Emmonsaspis

Emmonsaspis Temporal range: Cambrian Stage 4 PreꞒ Ꞓ O S D C P T J K Pg N [1]
Life restoration of Emmonsaspis
Fossil of Emmonsaspis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Genus:	† Emmonsaspis Resser & Howell, 1938
Species
Emmonaspis worthanellaResser & Howell, 1938 Emmonsaspis cambrensis(Walcott, 1891)

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 4.5 cm (1.8 in) 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 (Walcott(?) 1886(?) 1911(?)).

E. cambrensis has been described as a graptolite, a chordate, an arthropod and as a frond-like organism. ^{[2] [3]}

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., Conway Morris suggested in 1993 that it might be a Cambrian descendant of the Vendian form Pteridinium , and a frondose morphology was accepted, ^[4] until a 2024 study found Emmonsaspis to be in a polytomy with Metaspriggina and Nuucichthys as a stem-group vertebrate. ^[1]

Notes

1. Lerosey-Aubril, R.; Ortega-Hernández, J. (2024). "A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region". Royal Society Open Science. 11 (7). doi:10.1098/rsos.240350. PMC   11267725 .
2. "Cambrian Primitive Chordate Fossil". www.fossilmuseum.net. Retrieved 29 May 2018.
3. "Duffy: Chordate Origins". www.biology.ualberta.ca. Retrieved 29 May 2018.
4. Shu, D. -G.; Conway Morris, S.; Zhang, X. -L. (1996). "A Pikaia-like chordate from the Lower Cambrian of China". Nature. 384 (6605): 157–158. doi:10.1038/384157a0.