''Mesacanthus'' ('middle spine') is an extinct genus of acanthodian fish from early

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Scotland. It is among the more primitive of the Devonian acanthodians.

Description

''Mesacanthus'' body fossils have pectoral, pelvic, anal and dorsal fin

spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolog ...

s, as well as a pair of prepelvic spines, which are intermediate between the pectoral and pelvic fin spines. They also have small, unornamented, diamond shaped scales. According to Agassiz, the genus also has a distinct tail in which the upper lobe extends to a sharp point and the lower lobe forms a small triangle. Overall the genus is small (average length = 30mm) and fairly conservative, anatomically speaking, for acanthodians. Agassiz, L. (1833). Recherches sur les poissons fossiles.. (Vol. 1). chez l'auteur.

Taxonomy

The genus was erected by

Ramsay Traquair Ramsay Heatley Traquair Fellow of the Royal Society of Edinburgh, FRSE Fellow of the Royal Society of London, FRS (30 July 1840 – 22 November 1912) was a Scottish naturalist and palaeontologist who became a leading expert on fossil fish. Tra ...

in 1888 to accommodate certain species that had been previously assigned to Acanthodes by

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

.Traquair, R. H. (1888). Old Red Sandstone fishes. These species included ''Mesacanthus mitchelli'', ''Mesacanthus pusillus'', ''Mesacanthus peachi'' and ''Mesacanthus coriaceus''. The genus is found in both Lower Old Red Sandstone and Middle Old Red Sandstone assemblages, with ''M. pusillus'', ''M. peachi'' and ''M. coriaceus'' known from the Middle

and ''M. mitchelli'' being the only known species from the Lower Devonian. Arthur Smith Woodward formally synonymized ''M. peachi'' and ''M. coriaceus'' in 1891.Woodward, A. S. (1901). Catalogue of the fossil fishes in the British Museum (Natural History). Printed by order of the Trustees. In 2015 a study published in

PeerJ ''PeerJ'' is an open access peer-reviewed scientific mega journal covering research in the biological and medical sciences. It is published by a company of the same name that was co-founded by CEO Jason Hoyt (formerly at Mendeley) and publisher Pet ...

reassessed the two remaining Middle Devonian species (''M. pusillus'' and ''M. peachi'') and found that they also could not be distinguished from one another. Hence, only two species from the

Orcadian Basin The Orcadian Basin is a sedimentary basin of Devonian age that formed mainly as a result of extensional tectonics in northeastern Scotland after the end of the Caledonian orogeny. During part of its history, the basin was filled by a lake now known ...

and Midland Valley areas of Scotland are currently considered to be valid: ''M. mitchelli'' from the Lower Devonian and ''M. pusillus'' from the Middle Devonian.

References

{{Taxonbar, from=Q6821111 Acanthodii genera Devonian acanthodians Prehistoric life of Europe

Description

Taxonomy

See also

References