Vayuraptor

''Vayuraptor'' (meaning "wind thief") is a genus of basal coelurosaurian (possibly megaraptoran) theropod dinosaur that lived in the Early Cretaceous (Barremian) Sao Khua Formation of Thailand. The genus contains a single species, ''V. nongbualamphuensis'', known from a partial skeleton.

Discovery

The holotype and referred specimens of ''Vayuraptor'' (stored in the Sirindhorn Museum under the Department of Mineral Resources) were discovered in 1988 by Paladej Srisuk at Phu Wat Site A1, Nong Bua Lamphu Province, Thailand. The generic name means "wind thief", named after the Hindu god of wind Vayu and the Latin word ''raptor'', which means thief. This name was chosen because ''Vayuraptor'' possesses a long and gracile , which suggests it was very fast and agile. The specific name is named after the province ''Vayuraptor'' was found in ( Nong Bua Lamphu Province).

The holotype of ''Vayuraptor'' (SM-NB A1-2) is a left tibia with an associated and , which are fused together, collectively referred to as an astragalocalcaneum. Referred material of ''Vayuraptor'' consist of a right (PRC-NB A1-11), part of a (PRC-NB A1-4), a rib from an unknown part of the skeleton (PRC-NB A1-10), probably part of a (PRC-NB A1-3), a (PRC-NB A2-20), and a probable (PRC-NB A2-16).

Description

''Vayuraptor'' was a mid-sized theropod, estimated at in length. The holotype of ''Vayuraptor'' was inferred to be a mature individual, based on the fusion of its astragalus and calcaneum. As a possible megaraptoran, ''Vayuraptor'' would have had a long snout, large claws, light body, and long slender legs.

The elements that correspond to the forelimb of ''Vayuraptor'' are very fragmentary. In overall morphology, the (the bone which extends from the shoulder blade) is higher than long and is shaped like a semicircle. The posteroventral (runs from the rear to the bottom) process of the coracoid tapers from the back of the coracoid to the bottom due to breakage. The bottom of the coracoid is expanded beyond the rim of the glenoid facet. The infraglenoid groove is absent from the coracoid. The distal (farther from the body) part of a manual phalanx is preserved. It does not have distinct extensor pits on the upper surface proximal (closer to the body) to the distal articulation surface, which is a trait only found in coelurosaurs. Part of the pubis is preserved, and the morphology of the pubic shaft is generally similar to other theropods, such as ''Neovenator.''

The left tibia is complete, long, and slender, with an expanded cnemial crest. The distal cnemial process is rounded, and the lateral condyle forms a horizontal projection. The tibial shaft is nearly straight, with a slight medial curve at its distal portion. Its mid-shaft cross-section is sub-circular, with a flattened anterior side (D-shaped), similar to '' Australovenator'' and ''Aerosteon''. The cnemial crest does not project proximally, and the lateral condyle is small, offset from the lateral side of the proximal tibia by a posterior cleft. The fibular crest is a prominent ridge on the proximal half of the tibia, and remains distinct from the proximal articular surface. The lateral malleolus at the distal end extends further than the medial malleolus and is overlapped by the calcaneum.

The left astragalus and calcaneum are well preserved, with the ascending process of the astragalus missing its tip, but it can be discerned that it is sheet-like in morphology. The distal surface of the astragalus is concave, and in distal view, its trapezoidal outline is similar to that of ''Australovenator'' and other megaraptorans. The ascending process is 1.7 times the height of the astragalus body, matching that of '' Fukuiraptor''. Both the astragalus and calcaneum are unfused, and the calcaneum has a well-developed facet for the tibia.

Paleoenvironment

With the first fossils of the genus being discovered in the Sao Khua Formation, ''Vayuraptor'' possibly shared its habitat with the dinosaurs '' Phuwiangvenator'' (which was also named in the same paper as ''Vayuraptor''), ''Kinnareemimus'', '' Siamosaurus'', ''Siamotyrannus'' and '' Phuwiangosaurus''.

References

{{Taxonbar, from=Q63981557

Coelurosauria
Dinosaur genera
Barremian dinosaurs
Fossil taxa described in 2019
Dinosaurs of Thailand