Orthacanthus

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Orthacanthus
Live reconstruction of Orthacanthus senckenbergianus

Live reconstruction of Orthacanthus senckenbergianus

Temporal occurrence
Pennsylvania to Upper Cretaceous
315.2 to 66 million years
Locations
Systematics
Superclass : Jaw mouths (Gnathostomata)
Class : Cartilaginous fish (Chondrichthyes)
Subclass : Plate gill (Elasmobranchii)
Order : Xenacanthiformes
Family : Orthacanthidae
Genre : Orthacanthus
Scientific name
Orthacanthus
Agassiz , 1843

Orthacanthus is an extinct cartilaginous fish species , which is about 250 million years, from the early Pennsylvanian (Upper Carboniferous) to the Cretaceous-Paleogene boundary at the end of the Mesozoic fossil can be detected. It is one of the plate gills and had a predatory lifestyle as a nectic carnivore.

First description and origin of name

The name Orthacanthus is a combination of the Greek words ortho (ὀρθός) - 'straight', 'right' - and acanthos (ἄκανθος) - 'thorn'. It can therefore be reproduced as an arrow straight , which describes the external appearance of the animal very clearly. This cartilaginous fish was scientifically described for the first time by Louis Agassiz in 1843 .

Taxonomy

The genus Orthacanthus is part of the superiority of the Euselachii belonging family of Orthacanthidae within the order xenacanthida . Ginter et al. (2010) now count them among the Diplodoselachidae . Carroll (1988) placed it in the Xenacanthidae family .

The type species is O. milleri . There are also numerous other species such as O. arcuatus , O. bohemicus , O. buxieri , O. compressus , O. cylindricus , O. donnelljohnsi , O. gibbosus , O. kounoviensis , O. meridionalis , O. minor , O. pinguis , O. platypternus , O. pustulosus , O. senckenbergianus and O. texensis . Also Didymodus platypternus , acinaces Diplodus , D. minutus , D. parvulus and D. tenuis are as species of Orthacanthus viewed. Sister taxa are Dicentrodus , Diplodoselache , Hagenoselache and Lebachacanthus .

features

An Orthacanthus kept in the Natural History Museum in Vienna

The main characteristics of Orthacanthus were its highly specialized fins and the elongated, straight spine that began behind the skull . A dorsal fin ran almost over the entire back , which was only separated from the diphycercic caudal fin by a notch and gave the animal an eel-like appearance. In front of the dorsal fin was a long, hollow dorsal spine made of dentine , which was often fossilized along with the teeth. The animal also had two stalked anal fins lying one behind the other . The two pectoral fins were provided with an archipterygium - a long, centrally located, segmented axis from which the radials (bones) emanated both pre- (relatively short) and postaxial (long). This seemingly ancient structure may still come from the Symmoriids. The specializations in the structure of the fins are interpreted by Dick (1981) in such a way that the flapping side movements of the tail end were supported and the animals experienced a more powerful propulsion, which allowed them to glide more effectively through swamps rich in plants.

A tricuspid tooth of Orthacanthus from Whitehaven in Cumbria

Orthacanthus reached a length of nearly three meters. Its teeth were tricuspid (three pointed cones) with two long side spines and a tiny central spine. There could be other very small thorns in between. The side spines were bent slightly horn-shaped and their tips pointed away from each other. The side mandrel positioned further forward was slightly larger than the one set back a little. The tooth base was flat, but made a rough impression due to small punctiform indentations; behind a coronal elevation it also had a clear, central opening.

Way of life

As a nectobenthic predator, Orthacanthus was at the top of the food chain at the time. Aodhán Ó Gogáin et al. (2012) examined coprolites of Orthacanthus and found in them, among other things, teeth from young animals of this genus. This proves a cannibalistic way of life of the genus, which obviously did not spare its younger conspecifics in times of need. Orthacanthus fossils are found in a wide variety of facies , ranging from shallow marine to continental. Orthacanthus obviously not only lived in the open sea, but also sought out coastal areas , lagoons , estuaries , estuaries , bayous and freshwater swamps , so it could live in water with different salinity ( euryhalin ).

