Acronemus

Acronemus Temporal range: Anisian PreꞒ Ꞓ O S D C P T J K Pg N
A cast of a well-preserved fossil of Acronemus tuberculatus from Monte San Giorgio
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Eugnathostomata
Class:	Chondrichthyes
Clade:	Euselachii
Genus:	† Acronemus Rieppel, 1982

Acronemus is an extinct genus of euselachian from the Middle Triassic of Switzerland. ^{[1] [2]} It is an enigmatic genus with uncertain relations to other groups. Though originally placed within Ctenacanthiformes, it is now considered Euselachii incertae sedis , due to its mixture of features similar to hybodontiforms and neoselachians. Originally, teeth from this genus were attributed to " Acrodus bicarinatus" while fin spines were named " Nemacanthus tuberculatus". Associated material showed they were the same animal, with the older specific epithet (tuberculatus) taking precedence. The euselachian was given the new genus Acrocnemus, containing a single species (A. tuberculatus). Acronemus is found in the Anisian-age Grenzbitumenzone (also known as the Besano Formation) of Monte San Giorgio. ^[3] It was a small animal measuring 30–35 cm (0.98–1.15 ft) long. ^[4] A 2018 study considered it to be closely related to the early Carboniferous genus Tristychius as part of the family Tristychiidae as a basal euselachian, with hybodonts more closely related to neoselachians than to Tristychiidae. ^[5]

References

1. Rieppel, O. (1982). A new genus of shark from the Middle Triassic of Monte San Giorgio, Switzerland.
2. "Fossilworks: Acronemus". fossilworks.org. Retrieved 17 December 2021.
3. Maisey, John G. (2011). "The braincase of the Middle Triassic shark Acronemus tuberculatus (Bassani, 1886)". Palaeontology. 54 (2): 417–428. Bibcode:2011Palgy..54..417M. doi:10.1111/j.1475-4983.2011.01035.x. ISSN   1475-4983. S2CID   140697673.
4. Rieppel, O. (2019). Mesozoic Sea Dragons: Triassic Marine Life from the Ancient Tropical Lagoon of Monte San Giorgio. Indiana University Press. p. 50. doi:10.2307/j.ctvd58t86. ISBN   978-0253040114. S2CID   241534158.
5. Coates, Michael I.; Tietjen, Kristen (March 2017). "The neurocranium of the Lower Carboniferous shark Tristychius arcuatus (Agassiz, )" . Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 108 (1): 19–35. Bibcode:2017EESTR.108...19C. doi:10.1017/S1755691018000130. ISSN   1755-6910. S2CID   135297534.