Xampylodon

Xampylodon is an extinct genus of cow shark. Fossils assigned to this genus are known from the Late Cretaceous and early Paleocene. Xampylodon was recently erected after a revision on the taxonomy of hexanchid fossil teeth, and includes four species (X. dentatus, X. loozi,X. brotzeni, and X. diastemacron), most of them previously included in Notidanodon.^[1]

Xampylodon Temporal range: Valanginian–Thanetian PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of an anterolateral lower tooth, probably from Xampylodon loozi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	Hexanchiformes
Family:	Hexanchidae
Genus:	†Xampylodon Cappetta, Morrison & Adnet, 2021
Species
X. dentatus X. loozi X. brotzeni X. diastemacron

Morphology

Xampylodon is known exclusively from isolated teeth. These teeth have a unique morphology (especially the saw-like teeth from the lower jaw). Xampylodon teeth are characterized by having an acrocone (or main cusp) and cusplets bent distally, with a convex mesial cutting edge. The mesial cusplets are much smaller than the distal ones. The root is very deep, unlike the condition observed in Notidanodon.^[2] Xampylodon species differ from each other in aspects such as size, the number and shape of the mesial cusplets, the orientation of the acrocone, and the presence of a gap between cusplets.^{[3] [4]}

Species

• Xampylodon dentatus (Woodward 1886)
• Xampylodon loozi (Vincent 1876)
• Xampylodon brotzeni (Siverson 1995)
• Xampylodon diastemacron Santos et al. 2024

References

1. Cappetta, Henri; Morrison, Kurt; Adnet, Sylvain (2021-12-10). "A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages". Historical Biology. 33 (8): 1121–1182. Bibcode:2021HBio...33.1121C. doi:10.1080/08912963.2019.1681421. ISSN 0891-2963. S2CID 212878837.
2. Santos, Rodolfo Otávio; Riff, Douglas; Amenábar, Cecilia R.; Ramos, Renato Rodriguez Cabral; Rodrigues, Igor Fernandes; Scheffler, Sandro Marcelo; Carvalho, Marcelo de Araújo (2022-11-14). "New records of hexanchiform sharks (Elasmobranchii: Neoselachii) from the Late Cretaceous of Antarctica with comments on previous reports and described taxa". New Zealand Journal of Geology and Geophysics: 1–17. doi:10.1080/00288306.2022.2143382. ISSN 1175-8791.
3. Cappetta, Henri; Grant-Mackie, Jack (2018-09-21). "Discovery of the most ancient Notidanodon tooth (Neoselachii: Hexanchiformes) in the Late Jurassic of New Zealand. New considerations on the systematics and range of the genus". Palaeovertebrata. 42 (1): e1. doi:10.18563/pv.42.1.e1. ISSN 0031-0247. S2CID 92722893.
4. Santos, Rodolfo Otávio; Riff, Douglas; Ramos, Renato Rodriguez Cabral; Rodrigues, Igor Fernandes; Scheffler, Sandro Marcelo; Sucerquia, Paula Andrea; Carvalho, Marcelo de Araujo (2024-03-06). "A new species of cow shark (Hexanchiformes: Hexanchidae) from the Late Cretaceous of Seymour Island, Antarctica". Historical Biology: 1–12. doi:10.1080/08912963.2024.2316047. ISSN 0891-2963.