The oral cone of Anomalocaris is not a classic ‘‘peytoia’’
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The Cambro-Ordovician anomalocaridids are large ecdysozoans commonly regarded as ancestors of the arthropods and apex predators. Predation is indicated partly by the presence of an unusual “peytoia”-type oral cone, which is a tetraradial outer ring of 32 plates, four of which are enlarged and in perpendicular arrangement. This oral cone morphology was considered a highly consistent and defining characteristic of well-known Burgess Shale taxa. It is here shown that Anomalocaris has a different oral cone, with only three large plates and a variable number of smaller and medium plates. Its functional morphology suggests that suction, rather than biting, was used for food ingestion, and that anomalocaridids in general employed a range of different scavenging and predatory feeding strategies. Removing anomalocaridids from the position of highly specialized trilobite predators forces a reconsideration of the ecological structure of the earliest marine animal communities in the Cambrian.
KeywordsAnomalocaridids Cambrian Oral cone Peytoia Predation Burgess Shale
We thank G. Budd and J-B. Caron for discussions. Comments from G. Edgecombe, J. Esteve, B. Lieberman and an anonymous reviewer improved the manuscript. J. Dougherty provided access to specimens at GSC and D. Erwin, J. Thompson and M. Florence provided access to specimens at USNM. J-B. Caron and P. Fenton provided support at the ROM. X. Ma is thanked for the photography of USNM specimens. M. Stein provided photographs that led J.B. to this discovery. Burgess Shale specimens were collected with permission from Parks Canada Research (ROM, D. Collins, 1975 to 2000). Funding from the Swedish Research Council and the Palaeontological Association to A. C. D is gratefully acknowledged. This is Royal Ontario Museum Burgess Shale Research Project 39.
- Bergström J, Hou XG (2004) Arthropod origins. B Geosci 78:323–334Google Scholar
- Collins D (1996) The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (Nov.) and order Radiodonta (Nov.). J Paleontol 70:280–293Google Scholar
- Conway Morris S (1978) Laggania cambria Walcott: a composite fossil. J Paleontol 52:126–131Google Scholar
- Hagadorn JW (2009) Taking a bite out of Anomalocaris. Walcott 2009—International Conference on the Cambrian Explosion, abstract volume, 33–34.Google Scholar
- Hagadorn JW (2010) Putting Anomalocaris on a soft-food diet? Geol Soc Am Abstr Prog 42:320Google Scholar
- Walcott CD (1911) Middle Cambrian holothurian and medusae. Smith Misc Coll 57:41–68Google Scholar
- Whiteaves JF (1892) Description of a new genus and species of Phyllocarid Crustacea from the Middle Cambrian of Mount Stephen. BC Can Rec Sci 5:205–208Google Scholar