A new scaphognathine pterosaur from the Upper Jurassic Morrison Formation of Wyoming, USA

Abstract

A partial rostrum of a new species of scaphognathine pterosaur, distinguished by a thin median crest along its dorsal margin and a deep embayment of the dental margin, is the first identifiable cranial fragment of a pterosaur from the Upper Jurassic Morrison Formation of western North America. By contrast with pterodactyloids, cranial crests are rare in “rhamphorhynchoids” and this is the first record of such a structure. The new material provides fresh insights into the taxonomic diversity of Late Jurassic North American pterosaurs. Based on the ratio of the skull and skeleton of Scpahognathus, the fragment represents an individual with an estimated wing span of 2.5 m. Consequently, this is one of the largest “rhamphorhynchoids” found so far. A mandible fragment from the same quarry has closely spaced alveoli, therefore cannot be referred to the rostrum. Its large size indicates another large “rhamphorhynchoid” in the Morrison Formation.

Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy

“…The megaraptorid ulna narrows distally, a condition similar to that of Allosaurus (e.g., Madsen, 1976) or basal coelurosaurs (e.g. Guanlong, Ornitholestes, Coelurus; Ornithomimids; Nichols and Russel, 1985;Xu et al, 2006;Osborn, 1903;Carpenter, 2005). But absent in megalosauroids (Dong, 1984;Charig and Milner, 1997) and derived coelurosaurs (e.g.…”

“…The humerus of Megaraptor (Porfiri et al, 2014) and Australovenator (White et al, 2012) resembles basal tetanurans (e.g., Allosaurus, Acrocanthosaurus, Piatnitzkysaurus; Madsen, 1976;Currie and Carpenter, 2000;Bonaparte, 1986) and basal coelurosaurs (e.g., Coelurus, Ornitholestes, Guanlong; Osborn, 1903;Carpenter, 2005;Xu et al, 2006; fig. 1) in being sigmoidshaped in anterior and lateral views, with a prominent deltopectoral crest.…”

“…However, the humerus of both Megaraptor and Australovenator exhibits a deep longitudinal furrow that runs on the medial surface of the shaft, distally to the internal tuberosity, a feature also present in Fukuiraptor and some coelurosaurs (Deinonychus, tyrannosaurids;Ostrom, 1969;Brochu, 2002). This character is absent in other coelurosaurs like Chilantaisaurus, Ornitholestes, Coelurus, oviraptorosaurs (Benson and Xu, 2008;Osborn, 1903;Carpenter, 2005;Lu, 2002), and non-coelurosaurian tetanurans (e.g. Allosaurus, Acrocanthosaurus, Piatnizkysaurus; Madsen, 1976;Currie and Carpenter, 2000;Bonaparte 1986) ( fig.…”

“…2), and are separated by deep extensor and flexor grooves not present in non-celurosaurian tetanurans. In this regards, the distal end of the humerus of Australovenator (White et al, 2012) resembles coelurosaurs like Coelurus, Ornitholestes (Carpenter, 2005), Guanlong (IVPP IVPP V14531), Deinonychus (Novas, 1996) (fig. 2) and Aves, and may suggest a more complex folding system than in basal theropods, a hypothesis that needs to be tested properly.…”

“…proximodistally shallower semilunate carpal of basal tetanurans (e.g., Allosaurus, Acrocanthosaurus) and basal coelurosaurs, such as Tanycolagreus (Carpenter et al, 2005), Sinosauropteryx (Currie and Chen, 2001), Scipionyx (Dal Sasso and Maganuco, 2011), Coelurus, and ornithomimosaurs (Kobayashi and Lü, 2003).…”