spite of the paleontological importance of the Chorrillo Formation, there have been no detailed sedimentological studies that would provide insights into the depositional conditions under which it was accumulated. ...
... Afterwards, Chimento et al. (2020Chimento et al. ( , 2021 reported the presence of the gondwanatherian mammal Magallanodon baikashkenke found in roughly coeval beds from Chile (Goin et al., 2020). More recently, Rozadilla et al. (2021) added the occurrence of ankylosaur and hadrosaurid remains from the Chorrillo Formation. In sum, the vertebrate record of the Chorrillo Formation includes indeterminate teleosts, calyptocephalellid frogs, indeterminate and madtsoiid snakes, chelid turtles, theropod and sauropod eggshells, the titanosaur sauropod Nullotitan glaciaris, and ornithischians including indeterminate ankylosaurs, the elasmarian ornithopod Isasicursor santacrucensis and hadrosaurs. ...
... Furthermore, present findings demonstrate that the Chorrillo Formation has yielded one of the most taxonomically diverse ornithischian faunas from South America, with ankylosaurus, hadrosaurs, and two different kinds of basal euiguanodontians including Isasicursor santacrucensis Rozadilla et al., 2021, this study). This ornithischian abundance and diversity supports previous claims suggesting that they were far more abundant and diverse in southern Patagonia, Antarctica and Australasia (Novas and Cambiaso, 2004;Novas et al., 2004;Novas, 2009;Agnolín et al., 2010;Rozadilla et al., 2016Rozadilla et al., , 2021 than in northern parts of South America and Africa. ...
The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.
... The identification of the teeth from the micro-remains site studied here, allowed to determine the presence of certain taxa (such as theropod and ankylosaur-probably nodosaur-dinosaurs and peirosaurid crocodyliforms), whose skeletal remains are not yet recorded. The faunal assemblage of dinosaurs is, in part, taxonomically similar to that recently recovered in the Chorrillo Formation [9,10], which is dominated by ornithischians. ...
... At that time, the Antarctic Peninsula was connected to South America, allowing faunistic interchange between both continents, with the nodosaurids probably arriving to South America around the late Campanian, through Central America [e.g. 10,81]. The dinosaur assemblages including ankylosaur remains from Chorrillo [9,10] and Cerro Fortaleza formations are the first records filling the gap between Antarctica and North Patagonia, supporting an ankylosaurid common fauna. ...
... 10,81]. The dinosaur assemblages including ankylosaur remains from Chorrillo [9,10] and Cerro Fortaleza formations are the first records filling the gap between Antarctica and North Patagonia, supporting an ankylosaurid common fauna. ...
The Late Cretaceous dinosaur record in southern South America has been improved recently; particularly with findings from Chorrillo and Cerro Fortaleza formations, both bearing ankylosaur remains, a clade that was not previously recorded in the Austral Basin. The dinosaur fauna of the type locality of Cerro Fortaleza Formation is known from -and biased to- large-sized sauropod remains and a single described taxon, the titanosaur Dreadnoughtus schrani. Here, we report the taxonomic composition of a site preserving thirteen isolated teeth and several osteoderms belonging to three dinosaur clades (Abelisauridae, Titanosauria, and Nodosauridae), and at least one clade of notosuchian crocodyliforms (Peirosauridae). They come from sediments positioned at the mid-section of the Cerro Fortaleza Formation, which is Campanian-Maastrichtian in age, adding valuable information to the abundance and biodiversity of this Cretaceous ecosystem. Since non-titanosaur dinosaur bones are almost absent in the locality, the teeth presented here provide a window onto the archosaur biodiversity of the Late Cretaceous in southern Patagonia. The nodosaurid tooth and small armor ossicles represent the first record of ankylosaurs for this stratigraphic unit. The peirosaurid material also represents the most austral record of the clade in South America.
... In this context, the Chorrillo Formation (Feruglio, 1945) provides an important source of information for analyzing a Maastrichtian terrestrial community. Recent studies have revealed a highly diverse fossil assemblage preserved in this formation, containing snails, fish, anurans, turtles, snakes, sauropods, theropods, ornithischians, and mammals, as well as palynomorphs, woods and leaf impressions (e.g., Novas et al., 2019;Moyano-Paz et al., 2022a;Rozadilla et al., 2021;Chimento et al., 2020Chimento et al., , 2021Aranciaga Rolando et al., 2022). The diversity of clades in the Chorrillo Formation not only provides a unique opportunity for analyzing a Maastrichtian paleoflora, but also enables comparison of patterns in changes between floral and zoological diversity in the unit. ...
... These fine-grained deposits alternate with lenticular sandstone bodies interpreted as the infill of high sinuosity meandering fluvial channels and crevasse-splay deposits ( Fig. 1C; Moyano-Paz et al., 2022a). The Chorrillo Formation was also named as "Dinosaur-bearing strata" by Feruglio (1945) because of the abundance of fossil vertebrates within these deposits (e.g., Novas et al., 2019;Moyano-Paz et al., 2022a;Rozadilla et al., 2021;Fig. 2). ...
Few latest Cretaceous fossil floras are known for South America, and in particular for the Austral-Magallanes Basin. Recent studies carried out in the Chorrillo Formation (Maastrichtian) revealed a diverse array of fossil elements, including continental invertebrates, vertebrates, palynomorphs, fossil woods and leaf impressions. In this work, we describe the megafloristic elements identified in the unit from two fossiliferous levels, along with a palynological sample obtained from one such level. The first Mesozoic Nymphaeaceae (water lilies) remains for Argentina are reported, consisting of fragmentary leaves and seeds of a minute Nuphar-grade plant. Several leaf impressions referred to dicotiledonean and monocotiledonean morphotypes are also described. Additionally, microscopic remains reveal a diverse palynological assemblage containing terrestrial and aquatic ferns, conifers and angiosperms. A community that inhabited low energy, probably paludal, freshwater environments was identified, based on the sedimentology of the bearing strata such as the presence of hydromorphic paleosols and poorly decomposed organic matter suggesting poor drainage and eventual reducing and anoxic conditions, as well as the presence of Salviniaceae (water ferns), Marsileaceae (water-clovers), Nymphaeaceae and Zygnemataceae (freshwater conjugate algaes). Palynological elements suggest similarities with Campanian to Paleocene Patagonian units, mostly located in the Austral-Magallanes, Cañadón Asfalto and Golfo the San Jorge basins. Finally, aquatic communities from other Maastrichtian units (e.g. La Colonia and Lago Colhué Huapi formations) are compared with the Chorrillo Formation presented herein, suggesting similarities in functional groups even though taxa involved differ partially
... Although ankylosaur diversity is quite well known, this is mostly true for materials from Laurasian landmasses, whereas ankylosaur remains from Gondwana are still elusive (Novas 2009;Pereda-Suberbiola et al. 2015;Maidment et al. 2021;Rozadilla et al. 2021;Soto-Acuña et al. 2021;and references therein). Currently, the few species known from Gondwana are 'Antarctopelta oliveroi' (Late Cretaceous of Antarctica; Salgado & Gasparini 2006; discussed by Arbour & Currie 2016, and considered by them a nomen dubium), 'Minmi paravertebra' (Early Cretaceous of Australia; Molnar 1980; also considered a nomen dubium by Arbour & Currie 2016), Kunbarrasaurus ieversi (Early Cretaceous of Australia; Leahey et al. 2015; previously identified as Minmi sp. by Molnar 1996), Spicomellus afer (Middle Jurassic of Morocco; Maidment et al. 2021) and Stegouros elegassen (Upper Cretaceous of Chile; Soto-Acuña et al. 2021). ...
