Late Cambrian

Weeks Shale Formation

House Range, UT, USA

30mm (95mm if uncurled) worm on 90mm slab

Worm.

People think worms all belong to the same group but they are actually quite diverse and assigned to several different groups, some of which are only distantly related.

This worm lived at a time before there were fish with jaws so a time-traveling fisherman would have had a bad day no matter how many times he switched bait.  Not even a nibble.