Marrella was a primitive arthropod from the Middle Cambrian Burgess Shale. It is the most common fossil found in the formation.[1]


Marrella was a small creature, measuring 2 centimeters long at most. Its most prominent feature was its head shield, which had two pairs of rear-facing spikes. Marrella walked on the sea floor using around 50 individual legs, with each leg supporting a feathery gill-like structure. In life, the hard parts of Marrella would have been iridescent.[2]


At the current time, Marrella is best classified as a stem group arthropod, and not a type of trilobite as its morphology would suggest.


Marrella was the first type of fossil collected by Charles Walcott from the Burgess Shale in British Columbia.[3] He described it in 1912, identifying it as a possible trilobite. In 1971, Harry Whittington published a redescription of the animal and concluded that Marrella was not actually a trilobite, nor was it part of any extant arthropod group.[4] It was subsequently labeled as a stem group arthropod.

Since its discovery, over 25,000 specimens of Marrella have been collected, making up a significant portion of the specimens found in the Greater Phyllopod bed.[5]


Marrella is thought to have been a deep-sea scavenger, living on the ocean floor and feeding on small particles of organic material. One particular specimen shows that the animal molted its shell, rather like living marine invertebrates.[6]


  1. Bottjer, David J; Etter, Walter; Hagadorn, James W; Tang, Carol M (2002). Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life. Columbia University Press. p. 70. ISBN 978-0-231-10255-1. OCLC 47650949.
  2. Parker, A. R. (1998). "Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian". Proceedings of the Royal Society B: Biological Sciences 265 (1400): 967–972. doi:10.1098/rspb.1998.0385.
  3. Gould, Stephen Jay (2000). Wonderful Life: Burgess Shale and the Nature of History. Vintage. p. 108. ISBN 978-0-09-927345-5. OCLC 45316756. Also OCLC 44058853.
  4. Whittington, H. B. (1971). "Redescription of Marrella splendens (Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia". Bulletin – Geological Survey of Canada (Geological Survey of Canada) 209: 1–24.
  5. Caron, J. -B.; Jackson, D. A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS 21 (5): 451–465. doi:10.2110/palo.2003.P05-070R. edit
  6. García-Bellido, D. C.; Collins, D. H. (2004). "Moulting arthropod caught in the act". Nature 429 (6987): 40. Bibcode:2004Natur.429...40G. doi:10.1038/429040a. PMID 15129272.