Darwin's Dilema: The Burgess Shale, Hallucigenia

Hallucigenia is an organism that arose during the Cambrian explosion. It got its name from it strange and dreamlike appearance. It was 0.5-3 cm in length and lived on the sea floor. Figuring out how this creature functioned and whats its unique appendages were used for has proven difficult for scientists. While still debated, it is commonly thought that the blob on one of its ends functioned as a head-like structure even though it has no signs of a mouth, ears, or eyes. The six spines rising from one of its sides are paired with six tentacles on the other side. It is thought that it may have fed by either ingesting food through each of its tentacles or by passing food along with them to its 'head'.
An alternative interpretation considered Hallucigenia to be an appendage of a larger, unknown animal. There had been precedent for this, as the species Anomalocaris had been originally identified as three separate creatures before being identified as a single huge 3-foot-long creature. Given the uncertainty of its taxonomy, Hallucigenia was tentatively placed within the phylum Lobopodia.