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Euparkeria capensis is resolved as the sister taxon to Archosauria in many cladistic phylogenies and provides a key outgroup which may approximate the ancestral archo- saur morphology. Several other taxa have been referred to the family Euparkeriidae, but the monophyly of this taxon remains doubtful and largely untested. To test this mono- phyly, the archosauriform and putative euparkeriid Dorosu- chus neoetus from the Mid-Triassic of Russia is re-examined in the light of recent work on the evolution of stem archo- saurs. Dorosuchus neoetus is found to possess a number of morphological features that place it close to Archosauria, including a sigmoidal femur with a clear attachment region for the m. caudifemoralis musculature, but no unambiguous archosaurian apomorphies. Dorosuchus neoetus is included for the first time in a numerical cladistic analysis and is recovered as the sole sister taxon to Archosauria + Phytosauria. A monophyletic Euparkeriidae including D. neoetus and E. capensis is slightly less parsimonious. In addition, a mandible and pterygoid that were previously referred to D. neoetus subsequent to the original description of the species are also included separately within the phylo- genetic analysis and are recovered within Archosauria, possi- bly raising questions as to their correct taxonomic referral. However, this phylogenetic placement is based primarily on the absence of palatal teeth, but the presence or absence of palatal teeth exhibits considerable homoplasy within Archosauriformes. Based on other aspects of their morphol- ogy, we do not reject the referral of these elements to D. neoetus.

For the first time, a phylogenetic analysis including all putative euparkeriid taxa is conducted, using a large data matrix analysed with maximum parsimony and Bayesian analysis. Using parsimony, the putative euparkeriid Dorosuchus neoetus from Russia is the sister taxon to Archosauria + Phytosauria. Euparkeria capensis is placed one node further from the crown, and forms a euparkeriid clade with the Chinese taxa Halazhaisuchus qiaoensis and ‘ Turfanosuchus shageduensis ’ and the Polish taxon Osmolskina czatkowicensis . Using Bayesian methods, Osmolskina and Halazhaisuchus are sister taxa within Euparkeriidae, in turn sister to ‘ Turfanosuchus shageduensis ’ and then Euparkeria capensis . Dorosuchus is placed in a polytomy with Euparkeriidae and Archosauria + Phytosauria. Although conclusions remain tentative owing to low node support and incompleteness, a broad phylogenetic position close to the base of Archosauria is confirmed for all putative euparkeriids, and the ancestor of Archosauria +Phytosauria is optimized as similar to euparkeriids in its morphology. Ecomorphological characters and traits are optimized onto the maximum parsimony strict consensus phylogeny presented using squared change parsimony. This optimization indicates that the ancestral archosaur was probably similar in many respects to euparkeriids, being relatively small, terrestrial, carnivorous and showing relatively cursorial limb morphology; this Bauplan may have underlain the exceptional radiaton and success of crown Archosauria.

The South African species Euparkeria capensis is of great importance for understanding the early radiation of archosauromorphs (including archosaurs) following the Permo–Triassic mass extinction, as most phylogenetic analyses place it as the sister taxon to crown group Archosauria within the clade Archosauriformes. Although a number of species from Lower–Middle Triassic deposits worldwide have been referred to the putative clade Euparkeriidae, the monophyly of Euparkeriidae is controversial and has yet to be demonstrated by quantitative phylogenetic analysis. Three Chinese taxa have been recently suggested to be euparkeriids: Halazhaisuchus qiaoensis, ‘Turfanosuchus shageduensis’, and Wangisuchus tzeyii, all three of which were collected from the Middle Triassic Ermaying Formation of northern China. Here, we reassess the taxonomy and systematics of these taxa. We regard Wangisuchus tzeyii as a nomen dubium, because the holotype is undiagnostic and there is no convincing evidence that the previously referred additional specimens represent the same taxon as the holotype. We also regard ‘Turfanosuchus shageduensis’ as a nomen dubium as we are unable to identify any diagnostic features. We refer the holotype to Archosauriformes, and more tentatively to Euparkeriidae. Halazhaisuchus qiaoensis and the holotype of ‘Turfanosuchus shageduensis’ are resolved as sister taxa in a phylogenetic analysis, and are in turn the sister taxon to Euparkeria capensis, forming a monophyletic Euparkeriidae that is the sister to Archosauria+Phytosauria. This is the first quantitative phylogenetic analysis to recover a non-monospecific, monophyletic Euparkeriidae, but euparkeriid monophyly is only weakly supported and will require additional examination. Given their similar sizes, stratigraphic positions and phylogenetic placement, the holotype of ‘Turfanosuchus shageduensis’ may represent a second individual of Halazhaisuchus qiaoensis, but no apomorphies or unique character combination can be identified to unambiguously unite the two. Our results have important implications for understanding the species richness and palaeobiogeographical distribution of early archosauriforms.

