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New theropod: Austroraptor


The paper is:

Fernando E. Novas, Diego Pol, Juan I. Canale, Juan D. Porfiri and Jorge O. Calvo. in press. A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids. Proc. R. Soc. B doi:10.1098/rspb.2008.1554

The abstract:

Fossils of a predatory dinosaur provide novel information about the evolution of unenlagiines, a poorly known group of dromaeosaurid theropods from Gondwana. The new dinosaur is the largest dromaeosaurid yet discovered in the Southern Hemisphere and depicts bizarre cranial and postcranial features. Its long and low snout bears numerous, small-sized conical teeth, a condition resembling
spinosaurid theropods. Its short forearms depart from the characteristically long-armed condition of all dromaeosaurids and their close avian relatives. The new discovery amplifies the range of morphological disparity among unenlagiines, demonstrating that by the end of the Cretaceous this clade included large, short-armed forms alongside crow-sized, long-armed, possibly flying representatives. The new dinosaur is the youngest record of dromaeosaurids from Gondwana and represents a previously unrecognized lineage of large predators in Late Cretaceous dinosaur faunas mainly dominated by abelisaurid theropods.

Keywords: Theropoda; Dromaeosauridae; Unenlagiinae; Cretaceous; South America; forelimb

And some info on the critter:

(a) Systematic palaeontology

Theropoda (Marsh 1884)
Coelurosauria (Huene 1920)
Deinonychosauria (Colbert & Russell 1969)
Dromaeosauridae (Matthew & Brown 1922)
Unenlagiinae (Bonaparte 1999)
Austroraptor cabazai, new taxon.

(b) Holotype
Specimen number MML-195 consists of right frontal and postorbital, lacrimals, maxillae and dentaries with teeth, right surangular and prearticular, cervicals 3, 5, 6, 7 and 8, dorsals 2 and 4, isolated ribs and gastralia, right humerus, manual ungual of digit III, left pubic shaft, left femur, and right tibia, astragalus, calcaneum, metatarsal III and pedal phalanges I-2, II-2, III-4 and IV-2 (figure 1).

(c) Etymology
Austroraptor, from austral in reference to southern South America, and raptor, thief; and cabazai, in honour to the late He´ctor Cabaza, founder of the Museo Municipal de Lamarque.

(d) Locality and horizon
Allen Formation (Campanian?Maastrichtian; Martinelli & Foriasepi 2004), Bajo de Santa Rosa (408030 2800 S, 668480 0300 W), approximately 90 km southwest of Lamarque town, R?o Negro Province, Argentina. Theropod dinosaurs collected from the Allen Formation include the abelisaurid Quilmesaurus curriei (see Juarez Valieri et al. 2007), a yet unnamed alvarezsaurid (Agnol?´n et al. 2006), and indeterminate tetanurans (Coria & Salgado 2005).

(e) Diagnosis
A large dromaeosaurid with the following combination of characters that distinguish it from other members of this group (autapomorphies marked with an asterisk): lacrimal highly pneumatized, with descending process strongly curved rostraly, and caudal process flaring out horizontally above orbit (differing from Laurasian dromaeosaurids, but unknown for other unenlagiines); postorbital lacking dorsomedial process for articulation with the frontal, and with squamosal process extremely reduced (differing from Laurasian dromaeosaurids, but unknown for other unenlagiines); maxillary and dentary teeth small, conical-shaped, devoid of serrations and flutted (as in Buitreraptor); humerus short, representing slightly less than 50 per cent of femur length (a smaller ratio than in other dromaeosaurids and paravians); pedal phalanx II-2 transversely narrow, contrasting with the extremely robust phalanx IV-2 (differing from other dromaeosaurids, including unenlagines, but resembling the condition of advanced troodontids).

------------------------------------------- Jose Ignacio Ruiz-Omeñaca Museo del Jurásico de Asturias (MUJA) E-33328 Colunga, Spain www.museojurasicoasturias.com www.aragosaurus.com -------------------------------------------