Xenacanthus

<i>Xenacanthus</i>

Xenacanthus

Extinct genus of sharks

Quick Facts Scientific classification, Type species ...

Xenacanthus (from Ancient Greek ξένος, xénos, 'foreign, alien' + ἄκανθος, akanthos, 'spine') is a genus of prehistoric xenacanths. Fossils of various species have been found worldwide.

Description

Xenacanthus had a number of features that distinguished it from modern sharks. This freshwater fish 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. The teeth had an unusual "V" shape, and it probably fed on small crustaceans and heavily scaled palaeoniscid fishes.[3]

Detailed view of Xenacanthus skull at the American Museum of Natural History

As with many xencanths, Xenacanthus is mainly known because of fossilised teeth and spines.

Fossils are known from the Carboniferous-Permian of North America, Europe, and South America. Triassic species have been moved into the separate genus Mooreodontus.[4][5][6]

Species

  • X. texensis
  • X. atriossis
  • X. compressus
  • X. indicus
  • X. decheni
  • X. denticulatus
  • X. erectus
  • X. gibbosus
  • X. gracilis
  • X. howsei
  • X. laevissimus
  • X. latus
  • X. luedernesis
  • X. ossiani
  • X. ovalis
  • X. parallelus
  • X. parvidens
  • X. ragonhai - Rio do Rasto Formation, Brazil
  • X. robustus
  • X. serratus
  • X. slaughteri
  • X. taylori

References

  1. [1]
    Gaines, Richard M. (2001). Coelophysis. ABDO Publishing Company. p. 17. ISBN 1-57765-488-9.
  2. [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
  3. [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. [4]
    Carpenter, D.; Falcon-Lang, H. J.; Benton, M. J.; Nelson, W. J. (2011-10-01). "FISHES AND TETRAPODS IN THE UPPER PENNSYLVANIAN (KASIMOVIAN) COHN COAL MEMBER OF THE MATTOON FORMATION OF ILLINOIS, UNITED STATES: SYSTEMATICS, PALEOECOLOGY, AND PALEOENVIRONMENTS". PALAIOS. 26 (10): 639–657. doi:10.2110/palo.2010.p10-121r. ISSN 0883-1351.
  5. [5]
    Voigt, Sebastian; Schindler, Thomas; Tichomirowa, Marion; Käßner, Alexandra; Schneider, Joerg W.; Linnemann, Ulf (October 2022). "First high-precision U–Pb age from the Pennsylvanian-Permian of the continental Saar–Nahe Basin, SW Germany". International Journal of Earth Sciences. 111 (7): 2129–2147. doi:10.1007/s00531-022-02222-0. ISSN 1437-3254.
  6. [6]
    Pauliv, Victor E.; Dias, Eliseu V.; Sedor, Fernando A.; Ribeiro, Ana Maria (March 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. ISSN 0001-3765.
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