Xenacanthus

Xenacanthus; Temporal range: Late Devonian–Triassic PreꞒ Ꞓ O S D C P T J K Pg N
	Impression of the head and body of X. sessilis at the Museum für Naturkunde, Berlin
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	†Xenacanthida
Family:	†Xenacanthidae
Genus:	†Xenacanthus; Beyrich, 1848
Type species
	Xenacanthus decheni;
Species
	See text
Synonyms
	Pleuracanthus Agassiz 1837

Xenacanthus is a genus of prehistoric sharks. The first species of the genus lived in the later Devonian period, and they survived until the end of the Triassic, 202 million years ago. Fossils of various species have been found worldwide.

Description

Reconstruction of X. decheni

Xenacanthus had a number of features that distinguished it from modern sharks. This freshwater shark was usually about one meter (3.3 feet) in length^[1], and never longer than 2 m (6.6 ft).^[2] The dorsal fin was ribbonlike and ran the entire length of the back and round the tail, where it joined with the anal fin. This arrangement resembles that of modern conger eels, and Xenacanthus probably swam in a similar manner. A distinctive spine projected from the back of the head and gave the genus its name. The spike has even been speculated to have been venomous, perhaps in a similar manner to a sting ray. This is quite plausible as the rays are close relatives to the sharks. The teeth had an unusual "V" shape, and it probably fed on small crustaceans and heavily scaled palaeoniscid fishes.^[3]

As with all fossil sharks, Xenacanthus is mainly known because of fossilised teeth and spines.

Species

X. atriossis
X. compressus
X. decheni
X. denticulatus
X. erectus
X. gibbosus
X. gracilis
X. howsei
X. laevissimus
X. latus
X. luedernesis
X. moorei
X. ossiani
X. ovalis
X. parallelus
X. parvidens
X. ragonhai - Rio do Rasto Formation, Brazil^[4]
X. robustus
X. serratus
X. slaughteri
X. taylori

References

^ Gaines, Richard M. (2001). Coelophysis. ABDO Publishing Company. p. 17. ISBN 1-57765-488-9.
^ Beck, Kimberley G.; oler-Gijón, Rodrigo; Carlucci, Jesse R.; Willis, Ray E. (December 2014). "Morphology and Histology of Dorsal Spines of the Xenacanthid Shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and Palaeoenvironmental Implications". Acta Palaeontologica Polonica. 61 (1): 97–117. doi:10.4202/app.00126.2014
^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 27. ISBN 1-84028-152-9.
^ Victor E. Pauliv; Eliseu V. Dias; Fernando A. Sedor; Ana Maria Ribeiro (2014). "A new Xenacanthiformes shark (Chondrichthyes, Elasmobranchii) from the Late Paleozoic Rio do Rasto Formation (Paraná Basin), Southern Brazil". Anais da Academia Brasileira de Ciências. 86 (1): 135–145. doi:10.1590/0001-37652014107612. PMID 24676160.

External links

Data related to Xenacanthus at Wikispecies
Media related to Xenacanthus at Wikimedia Commons

[1] Gaines, Richard M. (2001). Coelophysis. ABDO Publishing Company. p. 17. ISBN 1-57765-488-9.

[2] Beck, Kimberley G.; oler-Gijón, Rodrigo; Carlucci, Jesse R.; Willis, Ray E. (December 2014). "Morphology and Histology of Dorsal Spines of the Xenacanthid Shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and Palaeoenvironmental Implications". Acta Palaeontologica Polonica. 61 (1): 97–117. doi:10.4202/app.00126.2014

[EoDP-3] Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 27. ISBN 1-84028-152-9.

[4] Victor E. Pauliv; Eliseu V. Dias; Fernando A. Sedor; Ana Maria Ribeiro (2014). "A new Xenacanthiformes shark (Chondrichthyes, Elasmobranchii) from the Late Paleozoic Rio do Rasto Formation (Paraná Basin), Southern Brazil". Anais da Academia Brasileira de Ciências. 86 (1): 135–145. doi:10.1590/0001-37652014107612. PMID 24676160.

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v t e Xenacanthidae
Genera	Plicatodus Triodus Xenacanthus
Related articles	Xenacanthida