#zoophycos

Not a fossil animal. Not a fossil plant, either, although that's what they were originally described as in 1855. They're actually an ichnofossil - a trace fossil preserving the activity of a long-dead animal. What the creature WAS is an open question - it was probably worm-like. Although of course there's no guarantee that it's the same animal that's been making these ichnofossils for 521 million years.

The ichnofossils can be a meter across and deep. In structure they're closely packed J- or U-shaped lobes around a burrow, although as the epochs rolled on Zoophycos traces have been getting more and more elaborate, with branching lobes or layers built up in a corkscrew-fashion. Earlier examples are from shallower depths, but later they're more often found in deepwater turbidite beds, where mud and sand was deposited by huge underwater landslides. However, even in more recent times they're also known from nearshore formations where storms deposit a lot of sediment.

From all the evidence, it would seem the Zoophycos organism (or organisms) lived in places where there aren't many other animals to compete with them, and were methodically searching freshly settled sediment around them for anything to eat.