Brachydeirus

Brachydeirus is a genus of small to moderately large-sized arthrodire placoderms from the Late Devonian of Europe, restricted to the Kellwasserkalk Fauna of Bad Wildungen and Adorf.

Brachydeirus
Temporal range: Late Frasnian
Restoration of B. grandis
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Subphylum:
Vertebrata
Class:
Placodermi
Order:
Arthrodira
Suborder:
Brachythoraci
Infraorder:
Coccosteina
Superfamily:
Brachydeiroidea
Family:
Brachydeiridae

Gross, 1932
Genus:
Brachydeirus

Gross, 1932
Type species
Brachydeirus carinatus
Gross, 1932
Species
  • B. bicarinatus Stensio, 1963
  • B. carinatus Gross, 1932
  • B. gracilis Gross, 1932
  • B. grandis Gross, 1932
  • B. magnus Gross, 1933
  • B. minor Gross, 1932
Synonyms
  • Brachydirus Gross, 1932
  • Anomalichthys (in part) Koenen, 1883
  • Auchenosteus Jaekel, 1911

Species have, in cross section, a highly compressed body, a pointed, sometimes highly elongated snout, and tremendous orbits.[1] The living animals would have superficially resembled modern-day trout or small mackerels. As per the family, the trunk shield is short. The genus is distinguished from other members of the family in that the median dorsal plate of the trunk shield is often keeled, with the keel often very high and prominent.

Species

B. carinatus

The type species. The length of the skull of the holotype is 11.7 cm. Has a broad nuchal plate that is convex posteriorly. The dermal bones are decorated with large, concentrically arranged tubercles.

B. bicarinatus

There is a postero-median process on the nuchal plate, and a pre-pineal fenestra in this species. The skull of the holotype is 8.5 cm long.

B. gracilis

The smallest species in this genus: the skull length of the holotype is 6 cm. Differs from B. minor by having a more steeply arched back, smaller facial plates and a lack of a postpineal fenestra.

B. grandis

One of the largest species in this genus: the skull length of the holotype is around 20 cm. Has a postpineal fenestra, an unusually long (for the genus/family) lateral trunk shield, and comparatively small orbits. The dermal bones are decorated with a pattern of small, evenly spaced tubercles.

B. magnus

A very large species originally described as a specimen of Anomalichthys.[1] Differs from B. grandis by having a very high, prominent thick keel on the posterior region of the median dorsal plate, and the dermal surface is covered in very large tubercles.

B. minor

Another small species: the skull length of the holotype is 7.4 cm long. It differs from B. gracilis by having a posterio-median notch on the nuchal plate, the presence of a postpineal fenestra, and larger facial plates.

See also

References
  1. Denison, Robert (1978). Handbook of Paleoichthyology, Volume 2, Placodermi. New York: Gustav Fischer Verlage. p. 74. ISBN 9780895740274.


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