Another way onto land: the extraordinary pelvic fin and unknown pelvis of Elpistostege.

The origin of tetrapods and terrestrial locomotion involved the transformation of small pelvic fins into large weight-supporting hind limbs. The closest fossil relatives of tetrapods are the elpistostegalian fishes, large predators from the Devonian period that were probably capable of moving over land. However, while their pectoral fins already begin to resemble tetrapod forelimbs, the smaller and more fish-like pelvic fins are very poorly known. This hampers our understanding of their locomotion. A recent paid-for experiment, IN-1148, scanned part of the best-preserved elpistostegalian fossil (a complete Elpistostege watsoni, MHNM 06-2067) and revealed a unique pelvic fin anatomy: adapted to movement on land, but not tetrapod-like. We now seek beamtime for a complete scan of the whole pelvic region. This will greatly improve our understanding of elpistostegalian locomotion and the beginning of terrestriality.