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Temporal range: Middle Cambrian
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
(unranked): stem-group Chelicerata[1]
Genus: Sanctacaris
Binomial name
S. uncata

Sanctacaris is a Middle Cambrian arthropod from the Burgess Shale of British Columbia. It was most famously regarded as a primitive chelicerate, a group which includes spiders and scorpions, although subsequent phylogenetic studies have not always supported this conclusion; it is best accommodated in the arachnate clade (i.e. as a stem-group chelicerate).[1]

Sanctacaris specimens range from 46 to 93 mm in length.[2] The head bears five pairs of grasping appendages and a sixth pair of large separate appendages. The grasping appendages each bear a short antenna-like second appendage. There are 11 body segments, each with a pair of walking legs and gills. There is a broad, flat paddle-like telson.

Originally Sanctacaris was called informally 'Santa Claws'. Its Latin name translates as "saintly crab".[3] Unlike most other Burgess forms, Sanctacaris is not present in Charles Walcott's 1909 quarry and was discovered at a different level by Desmond Collins in 1980–1981.[3]


  1. ^ a b G. E. Budd, S. Jensen (2000). "A critical reappraisal of the fossil record of the bilaterian phyla.". Biological Reviews of the Cambridge Philosophical Society 75 (2): 253–95. doi:10.1017/s000632310000548x. 
  2. ^ Briggs, Derek E. G.; Collins, Desmond (1988). "A Middle Cambrian chelicerate from Mount Stephen, British Columbia" (PDF). Palaeontology 31 (3): 779–798. Retrieved April 4, 2010. 
  3. ^ a b Briggs, D.E.G.; Erwin, D.H.; Collier, F.J. (1995), Fossils of the Burgess Shale, Washington: Smithsonian Inst Press, ISBN 1-56098-659-X, OCLC 231793738 

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