A new genus of tetrapod from the Devonian of East Greenland
18/12/2004 00:00 | Durée 00:13:52

Intervenants : Jennifer A Clack , University Museum of Zoology, Cambridge, Downing St., Cambridge CB2 3EJ, UK .  

A new genus and species of Devonian tetrapod has been identified from material collected in 1947 from the southern slope of Celsius Bjerg, Ymer Ø, East Greenland. The specimen preserves both lower jaws, partial palate, premaxillae and maxillae, with a natural mould of parts of the shoulder girdle. The new taxon shows many differences from both Acanthostega and Ichthyostega, though shows a closer resemblance to the latter. The dentition of Ichthyostega has also been reassessed in the light of fresh studies. Differences from Ichthyostega are most clearly seen in the dentition: tooth shape, number and proportions differ from that genus on all tooth-bearing bones. It also differs from Ichthyostega in skull ornamentation and lateral line expression. A cladistic analysis using characters of the palate, marginal bones, lower jaws and dentition shows that the specimen nests immediately below Ichthyostega, but above other Devonian tetrapods. Early and Late Carboniferous tetrapods stack robustly above these and suggest progressive modifications to the lower jaw associated with changes to feeding modes. Nine sites yielding Famennian tetrapods have now been recognised worldwide, producing a complement of at least 17 separate tetrapod taxa.