Finally, Jarvik investigated the anatomy of " Ichthyostega ", resulting in a monograph with an extensive photographic documentation of the material collected in 1929-1955.
22.
Swedish paleontologist Erik Jarvik, a member of the 1947 expedition, could not assign the skull to either " Ichthyostega " or " Acanthostega ".
23.
While the skull shape is closest to " Ichthyostega ", the teeth are smaller, more numerous and less curved, indicating the two exploited different foods.
24.
Although both were essentially four-footed fish, Ichthyostega is the earliest known tetrapod that may have had the ability to pull itself onto land and drag itself forward with its forelimbs.
25.
Tetrapodomorphs used their bodies and tails for locomotion and their fins for steering and braking; " Ichthyostega " may have used its forelimbs for locomotion on land and its tail for swimming.
26.
In the " Acanthostega " and " Ichthyostega ", which are considered to be more derived than other basal aquatic tetrapods, the pectoral girdle is decoupled from the skull.
27.
It does however show that " Ichthyostega " may have ventured onto land on occasions, unlike the very first tetrapods such as " Elginerpeton " and " Obruchevichthys ".
28.
Various foramina on the humeral surfaces are very similar to those seen in " Ichthyostega ", " Acanthostega ", and lobe-finned fishes like " Eusthenopteron ".
29.
Early tetrapods like " Ichthyostega " and " Acanthostega " differed from earlier tetrapodomorphs such as " Eusthenopteron " or " Panderichthys " in their increased adaptations for life on land.
30.
He has also analysed the basic structure of the paired limbs by comparing the pectoral and pelvic fins of the " Eusthenopteron " with the hindleg of the Devonian tetrapod " Ichthyostega " and embryonic humans.
