Palaeocarcharodon

Palaeocarcharodon; Temporal range: Middle Paleocene–Early Eocene, 61.7–55.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Fossil teeth of Palaeocarcharodon orientalis (the largest three) from Khouribga (Morocco), alongside teeth of Otodus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Division:	Selachii
Order:	Lamniformes
Family:	†Otodontidae
Genus:	†Palaeocarcharodon; Casier, 1960
Type species
	†Carcharodon orientalis; (Sinzow, 1899)
Species
	†P. orientalis Sinzow, 1899; †P. landanensis? Sinzow, 1899;
Synonyms
	Carcharodon orientalis? Sinzow, 1899; Palaeocarcharodon landanensis? (Casier, 1960); Carcharodon landanensis? Leriche, 1942;

Palaeocarcharodon, also known as the pygmy white shark, is a genus of shark within the family Cretoxyrhinidae,^[1] that lived about 61.7 to 55.8 Ma during the Middle Paleocene and Early Eocene. It currently contains a sole species P. orientalis.^[2] An additional species, P. landanensis, is now considered a possible synonym of P. orientalis.^[3]

Taxonomy

History

As is the case with most sharks, the classification of Palaeocarcharodon is still debated. In 1899, the paleontologist Sinzow^[who?] named the shark as a new species of the genus Carcharodon, C. orientalis, since the teeth were serrated and had features similar to those of the current Great white shark (Carcharodon carcharias).^[4] In addition to C. orientalis, another very close species was suggested, C. landanensis, which would have more serrations on the teeth, with the cusps more reduced or almost vestigial, being found in more recent layers in Morocco and Europe, while C. orientalis was found in intermediate or recent layers. However, soon after, in 1960 it was suggested that "C." orientalis and "C." landanensis would belong to a new genus, Palaeocarcharodon.

In 2013, it was suggested that P. landanensis could be a senior synonym of P. orientalis, among other older articles, since many of the proposed differences between the two were inconsistent or appeared in some specimens of P. orientalis.^{[citation needed]} However, this idea is still debated, as many of these articles were not peer-reviewed, but the current consensus is that P. orientalis is the only valid and definitive species of the genus, with new species potentially existing, but still under debate.^{[citation needed]} In the same year, it was theorized that Palaeocarcharodon was a member of Otodontidae, however, currently many recent articles place it in the family Cretoxyrhinidae.^[2]

Some teeth found in Russia, in Volgograd, show Palaeocarcharodon without serrations, usually classified as Palaeocarcharodon cf. orientalis or Palaeocarcharodon sp., since historically, Palaeocarcharodon in general has been considered a monospecific genus.^{[citation needed]}

Description

Like most prehistoric sharks, Palaeocarcharodon has an uncertain size, but it is estimated that it was comparable in size to mako sharks or the modern great white shark. Teeth of Palaeocarcharodon are triangular, labio-lingually compressed, with quite irregular serrations and serrate lateral cusplets. They can reach a size of about 3–6 centimetres (1.2–2.4 in).^[5]

Distribuition

Like most sharks, Palaeocarcharodon had a body made primarilly of cartilage, not bone, currently being known by a few possible vertebrae and several teeth.^{[clarification needed]} Fossils of Palaeocarcharodon have been found in the Americas, Asia, Russia, North Africa, and Europe.

References

^ Mikael Siverson; Johan Lindgren; Michael G. Newbrey; Peter Cederström; Todd D. Cook (2013). "Cenomanian–Campanian (Late Cretaceous) mid-palaeolatitude sharks of Cretalamna appendiculata type". Acta Palaeontologica Polonica. 60 (2): 339–384. CiteSeerX 10.1.1.1027.6182. doi:10.4202/app.2012.0137. S2CID 58906204.
^ ^a ^b Kordikova, E. G.; Polly, P. D.; Alifanov, V. A.; Roček, Z.; Gunnell, G. F.; Averianov, A. O. (2001). "Small vertebrates from the Late Cretaceous and early Tertiary of the northeastern Aral Sea Region, Kazakhstan" (PDF). Journal of Paleontology. 75 (2): 390–400. Bibcode:2001JPal...75..390K. doi:10.1666/0022-3360(2001)075<0390:svftlc>2.0.co;2.
^ Casier, E. (1960). "Note sur la collection des poissons paléocènes et éocènes de l'Enclave de Cabinda (Congo)". Annales du Musée du Congo Belge A. Série III. 1 (2): 1–48.
^ Sinzow, I.F. (1899). Notizen über die Jura-, Kreide- und Neogen-Ablagerungen der Gouvernements Saratow, Simbirsk, Samara und Orenburg. Odessa Universitet Zapiski. pp. 1–106.
^ G. R. Case. - Palaeocarcharodon Orientalis (SINZOW) (Neoselachii: Cretoxyrhinidae), from the Paleocene of Maryland - Lab. de Paléontologie des Vertébrés, 1989

[Siversonetal2013-1] Mikael Siverson; Johan Lindgren; Michael G. Newbrey; Peter Cederström; Todd D. Cook (2013). "Cenomanian–Campanian (Late Cretaceous) mid-palaeolatitude sharks of Cretalamna appendiculata type". Acta Palaeontologica Polonica. 60 (2): 339–384. CiteSeerX 10.1.1.1027.6182. doi:10.4202/app.2012.0137. S2CID 58906204.

[Kordikova-2] Kordikova, E. G.; Polly, P. D.; Alifanov, V. A.; Roček, Z.; Gunnell, G. F.; Averianov, A. O. (2001). "Small vertebrates from the Late Cretaceous and early Tertiary of the northeastern Aral Sea Region, Kazakhstan" (PDF). Journal of Paleontology. 75 (2): 390–400. Bibcode:2001JPal...75..390K. doi:10.1666/0022-3360(2001)075<0390:svftlc>2.0.co;2.

[3] Casier, E. (1960). "Note sur la collection des poissons paléocènes et éocènes de l'Enclave de Cabinda (Congo)". Annales du Musée du Congo Belge A. Série III. 1 (2): 1–48.

[4] Sinzow, I.F. (1899). Notizen über die Jura-, Kreide- und Neogen-Ablagerungen der Gouvernements Saratow, Simbirsk, Samara und Orenburg. Odessa Universitet Zapiski. pp. 1–106.

[5] G. R. Case. - Palaeocarcharodon Orientalis (SINZOW) (Neoselachii: Cretoxyrhinidae), from the Paleocene of Maryland - Lab. de Paléontologie des Vertébrés, 1989

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