Watsonosteus

Watsonosteus Temporal range: Middle Devonian: Late Givetian, 387.7–382.7 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Watsonosteus fossil specimen
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Arthrodira
Suborder:	†Brachythoraci
Family:	†Coccosteidae
Genus:	†Watsonosteus Miles & Westoll, 1963
Species
Watsonosteus fletti (Watson, 1932) (type)
Synonyms
Coccosteus fletti Watson, 1932

Watsonosteus is an extinct genus of coccosteid arthrodire placoderm from the Late Givetian stage of the Middle Devonian period. Fossils are found in the Orkney Islands, Scotland. It was a small placoderm with a total body length of 57 cm (22 in),[1] with the largest individuals reaching lengths of 1 m (39 in).[2] It is one of the few arthrodires for which complete body fossils are known.

Phylogeny

Watsonosteus is a member of the family Coccosteidae, which belongs to the clade Coccosteomorphi, one of the two major clades within Eubrachythoraci. The cladogram below shows the phylogeny of Watsonosteus:[3]

Eubrachythoraci

Coccosteomorphi Coccosteoidea Coccosteidae Millerosteus minor Coccosteus cuspidatus Dickosteus threiplandi Watsonosteus fletti Protitanichthys rockportensis Panxiosteidae Plourdosteus canadensis Panxiosteus ocullus Janiosteus timanicus Incisoscutoidea Harrytoombsia elegans Torosteus tuberculatus Torosteus pulchellus Mcnamaraspis kaprios Compagopiscis croucheri Trematosteus fontanellus Camuropiscidae Incisoscutum ritchiei Incisoscutum sarahae Rolfosteus canningensis Tubonasus lennardensis Fallacosteus turneri Camuropiscis laidlawi Latocamurus coulthardi Pachyosteomorphi

References

1. Engelman, Russell K. (2023). "A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira)". Diversity. 15 (3). 318. doi:10.3390/d15030318.
2. Newman, Michael J.; Blaauwen, Jan; Burrow, Carole; Jones, Roger (January 2021). "Earliest vertebrate embryos in the fossil record (Middle Devonian, Givetian)". Palaeontology. 64 (1): 21–30. Bibcode:2021Palgy..64...21N. doi:10.1111/pala.12511. S2CID 225001446.
3. 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.