The most representative ankylosaurian remains from Argentina have been found in sediments of the Allen Formation (Campanian–Maastrichtian) in Salitral Moreno, Río Negro Province. Several authors have discussed the identity and history of these remains. In this study, we review all published material along with some new remains in order to summarize all the knowledge about these ankylosaurs. Previously published material includes a tooth, dorsal and anterior caudal vertebrae, a femur and several osteoderms. The new remains include synsacral and caudal elements, a partial femur and osteoderms. The anatomy of the tooth, the synsacrum, the mid-caudal vertebra, the femur and the osteoderms, and the histology of the post-cervical osteoderms, support a nodosaurid identification, as proposed in previous descriptions of the Salitral Moreno material. Patagopelta cristata gen. et sp. nov. is a new nodosaurid ankylosaur characterized by the presence of unique cervical half-ring and femoral anatomies, including high-crested lateral osteoderms in the half rings and a strongly developed muscular crest in the anterior surface of the femur. The ∼2 m body length estimated for Patagopelta is very small for an ankylosaur, comparable with the dwarf nodosaurid Struthiosaurus. We recovered Patagopelta within Nodosaurinae, related to nodosaurids from the ‘mid’-Cretaceous of North America, contrasting the previous topologies that related this material with Panoplosaurini (Late Cretaceous North American nodosaurids). These results support a palaeobiogeographical context in which the nodosaurids from Salitral Moreno, Argentina, are part of the allochthonous fauna that migrated into South America during the late Campanian as part of the First American Biotic Interchange.
https://zoobank.org/urn:lsid:zoobank.org:pub:FBA24443-F365-49FD-A959-10D2848C2400
... On the other hand, further work will help to fill the extensive gap between the early thyreophorans and the Cretaceous remains from South America. Recent research is reflected in an increase in the thyreophoran fossil record from South America, with all its implications for thyreophoran evolution [11][12][13][14]69,70 ; and this paper). The discovery of Jakapil not only supports the presence of a new Gondwanan lineage of early thyreophoran dinosaurs that persisted in Gondwana for a long time, but has also brought to light the importance of the Gondwanan fossil record in the study of the origin and evolution of dinosaurs (and other clades). ...
The early evolution of thyreophoran dinosaurs is thought to have occurred primarily in northern continents since most evidence comes from the Lower and Middle Jurassic of Europe and North America. The diversification into stegosaurs and ankylosaurs is obscured by a patchy fossil record comprising only a handful of fragmentary fossils, most with uncertain phylogenetic affinities. Here we report the discovery of a new armoured dinosaur from the early Late Cretaceous of Argentina, recovered phylogenetically using various datasets either as a basal thyreophoran or a stem ankylosaur, closely related to Scelidosaurus. It bears unusual anatomical features showing that several traits traditionally associated with the heavy Cretaceous thyreophorans did not occur universally. Jakapil kaniukura gen. et sp. nov. is the first definitive thyreophoran species from the Argentinian Patagonia. Unlike most thyreophorans, it seems to show a bipedal stance, as in Scutellosaurus. Jakapil also shows that early thyreophorans had a much broader geographic distribution than previously thought. It is a member of an ancient basal thyreophoran lineage that survived until the Late Cretaceous in South America.
The Snow Hill Island Formation (SHIF; late Campanian-early Maastrichtian) crops out in the northeast of the Antarctic Peninsula and constitutes the basal part of the late Campanian-early Maastrichtian sedimentary succession of the James Ross Basin (NG Sequence). Its major exposures occur at the James Ross and Vega islands. Several fossil-bearing localities have been identifi ed in the SHIF providing a valuable fauna of invertebrates and vertebrates, and fl ora. Our study focuses on the vertebrate fauna recovered at Gamma and Cape Lamb members of the SHIF. The marine vertebrate assemblages include chondrichthyans, actinopterygians, and marine reptiles (elasmosaurid plesiosaurs and mosasaurs). A diverse terrestrial vertebrate as semblage has been reported being characterized by dinosaurs (sauropod, elasmarian ornithopods, nodosaurid ankylosaur, and a paravian theropod), pterosaurs and birds. Most SHIF dinosaurs share close affi nities with penecontemporaneous taxa from southern South America, indicating that at least some continental vertebrates could disperse between southern South America and Antarctica during the Late Cretaceous. The Snow Hill Island Formation provides the most diverse Late Cretaceous marine and continental faunas from Antarctica. The present study summarizes previous and new vertebrate fi ndings with the best actualized stratigraphical framework, providing a more complete fauna association and analyzing further perspectives.
We describe and incorporate fragmentary new cranial and postcranial materials of hadrosaurid ornithopods into the non-avian dinosaur assemblage of the Upper Cretaceous (Coniacian–Maastrichtian) Lago Colhué Huapi Formation of central Patagonia, south-central Chubut Province, Argentina. The fossils come from the upper part of the formation, probably from a stratigraphic interval close to the Cretaceous/Paleogene boundary. The materials belong to at least two ontogenetically distinct individuals that are assigned to Hadrosauridae due to their possession of anatomical features that characterize this derived ornithopod group. Sedimentological inferences reveal that the paleoenvironment of these hadrosaurids was characterized by high-sinuosity, meandering-type fluvial channels, whereas palynological data suggest the existence of low-energy freshwater bodies in the floodplains of these rivers and a warm and humid paleoclimate. The deposition of the upper part of the Lago Colhué Huapi Formation was probably influenced by the Patagonian Atlantic marine transgression, which may have played an important role in the distribution of this sedimentary unit. The new Lago Colhué Huapi Formation hadrosaurid specimens constitute the most stratigraphically recent records of this clade from Argentina. The materials contribute to the interpretation of Upper Cretaceous hadrosaurid paleobiogeography in Patagonian basins; moreover, sedimentological and palynological data suggest that paleoenvironmental conditions may have exerted an important influence on South American hadrosaur distribution, supporting hypotheses of ornithopod faunal turnover during the Late Cretaceous of central Patagonia. Finally, the new remains add to the generally depauperate record of Late Cretaceous ornithopods in the Southern Hemisphere.
The Late Cretaceous saw distinctly endemic dinosaur faunas evolve in the northern and southern hemispheres. The Laurasian continents of North America and Asia were dominated by hadrosaurid and ceratopsian ornithischians, with tyrannosaurs as apex predators. In Gondwanan communities, including Africa, South America, India and Madagascar, titanosaurian sauropods dominated as herbivores and abelisaurids as predators. These patterns are thought to be driven by the breakup of Pangaea and formation of seaways limiting dispersal. Here, we report a new lambeosaurine hadrosaurid, Ajnabia odysseus gen. et sp. nov., from the upper Maastrichtian of Morocco, North Africa, the first Gondwanan representative of a clade formerly thought to be restricted to Laurasia. The new animal shows features unique to Hadrosauridae and specifically Lambeosaurinae. Phylogenetic analysis recovers it within Arenysaurini, a clade of lambeosaurines previously known only in Europe. Biogeographic modelling shows that lambeosaurines dispersed from Asia to Europe, then to Africa. Given the existence of large, persistent seaways isolating Africa and Europe from other continents, and the absence of the extensive, bidirectional interchange characterizing land bridges, these patterns suggest dispersals across marine barriers, similar to those seen in Cenozoic mammals, reptiles, and amphibians. Dispersal across marine barriers also occurs in other hadrosaurid lineages and titanosaurian sauropods, suggesting oceanic dispersal played a key role in structuring Mesozoic terrestrial dinosaur faunas.
