[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Large archosauromorphs from Early Triassic of Antarctica



From: Ben Creisler
bh480@scn.org

In new issue of Journal of Vertebrate Paleontology:

Nathan D. Smith, Jake R. Crandall, Spencer M. Hellert, William R. Hammer &
Peter J. Makovicky (2011) 
Anatomy and affinities of large archosauromorphs from the lower Fremouw
Formation (Early Triassic) of Antarctica.
Journal of Vertebrate Paleontology 31(4): 784-797
DOI:10.1080/02724634.2011.586662
http://www.tandfonline.com/doi/abs/10.1080/02724634.2011.586662


The vertebrate assemblage of the lower Fremouw Formation has been studied
for nearly 50 years, but many components remain poorly known. We describe a
partial presacral vertebra and the distal end of a left humerus collected
just above the Permian?Triassic boundary in the Shackleton Glacier region
of the central Transantarctic Mountains. Our identification of these
specimens as archosauromorphs that represent at least one taxon of
large-bodied archosauriform increases the known reptile diversity of the
Fremouw Formation considerably, and provides the first definitive evidence
for the presence of Archosauriformes in the Early Triassic of Antarctica.
These records increase faunal similarities between the lower Fremouw
Formation and other Early Triassic assemblages. Although the lower Fremouw
assemblage is typically considered a subset of the coeval Lystrosaurus
Assemblage Zone (LAZ) of South Africa, the discrepancy in inferred body
size between the Antarctic specimens and Proterosuchus fergusi, coupled
with the fact that the LAZ of the Karoo Basin has been sampled much more
thoroughly, suggests a real disparity in the maximum body size of apex
carnivores between the lower Fremouw assemblage and the LAZ. The lower
Fremouw specimens also demonstrate that one or more lineages of
archosauriform had attained the large body size characteristic of later
members of the clade very soon after the end-Permian mass extinction. This
offers a point of contrast with the global pattern of post-extinction
terrestrial communities, which are typified by a marked reduction in body
size (the ?Lilliput effect?).



--------------------------------------------------------------------
mail2web LIVE ? Free email based on Microsoft® Exchange technology -
http://link.mail2web.com/LIVE