Geologoseminarium med Per Ahlberg, Uppsala Universitet: Have we completely misunderstood the origin of tetrapods?
Geologoseminarium med Per Ahlberg, Uppsala Universitet
Have we completely misunderstood the origin of tetrapods?
For nearly three decades our understanding of the origin of tetrapods has been built around the iconic fossil taxon Acanthostega from the Devonian of East Greenland. Its distinctive combination of limbs and digits with a fish-like tail fin and other correlates of an aquatic lifestyle has been interpreted as evidence for an aquatic origin of tetrapods: the morphological transition from fish to tetrapod has been seen as a gradual adaptation to life in shallow, weed-choked waters during the Late Devonian, with true terrestrially evolving much later. Now, a combination of new discoveries (some as yet unpublished) and reevaluation of old data suggests that this model is substantially inaccurate as regards both timing and mode. I will present a sketch of a new scenario for the transition, together with an overview of new discoveries that are currently under description and a brief discussion of the outstanding problems that remain to be solved.