The unusual raptorial appendage of Acanthosquilla. This spearer has a hatchet-like protrusion on the dactyl.
S. empusa is a spearing mantis shrimp common on the east coast of the US as far north as New England. The seem to have lost many of the visual specializations common in other mantis shrimp, perhaps due to living in murky water.
Midway through dissecting a mantis shrimp in the field at Lizard Island Australia, I noticed that some industrious ants had made away with a raptorial appendage. They made it a foot up the wall to the underside of a window sill. They then dragged it hanging across the window for several feet.
