Being an expert in deep-sea animals, I knew at a glance that this one was special when I first saw it in 2015.

It is one of a kind – the last known species of an ancient lineage, like the coelacanth or the tuatara.

We compared DNA from a range of different marine species, and concluded that Ophiojura is separated from its nearest living brittle star relatives by about 180 million years of evolution.

Scientists used to call animals like Ophiojura "living fossils", but this isn't quite right.

The ancestors of Ophiojura would have continued evolving, in admittedly very subtle ways, over the past 180 million years.

Perhaps a more accurate way to describe these evolutionary loners is with the term "paleo-endemics" – representatives of a formerly widespread branch of life that is now restricted to just a few small areas and maybe just a single solitary species.

This is where we find the "relicts" of ancient marine life – species that have persisted in a relatively primitive form for millions of years.

Seamounts, like the one on which Ophiojura was found, are usually submerged volcanoes that were born millions of years ago.

These seamounts are ancient – up to 100 million years old – and almost totally unexplored.