Hallucigeniidae

Hallucigeniidae is a family of extinct panarthropods belonging to the group Lobopodia that originated during the Cambrian explosion. It is based on the species Hallucigenia sparsa, the fossil of which was discovered by Charles Doolittle Walcott in 1911 from the Burgess Shale of British Columbia. The name Hallucigenia was created by Simon Conway Morris in 1977, from which the family was erected after discoveries of other hallucigeniid worms from other parts of the world. Classification of these lobopods and their relatives are still controversial, and the family consists of at least four genera.

== History of discovery == The first fossil of hallucigeniid worm was discovered by an American palaeontologist Charles Doolittle Walcott from the Walcott Quarry that contains the Cambrian Burgess Shale. In 1911, Walcott gave the name Canadia sparsa as he believed that it was related to the polychaete worm (Annelida) Canadia spinosa, which he described simultaneously. British palaeontologist Simon Conway Morris re-examined the specimen and concluded that it was not a Canadia species. He created a new genus Hallucigenia in 1977. With only a single species and fragmentary fossils available, the relationship of the worm with other animals was not obvious. The most prominent feature of the worm, its body projections were particularly difficult to understand as there were two distinct groups, the tube-like tentacles and thornlike spines. Morris described the spines as the legs and the tentacles as feeding apparatus. Two other species were later discovered from the Cambrian Maotianshan shales of China, H. fortis in 1995, and H. hongmeia in 2012.