Euparkeria capensis Broom, 1913 (fig. 7H–I) AGE: Anisian, Middle Triassic (Rubidge, 2005). OCCURRENCE: Cynognathus Assemblage Zone (B) (Beaufort Group) of South Africa. HOLOTYPE: SAM 5867, skull and partial skeleton. REFERRED MATERIAL: SAM 6050, partial skull; SAM 6047B, vertebrae, femur, pelvis, pectoral girdle; SAM 6049, dorsal, sacral, and caudal vertebrae, right hind limb, and partial pelvic and pectoral girdles; SAM 6047A, skull, vertebrae, and limb fragments; UMCZ T692, articulated foot with astragalus and calcaneum removed for study. REMARKS: See Nesbitt et al., 2009a. KEY REFERENCES: Broom, 1913; Ewer, 1965; Gower and Weber, 1998; Senter, 2003., Published as part of Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, pp. 1-292 in Bulletin of the American Museum of Natural History 2011 (352) on page 18, DOI: 10.1206/352.1, http://zenodo.org/record/5405335, {"references":["Broom, R. 1913. Note on Mesosuchus browni, Watson and on a new South African Triassic pseudosuchian (Euparkeria capensis). Records of the Albany Museum 2: 394 - 396.","Rubidge, B. S. 2005. Re-uniting lost continents - fossil reptiles from the ancient Karoo and their wanderlust. South African Journal of Geology 108: 135 - 172.","Nesbitt, S. J., M. R. Stocker, B. Small, and A. Downs. 2009 a. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157: 814 - 864.","Ewer, R. F. 1965. The anatomy of the thecodont reptile Euparkeria capensis Broom. Philosophical Transactions of the Royal Society of London Series B Biological Sciences 248: 379 - 435.","Gower, D. J., and E. Weber. 1998. The braincase of Euparkeria, and the evolutionary relationships of birds and crocodilians. Biological Reviews 73: 367 - 411.","Senter, P. 2003. New information on cranial and dental features of the Triassic archosauriform reptile Euparkeria capensis. Palaeontology 46: 613 - 621."]}

Archosaurs have a nearly 250 million year record that originated shortly after the Permian-Triassic extinction event and is continued today by two extant clades, the crocodylians and the avians. The two extant lineages exemplify two bauplan extremes among a diverse and complex evolutionary history, but little is known about the common ancestor of these lineages. Renewed interest in early archosaurs has led to nearly a doubling of the known taxa in the last 20 years. This study presents a thorough phylogenetic analysis of 80 species-level taxa ranging from the latest Permian to the early part of the Jurassic using a dataset of 412 characters. Each terminal taxon is explicitly described and all specimens used in the analysis are clearly stated. Additionally, each character is discussed in detail and nearly all of the character states are illustrated in either a drawing or highlighted on a specimen photograph. A combination of novel characters and comprehensive character sampling has bridged previou...

Desojo, Julia B., Ezcurra, Martin D., Schultz, Cesar L. (2011): An unusual new archosauriform from the Middle-Late Triassic of southern Brazil and the monophyly of Doswelliidae. Zoological Journal of the Linnean Society 161 (4): 839-871, DOI: 10.1111/j.1096-3642.2010.00655.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2010.00655.x

