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Acrotemnus
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| Acrotemnus Temporal range:
Turonian, | |
|---|---|
| |
| A. faba holotype, Natural History Museum, London | |
Scientific classification 
| |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | †Pycnodontiformes |
| Family: | †Pycnodontidae |
| Genus: | †Acrotemnus Agassiz, 1836 |
| Type species | |
| †Acrotemnus faba Agassiz, 1836
| |
| Species | |
| |
| Synonyms | |
| |
Acrotemnus is an extinct genus of marine pycnodontid ray-finned fish known from Europe, North America, and Africa during the Turonian stage of the Upper Cretaceous. North American species could reach comparatively giant sizes for pycnodonts.[1]
Taxonomy
[edit]The following species are known:[2]
- A. faba Agassiz, 1836 - Turonian of England (English Chalk)[3][4]
- A. megafrendodon (Shimada, Williamson & Sealey, 2010) - Turonian of New Mexico, USA (Mancos Shale) (=Macropycnodon megafrendodon Shimada, 2010)[1]
- A. streckeri (Hibbard, 1939) - Turonian of Kansas (Carlile Shale), potentially Texas (Boquillas Formation) (=Coelodus streckeri Hibbard, 1939)
An indeterminate potential species is also known from the Turonian of Nigeria (Benue Trough).[2][5]
Acrotemnus was initially known from just the type species A. faba described by Louis Agassiz in 1843 from specimens collected in England.[3] In 1939, Hibbard described a large-sized pycnodont from a tooth plate from Kansas, which he placed in Coelodus as C. streckeri. In 2010, Shimada, Williamson & Sealey described a gigantic pycnodont known from a few tooth plates found in New Mexico as Macropycnodon megafrendodon, placing C. streckeri in the same genus.[1] However, in 2021, Shimada, Portillo, and Cronin described a partial skeleton of a pycnodont from Texas as potentially being a specimen of A. streckeri. This specimen revealed close similarities between the anatomy of Macropycnodon and Acrotemnus, leading to the lumping of the former into the latter.[2]
Description
[edit]A. megafrendodon is known from isolated teeth, the largest being 1.75 centimetres (0.69 in) in width. A comparison between the tooth-to-body size ratio of more completely known relatives, such as Coelodus saturnus, suggests that A. megafrendodon could have reached comparatively gigantic body sizes of over 1–1.2 metres (3.3–3.9 ft). This would make it among the largest pycnodonts, especially given that the majority do not reach over 25 centimetres (9.8 in) in length.[1] The partial specimen of A. cf. streckeri described in 2021 is estimated to have been roughly 1 metre (3.3 ft) in length, supporting these estimates.[2]
See also
[edit]References
[edit]- ^ a b c d Kenshu Shimada, Thomas E. Williamson & Paul L. Sealey (2010). "A new gigantic pycnodont fish from the Juana Lopez Member of the Upper Cretaceous Mancos Shale of New Mexico, U.S.A.". Journal of Vertebrate Paleontology. 30 (2): 598–603. Bibcode:2010JVPal..30..598S. doi:10.1080/02724631003618298. S2CID 129687572.
- ^ a b c d Shimada, Kenshu; Portillo, Dianne; Cronin, Timothy (August 2021). "A new pycnodont specimen (Actinopterygii: Pycnodontiformes) from the Upper Cretaceous of Big Bend National Park, Texas, USA, confirming the bony fish genus Macropycnodon as a junior synonym of Acrotemnus". Cretaceous Research. 124. doi:10.1016/j.cretres.2021.104797. S2CID 233924239. Retrieved 1 December 2023.
- ^ a b L. Agassiz. 1836. Recherches Sur Les Poissons Fossiles. Tome I (livr. 18). Imprimerie de Petitpierre, Neuchatel
- ^ Friedman, Matt; Beckett, Hermione T.; Close, Roger A.; Johanson, Zerina (2016). "The English Chalk and London Clay: two remarkable British bony fish Lagerstätten". Geological Society, London, Special Publications. 430 (1): 165–200. doi:10.1144/SP430.18.
- ^ Vullo, Romain; Courville, Philippe (1 September 2014). "Fish remains (Elasmobranchii, Actinopterygii) from the Late Cretaceous of the Benue Trough, Nigeria". Journal of African Earth Sciences. 97: 194–206. doi:10.1016/j.jafrearsci.2014.04.016. ISSN 1464-343X.
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