|Similar Peytoia, Anomalocaridid, Hurdia, Aysheaia, Sidneyia|
Peytoia nathorsti is a species of anomalocarid from the Burgess Shale. It is the type species of Peytoia.
108 specimens of Peytoia nathorsti are known from the Greater Phyllopod bed, where they comprise 0.21% of the community.
Like other Burgess Shale anomalocarids, Peytoia nathorsti has a complicated taxonomic history. It and Laggania cambria were named in the same paper in 1911. The type specimen of Peytoia nathorsti consisted of an isolated oral cone, which Walcott interpreted as the body of a jellyfish. The type specimen of Laggania cambria was a poorly preserved body and oral cone, which Walcott interpreted as being a holothurian. In 1978, however, Simon Conway Morris recognized that the "mouthparts" of L. cambria were nearly identical to the "body" of P. nathorsti, so he suggested that L. cambria was a composite of a sponge, Corallio undulata, and a Peytoia nathorsti. Conway Morris regarded Laggania cambria as a synonym of Peytoia nathorsti, and in doing so made Peytoia nathorsti be the valid name among the simultaneously-named synonyms.
In 1985, Harry B. Whittington and Derek E. G. Briggs described the first full-body specimens of Peytoia nathorsti along with the first full-body specimen of Anomalocaris canadensis. Based on the newly apparent similarities between the two species, they considered P. nathorsti to be a species of Anomalocaris, as Anomalocaris nathorsti.
Finally, new data on the morphology of the oral cone of Anomalocaris canadensis confirmed that it was distinct from Peytoia nathorsti.