Helicoprionidae

Helicoprionidae (sometimes referred to as Agassizodontidae)^[2] is an extinct family of holocephalans within the order Eugeneodontida. Members of the Helicoprionidae possessed a "whorl" of tooth crowns connected by a single root along the midline of the lower jaw.^[2][3] While historically considered elasmobranchs related sharks and rays,^[2] the closest living relatives of the Helicoprionidae and all other eugeneodonts are now thought to be the ratfishes.^[4] The anatomy of the tooth-whorls vary between taxa, with some possessing highly specialized, coiling spirals (such as those of the namesake genus Helicoprion), while others such as Sarcoprion and Parahelicoprion possessed shorter whorls.^[2]

Helicoprionidae Temporal range: 358–252 Ma PreꞒ Ꞓ O S D C P T J K Pg N Early Carboniferous to Late Permian
Helicoprion
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali
Order:	†Eugeneodontida
Clade:	†Edestoidea
Family:	†Helicoprionidae Karpinsky, 1911
Type genus
Helicoprion Karpinsky, 1899[1]
Type species
Helicoprion bessonowi Karpinsky, 1899
Genera
Agassizodus Arpagodus Campyloprion Helicoprion Hunanohelicoprion Karpinskiprion Parahelicoprion Sarcoprion Shaktauites Sinohelicoprion Toxoprion
Synonyms
Agassizodontidae Zangerl, 1981[1]

References

1. Lebedev, O. A. (2009). "A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function". Acta Zoologica. 90: 171–182. doi:10.1111/j.1463-6395.2008.00353.x.
2. Zangerl, Rainer (1981). Chondrichthyes 1: Paleozoic Elasmobranchii (Handbook of Paleoichthyology). Friedrich Pfiell. pp. 74–94. ISBN 978-3899370454.
3. Cicimurri, D. J.; Fahrenbach, M. D. (2002). "Chondrichthyes from the upper part of the Minnelusa Formation (Middle Pennsylvanian: Desmoinesian), Meade County, South Dakota" (PDF). Proceedings of the South Dakota Academy of Science. 81: 81–92.
4. Nelson, Joseph S.; Grande, Terry; Wilson, Mark V. H.; Wilson, Mark V. (2016). Fishes of the world (5th ed.). Hoboken, New Jersey: John Wiley & Sons. pp. 48–50. ISBN 978-1-118-34233-6.

External links

• Palaeos Vertebrates 70.100 Chondrichthyes: Eugnathostomata at paleos.com
• JSTOR: Journal of PaleontologyVol. 70, No. 1 (Jan., 1996), pp. 162-165
• More about Chondrichthyes Archived 2017-10-22 at the Wayback Machine at Devonian Times