However, in 1987, nearly complete fossils of Acanthostega from about 363 Ma showed that this Late Devonian transitional animal had legs and both lungs and gills, but could never have survived on land: its limbs and its wrist and ankle joints were too weak to bear its weight; its ribs were too short to prevent its lungs from being squeezed flat by its weight; its fish-like tail fin would have been damaged by dragging on the ground.
Porén, en 1987, fósiles case completos de Acanthostega duns 363 Ma mostraron que este animal transicional do Devoniano tardío tiña patas e ademais tanto pulmóns coma branquias, pero nunca podería ter sobrevivido en terra: as súas patas, e articulacións dos nocellos e pulsos eran demasiado febles para aguantar o peso do animal; as súas costelas eran demasiado curtas para impedir que os seus pulmóns quedasen esmagados polo seu peso; a súa aleta da cola similar á dun peixe quedaría danada ao arrastrarse polo chan.