Redescription and systematic position of Pterocaris Heller, 1862 (Crustacea: Decapoda: Caridea)

The enigmatic caridean shrimp Pterocaris typica Heller, 1862, is redescribed and illustrated in detail after the rediscovery of the unique female holotype in the Crustacea Collection of the Museum of Natural History in Vienna. Heller did not specify the systematic position of the genus Pterocaris within the Caridea. Several subsequent workers (H. Coutiere, D. M. Banner & A.H. Banner, M.L. Christoffersen) discussed the systematic position of this curious shrimp in relation to the family Alpheidae without having the possibilty to examine the type. It is concluded here that the genus is indeed best placed within the Alpheidae. However, several highly unusual features (autapomorphies), which clearly indicate a specialized life style - especially the flattened and expanded abdominal pleura and the long simple setae covering almost the entire dorsal surface - make it difficult to find any close relatives among other alpheid genera. It is assumed that the extreme rarity of P. typica is due to a cryptic life style of the shrimp, which could live either inside galls among corals, on the surface of its invertebrate host or in a completely different habitat such as sedimentary bottoms.