Psephophorus

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]

• 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]

• List of organisms named after famous people (born 1900–1949)
• Archelon
• Gigantatypus
• Largest prehistoric animals

• Callaway, Jack M.; Nicholls, Elizabeth L. Ancient Marine Reptiles.
• Nielsen, Eigil (1959). "Eocene Turtles from Denmark" (PDF). Bulletin of the Geological Society of Denmark. 14 (2): 96–114.
• Wieland, G. R. (1900). "Some Observations on Certain Well-Marked Stages in the Evolution of the Testudinate Humerus". American Journal of Science. Series 4. 9 (54): 413–424 [p. 421]. doi:10.2475/ajs.s4-9.54.413.
• Hay, O. P. (1898). "On Protostega, the Systematic Position of Dermochelys, and the Morphogeny of the Chelonian Carapace and Plastron". The American Naturalist. 32 (384): 929–948. doi:10.1086/277069. S2CID 86769103.

• "geosites.dk".
• "zipcodezoo.com".
• "paleodb.org".
• "www.taxonomy.nl".
• "web.usal.es". Archived from the original on 2007-06-23.
• "www.charleston.net". Archived from the original on 2007-06-26.