Heptranchias howelli

Heptranchias howelli; Temporal range: Middle Eocene-Early Miocene; ~37.2–20.43 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	Hexanchiformes
Family:	Hexanchidae
Genus:	Heptranchias
Species:	H. howelli
Binomial name
	Heptranchias howelli; Reed, 1946[1]
Synonyms
	Heptranchias howellii[2]; Notidanion howellii;

Heptranchias howelli, the sevengill shark, is a nektonic carnivore in the genus Heptranchias. It is an extinct species that ranged from 37.2 to 20.43 Ma.[3]

Fossil record

Teeth from Heptranchias howelli have been found in Europe. An antero-lateral tooth and an upper lateral tooth were found in Faxe, Denmark in 2014 . In addition, two incomplete antero-lateral teeth and an upper anterior tooth are kept in a private collection.[4] A 2015 study in Trelde Næs yielded a complete lower tooth, 17 incomplete lower teeth, and an unidentified broken tooth.[5]

Description

Teeth

The upper lateral teeth of the species have a long, acute, strongly sigmoid main cusp. This cusp is serrated and has a dispal cusplet. The main cusp of the antero-lateral teeth is triangular and carries eight mesial cusplets that increase in size along the lower mesial face. The antero-lateral teeth have six main cusplets, the sixth of which is very small. The first cusplet is slightly lower than the others.[4] The cusps are inclined at about a 45 degree angle distally.

The largest tooth found in Trelde Naes was 17.5 millimetres (0.69 in) mesio-distally, 8.5 millimetres (0.33 in) apico-basally and 4.5 millimetres (0.18 in) labio-langually. The root height ranged from 3 to 5 millimetres (0.12 to 0.20 in).[5]

Distribution

Fossils of Heptranchias howelli have been found in:[3]

Eocene

Antarctica
Canada (British Columbia)
United States (New Jersey, Oregon, Washington)

Miocene

Uitpa Formation, Cocinetas Basin, Colombia

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gollark: It's not very interesting, though, you can stop them with a single shield.

References

M. D. Reed. 1946. New species of fossil shark from New Jersey. Notulae Naturae 172:1-4
Shark References
Heptranchias howelli at Fossilworks.org
Adolfssen, J. S. and Ward, D. J. 2015. Neoselachians from the Danian (early Paleocene) of Denmark. Acta Palaeontologica Polonica 60 (2): 313–338.
Carlsen, A.W. &Cuny, G. 2014. A study of the sharks and rays from the Lillebælt Clay (Early–Middle Eocene) of Denmark, and their palaeoecology by Bulletin of the Geological Society of Denmark, Vol. 62, pp. 39–88. ISSN 2245-7070. ([www.2dgf.dk/publikationer/bulletin Link])

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[1] M. D. Reed. 1946. New species of fossil shark from New Jersey. Notulae Naturae 172:1-4

[2] Shark References

[FWHeptranchiasHowelli-3] Heptranchias howelli at Fossilworks.org

[Adolfssen,_J.S._and_Ward-4] Adolfssen, J. S. and Ward, D. J. 2015. Neoselachians from the Danian (early Paleocene) of Denmark. Acta Palaeontologica Polonica 60 (2): 313–338.

[AGNETE_WEINREICH_CARLSEN_&_GILLES_CUNY-5] Carlsen, A.W. &Cuny, G. 2014. A study of the sharks and rays from the Lillebælt Clay (Early–Middle Eocene) of Denmark, and their palaeoecology by Bulletin of the Geological Society of Denmark, Vol. 62, pp. 39–88. ISSN 2245-7070. ([www.2dgf.dk/publikationer/bulletin Link])