Rhachiosteus is an extinct monospecific genus of arthrodire placoderm from the Middle to Late Devonian of Germany. It is known only from a single specimen, which may be a larval or juvenile form, as the skull of said specimen is only 19 millimetres long.[1]

Rhachiosteus
Temporal range: Devonian: Givetian - Frasnian, 387.7–372.2 Ma
Artist's reconstruction of Rhachiosteus (with Trematosteus in the background)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Placodermi
Order: Arthrodira
Suborder: Brachythoraci
Clade: Eubrachythoraci
Clade: Pachyosteomorphi
Genus: Rhachiosteus
Gross, 1938
Species
  • Rhachiosteus pterygiatus Gross, 1938 (type)

Phylogeny

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Rhachiosteus is a basal member of the clade Pachyosteomorphi, the sister taxon to Coccosteomorphi, which together are the two main sub-clades of Eubrachythoraci. The cladogram below shows the phylogeny of Rhachiosteus:[2]

Eubrachythoraci
Coccosteomorphi
Pachyosteomorphi

References

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  1. ^ Denison, Robert (1978). Placodermi Volume 2 of Handbook of Paleoichthyology. Stuttgart New York: Gustav Fischer Verlag. p. 128. ISBN 9780895740274.
  2. ^ Zhu, You-An; Zhu, Min; Wang, Jun-Qing (1 April 2016). "Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci". Zoological Journal of the Linnean Society. 176 (4): 806–834. doi:10.1111/zoj.12356. ISSN 0024-4082.