A new phylogenetic hypothesis of Tanystropheidae (Diapsida, Archosauromorpha) and other “protorosaurs”, and its implications for the early evolution of stem archosaurs

Abstract

The historical clade “Protorosauria” represents an important group of archosauromorph reptiles that had a wide geographic distribution between the Late Permian and Late Triassic. “Protorosaurs” are characterized by their long necks, which are epitomized in the genus Tanystropheus and in Dinocephalosaurus orientalis. Recent phylogenetic analyses have indicated that “Protorosauria” is a polyphyletic clade, but the exact relationships of the various “protorosaur” taxa within the archosauromorph lineage is currently uncertain. Several taxa, although represented by relatively complete material, have previously not been assessed phylogenetically. We present a new phylogenetic hypothesis that comprises a wide range of archosauromorphs, including the most exhaustive sample of “protorosaurs” to date and several “protorosaur” taxa from the eastern Tethys margin that have not been included in any previous analysis. The polyphyly of “Protorosauria” is confirmed and therefore we suggest the usage of this term should be abandoned. Tanystropheidae is recovered as a monophyletic group and the Chinese taxa Dinocephalosaurus orientalis and Pectodens zhenyuensis form a new archosauromorph clade, Dinocephalosauridae, which is closely related to Tanystropheidae. The well-known crocopod and former “protorosaur” Prolacerta broomi is considerably less closely related to Archosauriformes than was previously considered.

A new faunistic component of the Lower Triassic Panchet Formation of India increases the continental non-archosauromorph neodiapsid record in the aftermath of the end-Permian mass extinction

“…3.4). A similar emargination is present in some tanystropheids (e.g., Tanystropheus longobardicus Bassani, 1886; Spiekman et al, 2021), but this is because of the presence of a tuber-like, anteriorly projected, preacetabular process that it is absent in ISIR 1132. The iliac blade of ISIR 1132 is extremely low above the acetabulum, in which the ratio between the height of the iliac blade at the level of the dorsalmost extension of the supraacetabular crest (Fig.…”

Ancestral Body Plan and Adaptive Radiation of Sauropterygian Marine Reptiles

“…Although the monophyly of the marine reptile group combining Ichthyopterygia, Thalattosauria, and Sauropterygia is controversial, it is beyond our scope here focusing on the inner relationship within sauropterygians and their relationship with unsolved taxa such as saurosphargids and Atopodentatus . A larger matrix involving the basal members of Archosauromorpha and Lepidosauromorpha will be considered in our future work when their inner relationships 35,36,38,39 are better resolved respectively and more specimens are personally checked by us. The taxa of stem turtles (or pantestudines) were possibly related to sauropterygians in a few recent studies 40,41 , and we first-hand observed some specimens 41,42 and tentatively added them in our matrix to double test.…”

Puercosuchus traverorum n. gen. n. sp.: a new malerisaurine azendohsaurid (Archosauromorpha: Allokotosauria) from two monodominant bonebeds in the Chinle Formation (Upper Triassic, Norian) of Arizona

“…The top of the neural spine is flat dorsally but expanded laterally along its length (Fig. 9.4, 9.5), as in Malerisaurus robinsonae (ISIR 150); this feature is a character state that unites malerisaurines (Nesbitt et al, 2021), but it is also found in some tanystropheids, such as Macrocnemus fuyuanensis Li et al, 2007(Spiekman et al, 2021, Macrocnemus bassanii (Spiekman et al, 2021, supplemental information), and GR 269 (Pritchard et al, 2015, fig. 2a, d).…”

“…The top of the neural spine is laterally expanded only at its anteroposterior midpoint (Fig. 9.10, 9.15; = mammillary processes; Ezcurra and Butler, 2015;Ezcurra, 2016;Spiekman et al, 2021), like that of other malerisaurines (Nesbitt et al, 2021) and the archosauromorphs Prolacerta broomi (Gottmann-Quesada and Sander, 2009, fig. 21), Boreopricea funerea Tatarinov, 1978 (Benton andAllen, 1997, fig.…”

“…Earlier-diverging azendohsaurids now are recognized from previously known taxa (Nesbitt et al, 2021) such as Pamelaria dolichotrachela Sen, 2003, and the Malerisaurinae (e.g., Malerisaurus robinsonae Chatterjee, 1980, and Malerisaurus langstoni Chatterjee, 1986) that exhibit the tall-crowned, pointed marginal teeth found in most archosauromorphs. Unfortunately, the record of malerisaurine azendohsaurids currently is represented by fragmentary, ambiguously associated, and generally poorly preserved taxa (Nesbitt et al, 2021), which makes understanding the acquisition of azendohsaurid skeletal traits difficult to determine and difficult to compare with the morphologies of other allokotosaurs and closely related archosauromorphs such as rhynchosaurs, tanystropheids, and archosauriforms (Ezcurra, 2016;Pritchard and Sues, 2019;Pritchard et al, 2021;Spiekman et al, 2021).…”