page_title: Sidneyia
section_title: General description
hierarchical_section_title: Sidneyia / General description
caption_attribution_description: Plate 2: Middle Cambrian Merostomata (Sidneyia) 1. Sidneyia inexpectans (Walcott) = 2. Sidneyia inexpectans (Walcott) = 3. Sidneyia inexpectans (Walcott) =
context_page_description: Sidneyia is an extinct arthropod known from fossils found from the Early Cambrian-age Maotianshan Shales to the Mid Cambrian Burgess Shale formation of British Columbia. 144 specimens of Sidneyia are known from the Greater Phyllopod bed, where they comprise 0.27% of the community.
context_section_description: Sidneyia ranged from 2 to 5 inches (51 to 127 mm) in length and is one of the largest arthropods found at the site. It is thought to have been a benthic carnivore and scavenger that walked along the sea floor in search of hard-shelled prey. Gut contents have revealed that Sidneyia fed largely on small trilobites, as well as on brachiopods, hyoliths and small arthropods. The gut was narrow, but widens posteriorly to form a pocket where digestion presumably took place. The retention of feces likely indicates infrequent feeding Its exquisitely preserved gnathobases resemble those of Limulus, and were probably used to crush prey.
  Sidneyia was discovered in 1910 during the first day of Charles Walcott's exploration of the Burgess Shale. He named it after his elder son, Sidney, who had helped to locate the site and collect the specimen. The species name, Sidneyia inexpectans, is derived from the meaning of "Sidney's surprise".
  Sidneyia sinica was named in 2002 from a specimen found in the Maotianshan Shales.
  About 200 specimens have been documented.
caption: Fossils
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