The Litopterna is an extinct clade of endemic South American ungulates that range from Paleocene up to late Pleistocene times. Because of their unique anatomy, litopterns are of uncertain phylogenetic affinities. However, some nineteenth century authors, considered litopterns as related to perissodactyl ungulates, a hypothesis recently sustained by molecular data. The aim of the present contribution is to include litopterns and other South American related taxa in a comprehensive phylogenetic analysis together with several extant and extinct basal perissodactyl ungulates. The analysis resulted in the nesting of litopterns and kin as successive stem-clades of crown Perissodactyla. Further, litopterns are not phylogenetically grouped with any North American basal ungulate, in agreement with some previous proposals. Presence of pan-perissodactyls in South America and India indicates that southern continents probably played an important role in the early evolution of hoofed mammals.
This work attempts at providing a revised framework for ornithischian phylogeny, based on an exhaustive data compilation of already published analyses, a critical re-evaluation of osteological characters and an in-depth checking of characters scoring to fix mistakes that have accumulated in previous analyses; we have also included recently described basal ornithischians, marginocephalians and ornithopods. ‘Heterodontosaurids’ are recovered as a paraphyletic group of basal Marginocephalia that progressively lead to the dome-headed ‘true’ pachycephalosaurs. ‘Heterodontosaurids’ consequently fall within Pachycephalosauria sensu Sereno, 1998. The reconfiguration of basal cerapodan relationships pulls the origins of ornithopods to the earliest stages of the Jurassic. Based on the present analysis, we also discuss ornithopod relationships, with a particular focus on basal Iguanodontia. Tenontosaurus is found as the basalmost iguanodontian. The monophyly of Rhabdodontomorpha in a position more derived than Tenontosaurus is supported by the present analysis.
The geological and paleoenvironmental setting and the vertebrate taxonomy of the fossiliferous, Cenomanian-age deltaic sediments in eastern Morocco, generally referred to as the “Kem Kem beds”, are reviewed. These strata are recognized here as the Kem Kem Group, which is composed of the lower Gara Sbaa and upper Douira formations. Both formations have yielded a similar fossil vertebrate assemblage of predominantly isolated elements pertaining to cartilaginous and bony fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs, as well as invertebrate, plant, and trace fossils. These fossils, now in collections around the world, are reviewed and tabulated. The Kem Kem vertebrate fauna is biased toward largebodied carnivores including at least four large-bodied non-avian theropods (an abelisaurid, Spinosaurus, Carcharodontosaurus, and Deltadromeus), several large-bodied pterosaurs, and several large crocodyliforms.
No comparable modern terrestrial ecosystem exists with similar bias toward large-bodied carnivores. The Kem Kem vertebrate assemblage, currently the best documented association just prior to the onset of the Cenomanian-Turonian marine transgression, captures the taxonomic diversity of a widespread northern African fauna better than any other contemporary assemblage from elsewhere in Africa.
Keywords
Africa, Cretaceous, dinosaur, Gara Sbaa Formation, Douira Formation, paleoenvironment, vertebrate
The first fossil remains of vertebrates, invertebrates, plants and palynomorphs of the Chorrillo Formation (Austral Basin), about 30km to the SW of the town of El Calafate (Province of Santa Cruz), are described. Fossils include the elasmarian (basal Iguanodontia) Isasicursor santacrucensis gen. et sp. nov., the large titanosaur Nullotitan glaciaris gen. et sp. nov., both large and small Megaraptoridae indet., and fragments of sauropod and theropod eggshells. The list of vertebrates is also composed by the Neognathae Kookne yeutensis gen. et sp. nov., two isolated caudal vertebrae of Mammalia indet., and isolated teeth of a large mosasaur. Remains of fishes, anurans, turtles, and snakes are represented by fragmentary material of low taxonomical value, with the exception of remains belonging to Calyptocephalellidae. On the other hand, a remarkable diversity of terrestrial and freshwater gastropods has been documented, as well as fossil woods and palinological assemblages. The Chorrillo Formation continues south, in the Las Chinas River valley, southern Chile, where it is called Dorotea Formation. Both units share in their lower two thirds abundant materials of titanosaurs, whose remains cease to appear in the upper third, registering only elasmarians (Chorrillo Formation) and hadrosaurs (Dorotea Formation). Above both units there are levels with remains of invertebrates and marine reptiles. It is striking that the dinosaurs of the lower two thirds of the Chorrillo and Dorotea formations are represented by large basal titanosaurs and Megaraptoridae coelurosaurs, being the Saltasaurinae and Aeolosaurinae sauropods and Abelisauridae theropods totally absent. In contrast, these taxa are dominant components in sedimentary units of central and northern Patagonia (e.g., Allen, Los Alamitos, La Colonia formations). Such differences could reflect, in part, a greater antiquity (i.e., late Campanian-early Maastrichtian) for the Chorrillo fossils, or, more probably, different environmental conditions. Thus, knowledge of the biota of the southern tip of Patagonia is expanded, particularly those temporarily close to the K-Pg boundary.
Globally, non-hadrosauroid iguanodontians (‘basal iguanodontians’) reached their acme in terms of diversity during the Early Cretaceous. However, Gondwanan representatives of this clade are rare and are represented in Australia only by the enigmatic Muttaburrasaurus langdoni (upper Albian; Mackunda Formation). Here, we describe a new iguanodontian, Fostoria dhimbangunmal, gen. et sp. nov., from the Cenomanian Griman Creek Formation at Lightning Ridge, New South Wales, Australia. The holotype and referred specimens, preserved entirely in opal, pertain to at least four individuals from a monodominant bone bed excavated from an underground opal mine. This deposit constitutes the first ornithopod-dominated bone bed from Australia. Elements from most parts of the body are represented, including the first partial skull of a dinosaur recovered from New South Wales. The new taxon is identified by a number of autapomorphies that include, but are not restricted to, a stepped lateral margin of the frontal in dorsal view and a stout protuberance on the anterolateral corner of the frontal. Phylogenetic analysis based on a recently published data set recovers Fostoria as the sister taxon to a clade of Gondwanan iguanodontians that includes Anabisetia saldiviai, Talenkauen santacrucensis, and Muttaburrasaurus langdoni. The new taxon and M. langdoni represent the sole iguanodontians known from the eastern margin of the epeiric Eromanga Sea, whereas the group is conspicuously absent from the contemporaneous ornithopod-dominated ecosystems of the Australian-Antarctic rift valley in Victoria.
Talenkauen santacrucensis represents one of the most complete South American ornithopods yet discovered. This dinosaur comes from the Mata Amarilla Formation (Turonian) of Santa Cruz Province, Argentina. The aim of this contribution is to present a detailed description of Talenkauen santacrucensis. Features of the cervical series of Talenkauen, which are shared with other elasmarians, indicate that these dinosaurs have a proportionally longer neck than other ornithopods. These traits were convergently acquired by several saurischian clades. Additionally, some features, including an ornamented labial surface of the mandibular teeth and a sigmoidal greater trochanter of femur, are traits shared by most elasmarians, and may prove to be synapomorphies of this clade. A phylogenetic analysis recovers most Cretaceous Gondwanan ornithopods in the clade Elasmaria. This analysis indicates that Elasmaria was distributed more widely geographically and temporally than previously thought.
