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

Gracilisuchus (Archosauria) hind limb osteology

From: Ben Creisler

A paper from last year now available online:

Lecuona, A. and J. B. Desojo (2011)
Hind limb osteology of Gracilisuchus stipanicicorum (Archosauria:
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh 102: 105–128.

Gracilisuchus stipanicicorum Romer, 1972, from the Middle-Late
Triassic of the Ischigualasto–Villa Union Basin of Argentina, is an
extinct pseudosuchian archosaur on the stem to Crocodylomorpha. The
pelvic girdle and hind limb anatomy of a referred specimen of
Gracilisuchus stipanicicorum is described and compared with that from
a broad range of archosauriform taxa, including basal members such as
crurotarsans and basal ornithodirans. The description of this specimen
reveals new information on the anatomy of the pelvic girdle and hind
limb of Gracilisuchus, through a detailed examination of some
anatomical regions barely or not previously described, as well as
reinterpretations of previous features. The phylogenetic affinities of
Gracilisuchus within the Archosauria remain to be tested, but
Gracilisuchus shares two putative synapomorphies with some
non-crocodyliform crocodylomorphs, providing tentative support for the
monophyly of Sphenosuchia (e.g., Sereno & Wild 1992; Wu & Chatterjee
1993) and the close relationship of Gracilisuchus to that clade. These
characteristics are: (i) the morphology and poor development of the
femoral fourth trochanter, closely resembling the condition of
Pseudhesperosuchus and Trialestes; and (ii) a poor anterior
development of the femoral head, shared with Pseudhesperosuchus. On
the other hand there are characters that reject the inclusion of
Gracilisuchus within Crocodylomorpha (Nesbitt 2011), such as the
absence of an imperforated acetabulum, and that rather suggests a
sister-taxon position to Crocodylomorpha.