A Detailed description of <i>Rugarhynchos sixmilensis</i>, gen. et comb. nov. (Archosauriformes, Proterochampsia), and cranial convergence in snout elongation across stem and crown archosaurs

Wynd, Brenen M.; Nesbitt, Sterling J.; Stocker, Michelle R.; Heckert, Andrew B.

doi:10.1080/02724634.2019.1748042

Cited by 13 publications

(13 citation statements)

References 55 publications

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“…An asymmetrical development of the medial and lateral part of the paramedians similar to that of MFSN 46485 is observed in the paramedians of the doswelliid Jaxtasuchus salomoni (see Wynd et al, 2020 , fig. 2B–C), in the cervical osteoderms of the erpetosuchid Erpetosuchus granti (see Benton & Walker, 2002 , fig.…”

Section: Discussionmentioning

confidence: 69%

“…The peripheral pits of the osteoderms are groove-like and externally open. The external side of the osteoderm has a median blunt keel in Doswellia kaltenbachi and Jaxtasuchus salomoni , whereas it bears a spike-like dorsal eminence projecting outwardly from the midpoint in Rugarhynchus sixmilensis (see Wynd et al, 2020 ). Shape and ornamentation of the paramedian osteoderms of the erpetosuchids Tarjadia ruthae (Ladinian-Carnian boundary), Archeopelta arborensis (Ladinian-Carnian) and Parringtonia gracilis (Anisian) are similar to those of doswelliids, but the osteoderms are thicker in the erpetosuchids ( Ezcurra et al, 2017 ).…”

Section: Discussionmentioning

confidence: 99%

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Heteropelta boboi n. gen., n. sp. an armored archosauriform (Reptilia: Archosauromorpha) from the Middle Triassic of Italy

Vecchia¹

2021

PeerJ

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Heteropelta boboi is a new archosauriform reptile from the upper Anisian of northeastern Italy represented by a fragment of dorsal armor with a row of neural arches of the dorsal vertebrae. The dorsal armor of the new taxon is composed of two columns of paramedian osteoderms and at least six columns of lateral osteoderms. Unlike other armored archosaurs, the osteoderms are imbricated with the posterior osteoderm overlapping the anterior one. The low neural arches bear small neural spines and long postzygapophyses. The osteoderms of the lateral columns increase in size and change in shape from the most medial to the most lateral columns. Among the Archosauriformes, only the non-archosaur proterochampsians Vancleavea campi, Litorosuchus somnii, and the doswelliids have dorsal armor comprised of more than two columns of osteoderms per side, but the morphology and arrangement of their osteoderms is unlike those of the new Italian taxon. A cladistic analysis of Archosauromorpha positions Heteropelta boboi as either a basal phytosaur or a basal suchian. However, a second cladistic analysis focused on armored archosaurs alternatively positions the new taxon as a basal archosauriform, basal suchian, basal loricatan or crocodylomorph. Better resolution of the phylogenetic relationships of Heteropelta boboi will likely be obtained only with the discovery of cranial and postcranial remains associated with its diagnostic armor elements.

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Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Heteropelta boboi n. gen., n. sp. an armored archosauriform (Reptilia: Archosauromorpha) from the Middle Triassic of Italy

Vecchia¹

2021

PeerJ

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“…In these taxa, a small anteroventral process of the quadratojugal underlaps the jugal (Schoch, 2007). A similar articulation also occurs in the doswelliid archosauriform Rugarhychos sixmilensis (Wynd et al, 2020) suggesting this character state may be plesiomorphic.…”

Section: Quadratojugalmentioning

confidence: 79%

Osteology and relationships of Revueltosaurus callenderi (Archosauria: Suchia) from the Upper Triassic (Norian) Chinle Formation of Petrified Forest National Park, Arizona, United States

Parker

Nesbitt

Irmis

et al. 2021

The Anatomical Record

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Once known solely from dental material and thought to represent an early ornithischian dinosaur, the early‐diverging pseudosuchian Revueltosaurus callenderi is described from a minimum of 12 skeletons from a monodominant bonebed in the upper part of the Chinle Formation of Arizona. This material includes nearly the entire skeleton and possesses a combination of plesiomorphic and derived character states that help clarify ingroup relationships within Pseudosuchia. A phylogenetic analysis recovers R. callenderi in a clade with Aetosauria and Acaenasuchus geoffreyi that is named Aetosauriformes. Key autapomorphies of R. callenderi include a skull that is longer than the femur, a complete carapace of dermal armor including paramedian and lateral rows, as well as ventral osteoderms, and a tail end sheathed in bone. Histology of the femur and associated osteoderms demonstrate that R. callenderi was slow growing and that the individuals from the bonebed were not young juveniles but had not ceased growing. A review of other material assigned to Revueltosaurus concludes that the genus cannot be adequately diagnosed based on the type materials of the three assigned species and that only R. callenderi can be confidently referred to Revueltosaurus.

