Psephophorus is an extinctgenus 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]
Discovery and identification
Shell
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]
Relation to modern Leatherback sea turtles
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]
Species
restoration of Psephophorus californiensis based on morphological descriptionsHypothetical reconstruction of Psephophorus terrypratchetti
Psephophorus polygonus is the type species, and was discovered by von Meyer in 1846.[8]Fossils of the species have shown bony, carapacial ridges, adjacent, small and polygonal bony ossicles which measure about 22 × 25 mm.[10] When the ossicles extend further along the longitudinal axis, their size increases up to an average of 33 × 41 mm.[10]
Psephophorus calvertensis was first named by Palmer in 1909.[12] It was so named for being found in the Calvert Formation.[13]P. calvertensis is a rarely found specimen.[13]
Psephophorus eocaenus was first named by Andrews in 1901.[14]
Psephophorus californiensis was first named by Gilmore in 1937.[3]
Psephophorus terrypratchetti was discovered in the 1990s by Richard Köhler in New Zealand and named in 1995 after the author Terry Pratchett, who wrote a series of fantasy books set on a world carried on the back of a giant turtle.[1] This species reached 2.3–2.5 m (7.5–8.2 ft) in body length which is more than 80% bigger than P. eocaenus.[1]
^ ab"Sharktooth Hill Fauna, circa 2003". Shark Tooth Hill.com (optionally viewed as a Microsoft Word document). 2003. Archived from the original on 2012-12-09. Retrieved 2008-06-28.
^ abProceedings; page 8. By the Zoological Society of London; published 1891. Retrieved on June 28th, 2008.
^ abWeems, Robert E. (1974). "Middle Miocene sea turtles (Syllomus, Procolpochelys, Psephophorus) from the Calvert Formation". Journal of Paleontology. 48 (2): 279–303.
