Genus: Skorpiovenator Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009

Classification: Dinosauria - Saurischia - Theropoda - Ceratosauria - Abelisauroidea - Abelisauridae - Carnotaurinae

Etymology: The generic name derives from the Latin words skorpios (scorpion) and venator (hunter) because of the abundance of living scorpions moving around the excavation.

Synonyms: none

Type species: S. bustingorryi Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009

Other Species: none

Diagnosis: as for type species

Species: Skorpiovenator bustingorryi Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009

Etymology: The specific name honours the late Manuel Bustingorry, owner of the farm where the specimen was excavated.

Synonyms: none

Holotype: MMCH-PV 48 (Museo Municipal “Ernesto Bachmann”, Villa El Chocon, Neuquen, Argentina): an articulated skeleton represented by an almost complete skull and mandibles and most of the postcranial bones, lacking the right forearm and the distal half of the tail.

Referred Specimens: none

Time: Late Ctetaceous (Late Cenomanian–Early Turonian).

Horizon: The specimen was found in fluvial sandstones with intercalated mudstones, belonging to the lower levels of the Huincul Formation. This formation has yielded other theropod taxa, including the carcharodontosaurid Mapusaurus roseae and the abelisaurid Ilokelesia aguadagrandensis. Skorpiovenator differs from the latter taxon in the morphology of thepostorbital and quadrate bones.

Location: Bustingorry’s farm, 3 km NWof Villa El Chocon, Neuquen Province, NW Patagonia, Argentina.

Total length: The preserved length of the skeleton (taken from the premaxilla to the 12th caudal vertebra) is 4.35 m, thereby allowing a total length estimate of 6 m for the complete skeleton.

Mass: 500-700 kg.

Diagnosis: Skorpiovenator is distinguished from other abelisaurids on the basis of the following unique traits: (1) ascending process of maxilla homogeneously wide rostrocaudally, (2) maxillary horizontal ramus dorsoventrally deep with subparallel dorsal and ventral margins, (3) maxilla/jugal contact subvertical, (4) 19 maxillary teeth, (5) lacrimal rostrally projected and with well-developed suborbital process, (6) quadratojugal with pronounced caudal notch, (7) dentary with caudoventral process bifurcated to receive rostral end of angular, and (8) angular with rostral end dorsoventrally deep to fit between splenial and prearticular

Comments: The holotype Skorpiovenator bustingorryi (complete skeleton) was found in Late Cenomanian–Early Turonian outcrops of NW Patagonia, Argentina. This new taxon is deeply nested within a new clade of South American abelisaurids, named Brachyrostra. Within brachyrostrans, the skull shortening and hyperossification of the skull roof appear to be correlated with a progressive enclosure of the orbit, a set of features possibly related to shock-absorbing capabilities. Moreover, the development of horn-like structures and differential cranial thickening appear to be convergently acquired within Abelisauridae. Based on the similarities between Skorpiovenator and carcharodontosaurid tooth morphology, we suggest that isolated teeth originally referred as post-Cenomanian Carcharodontosauridae most probably belong to abelisaurids (Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009).

Skorpiovenator is one of the most complete and informative abelisaurids yet known. The almost complete and articulated skeleton of this new taxon offers valuable osteological details that help to clarify character distribution among abelisaurid theropods. The discovery of Skorpiovenator also helps to clarify the chronostratigraphical distribution of other Gondwanan theropods, such as carcharodontosaurids. These were large-sized predatory dinosaurs that some authors interpreted as surviving into the latest Cretaceous times. Such assumption was based on small-sized, carcharodontosaurid-like teeth collected in post-Cenomanian beds. However, these purportedly carcharodontosaurid teeth exhibit several features that are also present in Skorpiovenator among abelisaurids, such as straight dental crowns and well-demarkated enamel wrinkles . Thus, we consider the record of post-Cenomanian carcharodontosaurids as dubious. Given the possibility that these teeth actually represent abelisaurids, they cannot be used to contradict an early Late Cretaceous (Cenomanian) extinction of carcharodontosaurids in South America, as hypothesised by Novas et al. (2005) (Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009).

Illustrations:
Articulated skeleton of Skorpiovenator bustingorryi, still in the plaster jacket (modified from Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009).

Complete skull and jaws of S. bustingorryi, drawing with bone references (modified from Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009).

Skorpiovenator bustingorryi classification (modified from Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009).

References:
Canale, J. I., Scanferla, C. A., Agnolin, F. L., and Novas, F. E., 2009. New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods: Naturwissenschaften, v. 96, p. 409-414.

© Tetrapoda Database Roman Ulansky roman.ulansky@gmail.com or adios85@mail.ru