At first glance it looks exactly like a seahorse. It has the same horse-shaped head tilted down from the body, the same curled and grasping tail, and in the males a fully enclosed pouch for brooding the young.

But this little fish, no longer than your thumb, is not a seahorse, as we report in our new study published in the Journal of Lost Species. This is Australyichthys aegis, a newly described fish from the deep reefs off southern Australia. We have given it the common name helmethead sea muppet, after the domed, helmet-like crest on its head.

Its scientific name follows the same idea: in Greek mythology the aegis was a protective shield. Together with its two relatives, the bullneck sea muppet (A. minotaur) and the paradoxical sea muppet (A. paradoxus), it makes up a small group we nickname the sea muppets.

All three, we have now shown, belong on their own branch of the family tree. The seahorse look has arisen more than once, and these fish are a case of it evolving well away from the true seahorses. That evidence had been sitting in museum drawers, misfiled, for decades.

Bycatch from the deep

You will not find these fish while scuba diving.

Every known specimen........

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