A genus of amphibians that, together with Ichthyostegopsis and Acanthostega, first appeared in the Late Devonian. Ichthyostega shows refinements of the skull, and the development of strong limbs. It retained a long, rather fish-like tail, and links with the Crossopterygii are confirmed by the presence of teeth with a labyrinthine infolding of the enamel, as well as a notochordal tunnel (see notochord) underlying the brain case and a lateral-line system. Ichthyostega grew to just under 1 m in length. An unexpected finding about Ichthyostega and its relatives, from recently discovered, more complete specimens, is that they had more than the five digits per limb that characterizes modern tetrapods: Ichthyostega had seven on the hind feet (the forefeet are still unknown), and Acanthostega had eight on both fore and hind feet.
Subjects: Zoology and Animal Sciences — Earth Sciences and Geography.