Despite the new clues, this ancient fish has puzzled scientists for centuries.

“We know what it is not,” says paleontologist Donald Davesne of the National Museum of Natural History in Paris, “but we don’t know what it is.”

This organism shares the genus name Pegasus First described by Italian naturalist Giovanni Serafino Volta in 1796, the fish has been distinguished from sea moths, which are fish with flattened snouts. “They have nothing in common,” Devsne says. “I don’t know what the guy was thinking.”

The two known fossil specimens are P. volans (One photo) They’re 3.3 and 5.6 centimetres long, respectively, but both are missing parts of their tails, which may hold important clues about where the animals fit on the evolutionary tree.Donald Davesne

Using a stereomicroscope and ultraviolet light photography, D’Avesne and paleontologist Giorgio Carnevale of the University of Turin in Italy each examined the fossil of a fish less than two inches long. Based on the specimen’s skeletal structure and fin size, the pair also ruled out a close relationship to the oarfish, as some paleontologists have recently suggested.

Instead, Deivesne and Carnevale point out similarities to modern cusk eel larvae and other bony fishes, including the long dorsal fin rays that extend above the head.SN: May 1, 2015Because the fish’s abdomen was so small, its internal organs probably hung in a pouch underneath its body, similar to the larval stages of bony fish.

But the fossil fish itself is unlikely to have been a larva, due to its relatively large body size and fully ossified skeleton, the researchers say. Still, the fossil may represent an early appearance of larval characteristics, perhaps part of an explosion in spiny-fish diversity after the Cretaceous-Paleogene mass extinction about 66 million years ago, Devson says.

Devsne cautions that more information is needed to confirm the relationship, including parts of the fish’s tails, which are missing from both fossils. “Someday, someone will find another specimen that’s even better preserved,” Devsne says. “That would be amazing!”

The pair say the fish’s phylogenetic relationships are unclear, and that a new genus name is needed. Following Carnevale’s naming tradition, Deibsne chose the name to honor the late musician with whom he was personally close. The name will be announced once the paper is officially published.