Allopleuron

Allopleuron (meaning "other side") is a genus of extinct sea turtle, which measured 2-to-2.5-metre (6 ft 7 in to 8 ft 2 in) long in life. The type species is Allopleuron hofmanni. It is a basal member of the clade Pancheloniidae,^[3] closely related to Protosphargis. Similar to Protosphargis, it was characterized by shell reduction.^[4]

Allopleuron Temporal range: Late Cretaceous–Oligocene 94.3–28.4 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossil specimen, Royal Belgian Institute of Natural Sciences
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira
Superfamily:	Chelonioidea
Family:	Cheloniidae
Subfamily:	†Allopleuroninae
Genus:	†Allopleuron Gray, 1831[1]
Species[2]
†A. hofmanni (Gray, 1831) †A. insulare (Cope, 1872) †A. lipsiense Karl, 2007 †A. qazaqstanense (Hay, 1908)

Fossil history

Top view

Allopleuron lived from the Late Cretaceous (Cenomanian age, 94.3 Ma) to the Oligocene (Rupelian age, 28.4 Ma), therefore surviving the Cretaceous-Paleogene extinction event. Fossils have been found from Germany, the Netherlands, Kazakhstan and the United States.^[2][5]

Life history

Allopleuron was believed to have used the Laurasian-Holarctic southern continental shelf as a breeding area.^[6] The modern day location of the breeding ground is along the coast of Asia. Allopleuron is believed to have eaten jellyfish, seaweed, or carcasses.^[7] It is believed that adult male Allopleuron lived off the coast of southeast Netherlands, and northeast Belgium due to the large amount of fossils in these areas. The area is believed to have been a sea grass meadow that was able to sustain the large population. The lack of remains from juvenile Allopleuron indicate that the young of the species lived elsewhere.^[6]

Phylogeny

Evers et al. (2019):^[3]

Panchelonioidea	†Toxochelys †Protostegidae Chelonioidea †Corsochelys Dermochelyidae †Nichollsemys †Allopleuron Cheloniidae †Argillochelys †Procolpochelys †Eochelone †Puppigerus †Ctenochelys †Peritresius †Cabindachelys

References

1. Gray, J.E. (1831), Synopsis Reptilium, Part I: 54 and 79
2. Hans-Volker Karl; Elke Gröning; Carsten Brauckmann (2012). "New materials of the giant sea turtle Allopleuron (Testudines: Chelonioidea) from the marine Late Cretaceous of Central Europe and the Palaeogene of Kazakhstan". Studia Palaeocheloniologica IV, Studia Geologica Salmanticensia. 9: 153–173.
3. Evers, Serjoscha W.; Barrett, Paul M.; Benson, Roger B. J. (2019-05-01). "Anatomy of Rhinochelys pulchriceps (Protostegidae) and marine adaptation during the early evolution of chelonioids". PeerJ. 7: e6811. doi:10.7717/peerj.6811. ISSN 2167-8359. PMC 6500378. PMID 31106054.
4. Hirayama, Ren (2005). "SYSTEMATIC POSITION OF PROTOSPHARGIS VERONENSIS CAPELLINI, AN ENIGMATIC SEA TURTLE FROM THE LATE CRETACEOUS OF ITALY". Journal of Vertebrate Paleontology (25): 70A.
5. "Fossilworks: Allopleuron". fossilworks.org. Retrieved 17 December 2021.
6. Universidad de Salamanca, Ediciones (2013-12-20). "Índice". Studia Historica. Historia Moderna. 35: 1. doi:10.14201/11405. ISSN 0213-2079.
7. "Marine Turtles". oceansofkansas.com. Retrieved 2019-05-05.