Sanctacaris

Sanctacaris ("saintly crab") is a Middle Cambrian arthropod from the Burgess Shale.

Description
Specimens of Sanctacaris measure from 46 to 93 millimeters in length. Its head bears five pairs of grasping appendages and a sixth pair of separate appendages, which themselves each bear a short and antenna-like appendage. Fossils have 11 body segments, each possessing a pair of legs and gills. Its telson is broad and paddle-like.

Classification
Sanctacaris was originally considered to be a primitive chelicerate, but subsequent analyses have classified the genus with the basal arachnomorphs or in the stem lineage to the euarthropods.

History
Unlike many animals from the Burgess Shale, Sanctacaris was not discovered or described by Charles Walcott in the early 20th century. It was discovered in the early 1980s by Desmond Collins. The animal's distinctive clawed appendages inspired the fossils to be given the nickname "Santa Claws" in the field. When it was described in 1988, this nickname influenced the genus name Sanctacaris, which means "saintly crab" in Latin.

Diet
Sanctacaris was well adapted to a predatory lifestyle, and likely swam just above the sea floor to sense and grab potential prey with its appendages.