…Transitional between one extinct form and another …

This is a 95 million year old creature called Adriosaurus microbrachis. It is a lizard like creature with vestigial rear limbs and no forelimbs, adapted to an aquatic environment. The fossil was originally collected in 19th century Slovenia, and has remained unstudied in an Italian natural history museum until recently rediscovered by Michael Caldwell of the University of Alberta.

This is a little unusual because other cases of a lizard de-evolving it’s limbs (it’s happened a number of times) involve loss of the hind limbs first, then the forelimbs. This order of loss, however, while rare, is not unprecedented.

Source: University of Alberta Press Release