Latest Literature

Klembara, J., and J. Welman. 2009. The anatomy of the palatoquadrate in the Lower Triassic Proterosuchus fergusi (Reptilia, Archosauromorpha) and its morphological transformation within the archosauriform clade. Acta Zoologica 90(3):275-284. doi: 10.1111/j.1463-6395.2008.00358.x.

ABSTRACT- The anatomy of the palatoquadrate ossifications of the Lower Triassic archosauromorph Proterosuchus fergusi from South Africa is described. It consists of two ossifications, the epipterygoid and the quadrate, which were joined by cartilage in life. The margins of the cartilage are clearly indicated by ridges and grooves on the dorsal surface of the pterygoid. The epipterygoid ossification consists of two structures: the anteroposteriorly expanded basal portion and, dorsally from it, an extending, slender, ascending process. From the anterior margin of the basal portion of the epipterygoid, a plate-like structure, herein called the lamina epipterygoidea anteromedialis, extends anteromedially to form the anterolateral wall of the cavum epiptericum. Comparisons with the similarly constructed embryonal and adult epipterygoid components of Sphenodon punctatus show that the anteromedial lamina of the epipterygoid of P. fergusi is an additional component of the epipterygoid of this species and that this lamina is absent in the former species. However, a structure in a topologically similar position to the anteromedial lamina of the epipterygoid of P. fergusi is present in the palatoquadrate of Alligator mississippiensis. In the latter species, the structure is called the lamina palatoquadrati anterior; it ossifies in membrane and forms the dorsolateral cover of the huge trigeminal ganglion. It is hypothesized here that the anteromedial lamina of the epipterygoid of P. fergusi and the anterior lamina of the palatoquadrate of A. mississippiensis are most probably homologous structures and are present in both the basal and one of the crown taxa of the archosauromorph clade, respectively.

Renesto, S., Spielmann, J.A., and S.G. Lucas. 2009. The oldest record of drepanosaurids (Reptilia, Diapsida) from the Late Triassic (Adamanian Placerias Quarry, Arizona, USA) and the stratigraphic range of the Drepanosauridae. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 252(3):315-325. doi: 10.1127/0077-7749/2009/0252-0315.

ABSTRACT- Previous detailed descriptions of relatively complete drepanosaurid material make it possible to recognize isolated drepanosaurid elements from other localities. The identification of isolated elements from the USA and Great Britain extended the geographical distribution of the group and encouraged a review of Triassic collections for characteristic elements of this family. In this paper, isolated vertebrae previously described as problematic reptiles from the famous Placerias Quarry, near St. Johns, Arizona, USA are re-identified as drepanosaurids. These specimens represent the oldest occurrence of this family, which is earliest Adamanian.

This last paper is interesting as it again demonstates the homogeneous nature of the Chinle Formation faunal assemblages through the lowest to highest fossiliferous exposures. Thus with the exception of dicynodonts the Placerias Quarry, which is stratigraphically low, and contains dicynodonts, possesses pretty much the same faunal elements as the much higher quarries around Ghost Ranch New Mexico (Canjilon, Snyder, Hayden, Coelophysis), which lack dicynodonts. Thus you get phytosaurs, aetosaurs, rauisuchians, poposaurs, Vancleavea, crocodylomorphs, coelophysoids, lagerpetids, and now drepanosaurids throughout the Chinle section. Taxa and abundances in some groups (e.g., metoposaurs) change but the general faunal composition does not. Still, given that the Chinle Formation is now mostly restricted to the Middle and Late Norian (and possibly some of the Rhaetian) this is not too surprising.

No comments:

Post a Comment

Markup Key:
- <b>bold</b> = bold
- <i>italic</i> = italic
- <a href="">FoS</a> = FoS