Ancient Fish Looked And Probably Lived A Little Like A Platypus

Reconstruction of an early Devonian fish has disclosed a bill like a platypus, probably used only for similar purposes. The discovery surprised palaeontologists because the fish is so different from everything else we’ve detected from the era. It suggests fish were much more specialized early on in their evolution than previously thought.

In 1980 Dr Gavin Young of the Australian National University discovered a partial skeleton of a new species at Lake Burrinjuck in New South Wales. He named it Brindabellaspis stensioi after the nearby Brindabella mountain range, but the fossil was lacking what proved to be the really interesting parts. Young has since detected other specimen from the same species and Dr Benedict King, then at Flinders University, set them together to reconstruct Brindabellaspis .

“This was one strange-looking fish, ” King said in a statement. “The eyes were on top of the head, and the nostrils came out of the eye sockets. There was this long snout at the front, and the jaws were positioned very far forward.”

The fossilized bill from above( a) and below( b ), with the nerve channels visible. King et al/ Royal Society Open Science

In Royal Society Open Science King revealed that the long bill contained an advanced sensory system. “We imagine it utilized the bill to search for prey, somewhat like a platypus, while the eyes on top of the head appeared out for danger from above, ” said Professor John Long, who co-authored the paper and supervised King’s PhD.

King’s PhD was on electric sensory systems, like the ones platypuses and sharks possess. Long told IFLScience they initially guessed the bill might have been yet another example of this. However, King could find no evidence of anything resembling electric sensors. Instead, the authors concluded the bill housed a modified sort of the pressure sensor system that other fishes have, with two tubes running down the snout and restrictions on the sensory canal that likely allowed it to sense movements of prey.

On the other side of Australia, the Gogo deposits have amazed palaeontologists with early fish so well preserved they have been described as “swimming in stone”. The preservation at Lake Burrinjuck is not quite as good, but Long told IFLScience these deposits are even more important because at 405 million years old they precede Gogo by more than 20 million years.

This entails the site preserves the oldest instance we have of a tropical reef hosting diverse jawed fish suggesting- then as now- these were what Young called “hotspots for evolution”, rich in the placoderms that were the dominant fish of the day. “We have slightly earlier examples but they are isolated bits, ” Long said. So far 70 species have been received from this place alone, but none like Brindabellaspis . “It’s truly unusual to find something that is so specialized earlier today, ” Long said. We still haven’t found intact mouthparts, however, so we are largely guessing its diet.

Limestone outcrops around Lake Burrinjuck are the site of one of the most important fossil deposits we have from the early evolution of fish. Flinders University

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