The Flat Rocks locality in the Wonthaggi Formation (Strzelecki Group) of the Gippsland Basin, southeastern Australia, hosts fossils of a late Barremian vertebrate fauna that inhabited the ancient rift between Australia and Antarctica. Known from its dentary, Qantassaurus intrepidus Rich and Vickers-Rich, 1999 has been the only dinosaur named from this locality. However, the plethora of vertebrate fossils collected from Flat Rocks suggests that further dinosaurs await discovery. From this locality, we name a new small-bodied ornithopod, Galleonosaurus dorisae n. gen. n. sp. from craniodental remains. Five ornithopodan genera are now named from Victoria. Galleonosaurus dorisae n. gen. n. sp. is known from five maxillae, from which the first description of jaw growth in an Australian dinosaur is provided. The holotype of Galleonosaurus dorisae n. gen. n. sp. is the most complete dinosaur maxilla known from Victoria. Micro-CT imagery of the holotype reveals the complex internal anatomy of the neurovascular tract and antorbital fossa. We confirm that Q. intrepidus is uniquely characterized by a deep foreshortened dentary. Two dentaries originally referred to Q. intrepidus are reassigned to Q. ? intrepidus and a further maxilla is referred to cf. Atlascopcosaurus loadsi Rich and Rich, 1989. A further ornithopod dentary morphotype is identified, more elongate than those of Q. intrepidus and Q. ? intrepidus and with three more tooth positions. This dentary might pertain to Galleonosaurus dorisae n. gen. n. sp. Phylogenetic analysis recovered Cretaceous Victorian and Argentinian nonstyracosternan ornithopods within the exclusively Gondwanan clade Elasmaria. However, the large-bodied taxon Muttaburrasaurus langdoni Bartholomai and Molnar, 1981 is hypothesised as a basal iguanodontian with closer affinities to dryomorphans than to rhabdodontids.
UUID: http://zoobank.org/4af87bb4-b687-42f3-9622-aa806a6b4116
During the Early Cretaceous, dinosaur communities of the Australian-Antarctic rift system (Eumeralla and Wonthaggi formations) cropping out in Victoria were apparently dominated by a diverse small-bodied 'basal ornithopod' fauna. Further north, in Queensland (Winton and Mackunda formations), poorly-represented small-bodied ornithopods coexisted with large-bodied iguanodontians. Our understanding of the ornithopod diversity from the region between the Australian-Antarctic rift and Queensland, represented by Lightning Ridge in central-northern New South Wales (Griman Creek Formation), has been superficial. Here, we re-investigate the ornithopod diversity at Lightning Ridge based on new craniodental remains. Our findings indicate a diverse ornithopod fauna consisting of two-to-three small-bodied non-iguanodontian ornithopods (including Weewarrasaurus pobeni gen. et sp. nov.), at least one indeterminate iguanodontian, and a possible ankylopollexian. These results support those of previous studies that favour a general abundance of small-bodied basal ornithopods in Early to mid-Cretaceous high-latitude localities of southeastern Australia. Although these localities are not necessarily time-equivalent, increasing evidence indicates that Lightning Ridge formed a 'meeting point' between the basal ornithopod-dominated localities in Victoria and the sauropod-iguanodontian faunas in Queensland to the north. Subjects Paleontology, Taxonomy
The first African dinosaur to be discovered, Paranthodon africanus was found in 1845 in the Lower Cretaceous of South Africa. Taxonomically assigned to numerous groups since discovery, in 1981 it was described as a stegosaur, a group of armoured ornithischian dinosaurs characterised by bizarre plates and spines extending from the neck to the tail. This assignment has been subsequently accepted. The type material consists of a premaxilla, maxilla, a nasal, and a vertebra, and contains no synapomorphies of Stegosauria. Several features of the maxilla and dentition are reminiscent of Ankylosauria, the sister-taxon to Stegosauria, and the premaxilla appears superficially similar to that of some ornithopods. The vertebral material has never been described, and since the last description of the specimen, there have been numerous discoveries of thyreophoran material potentially pertinent to establishing the taxonomic assignment of the specimen. An investigation of the taxonomic and systematic position of Paranthodon is therefore warranted. This study provides a detailed re-description, including the first description of the vertebra. Numerous phylogenetic analyses demonstrate that the systematic position of Paranthodon is highly labile and subject to change depending on which exemplifier for the clade Stegosauria is used. The results indicate that the use of a basal exemplifier may not result in the correct phylogenetic position of a taxon being recovered if the taxon displays character states more derived than those of the basal exemplifier, and we recommend the use, minimally, of one basal and one derived exemplifier per clade. Paranthodon is most robustly recovered as a stegosaur in our analyses, meaning it is one of the youngest and southernmost stegosaurs.
A new small-bodied ornithopod dinosaur, Diluvicursor pickeringi , gen. et sp. nov., is named from the lower Albian of the Eumeralla Formation in southeastern Australia and helps shed new light on the anatomy and diversity of Gondwanan ornithopods. Comprising an almost complete tail and partial lower right hindlimb, the holotype (NMV P221080) was deposited as a carcass or body-part in a log-filled scour near the base of a deep, high-energy river that incised a faunally rich, substantially forested riverine floodplain within the Australian–Antarctic rift graben. The deposit is termed the ‘Eric the Red West Sandstone.’ The holotype, interpreted as an older juvenile ∼1.2 m in total length, appears to have endured antemortem trauma to the pes. A referred, isolated posterior caudal vertebra (NMV P229456) from the holotype locality, suggests D. pickeringi grew to at least 2.3 m in length. D. pickeringi is characterised by 10 potential autapomorphies, among which dorsoventrally low neural arches and transversely broad caudal ribs on the anterior-most caudal vertebrae are a visually defining combination of features. These features suggest D. pickeringi had robust anterior caudal musculature and strong locomotor abilities. Another isolated anterior caudal vertebra (NMV P228342) from the same deposit, suggests that the fossil assemblage hosts at least two ornithopod taxa. D. pickeringi and two stratigraphically younger, indeterminate Eumeralla Formation ornithopods from Dinosaur Cove, NMV P185992/P185993 and NMV P186047, are closely related. However, the tail of D. pickeringi is far shorter than that of NMV P185992/P185993 and its pes more robust than that of NMV P186047. Preliminary cladistic analysis, utilising three existing datasets, failed to resolve D. pickeringi beyond a large polytomy of Ornithopoda. However, qualitative assessment of shared anatomical features suggest that the Eumeralla Formation ornithopods, South American Anabisetia saldiviai and Gasparinisaura cincosaltensis , Afro-Laurasian dryosaurids and possibly Antarctic Morrosaurus antarcticus share a close phylogenetic progenitor. Future phylogenetic analysis with improved data on Australian ornithopods will help to test these suggested affinities.
