Bobbit worm

An iridescent purple-black segmented worm, only about 25 mm across the body but reaching three metres in length, of which almost all is buried. What shows is the head: five antennae fanned out on the sand around a burrow opening, and a pair of sclerotised jaws on an eversible pharynx. Nothing else in muck looks like it. The name is the problem. Eunice aphroditois is a valid name, but it was described from a single 45 cm animal from Sri Lanka and was subsequently applied to large eunicids worldwide, manufacturing a false cosmopolitan species. A 2011 review restricted it to the Indian Ocean and western Pacific and said plainly that the other animals lumped into it are probably undescribed; a reply in the same issue pointed out that eunicid taxonomists do not agree on what the name means. Nobody has matched the Indo-Pacific muck giant to the type. This site therefore writes Eunice cf. aphroditois.

The famous behaviour is real and the famous details mostly are not. It lies buried with the antennae spread as tripwires and takes fish and invertebrates with a strike too fast to follow, dragging them under. That it slices fish in half is repeated by serious institutions but no measurement of the strike, its speed or its force appears to have been published. That it injects a toxin is asserted in the same places and no primary evidence of venom in eunicids could be found. What is well evidenced is the lineage: a trace fossil described in 2021 from Miocene Taiwan records L-shaped burrows up to two metres deep with feather-like collapse structures around the opening, interpreted as the lair of an ambush-predatory worm about twenty million years ago. The authors were careful not to attribute it to this species. Sand, mud and rubble, recorded to about 95 m.