Emmonsaspis

Emmonsaspis is a Cambrian chordate, and its fossils were found in the Cambrian-age Parker Slate of Vermont in the late 19th century.

Description

Emmonsaspis is a chordate related to Metaspriggina and Nuucichthys. It grew to roughly in length and probably fed on plankton in the water column. No trace of a spinal cord is present, although roughly 50 myomeres can be seen in the fossils. It had large eyes and a large organ behind its branchial chamber, probably a liver.
There are two species: Emmonaspis worthanella and Emmonaspis cambriensis 1886 1911).
E. cambrensis has been described as a graptolite, a chordate, an arthropod and as a frond-like organism.

Affinities

It was interpreted by paleontologist C. D. Walcott in 1911 as a polychaete worm. Although some paleontologists regarded it as an early chordate allied with Pikaia et al., Simon [Conway Morris|Conway Morris] suggested in 1993 that it might be a Cambrian descendant of the Vendian form Pteridinium, and a frondose morphology was accepted, until a 2024 study found Emmonsaspis to be in a polytomy with Metaspriggina and Nuucichthys as a stem-group vertebrate.