Internal skull elements of Eusthenopteron include a pterygoid (dark red), ectopterygoid (orange), palatine (blue), nasal capsule (pink), intertemporal (yellow-green) hyomandibular (= stapes, dark green) and quadrate (red).

Eusthneopteron foordi (Whiteaves 1881; Late Devonian, 385 mya; 1.8m in length) was one of the first fish genera known to share a long list of traits with basal tetrapods. It was a terminal taxon derived from a sister to Cabbonichthys.

Distinct from Cheirolepis, Eusthenopteron had choanae (palate openings for the passage of air). Bones within the pectoral and pelvic fins are homologous with those in tetrapods, but no distinct wrist, ankle, metapodials or digits are yet present and fin rays remain. The jaws were rimmed with tiny teeth. The palate had several large fangs. The tail was not so heterocercal, but stretched out more or less in line with the vertebral column.

Eusthneopteron foordi (juvenile—Schultze 1984)

Osteolepis macrolepidotus (Agassiz 1835) Middle Devonian ~375 mya; 8 cm in length) is a crossopterygiid lobe-fin fish close to the ancestry of tetrapods. Several of the skull bones seen in later tetrapods are found here. The cleithrum is the dermal bone preceding the front fin. The bones over the gill covers and the preopercular shrink and disappear, as do the two dorsal fins. The posterior external nares migrated to the orbits to become tear ducts.