Psephophorus
Psephophorus is an extinct genus of sea turtle that lived from the Oligocene to the Pliocene. Its remains have been found in Europe, Africa, North America, and New Zealand.[1] It was first named by Hermann von Meyer in 1847, and contains seven species, P. polygonus, P. calvertensis, P. eocaenus, P. oregonesis,[2] P. californiensis,[3] P. rupeliensis,[4] P. scaldii,[4] and a species discovered in 1995,[1][5] P. terrypratchetti.
Psephophorus is the only Miocene dermochelyid turtle found in Europe.[6] One species of Psephophorus could measure up to ten feet in length.[7]
Von Meyer originally named Psephophorus in 1846.[8] At first he was unable to identify the creature beyond its dermal plates, but when he later received a drawing he was able to describe the specimen, which was then in Pressburg, as a fragment of a carapace, which contained seventy bones.[8]
In 1879, H. G. Seeley was asked to study the Psephophorus specimen by Franz Ritter von Hauer, the Director of the Austro-Hungarian Imperial and Royal Geological Survey.[8] Up until then, the specimen's identity had been undeterminable, with even Seeley describing it at first to seem like "the dermal covering of an Edentate closely allied to the Armadilloes."[8] Seeley examined some bone fragments and concluded the specimen was that of a reptilian creature,[8] furthermore a chelonid. It also proved to be more closely related to Sphargis than any other type in the Chelonian order.[8]
For a long time, modern Leatherback sea turtles (Dermochelys) were believed to be descended directly from Psephophorus,[9] specifically the species P. polygonus.[10] However, a 1996 analysis by Wood et al. proved that most of the taxa in the two genera were not connected, meaning Psephophorus could not be a direct ancestor of the modern leatherbacks.[9] The platelets on Psephophorus are quite similar to those on Dermochelys, despite differences in outer morphology and size.[11] The platelet comprises an external compact layer and an internal zone of cancellous bone.[11]
