Xenacanthus Explained

Xenacanthus (from Ancient Greek ξένος, xénos, 'foreign, alien' + ἄκανθος, akanthos, 'spine') is an extinct genus of xenacanth cartilaginous fish. It lived in freshwater environments, and fossils of various species have been found worldwide.

Description

Xenacanthus is relatively small member in its order.[1] X. decheni reached about 1m (03feet),[2] X. meisenheimensis reached up to 1.2m (03.9feet),[3] X. (Expleuracanthus) gaudryi reached 58cm (23inches).[4] X. parallelus is one of the smallest xenacanth, male reached 20cm (10inches) and female reached 34cm (13inches), both are fully grown.[5]

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.[6] 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.[7] [8] [9]

Species

Notes and References

  1. 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.
  2. Schneider . Joerg W. . Zajíc . Jaroslav . 1994 . Xenacanths (Pisces, Chondrichthyes) of the Middle European Upper Carboniferous and Permian - revision of the originals to Goldfuss 1847, Beyrich 1848, Kner 1867 and Fritsch 1879-1890 . Freiberger Forschungshefte-Reihe C-Geowissenschaften . 452 . 101-152.
  3. Heidtke . U.H.J. . 2003 . Neue Rekonstruktionen xenacanthider Haie aus dem Permokarbon des Saar-Nahe-Beckens (SW-Deutschland) . Mitteilungen der Pollichia . 90 . 19–28.
  4. Albert . James S. . Johnson . Derek M. . Knouft . Jason H. . 2009 . Fossils provide better estimates of ancestral body size than do extant taxa in fishes . Acta Zoologica . en . 90 . s1 . 357–384 . 10.1111/j.1463-6395.2008.00364.x . 0001-7272.
  5. Soler-Gijón . R. . 2004 . Development and growth in xenacanth sharks: new data from Upper Carboniferous of Bohemia. . G. Arratia, M.V.H. Wilson, and R. Cloutier (eds.), Recent Advances in the Origin and Early Radiation of Vertebrates . 533–562 .
  6. Book: Palmer, D.. 1999 . The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. Marshall Editions. London. 27. 1-84028-152-9.
  7. 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 . en . 26 . 10 . 639–657 . 10.2110/palo.2010.p10-121r . 0883-1351.
  8. 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 . en . 111 . 7 . 2129–2147 . 10.1007/s00531-022-02222-0 . 1437-3254.
  9. 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 . 10.1590/0001-37652014107612 . 0001-3765. free .

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