Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation, Argentina), its inclusivity, and relationships amongst early dinosauromorphs

  title={Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Cha{\~n}ares Formation, Argentina), its inclusivity, and relationships amongst early dinosauromorphs},
  author={Jonathas S. Bittencourt and A. Arcucci and Claudia A. Marsicano and Max Cardoso Langer},
  journal={Journal of Systematic Palaeontology},
  pages={189 - 219}
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… 

New specimens provide insights into the anatomy of the dinosauriform Lewisuchus admixtus Romer, 1972 from the upper Triassic levels of the Chañares Formation, NW Argentina

The cranial bones, presacral series, femur, tibia, and proximal tarsals of the new specimens match the preserved overlapping anatomy of the holotype and previously referred specimens of L. admixtus, improving the understanding of the anatomy and taxonomy of early dinosauriforms and reinforces the role of Argentinean beds on the study of the origin of dinosaurs.

The Osteology and Phylogenetic Position of Luperosuchus fractus (Archosauria: Loricata) from the Latest Middle Triassic or Earliest Late Triassic of Argentina

It is confirmed that Luperosuchus is a loricatan (composed mostly of the taxa classically termed as ‘rauisuchians’) using a well sampled phylogeny and find a close relationship with the other large southwestern Pangean forms, Prestosuchu chiniquensis and Saurosuchus galilei.

Craniomandibular osteology of Macrocollum itaquii (Dinosauria: Sauropodomorpha) from the Late Triassic of southern Brazil

  • R. Müller
  • Biology, Environmental Science
    Journal of Systematic Palaeontology
  • 2019
A detailed description of the craniomandibular anatomy of M. itaquii is presented, based on the holotype, a paratype and a newly referred specimen, to elucidate the transition from slender basal sauropodomorphs to more robust derived members within this group.


Lagosuchus talampayensis is here considered a senior synonym of “Marasuchus lilloensis” (Romer, 1972) and its conclusions have implications in the knowledge about early dinosauromorph diversity and the taxonomic richness of the group in the Chañares Formation.

An enigmatic new archosauriform from the Carnian– Norian, Upper Triassic, Ischigualasto Formation of northwestern Argentina

The analyses recover the new taxon in three main general phylogenetic placements within Archosauria, as well as one position outside this clade, highlighting widespread morphological evolutionary convergence towards neck elongation in several clades of Triassic archosauriforms.

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 Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

The morphology of the new specimen is completely congruent with that of specimens of Pseudolagosuchus major, bolstering the hypothesis that the latter species is a subjective junior synonym of Lewisuchus admixtus.

A new dinosaur with theropod affinities from the Late Triassic Santa Maria Formation, south Brazil

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.

Anatomy of the dinosaur Pampadromaeus barberenai (Saurischia—Sauropodomorpha) from the Late Triassic Santa Maria Formation of southern Brazil

A novel phylogenetic study shows that relationships among the Carnian sauropodomorphs are poorly constrained, possibly because they belong to a “zone of variability”, where homoplasy abounds, and there is some evidence that Pam.

The osteology of the early-diverging dinosaur Daemonosaurus chauliodus (Archosauria: Dinosauria) from the Coelophysis Quarry (Triassic: Rhaetian) of New Mexico and its relationships to other early dinosaurs

The osteology of the unusual early-diverging dinosaur Daemonosaurus chauliodus from the latest Triassic Coelophysis Quarry in northern New Mexico, USA is fully detail and demonstrates that members of the original diversification of dinosaurs survived until nearly the end of the Triassic Period.



Osteology of the Middle Triassic pseudosuchian archosaur Arizonasaurus babbitti

Arizonasaurus babbitti is rediagnosed from a well-preserved partial skeleton from the early Middle Triassic Moenkopi Formation of northern Arizona. The skull, excluding the braincase, is described

The anatomy and phylogenetic position of the Triassic dinosaur Staurikosaurus pricei Colbert, 1970

The phylogenetic position of S. pricei is constrained by that of its sister taxon H. ischigualastensis, which is known from much more complete material, and the absence of some characters observed in the clades Theropoda and Sauropodomorpha suggests that S.pricei is not a member of Eusaurischia.

Erpetosuchus , a crocodile-like basal archosaur from the Late Triassic of Elgin , Scotland

Erpetosuchus , a small archosaurian reptile from the Late Triassic of Scotland and North America, has often been implicated in the ancestry of crocodilians. A restudy of the type specimen, using new

Erpetosuchus, a crocodile-like basal archosaur from the Late Triassic of Elgin, Scotland

A cladistic analysis of crurotarsan archosaurs indicates that Erpetosuchus is the closest sister group of Crocodylomorpha among known basal archosaurs, and the remains suggest that Er petrosuchus was a light, cursorial animal that may have fed on insects.

A reassessment of the basal dinosaur Guaibasaurus candelariensis, from the Late Triassic Caturrita Formation of south Brazil

ABSTRACT The dinosaur record of the Santa Maria beds of Rio Grande do Sul (Mid–Late Triassic; south Brazil) includes the herrerasaur Staurikosaurus pricei, and two basal members of the sauropodomorph


Abstract Recent fieldwork in the Upper Cretaceous (Maastrichtian) Maevarano Formation, northwest Madagascar, has yielded important new skull material of the abelisaurid theropod, Majungasaurus

A Revision of Sphenosuchus acutus Haughton, a Crocodylomorph Reptile from the Elliot Formation (Late Triassic or Early Jurassic) of South Africa

It is concluded that the most important steps in crocodylomorph evolution, particularly in the skull, had taken place in sphenosuchians, hence they should be included in the same taxon as protosuchian and more advanced crocodilians, rather than with thecodontians.

Dinosaurian precursors from the Middle Triassic of Argentina: Marasuchus lilloensis, gen. nov.

Several synapomorphies unite Marasuchus and dinosaurs (as Dinosauriformes) to the exclusion of the contemporary dinosauromorph Lagerpeton and pterosaurs.

The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial anatomy, functional morphology, taxonomy, and relationships

Details of the cranial anatomy are revealed and show that the skull is unexpectedly specialized in such an early representative of the Ornithischia, including the closely packed, hypsodont crowns and ‘warping’ of the occlusal surfaces seen in the cheek dentition and jaw musculature.

A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs

Synopsis Juvenile sauropodomorph specimens from a Late Triassic/Early Jurassic fissure fill in Pant‐y‐ffynnon Quarry, South Wales are redescribed and named as a new species, Thecodontosaurus caducus.