A New Species of Istiodactylus (Pterosauria, Pterodactyloidea) from the Lower Cretaceous of Liaoning, China

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Istiodactylus sinensis, sp. nov., from the Jiufotang Formation of Liaoning, People's Republic of China, is described on the basis of a single nearly complete and nearly osteologically adult specimen. This is the tenth pterosaur described from this formation and the eighteenth pterosaur species described from northeastern China in almost half as many years. The species is placed in the Istiodactylidae, which was previously a monospecific family of pterodactyloid pterosaurs known only from the Isle of Wight, England. The new form is distinct from the two other istiodactylid species. It is smaller, more plesiomorphic, and younger than Istiodactylus latidens, but larger and more derived than the contemporaneous Nurhachius ignaciobritoi. Istiodactylus sinensis is very similar to I. latidens, so that almost all of the previous autapomorphies of I. latidens are now synapomorphies of Istiodactylus. They differ most in that I. sinensis is much smaller than I. latidens. The length of the wingspan, skull, and most of the preserved limb elements of I. sinensis are about 63 percent of the wingspan and elements of I. latidens. This new specimen demonstrates that Istiodactylus is diagnosed by, among other characters, a dorsoventrally depressed but not laterally expanded rostrum, and the presence of a suborbital vacuity. A dorsal deflection of the alveolar margins of the jaws and a humerus between 55 percent and one and a half times the length of metacarpal IV are synapomorphies uniting the Istiodactylidae and the Anhangueridae.

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Journal of Vertebrate Paleontology, v. 26, issue 1, p. 70-78