When alive, Pikaia was a compressed, leaf-shaped animal.
It swam by throwing its body into a series of S-shaped, zigzag curves, similar to the movement of eels.
Fish inherited the same swimming movement, but they generally have stiffer backbones.
Pikaia had a pair of large head tentacles 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 living lancelet.
Burgess Shale, Stephens Formation
Field, British Columbia, Canada
34mm on 106mm slab. Mildly weathered, but extremely rare and hard to obtain.
Problematica, Burgess Shale