Coccosteus

Coccosteus Temporal range: Middle to Late Devonian,
C. cuspidatus specimen IVPP V19322, Paleozoological Museum of China
Artist's reconstruction of C. cuspidatus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Arthrodira
Suborder:	†Brachythoraci
Clade:	†Eubrachythoraci
Clade:	†Coccosteomorphi
Superfamily:	†Coccosteoidea
Family:	†Coccosteidae
Genus:	†Coccosteus Agassiz, 1843
Type species
Coccosteus cuspidatus Miller, 1841
Species
Coccosteus canadensis Woodward, 1892 Coccosteus carbonarius M'Coy, 1848 Coccosteus chamberlini Bryant, 1932 Coccosteus cuspidatus Miller, 1841 (type) Coccosteus cuyahogae Claypole, 1998 Coccosteus decipiens Agassiz, 1841 Coccosteus disjectus Woodward, 1891 Coccosteus grossi Obrucheva, 1962 Coccosteus hercynius von Meyer, 1852 Coccosteus macromus Cope, 1892 Coccosteus markae Obrucheva, 1962 Coccosteus minor Miller, 1858 Coccosteus occidentalis Newberry, 1875 ? Coccosteus orvikui Gross, 1940 Coccosteus terranovae Obruchev, 1934

Coccosteus (from Greek: κόκκος kókkos, 'berry' and Greek: ὀστέον ostéon 'bone') is an extinct genus of arthrodire placoderm from the Devonian period. Its fossils have been found throughout Europe and North America. The majority of these have been found in freshwater sediments, though such a large range suggests that they may have been able to enter saltwater. The largest specimens were about 40 centimetres (16 in), although the average length was 20 to 24 centimetres (7.9 to 9.4 in).

Description

Like all other arthrodires, Coccosteus had a joint between the armor of the body and skull. It also had an internal joint between its neck vertebrae and the back of the skull, allowing for the mouth to be opened even wider. Along with the longer jaws, this allowed Coccosteus to feed on fairly large prey. The up-and-down movement of the skull also allowed for more water to be pumped through the gills. Possibly, the creature supplemented its diet with organic material filtered from mud using the gills. As with all other arthrodires, Coccosteus had bony dental plates embedded in its jaws, forming a beak. The beak was kept sharp by having the edges of the dental plates grind away at each other. Overall the creature looked similar to its gigantic cousin Dunkleosteus, save that its eyes were closer to the end of its snout than in its larger relative.

Phylogeny

Coccosteus is the type genus for family Coccosteidae, which belongs to the clade Coccosteomorphi, one of the two major clades within Eubrachythoraci. The cladogram below shows the phylogeny of Coccosteus:

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

Coccosteus cuspidatus restoration, shown attacking multiple Palaeospondylus

Species

C. cuspidatus

This is the type species, and is an important index fossil in the continental Devonian sequence of northern Scotland deposited in the Orcadian Basin. It is only present at and below the Upper Eifelian Achanarras limestone level.

See also

• List of placoderms