Acanthostega

Acanthostega gunnari, skeletal reconstruction

• Greenland

Acanthostega ( AltGr. Άκανθα, akantha = thorn, prickle and στέγη, webs = ceiling coverage) is an extinct genus of vertebrates ( Vertebrata ), which is one of the core group of representatives of land vertebrates ( Tetrapoda ), but spent her entire life in the water. Acanthostega is for evolutionary biology of particular importance as it is the mosaic form is near the origin of tetrapods. Only the type species A. gunnari whose fossil was found in 1933 in 365 million year old sedimentary rocks dating from the Upper Devonian in Greenland, has so far been scientifically described.

The anatomy of its front and rear hand proves that the typical four limbs of land vertebrates must have developed already in the water. The still widespread assumption that the land vertebrates have evolved from coelacanths, who used her muscular, tassel -like fish fins occasional shore leave, is thus questionable. Rather, Acanthostega moved already with four leg-like limbs on the sump floor covered with water plants continue, similar to do as well as today's lungfish with their fleshy fins. A reconstruction of its limb bones shows that they would not have the heavy body in the country can carry. In addition, Acanthostega still breathing through gills and not lungs, was clearly an aquatic species, which was moving along with four legs and not by kicking in the water. An analysis of the skull bones also revealed that Acanthostega may already took a bite technique for the acquisition of food and not, as the fish living in the water, by means of on and sucking caught the prey.