The taxonomic diversity of British Jurassic pterosaurs
Student thesis: Doctoral Thesis
The taxonomic diversity of Jurassic pterosaurs is more poorly understood than that of their Cretaceous counterparts. Early to Middle Jurassic pterosaur-bearing formations are rare and suffer from a low fossil yield, resulting in an apparent Late Jurassic diversity spike. Recent studies have suggested this is a preservational bias rather than a taxonomic signal, however this is difficult to test given the low number of sizeable Jurassic pterosaur collections. The United Kingdom possesses Lower, Middle and Upper Jurassic pterosaur bearing horizons containing hundreds of fossils, making it one of the best Jurassic assemblages suitable for testing taxic diversity. Lower Jurassic deposits remain low yield but include the holotypes of Dimorphodon and Parapsicephalus. Parapsicephalus has previously been synonymised with Dorygnathus but is found to be a unique genus. An isolated humerus is identified as a campylognathoidid, marking the first occurrence of the group in Britain. The Middle Jurassic Taynton Limestone Formation (informally known as the Stonesfield Slate) has yielded more than 400 isolated pterosaur fossils with only one named genus, Rhamphocephalus. The type of Rhamphocephalus, is identified here as a teleosaurid skull table with the genus considered a nomen dubium. A new genus is erected for an isolated mandible and the Taynton Limestone Formation is found to include at least 3 pterosaur taxa. The Middle-Upper Jurassic Oxford Clay Formation is found to have a low diversity with the only named genus, Rhamphorhynchus jessoni, identified as a nomen dubium. The Upper Jurassic Kimmeridge Clay Formation has produced at least 4 pterosaurs, including a new species of Rhamphorhynchus. These findings suggest that Jurassic pterosaur diversity has been underestimated and is most likely higher than traditionally believed.
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