New cranial remains of Comahuesuchus brachybuccalis (Archosauria, Crocodyliformes) from the Late Cretaceous of Rio Negro province, Argentina

AGUSTIN MARTINELLI

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2003 vol. 40 p. 559 - 572

0002-7014

New cranial remains of Comahuesuchus brachybuccalis from the Late Cretaceous Bajo La Carpa Formation of Río Negro Province (Argentina) are described. C. brachybuccalis differs from all other crocodyliforms in having the association of the following derived features: extremely short, wide and circular snout; five anterior small teeth in the maxilla except the third hypertrophied caniniform; eleven teeth in the dentary with the anterior ones procumbent; all lower teeth small and circular in cross section except the tenth hypertrophied caniniform; dorsally opened paracanine fossa in the posterior maxillary region; contact among the ectopterygoid, pterygoid and palatine in the ventral region of the pterygoid wing; lachrymal with a long and thin process projecting laterally; and anterior portion of the dentary low and transversaly broad, with an anteroposterior elongated symphysis extending at the level of the ninth tooth. The phylogenetic analysis nests C. brachybuccalis within the notosuchian clade, also represented by Malawisuchus mwakasyungutiensis and Chimaerasuchus paradoxus from the Early Cretaceous of Africa and China, and Notosuchus terrestris and Sphagesaurus huenei from the Late Cretaceous of South America. This group is diagnosed by having the external surface of the premaxilla and maxilla with two plane of exposure, one facing laterally (almost vertical) and the other dorsolaterally (almost horizontal); the dentary extending beneath the mandibular fenestra; a reduced number of maxillary teeth; and the articular facet for the quadrate condyle almost twice as long as wide lacking a posterior transversely ridge (uncertain in Comahuesuchus and Sphagesaurus).