The osteology and relationships ofVancleavea campi(Reptilia: Archosauriformes)

Abstract

Vancleavea campi Long & Murry, 1995, from the Late Triassic of western North America, represents the latest surviving non-archosaurian archosauriform known to date. We present here a detailed comparative description based on a nearly complete, articulated skeleton from the Coelophysis Quarry in north-central New Mexico and other fragmentary specimens. The unique combination of morphological features of Vancleavea is unparalleled within Reptilia; it has four unique morphologies of imbricated osteoderms covering the entire body, a short, highly ossified skull, relatively small limbs and morphological features consistent with a semi-aquatic lifestyle. Vancleavea is placed in a rigorous phylogenetic analysis examining the relationships of non-archosaurian archosauriforms, and is found to be more closely related to Archosauria than both Erythrosuchus and Proterosuchus, but outside of the crown group. The analysis confirms previously hypothesized relationships, which found Euparkeria to be the closest sister taxon of Archosauria. It is not clear whether specimens referred to Vancleavea campi represent a single species-level taxon or a clade of closely related taxa that lived through much of the Late Triassic of North America, given the poor fossil record of the taxon.

Supplemental Material for 'Postcranial osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its systematic position among stem archosaur reptiles. (Bulletin of the American Museum of Natural History, no. 398)'

“…This division complicates previous treatments of Proterosuchus fergusi in recent phylogenetic analyses (e.g., Nesbitt et al, 2009; of archosauriform relationships given that each Proterosuchus species is now known by less material. However, much of the scoring of Proterosuchus fergusi in Nesbitt et al, (2009) and was based on the new taxon Proterosuchus alexanderi.…”

“…This division complicates previous treatments of Proterosuchus fergusi in recent phylogenetic analyses (e.g., Nesbitt et al, 2009; of archosauriform relationships given that each Proterosuchus species is now known by less material. However, much of the scoring of Proterosuchus fergusi in Nesbitt et al, (2009) and was based on the new taxon Proterosuchus alexanderi. Therefore, in this study we ran the analysis twice regarding Proterosuchus, once scoring only the holotype of Proterosuchus alexanderi and once scoring Proterosuchus as a composite based on specimens assigned to both Proterosuchus alexanderi and Proterosuchus fergusi (see above).…”

“…67B), as in other nonarchosauriform archosauromorphs (Gower, 1996;Nesbitt et al, 2009). This gap (groove) is deeper posteriorly than dorsally.…”

“…We scored a terminal taxon Proterosuchus based on all of the Proterosuchus spp. from the Lystrosaurus AZ of South Africa, following the previous work of Nesbitt et al (2009), and Pritchard et al (2015. We also scored only the holotype of Proterosuchus alexanderi as a terminal taxon (see appendix 3).…”

“…Descriptions of those taxa not previously included in phylogenetic analyses are provided in appendix 3. Character sampling includes the 200 archosauromorph characters from Pritchard et al (2015) combined with additional archosauromorph characters from previous diapsid datasets (Juul, 1994;Gower and Sennikov, 1996;Dilkes, 1998;Nesbitt et al, 2009;, as well as characters employed here for the first time. Novel characters are described in appendix 4.…”