Fossil record

Orthacanthus dentition with tricuspid teeth

Sites of Orthacanthus are:

literature

  • Hampe, O .: About the dentition of the Orthacanthus (Chondrichthyes: Xenacanthida; Oberkarbon-Unterperm) . In: Paleontological Journal . tape 62 , 1988, pp. 285-296 .

Individual evidence

  1. ↑ L. Agassiz: Recherches sur les poissons fossiles . Tome III (livr. 15-16). Imprimérie de Petitpierre, Neuchatel 1843, p. 157-390 .
  2. ↑ M. Ginter, O. Hampe and CJ Duffin: Chondrichthyes, Paleozoic Elasmobranchii: Teeth . In: HP Schultze (Ed.): Handbook of Paleoichthyology 3D . 2010, p. 1-168 .
  3. ^ Robert L. Carroll: Vertebrate Paleontology and Evolution . WH Freeman and Company, New York 1988, ISBN 0-7167-1822-7 .
  4. ↑ Rodrigo Soler-Gijón: Development and growth in xenacanth sharks: new data from Upper Carboniferous of Bohemia . In: G. Arratia, MVH Wilson and R. Cloutier (Eds.): Recent Advances in the Origin and Early Radiation of Vertebrates . Dr. Friedrich Pfeil, Munich 2004, ISBN 3-89937-052-X .
  5. ↑ Kimberly G. Beck et al: Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and palaeoenvironmental implications . In: Acta Palaeontologica Polonica . tape 61 (1) , 2016, pp. 97-117 .
  6. ↑ Gogáin, Aodhán Ó, Falcon-Lang, Howard J., Carpenter, David K., Miller, Randall F., Benton, Michael J., Pufahl, Peir K., Ruta, Marcello, Davies, Thomas G., Hinds, Steven J. and Stimson, Matthew R .: Fish and tetrapod communities across a marine to brackish salinity gradient in the Pennsylvanian (early Moscovian) Minto Formation of New Brunswick, Canada, and their palaeoecological and palaeogeographical implications . In: Palaeontology . ISSN  1475-4983 .
  7. ↑ Dick, JRF: Diplodoselachi woodi gen. Et sp. nov., an early Carboniferous shark from the Midland Valley of Scotland . In: Trans. Roy. Soc. Edinburgh, Earth Sciences . tape 72 , 1981, pp. 99-113 .
  8. ↑ D. Heyler and C. Poplin: Systematics and relationships among the Xenacanthiformes (Pisces, Chondrichthyes) in the light of Carboniferous and Permian French material . In: Acta Musei Reginaehradecensis SA: Scientiae Naturales . tape 22 , 1989, pp. 69-78 .
  9. ↑ M. Manabe, Y. Hasegawa and T. Takahashi: A hadrosaurid vertebra from the Ashizawa Formation, Futaba Group, Fukushima, Japan . In: Bulletin of the Gunma Museum of Natural History . tape 7 , 2003, p. 7-10 .
  10. ↑ J. Liszkowski: The Selachierfauna of the shell limestone in Poland: Composition, stratigraphy and paleoecology . In: Muschelkalk, Schöntaler Symposium 1991. Special volumes of the Society for Natural History in Württemberg . tape 2 , 1993, p. 177-185 .
  11. ↑ Soler-Gijón, R .: Orthacanthus meridionalis, a new xenacanth shark (Elasmobranchii) from the Upper Carboniferous of the Puertollano basin, Spain . In: New Yearbook of Geology and Paleontology, Treatises . tape 204 , 1997, pp. 141-169 .
  12. ↑ Zidek, J .: Juvenile Orthacanthus platypternus (Cope 1883) (Elasmobranchii: Xenacanthiformes) from the Upper Carboniferous near Hamilton, Kansas, USA In: U.- HJ Heidtke, New Research on Permo-Carboniferous faunas (Ed.): Pollichia- Book . tape 29 , 1993, pp. 53-65 .
  13. ↑ Donelan, C. and Johnson, GD: Orthacanthus platypternus (Chondrichthyes: Xenacanthida) occipital spines from the Lower Permian Craddock Bonebed, Baylor County, Texas . In: Journal of Vertebrate Paleontology . 17 (Supplement), 1997, p. 43A .