If you ever find yourself playing a game of twenty questions, there’s a little-known life form you can pick that is sure to leave your opponent stumped.

It is neither animal, vegetable, nor mineral. It’s not even a bacterium or fungi.

It’s called a Euglenid – and it’s a weird fusion of a bunch of different living things.

Euglenids are a group of unicellular eukaryotes that gain energy through both photosynthesis, like a plant, and through consuming other beings, like an animal.

These aquatic organisms split off from other eukaryotes roughly a billion years ago, and yet their fossil record for all that time on Earth is scarce.

Now, an international team of scientists argues that they have found ancient Euglenid fossils hiding in ‘an extensive paper trail’ of already published scientific research.

For years, the shell-like fossils were misidentified as possible worm eggs, algal cysts, or fern spores, partly because of their tiny circular ‘ribs’ on the inside.

The fossils didn’t really fit into any taxonomical box, so in 1962, scientists called them Pseudoschizaea shells.

Their similarities over the years have stumped experts, as these fossils span immense timelines, from almost half a billion years ago to the present.

Andreas Koutsodendris studies microscopic fossils at Heidelberg University in Germany, and he says that while analyzing drill cores from lakes in Greece, he regularly encounters fossils of these thin-walled, oval lifeforms.

‘Their biological affinity has never been cleared,’ says Koutsodendris, a co-author of the new study, ‘In fact, the cysts are commonly figured in publica