Moythomasia nitida
Name: Moythomasia nitida [Shining fish in honor of Moy-Thomas]
When: Middle - Late Devonian Period, about 350 - 370 million years ago
Where: Numerous localities in Europe and Australia
Claim to fame: The Devonian Period is called not called "the age of fishes" because the first fish lived then. Fish have been around much longer, but the diversification of fish accelerated in the Devonian. A huge part of this the explosion of the bony fish - Osteichthyes. Living bony fish fall into two great groups:
- Ray-finned fish - including most living bony fish
- Lobe-finned fish - common in early oceans, but rare today as fish - limited to coelacanths and lungfish. (Psst! Land vertebrates are lobe-finned fish whose ancestors left the water!)
So, what about Moythomasia? This little fish is fun because it gives us a snapshot of what ray-finned fish looked like just barely after their split with lobe-finned fish. Moythomasia shows the characteristic primordial features of ray-fins, including the single dorsal fin and shark-like heterocercal tail fin (still preserved in living sturgeons.) But in other respects, Moythomasia is more primitive than any living ray-finned fish. For example, its mouth is long and opens and closes like scissors, rather than forming a tube like in many modern ray-fins. So, a tiny snapshot of the beginnings of ray-fin evolution.
