A strange new fossil specimen is giving paleontologists insight into the evolution of vertebrates. A group of scientists led by Robert Sansom, from the University of Manchester in the United Kingdom, recently published a study in the journal Biology Letters that describes a new jawless fossil fish named Euphanerops longaevus.

Euphanerops swam through the ancient seas that once covered Quebec 370 million years ago. It was an eel-like in appearance, and 3.9 inches long. The weirdest thing about this fish? The fossil specimen appeared to have a pair of fins extending from its anus.

When the researchers first began analyzing E. longaevus’ anal fins, they thought the fins must have moved to the anal region from another part of the fish’s body during the fossilization process, making the fish appear to have appendages where it did not. Further study revealed that the fins were actually appendages that began just under the anus. This makes Euphanerops the first jawless fish to have been discovered with anal fins. Even more interesting, anal fins that are paired have never been found on any fish species, extinct or extant.

Euphanerops may fill some gaps in the history of vertebrate evolution. It was one of the earliest vertebrates to have paired appendages, a trait that became common across the board later on in vertebrate evolution. This fish also existed right around the time when jawed fish branched off from jawless fish, creating the two main categories of vertebrates that scientists study today. Paleotnlogists and evolutionary biologists hope that further study of this fish will uncover some of the mystery behind the jawed/jawless divergence.

Sansom and his colleagues aren’t sure what purpose these rear-positioned fins served, or how they came in handy millions of years ago for jawless fish. But the study authors see this fossil as continuing evidence that evolution isn’t a straight line: different morphologies are experimented with until a species finds a body plan that works. It’s a trial and error process that continues to occur today, and one we should be grateful for: wthout it, humans may have had appendages where they don’t belong.

Read the original study in the journal Biology Letters.

Published On: May 1, 2013

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