Osteolepiformes

Skull of Platycephalichthys

The Osteolepiformes are an extinct group of bony fish from the class of meat -finned fishes ( Sarcopterygii ). They lived from the Middle Devonian to Middle Permian and are of particular importance because they are close to the origin of land vertebrates ( Tetrapoda ). To them Eusthenopteron, which is one of the most studied fossil fish belongs.

According to the results of a recent cladistic analysis of the Osteolepiformes not form a natural group ( clade, a monophyletic group ), because some families are more closely related to tetrapods than others. The Osteolepiformes represent therefore only a level of development (English: grade) between the still relatively fishy Fleischflossern and the already very tetrapod Fleischflossern.

Features

Your thick, rhombic scales ( Kosmoidschuppen ) covered body was slender, the pectoral fins were relatively low in the hull. Breast and pelvic fins were short and rounded. The tail fin may have been homosexual or heterocercal ( gleichlappig or ungleichlappig ).

The skull and dentition are similar to those of the basal land vertebrates ( Acanthostega, Ichthyostega ). The Osteolepiformes had developed an outer nostril and a choana. The Scapulocoracoid, part of the shoulder girdle, had a pit in which the from the fuselage pointing ( proximal ), spherical end of the " humerus " (humerus ) was stored the pectoral fins very mobile ( " Tetrapodengelenk ").

System

Traditionally, the Osteolepiformes include the following families and genera:

• Canowindridae ( Beelarongia, Canowindra, Koharolepis ), limited to Ostgondwana (Australia, Antarctica )
• Osteolepidae ( Osteolepis, Gryoptychus, Thursius ), less than 50 cm, two dorsal fins, heterocerke tail fin.
• Megalichthyidae
• Tristichopteridae ( = Eusthenopteridae: Marsdenichthys, Eusthenopteron, Platycephalichthys )
• Rhizodopsidae
• Gogonasus?