Sunday 15 January 2012

A Pterosaur from the Jurassic of Dorset, England.

The Pterosaurs were winged archaeosaurian reptiles that lived during the Mesozoic. They are divided into two groups, the more primitive Rhamphorhynchoids, which were generally small animals, with long tails and teeth, and the more derived Pterodactyls which had mostly lost their tails and teeth, and grew to large, even immense sizes. The Rhamphorhynchoids arose in the Middle Triassic, and were the dominant group till the end of the Jurassic, when the the majority of lineages died out, though a few groups survived into the Early Cretaceous. The Pterodactyls arose from within the Rhamphorhynchoids in the Middle Jurassic, and reached their peak diversity in the Cretaceous, going extinct at the end of the period.

In a paper published in a draught form on the Acta Palaeontologica Polonica website in November 2011, and accepted for publication in the journal at a later date, David Martill of the School of Earth and Environmental Sciences at the University of Portsmouth and amateur palaeontologist Steve Etches describe a new Pterosaur specimen from the Late Jurassic of Kimmeridge Bay in Dorset.

The new specimen belongs to a group of Rhamphorhynchoids called the Monofenestratens, considered to be the closest relatives of the Pterodactyls, which are not well known outside of China, making the new find significant. Late Jurassic pterosaurs have a patchy record in the UK, with quite a few specimens, but most not well enough preserved for good taxonomic analysis; in particular many specimens lack their heads, which is the most important part of the body in Pterosaur Taxonomy.

The new specimen consists of a flattened skull preserved in dark grey mudstone, from the Lower Kimmeridge Clay Formation. It was found within the Autissiodorensis ammonite biozone, making it about 155 million years old. It consists of a skull 326 mm long and 55 mm high at its highest point (the rear). The skull is extremely pointed, and has been named Cuspicephalus scarfi; making it Scarf's Pointy-Headed Pterosaur, in honour of the cartoonist Gerald Scarf, who often draws caricatures with very pointy noses.

(A) Photograph of the skull of Cuspicephalus Scarfi in the original matrix, scale bar = 50 mm, by Bob Loverage of the School of Earth and Environmental Sciences at the University of Portsmouth and used in Martill and Etches (2011). (B) Line drawing of the skull showing (j) Jugal, (naof) Nasoantorbital fenestra, (m) Maxilla, (o) Orbit, (pm) Premaxilla, (q) Quadrate, (sc) Sagital Crest, (sq) Squamosal, (tr np) Traces of Nasal Process. From Martill and Etches (2012). (C) Reconstruction of the intact skull. From Martill and Etches (2012).

The specimen was discovered by Steve Etches in 2009 on the foreshore at Kimmeridge Bay, Dorset, part of the Jurassic Coast World Heritage Site. The area is well known for the discovery of vertebrate fossils, having in the past produced sharks, boney fish, ichthyosaurs, plesiosaurs, crocodiles and a variety of dinosaurs. Despite the area's World Heritage Site status, it is still quite possible to collect fossils there legally, since the area is an eroding coast, and fossils left in place will be consumed by the sea.

Simplified geological map of the area where the fossil was found. From Martill and Etches (2011).