Osteolepis (closely related animal)

Geologic Era: Devonian

Location Discovered: Caithness, Scotland

Size:  Roughly 20 centimeters (would be closer to 25 if head was present)

Estimated Range: Scotland, Estonia, Latvia

Extinction Date:  Late Devonian (386 million years ago)

This Thursius fish is nearly complete, missing only the head. The fins, scales, and overall body are in beautiful condition. The scales are coated in a sheen of pyrite, which gives them a brassy look under certain lights.

Thursius would have been a mid-range predator in its environment, preying on smaller animals but likely being eaten by larger fish. Thursius belonged to a group of fish called the sarcoptergian, or lobe finned fish. This is the group of fish that ultimately gave rise to amphibians and other tetrapod animals. The difference between a ray-finned fish (most modern fish) and lobe-finned fish is that the lobe finned fish have bones further down in their limbs, allowing for a primitive elbow-wrist system. While this structure would not have allowed Thursius to walk on land, it could have propped itself up on a river or lake bottom.

Lobe finned fish are not terribly common today, though a few types, such as lungfish and coelocanths still exist.

Image Credits:

Life Restoration: By Nobu Tamura (http://spinops.blogspot.com) – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=19460284