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Pristichampsus (Paleogene eusuchian) a nomen dubium and Sebecus jaws



From: Ben Creisler
bcreisler@gmail.com

Two new non-Mesozoic archosaur papers that may be of interest:


Christopher A. Brochu (2013)
Phylogenetic relationships of Palaeogene ziphodont eusuchians and the
status of Pristichampsus Gervais, 1853.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000200
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9016345&fulltextType=RA&fileId=S1755691013000200

Eusuchians with deep snouts and labiolingually compressed teeth are
known from the Palaeogene of Laurasia. These are usually referred to
Pristichampsinae, but the type species, Pristichampsus rollinati, is
based on insufficiently diagnostic material and should be treated as a
nomen dubium. At least two Lutetian species formerly referred to
Pristichampsus can be recognised – Boverisuchus magnifrons in Germany
and possibly elsewhere in Europe, and Boverisuchus vorax, new
combination, in western North America. Material from the middle Eocene
of Italy and Texas may represent distinct species. A phylogenetic
analysis confirms their close relationship and also supports a
relationship with two Asian forms – early Eocene Planocrania
datangensis and Palaeocene Planocrania hengdongensis. The name
Planocraniidae Li 1976 is applied to this group. A distinctive
quadrate with a prominent dorsal peak between medial and lateral
hemicondyles is known only in Boverisuchus, and although the teeth of
Planocrania are flattened, they are not serrated. Planocraniids
maintain a phylogenetic position as the sister group to
Crocodyloidea+Alligatoroidea, but this part of the tree is unstable
and discovery of older, more primitive planocraniids will help resolve
conflicts on the phylogenetic relationships of extant crocodylian
lineages.

====

Ralph E. Molnar (2013)
Jaw musculature and jaw mechanics of Sebecus icaeorhinus Simpson, 1937
(Mesoeucrocodylia, Sebecosuchia).
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000285
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9015645&fulltextType=RA&fileId=S1755691013000285

Sebecus icaeorhinus possessed a narrow, elevated snout and laterally
compressed, serrate teeth, unlike modern crocodilians, but
superficially similar to those of theropod dinosaurs. Lever arms of
the mandibular adductors were generally relatively greater than those
of Crocodylus niloticus. Some of the adductors and the depressor
mandibulae were relatively larger than in Alligator mississippiensis.
Thus Sebecus may have had a stronger bite than the modern forms
examined. The form of the teeth suggests use in cutting. Some theropod
dinosaurs are similar to sebecosuchians in the possession of
relatively deep, narrow snouts and laterally-compressed, serrate
teeth. However, the adductor structure was substantially different
from that of Sebecus. The presence of muscle and tendon attachments in
Sebecus suggests the adductor structure of mesoeucrocodylians is
conservative and was established before divergence of the
sebecosuchian and neosuchian lineages. No results presented here
contradict the interpretation of sebecosuchians as land-dwelling
predators.