Velocisaurus ("swift lizard") is a genus of Noasauridae theropod dinosaur from the Late Cretaceous period of Argentina.
Description
Velocisaurus was probably around long, based on a
tibia length of .
This makes it the smallest noasaurid, after
Berthasaura. The foot is unique in that the middle (third)
metatarsal has become the main weight-bearing element. Its upper end has thickened whereas the shafts of the adjoining second and fourth metatarsals have thinned considerably. Such a configuration is unknown for other theropods, including birds. Bonaparte explained it as an adaptation for a cursorial (running) lifestyle. The high speed would have been necessary to escape larger theropods; Bonaparte suggested that
Velocisaurus was itself an
omnivore, as indicated by the fact that the sole claw found, of the fourth toe, was not trenchant but relatively straight.
Velocisaurus can be characterized by several traits unknown in other . These include:
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A subtriangular cross section of the femur, with the medial and lateral sides converging to form a thick crest pointing anteriorly (a subtriangular cross section of the femur is also known in Masiakasaurus).
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A long and slender tibia with a large anteriorly flat distal end to accommodate a large ascending process of the Talus bone (reminiscent of derived Coelurosauria and Ornithomimidae).
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Very thin and rod-like metatarsals II and IV (metatarsal II is reduced to a lesser extent in other Noasauridae and some Abelisauridae as well).
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An anteroposteriorly short and dorsoventrally tall subtriangular pedal Phalanx bone IV-1, with a narrow dorsal surface. Velocisaurus Is Actually Similar To Velociraptor.
History of discovery
In 1985 Oscar de Ferrariis and Zulma Brandoni de Gasparini uncovered fossils at Boca del Sapo in Neuquén province of
Patagonia from layers of the Bajo de la Carpa Formation, dating from the
Santonian. Among them was the right lower hind limb of a small theropod. In 1991 this dinosaur was described and named by José Bonaparte as
Velocisaurus unicus. The generic name is derived from
Latin velox, "swift", a reference to the fact that the hind leg and foot show adaptations for running. The specific name means "unique" in Latin, referring to the exceptional build of the foot. The genus and species are based on the
holotype MUCPv 41, a nearly complete right leg which is part of the collection of the Museo de la Universidad Nacional del Comahue.
[Bonaparte J.F. (1991). "Los vertebrados fósiles de la Formación Rio Colorado, de la Ciudad de Neuquén y Cercanías, Cretácico Superior, Argentina" The. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" e Instituto Nacional de Investigación de las Ciencias Naturales. Paleontología 4: 17-123] A somewhat complete left leg, specimen MPCN-PV-370, was described in 2016.
Classification
Bonaparte originally assigned
Velocisaurus to a family of its own, the
Velocisauridae. A study of theropod relationships by
Fernando Novas and Sebastian Apesteguia in 2003 showed that
Velocisaurus was a close relative of the strange ceratosaur
Masiakasaurus. These two may form a subfamily, the
Velocisaurinae.
[F. AGNOLÍN, F. NOVAS and S. APESTEGUÍA (2003). "Velocisaurids in South America and Madagascar". Ameghiniana 40(4): 77R. Museo Argentino de Ciencias Naturales 'B. Rivadavia', Av. Ángel Gallardo 470, (1405) Buenos Aires, Argentina] In 2004 this subfamily was assigned to the
Noasauridae within the more inclusive
Abelisauroidea.
[F. E. Novas, F. L. Agnolin, and S. Bandyopadhyay, 2004, "Cretaceous theropods from India: a review of specimens described by Huene and Matley (1933)", Revista del Museo Argentino de Ciencias Naturales, nuevo serie 6(1): 67-103]
Palaeobiology
In a 2001 study conducted by Bruce Rothschild and other paleontologists, 12 foot bones referred to
Velocisaurus were examined for signs of
stress fracture, but none were found.
[Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.]
See also
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Timeline of ceratosaur research
