''Diplognathus'' is a genus of

arthrodire Arthrodira (Greek for "jointed neck") is an Order (biology), order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetratin ...

placoderm Placoderms (from Ancient Greek πλάξ 'plax'', ''plakos'''Plate (animal anatomy), plate' and δέρμα 'derma'''skin') are vertebrate animals of the class (biology), class Placodermi, an extinct group of prehistoric fish known from Pal ...

from the Late

Famennian The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...

Cleveland Shale The Cleveland Shale, also referred to as the Cleveland Member of the Ohio Shale, is a Late Devonian (Famennian) shale Member (geology), geologic member in the eastern United States. Identification and name The Cleveland Shale was identified in ...

of Late Devonian

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

, known only from incomplete fragments of jaws and skulls. What fragments are known suggest that the living animals were large-eyed

piscivore A piscivore () is a carnivorous animal that primarily eats fish. Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted repti ...

s with weak, but widely gaping jaws. ''D. mirabilis'' is thought to be fairly large, with infragnathals up to 45 centimeters in length. The second species, ''D. larfargei'', was much smaller, with inferognathals averaging about 4 centimeters in length. Diplognathus mirabilisDB24

In 1967, Obruchev placed this genus within Hadrosteidae, on the basis of how the two genera have similar denticle ("teeth") patterns of the inferognathals, though Denison (1978) contested this placement, preferring to leave the taxon as Arthrodira ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

''.

References

Enigmatic arthrodire taxa Placoderms of North America Fossil taxa described in 1878 Paleontology in Ohio Famennian life Famennian genus first appearances Famennian genus extinctions {{Placoderm-stub