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Ankylosuchus, new doswelliid archosauromorph from Upper Triassic of Texas (free pdf)



From: Ben Creisler
bcreisler@gmail.com

A new recent paper not yet mentioned. The pdf is free at the link:

Spencer G. Lucas, Justin A. Spielmann and Adrian P. Hunt (2013)
A new doswelliid archosauromorph from the Upper Triassic of West Texas.
in Tanner, L.H., Spielmann, J.A. and Lucas, S.G., eds., 2013, The
Triassic System.
New Mexico Museum of Natural History and Science, Bulletin 61 : 382-388
Free pdf:
http://paleo.cortland.edu/globaltriassic2/Bulletin%2061%20Final/31-Lucas%20et%20al%20(Ankylosuchus).pdf

Ankylosuchus chinlegroupensis is a new genus and species of
heavily-armored archosauromorph from the Otischalkian Colorado City
Formation of the Chinle Group in Howard County, West Texas. The
incomplete holotype skeleton consists of cranial and pelvic (?)
elements, vertebral centra, a partial limb shaft and numerous
osteoderms. The skull elements reveal a thick, heavily armored
braincase and skull roof with parasagittal crests. The relatively
short sacral vertebrae suggest an animal less than 1 meter in total
body length, not including the tail. The morphology of the osteoderms
does not match any currently known armored archosauromorph, but it is
most similar to doswelliids. Most of the osteoderms possess large,
closely packed pits that form no obvious pattern. Some osteoderms have
raised, linear ridges running across them and others have anterior
laminae with faint patterning on the articular surface. Some of the
osteoderms are tightly sutured to each other via digitate sutures; all
are relatively thick. The patterning of the ostoderms matches well
with that of doswellids in being coarse, deeply incised and mostly
composed of equal-sized pits and in the possession of anterior
laminae. Even so, these osteoderms are readily distinguished from
those of Doswellia, the only doswelliid previously reported from the
Chinle Group, by their coarser pitting, greater thickness and (at
least in some osteoderms) fusion with laterally adjacent osteoderms
along their mutual sutural boundaries. A. chinlegroupensis is derived
from the oldest strata of the Texas Chinle Group, the Otischalkian,
whereas the genus Doswellia is known from the Chinle Group in Texas,
New Mexico and Utah, in strata of Otischalkian-Adamanian (late
Carnian) age. Doswelliids are very rare, but visible components of
global Triassic faunas. They include Tarjadia (= Archeopelta) from the
Berdyankian (Ladinian) of Argentina and Brazil, Doswellia from the
Otischalkian-Adamanian of the American Southwest and the Otischalkian
of the Newark Supergroup in the eastern USA, and now Ankylosuchus from
the Otischalkian of West Texas.