Emmonaspis

Emmonaspis is a fossil that was found in the Cambrian-age Parker Slate of Vermont in the late 19th Century.

Description
Emmonaspis is described as a tadpole or worm-like animal. No trace of a spinal cord is present.

There are two species: Emmonaspis worthanella and Emmonaspis cambriensis (Walcott(?) 1886(?) 1911(?)).

What it is thought to be
It was interpreted by paleontologist C. D. Walcott in 1911 as a Polychaete worm. Conway Morris suggested in 1993 that it might be a Cambrian descendant of the Vendian form Pteridinium. Some paleontologists regard it as an early chordate allied with Pikaia et al.