Hallucigenia finds a home...

To quote Gould in Wonderful Life, “Walcott, mistaking the strangest of all Burgess creatures for an ordinary worm, referred to this oddball as Canadia sparsa.” (1989).


However, it now appears that Gould, Morris, and others may have mistaken an ordinary worm for the strangest of all Burgess creatures!

 

Hallucigenia as a lobopod, reconstruction taken from Natural Resources Canada, http://www.nrcan.gc.ca/gsc/calgary/canpal/pastlives/09_e.html


After a careful excavation of one of the better preserved specimens of Hallucigenia, the outline of a second set of tentacle-like appendages was discovered. This turned the interpretation of Hallucigenia upside down! It made more sense for the organism to walk on these appendages than the spines, which would have been very difficult. The spines on the dorsal surface suggested a protective function, and the small masses on the ends of the tentacles were then interpreted as claws, rather than mouths. This interpretation makes Hallucigenia a little more consistent with what we observe in modern animals. The digestive tract would have to have several branches opening up to the environment to have these serial mouths. This would suggest a completely different pattern of development than that which we find in protostomes and deuterostomes, where the basic body plan is that of a tube with two openings.


With its more predictable anatomy, new attempts were made to classify Hallucigenia. A Cambrian bed was found in China with several “armored lobopods,” which are basically a worm with protective plates on the dorsal surface. Some of these worms even had spikes. Thus, Hallucigenia no longer seemed quite so odd, and its anatomy is consistent with other lobopods in the phylum Onychophora, which today contains the velvet worms.