The Osteology and Relationships of Vancleavea campi (Reptilia: Archosauriformes)

Um...OK, this came out a bit earlier than I expected and is now available online from the Journal of the Linnaean Society. This is the long awaited full description of this taxon, which supersedes my 2008 publication which came out when this paper was in press and therefore not cited. Sterling felt that the new PEFO material should be dealt with in a separate publication, but unfortunately I did not get it out in time for him to use, and to ask him and his coauthors to go back through this manuscript in the proof stages and add info from my paper would have been too much. So we are left with a weird case in which two papers come out on the same taxon and neither cite each other, but I assure you that we were all aware of each other's work before anyone questions ethics. Sterling did compare the GR material to one of the PEFO specimens; whereas I did not describe or code any of the Ghost Ranch material, thus this new paper is up to date in that regard.

I guarantee you that this is one of the most bizarre archosauriforms you may ever encounter, see the above reconstruction courtesy of Sterling Nesbitt. Enigmatic since its initial discovery in 1962 (from Petrified Forest National Park) and initial description by Long and Murry in 1995, recent collection of better specimens has elucidated its osteology and broader relationships. Vancleavea is actually common at most levels of the Chinle Formation; however, due to the scrappy nature of most of the materials it is difficult to compare specimens across stratigraphic levels. Are we looking at one species or several? I congratulate Sterling, Michelle, Bryan, and Alex on a great discovery and paper.

Nesbitt, S. J., Stocker, M. R., Small, B. J., and A. Downs. 2009. The osteology and relationships of Vancleavea campi(Reptilia: Archosauriformes). Zoological Journal of the Linnaean Society 157:814–864 doi: 10.1111/j.1096-3642.2009.00530.x

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.