A stegosaurian "dermal plate" was reported from the Kallamedu Formation (Upper Cretaceous, Maastrichtian) of southern India. However, histologically the dermal plates of stegosaurs, typified by Stegosaurus (Upper Jurassic, USA), have a thin outer cortex enclosing very cancellous bone having large vascular spaces. The Kallamedu fragment of eroded compact bone has no cortex and is probably from a sauropod dinosaur. Bones found in situ in this formation typically disintegrate very quickly pon exposure to the air, but this bone is well preserved, although worn. It was found as float in a stream bed, indicating that there is a stratum upstream with well-preserved bones, that is still to be discovered in the Maastrichtian of southern India. Stegosaur remains from the underlying Coniacian (Upper Cretaceous) of southern India represents the most recent osteological record of a stegosaur. However, stegosaurs may have continued into the Maastrichtian (Lameta Formation) of western India as indicated by a pes print of Deltapodus sp., a stegosaurian ichnotaxon. © 2017 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
The Guará Formation (Paraná Basin, southern Brazil) is an Upper Jurassic unit that yielded a dinosaur ichnoassemblage composed of theropod, ornithopod, and sauropod tracks. A new set of footprints is described herein and its major features are heteropody, paraxony, and both manual and pedal tetradactyly, among others. Using ichnological, osteological, and stratigraphic approaches, we interpret these tracks as produced by an ankylosaur dinosaur. The record of these armored dinosaurs in South America is scarce and restricted to the Cretaceous units of Argentina, Bolivia, and Brazil. Therefore, the presence of these tracks in the Guará Formation provides the oldest evidence of ankylosaurs in western Gondwana and the first uncontroversial record of this group in Brazil. In addition, a comparison between the Guará Formation fossil record and other Kimmeridgian– Tithonian dinosaur-bearing units worldwide indicates that more efforts are needed to better understand the geographical distribution of Late Jurassic dinosaurs.
Disarticulated and incomplete remains from a new diminutive ornithopod are described. They come from the Cameros Basin in the north of Spain and were collected from the red clays of the Castrillo de la Reina Formation, ranging from Upper Barremian to Lower Aptian. The new ornithopod described here is slender and one of the smallest ever reported. An up-to-date phylogenetic analysis recovers this taxon as a basal iguanodontian. Its unique combination of characters makes it more derived than slender ornithopods like Hyphilophodon and Gasparinisaura, and bring very interesting insights into the basal iguanodontian phylogeny. Though possessing a minimum of three premaxillary teeth, this taxon also bears an extensor ilio-tibialis groove on the distal part of its femur. Moreover, its dentary and maxillary teeth are unique, remarkably similar to those regarded as having a "rhabdomorphan" affinity. This unknown taxon is suggested to be a stem taxon within Rhabdodontidae, a successful clade of basal iguanodonts from the Late Cretaceous of Europe. The Gondwanan ornithopods share the strongest affinities with this family, and we confirm Muttaburrasaurus as a sister taxon of the Rhabdodontidae within a newly defined clade, the Rhabdodontomorpha.
The holotype individual of the small-bodied ornithopod dinosaur, Leaellynasaura amicagraphica from
Dinosaur Cove in the Lower Cretaceous of Victoria, southeastern Australia, traditionally comprises the holotype,
a left-side cheek fragment of a juvenile (MV P185991), and three other specimens: a cranial table (P185990) and a partial postcranium (P185992, P185993), discovered at the same site and at about the same time as the holotype. The latter three specimens have significantly contributed to the systematics of Leaellynasauria amicagraphica and anatomical arguments for its status as a “dinosaur of darkness,” pre-adapted to existence in the Antarctic polar circle. The original attribution of the scattered material (cranial table and partial postcranium) to the Leaellynasaura amicagraphica holotype was based on the assumption that the sizes of the specimens were comparable, and the interpretation of the facies in which these associated fossils accumulated as a quiet-water deposit, such as an oxbow lake, billabong or pond. The inferred low-energy depositional conditions were used to suggest that associated material, other than that attributable to the holotype, was unlikely to be present in the facies hosting the holotype individual. However, a detailed sedimentological study supporting the interpretation of a quiet-water deposit hosting the Dinosaur Cove material is lacking, and the presence of a larger second partial ornithopod postcranium (P186047) in the same deposit, seems contradictory to arguments that all of the scattered associated skeletal specimens from this site are attributable to the Leaellynasaura amicagraphica holotype.
Our revised sedimentological investigation indicates that all vertebrate remains from the Leaellynasaura
amicagraphica holotype locality were deposited under active hydraulic flow on a migrating point bar in a
meandering river. We term the host deposit the “Tunnel Sandstone.” As a result of this new interpretation, we
regard the total vertebrate fossil assemblage from this site as time-averaged, and interpret the associated ornithopod remains as an allochthonous accumulation of up to four separate individuals, some potentially with unknown taxonomic affinities. Without unequivocal anatomical evidence of skeletal association, we regard the traditional attribution of the scattered cranial table and partial postcranium to the Leaellynasaura amicagraphica holotype as inadequately supported. We consider the referral of any specimen to Leaellynasaura amicagraphica should contain features that are compliant with those features on the holotype cheek fragment or other conclusively referred specimens.
The fauna has many similarities to Late Cretaceous faunas of the Hell Creek and Lance Creek formations of the northern US. This probably reflects both the relative case of terrestrial dispersal during the Mesozoic and physical similarities between the three formations. All three formations appear to be predominantly fluviatile deposits laid down on flood plains near sea level. All three collection areas were roughly the same distance from the palaeoequator.-from Authors
The systematic relationships of taxa traditionally referred to as ‘basal ornithopods’ or ‘hypsilophodontids’ remain poorly resolved since it was discovered that these taxa are not a monophyletic group, but rather a paraphyletic set of neornithischian taxa. Thus, even as the known diversity of these taxa has dramatically increased over the past two decades, our knowledge of their placement relative to each other and the major ornithischian subclades remained incomplete. This study employs the largest phylogenetic dataset yet compiled to assess basal ornithischian relationships (255 characters for 65 species level terminal taxa). The resulting strict consensus tree is the most well-resolved, stratigraphically consistent hypothesis of basal ornithischian relationships yet hypothesized. The only non-iguanodontian ornithopod (=basal ornithopod) recovered in this analysis is
Hypsilophodon foxii
. The majority of former ‘hypsilophodontid’ taxa are recovered within a single clade (Parksosauridae) that is situated as the sister-taxon to Cerapoda. The Parksosauridae is divided between two subclades, the Orodrominae and the Thescelosaurinae. This study does not recover a clade consisting of the Asian taxa
Changchunsaurus
,
Haya
, and
Jeholosaurus
(=Jeholosauridae). Rather, the former two taxa are recovered as basal members of Thescelosaurinae, while the latter taxon is recovered in a clade with
Yueosaurus
near the base of Neornithischia.The endemic South American clade Elasmaria is recovered within the Thescelosaurinae as the sister taxon to
Thescelosaurus
. This study supports the origination of Dinosauria and the early diversification of Ornithischia within Gondwana. Neornithischia first arose in Africa by the Early Jurassic before dispersing to Asia before the late Middle Jurassic, where much of the diversification among non-cerapodan neornithischians occurred. Under the simplest scenario the Parksosauridae originated in North America, with at least two later dispersals to Asia and one to South America. However, when ghost lineages are considered, an alternate dispersal hypothesis has thescelosaurines dispersing from Asia into South America (via North America) during the Early Cretaceous, then back into North America in the latest Cretaceous. The latter hypothesis may explain the dominance of orodromine taxa prior to the Maastrichtian in North America and the sudden appearance and wide distribution of thescelosaurines in North America beginning in the early Maastrichtian. While the diversity of parksosaurids has greatly increased over the last fifteen years, a ghost lineage of over 40 myr is present between the base of Parksosauridae and Cerapoda, indicating that much of the early history and diversity of this clade is yet to be discovered. This new phylogenetic hypothesis provides a comprehensive framework for testing further hypotheses regarding evolutionary patterns and processes within Ornithischia.
