Pederpes finneyae, AN ARTICULATED TETRAPOD FROM THE TOURNAISIAN OF WESTERN SCOTLAND
The Tournaisian tetrapod Pederpes finneyae is described in detail, from the holotype and only specimen. The specimen derives from the Ballagan Formation, Tournaisian CM palynozone and is the earliest post-Devonian tetrapod known from articulated remains. It is preserved almost complete except for the tail, some skull regions and a few limb extremities. The animal resembles Whatcheeria deltae from the Viséan of Iowa, especially in the skull morphology, although the two differ in characters such as the lateral line expression, dermal ornament expression, proportions of the sub-orbital portion of the jugal and several other dermal skull characters. The postcranial skeleton of Pederpes shows several unique features, including the structure of the leading edges of the cleithrum and clavicle, the form of the rib flanges and a possible supernumerary digit on the manus. The humerus is also unusual in possessing a spike-like latissimus dorsi process, most like that of Baphetes. An investigation of the phylogenetic position of the whatcheeriids is carried out by comparing the results from two recently published databases. The clade lies very close to the base of the tetrapod stem group, although according to the dataset employed, the whatcheeriids compete with Crassigyrinus for the next most basal node after the Devonian forms. Possible whatcheeriids also occur in the Viséan of Australia and the Tournaisian of Ireland and less certainly elsewhere, making the whatcheeriids a long-lasting clade, widely distributed in time and space.
Key Words: anatomy; Carboniferous; Calciferous Sandstones; phylogeny; skeleton; whatcheeriid.
p1 Current address, Department of Earth Sciences, University of Cambridge CB2 3EQ.