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
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
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]
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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.
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abProceedings; page 8. By the Zoological Society of London; published 1891. Retrieved on June 28th, 2008.
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abWeems, Robert E. (1974). "Middle Miocene sea turtles (Syllomus, Procolpochelys, Psephophorus) from the Calvert Formation". Journal of Paleontology. 48 (2): 279–303.