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Euparkeria capensis Broom, 1913 Age. Scythian-Anisian. Occurrence. Cynognathus assemblage zone of the Beaufort Group, South Africa. Diagnosis. Premaxilla with a vertical, dorsally rounded postnarial process. Remarks. Ever since its original description (Broom 1913), Euparkeria (Text-fig. 4a) has played a pivotal role in the discussion of archosaur interrelationships. Long believed to be ancestral to dinosaurs and sometimes birds (Heilmann 1926; Welman 1995), it is now generally considered to be the sister group of the clade comprising all the recent representatives of Archosauria (see Gower and Wilkinson 1996 and references therein). Because of this basal phylogenetic position, its unspecialized morphology and our relatively complete knowledge of its anatomy, Euparkeria is used here as the most basal outgroup to dinosaurs, and it is the taxon used to root the tree., Published as part of Rauhut, Oliver W. M., 2003, The interrelationships and evolution of basal theropod dinosaurs, pp. 1-213 in Special papers in palaeontology 69 on page 12, DOI: 10.5281/zenodo.3382576, {"references":["BROOM, R. 1913. Note on Mesosuchus browni, Watson, and on a new South African riassic pseudosuchian (Euparkeria capensis). Records of the Albany Museum, 2, 394 - 396.","HEILMANN, G. 1926. The origin of birds. H. F. & G. Witherby, London, 210 pp.","WELMAN, J. 1995. Euparkeria and the origin of birds. South African Journal of Science, 91, 533 - 537."]}

The basis of this classificatory essay includes a reconsideration of the Thecodontia-Crocodylia boundaries, an evaluation of the temporal region of the thecodont skull, and some observations on the carpus, pelvis and tarsus of the group. The Proterosuchia include the Lower Triassic families Proterosuchidae-Erythrosuchidae and also the Middle and Late Triassic families Rauisuchidae and Cerritosauridae-Proterochampsidae, and the suborder is made up of two different lineages: the infraorders Rauisuchia and Proterochampsia. The Pseudosuchia is restricted to the families Euparkeriidae, Ornithosuchidae, Lagosuchidae and Scleromochlidae, with crurotarsal and mesotarsal tarsi, and short carpus. The Sphenosuchia are defined as the crocodilelike thecodonts, lightly built, with derived characters in the temporal region of the skull, elongated carpus and coracoid, and mesotarsal tarsi. The Aetosauria include the Stagonolepididae and the Doswelliidae, the latter recently described by R.E. Weems (1980) . The Phytosauria are briefly cited as it is a very well defined natural group.

The South African species Euparkeria capensis is of great importance for understanding the early radiation of archosauromorphs (including archosaurs) following the Permo–Triassic mass extinction, as most phylogenetic analyses place it as the sister taxon to crown group Archosauria within the clade Archosauriformes. Although a number of species from Lower–Middle Triassic deposits worldwide have been referred to the putative clade Euparkeriidae, the monophyly of Euparkeriidae is controversial and has yet to be demonstrated by quantitative phylogenetic analysis. Three Chinese taxa have been recently suggested to be euparkeriids: Halazhaisuchus qiaoensis, ‘Turfanosuchus shageduensis’, and Wangisuchus tzeyii, all three of which were collected from the Middle Triassic Ermaying Formation of northern China. Here, we reassess the taxonomy and systematics of these taxa. We regard Wangisuchus tzeyii as a nomen dubium, because the holotype is undiagnostic and there is no convincing evidence that the previously referred additional specimens represent the same taxon as the holotype. We also regard ‘Turfanosuchus shageduensis’ as a nomen dubium as we are unable to identify any diagnostic features. We refer the holotype to Archosauriformes, and more tentatively to Euparkeriidae. Halazhaisuchus qiaoensis and the holotype of ‘Turfanosuchus shageduensis’ are resolved as sister taxa in a phylogenetic analysis, and are in turn the sister taxon to Euparkeria capensis, forming a monophyletic Euparkeriidae that is the sister to Archosauria+Phytosauria. This is the first quantitative phylogenetic analysis to recover a non-monospecific, monophyletic Euparkeriidae, but euparkeriid monophyly is only weakly supported and will require additional examination. Given their similar sizes, stratigraphic positions and phylogenetic placement, the holotype of ‘Turfanosuchus shageduensis’ may represent a second individual of Halazhaisuchus qiaoensis, but no apomorphies or unique character combination can be identified to unambiguously unite the two. Our results have important implications for understanding the species richness and palaeobiogeographical distribution of early archosauriforms.