Canadia sparsa Hallucigenia is a genus of lobopodian known from Cambrian aged fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world.

[4] The generic name reflects the type species' unusual appearance and eccentric history of study; when it was erected as a genus, H. sparsa was reconstructed as an enigmatic animal upside down and back to front.

[15] In 1991, Lars Ramskold and Hou Xianguang, working with additional specimens of a "hallucigenid", Microdictyon, from the lower Cambrian Maotianshan shales of China, reinterpreted Hallucigenia as a lobopodian, a legged worm-like taxon which were still thought to be exclusively related to onychophoran (velvet worm) at that time.

[16] Further preparation of fossil specimens showed that the 'second legs' were buried at an angle to the plane along which the rock had split, and could be revealed by removing the overlying sediment.

Hallucigenia has long been interpreted as a stem-group onychophoran (velvet worms) – a position that has found support from multiple phylogenetic analysis.

[10][7][18][19] A key character demonstrating this affinity is the cone-in-cone construction of Hallucigenia claws, a feature shared only with modern onychophorans.

[8][21] Hallucigenia also exhibits certain characters inherited from the ancestral ecdysozoan, but lost in the modern onychophorans – in particular its distinctive foregut armature.

Isolated hallucigeniid spines, however, are widely distributed in a range of Cambrian deposits, preserved both as carbonaceous and mineralized fossils.