Eusthenopteron is a tristichopterid lobe-finned bony fish from the Middle Devonian of Canada. It was named in 1881 by Joseph Frederick Whiteaves. It was the ancestor of amphibious lobe-finned fish like Tiktaalik as well as amphibians like Ichthyostega, and was the earliest known animal with bone marrow.
Physiology[]
Eusthenopteron resembled the generic lobe-finned fish. It was a coelacanth-like fish with a bulky body, fleshy, lobe-like fins, and a big head with semi-small jaws. Its body would have been covered in scaly skin.
Diet[]
Eusthenopteron was a predator, preying on smaller fish. Its teeth were small yet sharp, and were used to get a hold of struggling prey as the lobe-finned fish swallowed them whole.
Ecology[]
Eusthenopteron had a body plan somewhat similar to tetrapods; its fin bones were very comparable to tetrapod leg bones, which would mean that primitive legs had evolved in creatures that were still primarily aquatic, like Tiktaalik. As well as this, its head was very similar to those of amphibians, having jaws capped with teeth with infolded dentin and enamel, as well as internal nostrils. For a while, it has been suspected that Eusthenopteron could crawl out of the water and onto dry land; however, scientists now agree that it was limited to the water. As well as this, it was the biggest vertebrate predator in Middle Devonian Canada, often grabbing smaller fish in its jaws and swallowing them whole.