Charles W. Gilmore named
Pinacosuchus in 1942 for
USNM 16592, consisting of a fragment of
upper jaw, seven partial
vertebrae, a partial
coracoid, a partial
thigh bone, numerous pieces of
bony armor, and other fragments. This specimen was discovered at the "Lizard Locality" in the
Manti National Forest,
Emery County, Utah. The
type species is
P. mantiensis. Gilmore had difficulty classifying the specimen, due to its fragmentary nature. He ruled out all then-known
orders of reptiles on anatomical ground except for
Crocodilia (which had a more expansive definition at the time) and the nebulous
thecodontia. He considered a
pseudosuchian thecodont identity, but eliminated it because all members were of
Triassic age or older.
Pinacosuchus would have been an archaic crocodilian because it lacked the
procoelous vertebrae (concave articulation surface on the
anterior face of the bone, and convex articulation on the posterior face) of more
derived crocodilians, instead having
amphicoelous vertebrae (concave articulations on both faces).
Pinacosuchus would have been a very small crocodylomorph. The
sacrum (the vertebra supporting the hips) of USNM 16592 was only long. Gilmore regarded the specimen as an adult because the vertebrae lacked sutures for their
neural arches, a sign of maturity. The armor of
Pinacosuchus was found disarticulated. Gilmore divided the armor into five categories: simple rectangular scutes; ridged rooflike scutes; thickened rectangular scutes with asymmetrically-positioned sharp spines overhanging the borders; small pointed spines with thickened bases; and more elongate pointed spines with thickened bases. ==References==