A tiny shrimp, Vercoia interrupta, only about 6 or 7 mm long, seems to have evolved to resemble a snail shell in its superficial, external appearance (Anker, 2010).
Photo of live Vercoia interrupta (by Guido Poppe) from Anker (2010).
Anker notes that the shrimp “remarkably resembles a dead and encrusted cerithiid shell, more specifically that of Cerithium rostratum G.B. Sowerby II, 1855, which is common in the area”. New sightings of this species, previously known only from southern Japan, come from the central Philippines.
Thanks to the reader Andrew Broome for bringing this paper to my attention.
Anker, A. 2010. A second finding of Vercoia interrupta Kim & Fujita, 2004 (Crustacea, Decapoda, Crangonidae), a remarkable shrimp imitating dead snail shells. Raffles Bulletin of Zoology 58:27-30. pdf