Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira

  title={Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira},
  author={Sterling J. Nesbitt and Christian A. Sidor and Randall B. Irmis and Kenneth D. Angielczyk and Roger M. H. Smith and Linda Akiko Tsuji},
The early evolutionary history of Ornithodira (avian-line archosaurs) has hitherto been documented by incomplete (Lagerpeton) or unusually specialized forms (pterosaurs and Silesaurus). Recently, a variety of Silesaurus-like taxa have been reported from the Triassic period of both Gondwana and Laurasia, but their relationships to each other and to dinosaurs remain a subject of debate. Here we report on a new avian-line archosaur from the early Middle Triassic (Anisian) of Tanzania. Phylogenetic… 
A paraphyletic ‘Silesauridae' as an alternative hypothesis for the initial radiation of ornithischian dinosaurs
Ornithischia changes from an obscure to a well-documented clade in the Triassic and is represented by records from Gondwana and Laurasia and was the first group of dinosaurs to adopt an omnivorous/herbivorous diet.
Phylogenetic reassessment of Pisanosaurus mertii Casamiquela, 1967, a basal dinosauriform from the Late Triassic of Argentina
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.
New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil
A new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil is reported, showing dinosaur plesiomorphies together with some neotheropod traits.
Systematics and evolutionary history of proterosuchian archosauriforms
The results obtained here suggest that the evolutionary history of the archosauriforms during the Early Triassic can be subdivided into a first phase characterized by the short-lived “disaster-clade” Proterosuchidae and a second phase that witnessed the initial morphological and probably palaeoecological diversification of the group.
The systematic relationships and biogeographic history of ornithischian dinosaurs
The resulting strict consensus tree is the most well-resolved, stratigraphically consistent hypothesis of basal ornithischian relationships yet hypothesized and provides a comprehensive framework for testing further hypotheses regarding evolutionary patterns and processes within Ornithischia.
The origins of Dinosauria: much ado about nothing
  • M. Langer
  • Geography, Environmental Science
  • 2014
Research this century has greatly improved our knowledge of the origin and early radiation of dinosaurs. The unearthing of several new dinosaurs and close outgroups from Triassic rocks from various
A New Silesaurid from the Upper Ntawere Formation of Zambia (Middle Triassic) Demonstrates the Rapid Diversification of Silesauridae (Avemetatarsalia, Dinosauriformes)
ABSTRACT Recent discoveries have shown that non-dinosaurian dinosauromorphs were morphologically diverse, globally distributed, and have a stratigraphic range extending into the Upper Triassic.
New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation
The recognition of Gracilisuchidae provides further support for a rapid phylogenetic diversification of crown archosaurs by the Middle Triassic, and falsify previous hypotheses suggesting that T. dabanensis and Y. sangbiensis are not members of the archosaur crown group.
The Late Triassic dinosauromorph Sacisaurus agudoensis (Caturrita Formation; Rio Grande do Sul, Brazil): anatomy and affinities
Abstract Silesauridae is an exclusively Triassic group of dinosauromorphs, knowledge on the diversity of which has increased dramatically in the last few years. Silesaurid relationships are still


Early dinosaurs: A phylogenetic study
A new cladistic analysis of the early dinosaur radiation was performed to assess the relationships among the three major clades (Ornithischia, Sauropodomorpha and Theropoda) and to define the phylogenetic position of the basal members of the group.
  • J. Dzik
  • Environmental Science, Geography
  • 2003
Abstract An accumulation of skeletons of the pre-dinosaur Silesaurus opolensis, gen. et sp. nov. is described from the Keuper (Late Triassic) claystone of Krasiejów in southern Poland. The strata are
A Possible Ctenosauriscid Archosaur from the Middle Triassic Manda Beds of Tanzania
An anterior dorsal vertebra from the Lifua Member of the Manda Beds of Tanzania is described as the holotype of a new taxon, Hypselorhachis mirabilis, similar to other early Middle Triassic archosaurs with elongate neural spines, including Arizonasaurus, Ctenosauriscus, and Lotosaurus.
Arizonasaurus and its implications for archosaur divergence
  • S. Nesbitt
  • Environmental Science, Geography
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 2003
Characteristics of the skeleton of Arizonasaurus show that it belongs to a poorly known group of Middle Triassic archosaurs called the ctenosauriscids, and that cteno-poposaurs are or are closely related to poposaurs, which suggests that the divergence of birds and crocodiles occurred earlier than previously thought.
A Basal Sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the Early Evolution of Sauropodomorpha
The presence of Panphagia at the base of the early Carnian Ischigualasto Formation suggests an earlier origin of Sauropodomorpha during the Middle Triassic, and is regarded as the most basal sauropodomorph.
A new North American therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution
It is suggested that hypercarnivory in paravian dinosaurs is a secondarily derived dietary specialization and provide a potential mechanism for the invasion of novel morpho- and ecospace early in coelurosaurian evolution—the loss of obligate carnivory and origin of dietary opportunism.
A critical re‐evaluation of the Late Triassic dinosaur taxa of North America
Synopsis The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that
On some Triassic cynodonts from Tanganyika
It has been concluded that the Triassic cynodonts of the Ruhuhu valley compare more closely with those of the Brazilian Rio do Rasto Series than withThose of South African deposits.
Hindlimb Osteology and Distribution of Basal Dinosauromorphs from the Late Triassic of North America
An ontogenetic series of the femur of Dromomeron indicates that some character states previously used in phylogenetic analyses of early dinosaurs may be ontogenetically variable.
27th Du Toit Memorial LectureRe-uniting lost continents – Fossil reptiles from the ancient Karoo and their wanderlust
Fossil discoveries from South Africa have greatly expanded knowledge of the development of life on Earth. In particular, the enormous palaeontological wealth of the Karoo, covering a period of almost