"Pikaia" was a primitive chordate that lacked a well-defined head and averaged about in length. Once thought to be closely related to the ancestor of all vertebrates, it has for that reason received particular attention among the multitude of animal fossils found in the famous Burgess Shale in the mountains of British Columbia, Canada. "Pikaia" had a pair of large, antenna-like tentacles on its head, and a series of short appendages, which may be linked to gill slits, on either side of its head. In these ways, it differs from the modern lancelet. The "tentacles" on its head may be comparable to those in the present-day hagfish, a jawless chordate.