Since the second half of the 20th Century, the study of fossil tracks in South America has steadily increased. A large number of tetrapod ichnogenera is currently known mainly from Argentina, Bolivia and Brazil. In this study, we present a new record consisting of several trackways that we refer to cf. Tetrapodosaurus, representing the first explicit mention of the ichnogenus in South America. These tracks come from the lacustrine to transitional El Molino Formation, deposited in Maastrichtian-Danian times, at the locality of Niñu-Mayu, near Sucre, Bolivia. These tracks preserve a quite similar manual morphology to that of Tetrapodosaurus borealis and minor differences in its pedal prints. Tetrapodosaurus is a typical ichnogenus of the northern hemisphere and commonly assigned to an ankylosaurian trackmaker. Tracks assigned to ankylosaurs were already reported from other sites of Bolivia, Brazil and possibly Argentina; the new finding further improves our understanding of the ankylosaurian record from South America. A detailed morphological analysis allows us to make an accurate trackmaker identification and footprints are attributed to a member of the ankylosaurian family, the Nodosauridae. The trackways from Niñu-Mayu also have paleobiological implications. Manus prints are complete, pes prints generally lack the proximal region of the pes, the sole pad, expulsion rims are proximally placed in pes prints and the trackway parameters are highly variable, suggesting registration influenced by certain buoyancy of the trackmakers.
The fossil record of dinosaurs from India provides a highly significant contribution to understanding the origin and evolution of dinosaurs and their paleobiogeographic significance. As India rifted from Gondwana and drifted northwards during the age of dinosaurs, the mobile episode in Indian geology provides a unique opportunity to study the diversity of dinosaurs in time and space. The dinosaurs from the Gondwana and post-Gondwana sediments of India have been collected and studied since their discovery in the 1920s, but the full range of their significance and evolutionary history remained fragmentary. After the independence of India, a renaissance arose in the study of dinosaurs at the Indian Statistical Institute (ISI) under the leadership of Pamela Robinson, as more and more dinosaur skeletons were discovered from different localities. This exploration by ISI paleontologists represented a pivotal moment in the history of vertebrate paleontology in India and became a starting point for a remarkable increase in our knowledge of Triassic, Jurassic, and Cretaceous dinosaur faunas. It inspired a new generation of students working under Ashok Sahni’s direction at Panjab University to engage in the Cretaceous research. This paper offers an updated and comprehensive review of the anatomy, systematics, and evolution of Indian dinosaurs within historical, paleobiogeographic, and paleoecologic contexts. The occurrence of Indian dinosaurs is currently restricted to central and southern India, and the record extends across all three Mesozoic periods. It is generally regarded that dinosaurs originated in the Late Triassic Period in Argentina, about 230 million years ago. However, Alwalkeria, a theropod discovered in the Lower Maleri Formation of India, was contemporaneous with the oldest Argentinean dinosaurs. Similarly, Barapasaurus from the Early Jurassic Kota Formation is considered as one of the oldest, gigantic sauropod dinosaurs with a quadrupedal pose. The Late Triassic and Early Jurassic dinosaurs of India are diverse and document their early radiation. With the breakup of Gondwana, India began to disintegrate and drifted northwards, carrying its dinosaur fauna like a passenger ship, until it collided with the Oman-Kohistan-Ladakh Arc in the Late Cretaceous, forming a biotic corridor to Africa and Europe. The Late Cretaceous dinosaurs from the Lameta Formation, consisting of several species of titanosaurs and abelisaurs, provide intimate documentation of the last ‘geologic minutes’ before their extinction. Along with dinosaur bones, the largest titanosaurid hatchery is known from the Lameta Formation, extending for more than 1,000 km. Most egg clutches contain about 10 to 12 spherical eggs ranging in diameter from 15 to 20 cm. Surprisingly, these eggs were empty, showing no signs of embryos, perhaps indicating hatching failure during some environmental crisis. At the Cretaceous-Paleogene boundary, India was ground zero for two catastrophic events—the Shiva impact and Deccan volcanism—both linked to dinosaur extinction. The combination of twin asteroid impacts (Chicxulub and Shiva), with prolonged Deccan volcanism created an unprecedented and ultimately catastrophic environmental crisis across the globe, triggering the end-Cretaceous mass extinction.
The Middle Jurassic Kota Formation of the Pranhita-Godavari Valley in peninsular India is well known for its vertebrate fauna comprising fishes, sphenodontians, iguanian lizards, cryptodire turtle, crocodilians, pterosaurs, sauropod dinosaurs and early mammals. However, no theropod and undoubted ornithischian dinosaur remains have been reported from the Jurassic of India until now. Here we describe the first theropod dinosaur teeth representing five morphotypes of Dromaeosauridae, one Richardoestesia-like form, and one Theropoda indet. The ornithischian dinosaur teeth are described under five morphotypes of Ornithischia indet. The new dinosaur fauna improves the diversity of the Jurassic vertebrate fauna of India significantly. It also improves the impoversished Jurassic record of dromaeosaurid and primitive ornithischian dinosaurs of the Gondwana. At higher taxonomic levels, the Kota fauna demonstrates close compositional similarities with Laurasian Jurassic faunas, such as the Middle Jurassic fauna of England, and limited Gondwanan affinities, which may suggest closer connection with the Laurasian continents and existence of some biogeographic partitioning within the Gondwana in the Jurassic.
A layer of keratinous scutes encased the skull of Scelidosaurus. The neurocranium and the associated principal sensory systems of this dinosaur are described. The cranial musculature is reconstructed and a subsequent functional analysis suggests that jaw motion was orthal, allowing pulping of vegetation and some high-angle shearing between opposing teeth. Wishboning of the lower jaw was enabled by transverse displacement of the quadrates, and the long-axis mandibular torsion that occurred during the chewing cycle was permitted by flexibility at the dentary symphysis. Limb proportions and pectoral and pelvic musculature reconstructions suggest that Scelidosaurus was a facultative quadruped of ‘average’ locomotor ability. It retained some anatomical features indicative of a bipedal-cursorial ancestry. Hindlimb motion was oblique-to-parasagittal to accommodate the girth of the abdomen. Scelidosaurus used a combination of costal and abdominally driven aspiration. The hypothesis that respiration was an ‘evolutionary driver’ of opisthopuby in all dinosaurs is overly simplistic. A critical assessment of datasets used to analyse the systematics of ornithischians (and thyreophoran subclades) has led to a revised dataset that positions Scelidosaurus as a stem ankylosaur, rather than a stem thyreophoran. The value of phylogenetic definitions is reconsidered in the light of the new thyreophoran cladogram.
