Friday, 6 September 2013

A Thalattosuchian Crocodiliforme from the Late Cretaceous of Argentina.

The Thalattosuchians were a group of marine Crocodiliformes (the group of Archosaurs that includes modern Crocodiles and a diverse range of Mesozoic animals) that were found in seas around the world from the Early Jurassic to the Early Cretaceous. They are not closely related to modern Crocodiles, but resembled them superficially due to their aquatic adaptations, and are often referred to as 'Marine Crocodiles'.

In a paper published in the May 2013 edition of the journal Palaeontology, Yanina Herrera, Zulma Gasparini and Marta Fernández of the División Paleontología Vertebrados at the Museo de La Plata in Argentina, describe a new species of Thalattosuchian from Late Cretaceous lithographic limestone at Los Catutos in Neuquén Province, Argentina.

The new species is placed in the genus Cricosaurus, and given the specific name lithographicus, in reference to the lithographic limestone in which it was found. The specimen comprises a complete skull with articulated lower jaws, dorsal, sacral and caudal vertebrae, pectoral girdle element, incomplete forelimb, pelvic girdle elements and an incomplete hind limb, preserved in five slabs. The Skull and mandible are on a single slab; they are somewhat crushed but essentially retain their life position. The other bones are more articulated. 

Cricosaurus lithographicus, skull and mandible. (A–B) Dorsal view; (A) photograph, (B) drawing. (C–D) Ventral view; (C) photograph, (D) drawing. (E) Snout in left lateral view. Abreviations: an, angular; ar, articular; bo, basioccipital; bsp, basisphenoid; cor, coronoid; cr. B, crest B; d, dentary; en, external nares; eo, exoccipital; fm, foramen magnum; fr, frontal; j, jugal; la, lacrimal; mx, maxilla; mef, medial eustachian foramen; na, nasal; oc, occipital condyle; pa, parietal; pl, palatine; pmx, premaxilla; po, postorbital; pref, preorbital fossa; pfr, prefrontal; pt, pterygoid; q, quadrate; r.ar, retroarticular process; san, surangular; sdg, surangular-dentary groove; so, supraoccipital; sof, suborbital fenestra; sq, squamosal; stf, supratemporal fenestra. All scale bars represent 100 mm.



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