At only 13 and 3 millimeters (about 0.5 and 0.1 inches), these minuscule fossils from the Ordovician period may not seem like much to look at, but their familiarity kept paleontologists up at night.
The fossils look like opabiniids – extinct soft-bodied animals with snouts – yet they were dated to 40 million years after any known opabiniid fossil.
Dinocaridida, which include opabiniids and radiodonta, were abundant after the Cambrian explosion; these creatures scuttled through an ocean-dominated Earth around 500 million years ago.
If they are part of the opabiniids, these fossils extend this group's known existence on Earth by 40 million years.