Eurypoda, the major radiation of armoured dinosaurs, comprises the ankylosaurs and their sister group, the stegosaurs. As the earliest-branching major clade of ornithischian dinosaurs, the evolutionary history of Eurypoda is significant for understanding both the palaeobiology of bird-hipped dinosaurs and the composition of middle Mesozoic ecosystems. Eurypodans were diverse and abundant throughout the Late Jurassic and Cretaceous in Laurasia; in contrast, their remains are extremely rare in Gondwana. Herein, we describe a new genus and species of stegosaur from the Middle Jurassic of Morocco, Adratiklit boulahfa. Adratiklit is the first eurypodan from north Africa and the oldest definitive stegosaur from anywhere in the world. The genus is more closely related to the European stegosaurs Dacentrurus and Miragaia than it is to the southern African taxa Kentrosaurus and Paranthodon. Statistically significant correlations between the number of dinosaur-bearing formations, dinosaur-bearing collections, and eurypodan occurrences in Gondwana indicates that their fossil record is biased by both geological and anthropogenic factors. Tantalizing but fragmentary remains and trackways suggest that eurypodan diversity in Gondwana may have been as rich as that of Laurasia, and the prospects for future discoveries of new genera across Gondwana are therefore very good.
The outcrops of the Lajas Formation at the Covunco section expose a succession that contrasts with the classical localities for the unit, due to subaerial exposure confirmed by a vertebrate track documented in the basal section of the unit. The stacking pattern, facies distribution, subaerial exposure in the previously interpreted prodelta facies and the documented unconformity in the middle part of the unit are incompatible with the continuous deltaic evolution suggested previously for the studied locality. Regardless of the absence of a precise age for the succession, the regional literature of subsurface data, the paleontological remains and the intra-Callovian unconformity at the top of the unit, suggest a Bathonian (late?) up to Early Callovian age for the unit in the area. It is younger than the classical deltaic deposits extensively studied in outcrops or subsurface to the north-east and south of the Huincul High and confirms the diachronism between the south and north of the high and it sheds light on the late evolution of the unit. The younger age in Covunco section is compatible with the suggested age differences. The sedimentary record in the logged section was divided in three parts: a lower section containing marginal-marine deposits with tidal features like sigmoidal structures and muddy and coaly drapes, marine trace fossils (Asteriacites quinquefolius) and bioclastic deposits that are transitionally overlying the Los Molles Formation and end with fluvial deposits containing the vertebrate track. It is documentedat the top of an interval with3D dunes. The track is tridactyl and assigned to cf. Deltapodus. It constitutes the oldest record in Gondwana of a track attributed to tyreophorans. Isaberrysaura (Neoornitischia/Tyreophora) is the candidate producer, taking into account the stratigraphic and geographical proximity of the underlying Los Molles Formation that contains the skeletal remains. The track has some morphological features that suggest a possible swimming-wading behaviour as was previously proposed for stegosaurs. Overlying the fluvial interval, the middle section is composed of transgressive deposits containing abundant bioclastic conglomerates and channels with trunks. The upper section was deposited after a facies dislocation overlying a previously interpreted unconformity that suggests an abrupt change in the sedimentary record, containing pebbly sandstones intercalated with sandstone beds with Skolithos resembling “pipe rocks”. They are replaced upward by fine-grained sandstones with HCS, suggesting open marine conditions over the storm wave base level and a deepening upward trend. Then, the succession becomes sandier and highly bioturbated with abundant Rhizocorallium specimens and some lenticular channels with lateral accretion and abundant symmetrical wave ripple levels developed during a regressive phase.
A new ornithopod dinosaur, the medium-sized Sektensaurus sanjuanboscoi gen. et sp nov. from the Coniacian–Maastricthian strata of the Lago Colhué Huapi Formation, Golfo San Jorge Basin, Patagonia, is here described. The specimen consists of disarticulated postcranial bones belonging to a single individual. It is diagnosed by an unique association of five autapomorphies on the dorsal and sacral vertebrae and the humerus. A cladistics analysis indicates that Sektensaurus was an iguanodontian ornithopod which inhabited Patagonia during the Late Cretaceous. Likewise, Sektensaurus is the first non-hadrosaurid, probably elasmarian, ornithopod recorded from the uppermost Cretaceous of central Patagonia. In a broad context, this discovery increases the anatomical knowledge of ornithopods and adds new data on the composition of dinosaur faunas that lived in Patagonia close to the Antarctica, at the end of the Cretaceous.
Dermal armor was collected from the Pranhita-Godavari Valley of south-central India. It was found in situ by shallow trenching in a red clay bed 2 m below the prominent limestone marker unit of the Lower Kota Formation (Lower Jurassic, Sinemurian-Pliensbachian). The plates of this important material cannot currently be located, so they are re-described based on published and unpublished photos. There are no symmetrical median scutes or small ossicles as occur in basal thyreophorans (Scutellosaurus, Scelidosaurus, Emausaurus; Lower Jurassic). The numerous small Kota lateral body scutes are more similar to the lateral body scutes of “polacanthid” ankylosaurs than to those of basal thyreophorans. The Kota cervical half ring is very similar to the second cervical half ring of Scelidosaurus and the first and second rings of an Argentinian Upper Cretaceous nodosaurid. The remaining types of Kota plates do not occur in basal thyreophorans but are present in ankylosaurs. The large Kota lateral plates match those of Upper Cretaceous nodosaurids from Kansas, viz., those of Hierosaurus for the very large symmetrical plates and Niobrarasaurus for the large asymmetrical plates. The latter are also matched by some plates of the basal ankylosaurid Gastonia (Lower Cretaceous, USA) and, apart from the presence of a prominent spine, by other plates. The Kota large flat plates with a small cone-like spine have bases that are either irregular or hexagonal. The former were probably part of a dorsal or pelvic shield, being separated by small ossicles from other irregular flat plates as in ankylosaurs. The hexagonal plates were definitely part of such a shield, being adjacent to other hexagonal plates that were either smaller or about the same size. It is concluded that the Kota dermal plates represent an ankylosaur. The earliest fossil records for the Ankylosauria, Stegosauria and Eurypoda are all Middle Jurassic whereas the Kota ankylosaur is from the middle Early Jurassic, indicating a probable early Early Jurassic origin for these groups. © 2019 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.
Ankylosaurian fossils are usually standard elements of Cretaceous continental vertebrate localities; however, bone-yielding horizons including more than one individual are extremely rare. Here, we present a unique assemblage of 12 partial, articulated or associated ankylosaurian skeletons and thousands of isolated bones and teeth discovered from the Santonian Iharkút vertebrate locality, western Hungary. Collected from an area of 600 m2 and from a single bone bed, this material is one of the richest ankylosaurian accumulation worldwide. The 12 skeletons are not monospecific but mostly based on the pelvic armour composition: six of them are from Hungarosaurus, two are referred to Struthiosaurus and four can be assigned to Nodosauridae indet. Sedimentological and taphonomical examinations revealed a single mass mortality event as the cause of the death and accumulation of these quadruped animals that are described here. The ankylosaur assemblage from Iharkút suggests at least a temporarily gregarious behaviour of these animals and also shows that Hungarosaurus and Struthiosaurus might live in the same moist habitat or at least preferred relatively close environments.
