Xenodens

Xenodens; Temporal range: Late Cretaceous, late Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
	Potentially forged holotype maxilla
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	†Mosasauria
Family:	†Mosasauridae
Genus:	†Xenodens; Longrich et al., 2021
Species:	†X. calminechari
Binomial name
	†Xenodens calminechari; Longrich et al., 2021

Xenodens (from Greek and Latin for "strange tooth") is a potentially dubious extinct genus of marine lizard belonging to the mosasaur family. It contains a single species, X. calminechari (From Arabic کالمنشار, meaning "like a saw"), which is known from Late Maastrichtian phosphate deposits in the Ouled Abdoun Basin, Morocco.^[1]

Description

Skull reconstruction and a speculative life reconstruction based on initial interpretations of the fossil material

Initial estimates suggested the fossil material could belong to an animal with a body length of around 1 meter (3.3 ft).^[2] The genus and type species were named for the purported short and flattened blade-like teeth that collectively form a set of saw-like jaws in this taxon. This is a strange feature that had never been seen in any other tetrapod but converge with the jaws of modern dogfish sharks and piranhas. In their 2021 description of this taxon, Longrich et al. hypothesized that these similarities were indicative of a broad diet of cephalopods, crustaceans, fish, and scavenged marine reptiles in Xenodens.^[1]

Classification

Xenodens is placed within Mosasaurinae, and its closest known relative is believed to be the durophagous Carinodens.^[1] In 2024, Sharpe, Powers & Caldwell reassessed the established holotype of Xenodens and argued that it represents a chimeric forged fossil. Their review suggested that the four teeth preserved in the specimen had been artificially added over two alveoli in the maxilla. The unusual morphology of the preserved teeth may result from intraspecific variation, as tooth shape can vary through ontogeny, so the possibility that the taxon represents an immature Carinodens cannot be precluded. As such, they interpreted the taxon as a nomen dubium in need of more detailed research based on CT scans to determine if the specimen is authentic.^[3]

External links

This ancient sea reptile had a slicing bite like no other, Xenodens calminechari, with life-restoration. Science News, February 2, 2021
Xenodens, a weird shark-toothed mosasaur from Morocco- Nick Longrich

References

^ ^a ^b ^c Longrich, N.R.; Bardet, N.; Schulp, A. S.; Jalil, N (2021). "Xenodens calminechari gen. et sp. nov., a bizarre mosasaurid (Mosasauridae, Squamata) with shark-like cutting teeth from the upper Maastrichtian of Morocco, North Africa" (PDF). Cretaceous Research. 123: 104764. doi:10.1016/j.cretres.2021.104764. S2CID 233567615.
^ Cooper, S.L.A.; Marson, K.J.; Smith, R.E.; Martill, D. (2022). "Contrasting preservation in pycnodont fishes reveals first record of regurgitalites from the Upper Cretaceous (Maastrichtian) Moroccan phosphate deposits". Cretaceous Research. 131 (4). 105111. doi:10.1016/j.cretres.2021.105111. S2CID 244884113.
^ Sharpe, Henry S.; Powers, Mark J.; Caldwell, Michael W. (2024-12-16). "Reassessment of Xenodens calminechari with a discussion of tooth morphology in mosasaurs". The Anatomical Record. doi:10.1002/ar.25612. ISSN 1932-8486.

[Longrichetal-1] Longrich, N.R.; Bardet, N.; Schulp, A. S.; Jalil, N (2021). "Xenodens calminechari gen. et sp. nov., a bizarre mosasaurid (Mosasauridae, Squamata) with shark-like cutting teeth from the upper Maastrichtian of Morocco, North Africa" (PDF). Cretaceous Research. 123: 104764. doi:10.1016/j.cretres.2021.104764. S2CID 233567615.

[2] Cooper, S.L.A.; Marson, K.J.; Smith, R.E.; Martill, D. (2022). "Contrasting preservation in pycnodont fishes reveals first record of regurgitalites from the Upper Cretaceous (Maastrichtian) Moroccan phosphate deposits". Cretaceous Research. 131 (4). 105111. doi:10.1016/j.cretres.2021.105111. S2CID 244884113.

[Sharpe2024-3] Sharpe, Henry S.; Powers, Mark J.; Caldwell, Michael W. (2024-12-16). "Reassessment of Xenodens calminechari with a discussion of tooth morphology in mosasaurs". The Anatomical Record. doi:10.1002/ar.25612. ISSN 1932-8486.

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