[4] Its generic name means "Crab of Stanley Glacier"; hirpex, L. "large rake", reflects the rake-like nature of its spiny frontal appendages.

[3] The original description of the taxon appeared in an online supplement to the article published by Jean-Bernard Caron, Robert R. Gaines, M. Gabriela Mángano, Michael Streng and Allison C. Daley in 2010.

[6] The specimen KUMIP 153923 from the Cambrian Wheeler Formation (Utah, United States), which was described by Robison (1985) as a whole body of new lobopodian species Aysheaia prolata, was reinterpreted as an isolated frontal appendage of Stanleycaris sp.

They reported segmental boundaries between the structures previously thought to be 'lobopods' and curved terminal spines that resemble the frontal appendages of radiodonts, and thus they considered A. prolata as a nomen dubium and synonymised it with Stanleycaris on the basis of their interpretation.

[3] Unlike most hurdiids with large head and broad neck region, the body of Stanleycaris was streamlined like those of anomalocaridids and amplectobeluids.

[3] Unlike other radiodonts, the paired lateral sclerites (P-element) are not evident in any Stanleycaris specimens, suggesting they were exclusively absent in this genus.

[10][5][11][3] This suggests that the anomalocaridid/amplectobeluid-like traits (e.g. streamlined body; small head sclerites; frontal appendages with curved dorsal spines) found in these hurdiids represent radiodont ancestral characters.