During their long evolutionary history, neornithischian dinosaurs diverged into several clades with distinctive adaptations. However, the early evolution within Neornithischia and the resolution of the phylogenetic relationships of taxa situated near the base of the clade remain problematic. This is especially true for those taxa traditionally placed at the base of Ornithopoda, either as ‘hypsilophodontids’ or at the base of the diverse clade Iguanodontia. Recent studies are improving our understanding of the anatomy and relationships of these taxa, with discoveries of several new non-ankylopollexian ornithopods from South America and Europe providing key insights into early ornithopod evolution and palaeobiogeography. Here, we describe a new basal ornithopod, Burianosaurus augustai gen. et sp. nov., based on a well-preserved femur from the upper Cenomanian strata (Korycany Beds of the Peruc-Korycany Formation) of the Czech Republic. The new taxon is diagnosed by a unique suite of characters and represents the only occurrence of a Cenomanian non-avian dinosaur in Central Europe north of the Alpine Tethyan areas. Histological examination of the type specimen reveals the presence of a loosely packed Haversian system which suggests relatively mature bone from a possible young adult. Phylogenetic analyses of two different data sets, selected to test the placement of B. augustai in various parts of the neornithischian tree, reconstruct B. augustai as a basal ornithopod, firmly nested outside Ankylopollexia. These results also support a diverse Elasmaria as a basal clade within Ornithopoda and reconstruct Hypsilophodon outside Ornithopoda as the sister taxon to Cerapoda. However, the relationships of ‘hypsilophodontids’ within Neornithischia remain contentious.
http://zoobank.org/urn:lsid:zoobank.org:pub:D28A9FB8-A253-4032-8710-4F51668A1E4F
Ceratopsia includes some of the best-known ornithischian dinosaurs. Many species are erected based on cranial elements alone, and the postcranial skeletons are either missing or undescribed in many taxa. Here we provide the first detailed postcranial description of Yinlong downsi based on the holotype and eight other well-preserved skeletons. Yinlong downsi from the early Late Jurassic Shishugou Formation of the Wucaiwan area, Xinjiang, China, represents one of the most basal ceratopsians. The detailed study of the postcranial skeleton reveals one feature unique to it among ceratopsians: a blade-like prepubic process of the pubis with an elongate notch near its ventral margin. The postcranial material of Yinlong shares some unique features with that of the ornithischian Stenopelix valdensis from the Early Cretaceous of Germany, and provides further evidence that the latter is a basal ceratopsian. A comprehensive phylogenetic analysis of basal ornithischians was built based on 72 taxa and 380 characters. Most of the characters are illustrated for the first time in order to clarify character states. The new ornithischian phylogeny confirms that Yinlong belongs to Chaoyangsauridae. Chaoyangsaurids and Psittacosaurus form a monophyletic group that is sister to all other ceratopsians. The new phylogeny also supports Stenopelix valdensis as a basal ceratopsian, and Mosaiceratops to be close to Coronosauria. Additionally, the new phylogeny agrees with other recent analyses that place heterodontosaurids as the most basal ornithischians rather than with marginocephalians. Furthermore, Isaberrysaura, which has been hypothesized to be a basal ornithopod, is recovered as one of the most basal stegosaurs for the first time. The former ‘hypsilophodontid’ taxa are recovered within Ornithopoda rather than outside Cerapoda, and Jeholosauridae is shown to be valid in this analysis.
In the last decades, the Argentinian ornithopod record has been increased with new and diverse bone remains found along all the Upper Cretaceous. Most of them are very incomplete and represent taxa of different size. As result, the studies about the palaeobiodiversity of the Ornithopoda clade in South America are complex. In this paper, new postcranial remains of an indeterminate medium-sized ornithopod from the Santonian Bajo de la Carpa Formation (Rincón de los Sauces, Neuquén province) are presented. They present diagnostic features of the Ornithopoda clade, and several characters that relate them with other Argentinian ornithopods, especially with the medium-sized members of the Elasmaria clade sensu Calvo et al. (2007) (Macrogryphosaurus and Talenkauen). The postcranial material allows to identificate at least three different ontogenetic stages: adult, subadult more immature and subadult. These bones are the first record of Ornithopoda for the Bajo de la Carpa Formation and one of the very scarce Santonian records of this clade in South America. The diversity of the Late Cretaceous South American ornithopods presents two clear distributions: the Cenomanian-Santonian was characterized by small and medium euiguanodonts and elasmarian; and the Campanian-Maastrichtian by the medium sized elasmarian and large sized hadrosaurids.
The Gondwanan hadrosaurid dinosaur record is relatively poorly known and very complicated. A new hadrosaurid, Bonapartesaurus rionegrensis, gen. et sp. nov., from the late Campanian–early Maastrichtian of the Salitral Moreno site, Argentina, is characterized by the following combination of characters: the ratio between the height of the neural spines and that of the centrum of the sacral vertebrae greater than 3.5; neural spines of the anterior section of the caudal vertebrae extremely long and evenly expanding distally; a preacetabular process of the ilium slightly deflected ventrally, with the angle greater than 150°; the ratio between the maximum dorsoventral depth of the posterior end of the preacetabular process and the dorsoventral distance from the pubic peduncle to the dorsal margin of the ilium less than 0.50; the ratio between the dorsoventral height and anteroposterior length of the iliac blade 0.8 or greater; asymmetrical lateral profile of the supraacetabular process; the posterior portion of the postacetabular process markedly thicker mediolaterally as a result of the dorsomedial twist of the postacetabular process; an anteriorly expanded cnemial crest restricted to the proximal end of the tibia; and articular surface of the astragalus for the internal malleolus of the tibia moderately expanded medially, articulating with only part of the ventral surface of the tibial internal malleolus. Our phylogenetic analysis indicates that Bonapartesaurus is located within the Tribe Saurolophini. Paleobiogeographically, its presence suggests at least two saurolophine dispersal events from North America, one toward South America and another toward Asia, no later than the late Campanian.
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Citation for this article: Cruzado-Caballero, P., and J. Powell. 2017. Bonapartesaurus rionegrensis, a new hadrosaurine dinosaur from South America: implications for phylogenetic and biogeographic relations with North America. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1289381.
Ornithopods are the least known dinosaurs within the Upper Cretaceous record of Argentina. For this reason every new record is very important to know their evolution in South America. Here, we describe a new remain of an indeterminate ornithopod recovered in the Petrobrasaurus quarry of the Puesto Hernández area, northeastern Neuquén province (Argentina), late Coniacian–early Santonian in age. MAU-Pv-PH-458 is the northernmost bone record of an ornithopod in Argentina. This is a fragmentary neural arch from the middle section of the dorsal series of similar size to Macrogryphosaurus gondwanicus. MAU-Pv-PH-458 has typical ornithopod characters such as a lateromedial narrow neural spine and transverse processes dorsoposteriorly to posteriorly oriented. It shares with Macrogryphosaurus the presence of a deep channel between the bases of the postzygapophysis, which is a continuation of the channel that separates the postzygapophyses in posterior view. MAU-Pv-PH-458 increases the ornithopod record from the Plottier Formation.
For the first time, skeletal remains of an armoured dinosaur (Ornithischia: Ankylosauria) were found in the red clay bed of the Kota Formation, Pranhita-Godavari Valley, Andhra Pradesh. The bed occurs 2 m below the marker limestone unit of the Kota Formation. The collection includes parts of skull, 30 specimens of body armour, vertebrae and parts of girdle bones. The characteristics of armour plates, skull and teeth indicate that these fossils belong to ankylosauria. The ankylosaurs are less known from the Lower Jurassic period. The detailed studies of the present material are likely to throw light on the evolutionary history of these dinosaurs.