Emmonsaspis

Emmonsaspis
Temporal range: Cambrian Stage 4
Life restoration of Emmonsaspis
Fossil of Emmonsaspis
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Genus: †Emmonsaspis
Resser & Howell, 1938
Species
  • Emmonaspis worthanella Resser & Howell, 1938
  • Emmonsaspis cambrensis (Walcott, 1891)

Emmonsaspis is an extinct genus of chordate of likely vertebrate affinity, and its fossils were found in the Cambrian-age Parker Slate of Vermont in the late 19th century.

Description

Size of Emmonsaspis (red) compared to other Cambrian chordates and a human hand

Emmonsaspis is a chordate related to Metaspriggina and Nuucichthys. It grew to at least 4.5 cm (1.8 in) in length, and probably was a filter feeder on small particles and animals in the water column. No trace of a spinal cord is present, although roughly 50 myomeres (muscle blocks) 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, though recent studies have interpreted it as a chordate.

Phylogeny

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, until a 2024 study found Emmonsaspis to be in a polytomy with Metaspriggina and Nuucichthys as a stem-group vertebrate.

Cladogram following Lerosey-Aubril and Ortega-Hernández 2024 (note that the finding of a closer relationship between cephalochordates and tunicates than either is to vertebrates is contradicted by genetic evidence)

Chordata

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) 240350. Bibcode:2024RSOS...1140350L. doi:10.1098/rsos.240350. PMC 11267725. PMID 39050723.
  2. ↑ Pari, Giovanni; Briggs, Derek E.G.; Gaines, Robert R. (July 2022). "The soft-bodied biota of the Cambrian Series 2 Parker Quarry Lagerstätte of northwestern Vermont, USA". Journal of Paleontology. 96 (4): 770–790. Bibcode:2022JPal...96..770P. doi:10.1017/jpa.2021.125. ISSN 0022-3360.
  3. 1 2 3 4 Lerosey-Aubril, Rudy; Ortega-Hernández, Javier (July 2024). "A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region". Royal Society Open Science. 11 (7) 240350. Bibcode:2024RSOS...1140350L. doi:10.1098/rsos.240350. ISSN 2054-5703. PMC 11267725. PMID 39050723.
  4. ↑ "Cambrian Primitive Chordate Fossil". www.fossilmuseum.net. Retrieved 29 May 2018.
  5. ↑ "Duffy: Chordate Origins". www.biology.ualberta.ca. Archived from the original on 21 February 2008. Retrieved 29 May 2018.
  6. ↑ 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. Bibcode:1996Natur.384..157S. doi:10.1038/384157a0.
  7. ↑ Nanglu, Karma; Cole, Selina R.; Wright, David F.; Souto, Camilla (February 2023). "Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development". Biological Reviews. 98 (1): 316–351. doi:10.1111/brv.12908. ISSN 1464-7931. PMID 36257784.