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
Temporal range: Oligocene-Pliocene
Shell
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Suborder: Cryptodira
Superfamily: Chelonioidea
Family: Dermochelyidae
Genus: †Psephophorus
von Meyer, 1847
Type species
†P. polygonus
Species
  • †P. polygonus
  • †P. calvertensis
  • †P. eocaenus
  • †P. oregonesis
  • †P. californiensis
  • †P. terrypratchetti
  • †P. rupeliensis
  • †P. scaldii

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]
Hypothetical reconstruction of Psephophorus terrypratchetti

See also

References
  1. Kohler, R. (September 1995). "Köhler - A new species of Psephophorus". Journal of the Royal Society of New Zealand. 25 (3): 371–384. doi:10.1080/03014223.1995.9517495. Retrieved 18 June 2020.
  2. "The Oregon Fossil Guy". www.mailtribune.com. 2008-04-27. Retrieved 2008-06-28.
  3. "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.
  4. Proceedings; page 8. By the Zoological Society of London; published 1891. Retrieved on June 28th, 2008.
  5. "New Zealand species of Psephophorus". Everything2.com (partially derived from an interview with Terry Pratchett on The Discworld Companion). 2001-11-01. Retrieved 2008-06-27.
  6. "New Remains of Psephophorus polygonus (Chelonii: Dermochelyidae) from the Miocene of Southern Italy" (PDF). digilander.libero.it. 2004. Retrieved 2008-06-27.
  7. A Manual of Palaeontology; page 1091. By Henry Alleyne Nicholson and Richard Lydekker; published 1889, Blackwood. Retrieved on June 28th, 2008.
  8. Seeley, H. G. (1880). "Note on Psephophorus polygonus, v. Meyer, a new Type of Chelonian Reptile allied to the Leathery Turtle". Quarterly Journal of the Geological Society. 36 (406–413): 406–413. doi:10.1144/GSL.JGS.1880.036.01-04.32.
  9. "Turtles of the World". nlbif.eti.uva.nl. Archived from the original on 2011-06-08. Retrieved 2008-06-27.
  10. "Fossil sea turtles (Chelonii, Dermochelyidae and Cheloniidae) from the Miocene of Pietra Leccese (late Burdigalian-early Messinian), Southern Italy" (PDF). 2007. Archived from the original (PDF) on 2009-04-19. Retrieved 2008-06-27.
  11. "Bone histological results of Testudinata" (PDF). hss.ulb.uni-bonn.de. Retrieved 2008-06-27.
  12. "Psephophorus calvertensis at the Paleobiology Database". paleodb.org. Retrieved 2008-06-27.
  13. Weems, Robert E. (1974). "Middle Miocene sea turtles (Syllomus, Procolpochelys, Psephophorus) from the Calvert Formation". Journal of Paleontology. 48 (2): 279–303.
  14. "Psephophorus eocaenus at the Paleobiology Database". paleodb.org. Retrieved 2008-06-27.

Further reading
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