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“…(2) conversely, many early-diverging archosauromorphs and archosauriforms are known to have persisted into the Late Triassic (e.g., doswelliids, Weems 1980;Heckert et al 2012; Communicated by: Robert Reisz Sues et al 2013;Wynd et al 2020;Vancleavea, Nesbitt et al 2009;tanystropheids;Olsen 1979;Pritchard et al 2015); and…”

Section: Introductionmentioning

confidence: 99%

“…That clade rose from relative rarity in the Permian Period to dominate the mid- and large-body size (>10 kg) guilds in terrestrial and freshwater aquatic realms by the end of the Triassic (e.g., Fraser 2006 ; Sues and Fraser 2010 ; Nesbitt et al 2013 ; Ezcurra et al 2014 ). Several consistent themes have emerged from the past two decades of discovery and study of this evolutionary event: (1) the origins of many crown-group archosaurs have been pulled down into the Middle, or even Early, Triassic (e.g., Brusatte et al 2010 ; Nesbitt 2011 ; Nesbitt et al 2017a , b ); (2) conversely, many early-diverging archosauromorphs and archosauriforms are known to have persisted into the Late Triassic (e.g., doswelliids, Weems 1980 ; Heckert et al 2012 ; Sues et al 2013 ; Wynd et al 2020 ; Vancleavea , Nesbitt et al 2009 ; tanystropheids; Olsen 1979 ; Pritchard et al 2015 ); and (3) the radiation of archosauromorphs includes many examples of convergent evolution, where Triassic taxa established the bounds of a morphospace that was only much later explored by dinosaurs and other taxa (e.g., Nesbitt and Norell 2006 ; Stocker et al 2016 ; Sengupta et al 2017 ). Though many of the new discoveries that define these trends have resulted from the discovery of fossils from previously unexplored regions, it is clear that even well-studied stratigraphic intervals and localities are continuing to yield unexpected new taxa.…”

Section: Introductionmentioning

confidence: 99%

A new short-faced archosauriform from the Upper Triassic Placerias/Downs’ quarry complex, Arizona, USA, expands the morphological diversity of the Triassic archosauriform radiation

Heckert

Nesbitt

Stocker

et al. 2021

Sci Nat

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The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shallow, densely packed, irregular, fine pits and narrow, arcuate grooves. This combination of character states allows an archosauriform assignment; however, an associated and similarly sized braincase indicates that Syntomiprosopus n. gen. may represent previously unsampled disparity in early-diverging crocodylomorphs. The Placerias Quarry is Adamanian (Norian, maximum depositional age ~219 Ma), and this specimen appears to be an early example of shortening of the skull, which occurs later in diverse archosaur lineages, including the Late Cretaceous crocodyliform Simosuchus. This is another case where Triassic archosauriforms occupied morphospace converged upon by other archosaurs later in the Mesozoic and further demonstrates that even well-sampled localities can yield new taxa.

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A Detailed description of Rugarhynchos sixmilensis, gen. et comb. nov. (Archosauriformes, Proterochampsia), and cranial convergence in snout elongation across stem and crown archosaurs

Cited by 13 publications

References 55 publications

Heteropelta boboi n. gen., n. sp. an armored archosauriform (Reptilia: Archosauromorpha) from the Middle Triassic of Italy

Heteropelta boboi n. gen., n. sp. an armored archosauriform (Reptilia: Archosauromorpha) from the Middle Triassic of Italy

Osteology and relationships of Revueltosaurus callenderi (Archosauria: Suchia) from the Upper Triassic (Norian) Chinle Formation of Petrified Forest National Park, Arizona, United States

A new short-faced archosauriform from the Upper Triassic Placerias/Downs’ quarry complex, Arizona, USA, expands the morphological diversity of the Triassic archosauriform radiation

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