Australia: The Land Where Time Began

A biography of the Australian continent 

Anomalocaris Canadensis Morphology from the Burgess Shale

Significant differences from published accounts of the iconic species Anomalocaris Canadensis from the Burgess Shale, Cambrian Series 3, Stage 5, are highlighted, prompting new evaluation of its morphology as a whole. In this study the authors¹ used all known specimens of A. Canadensis, including material that was previously unpublished, were examined with the aim of providing a cohesive morphological description for this stem lineage arthropod. Unlike earlier descriptions, the dorsal surface of the head is shown to be covered by a small, oval carapace closely associated with paired stalked eyes, the ventral surface bearing only the triradial oral cone, and there is no evidence of a hypostome or an anterior sclerite. Frontal appendages reveal new details of the arthroidial membranes, and in dorsal view a narrower cross-section than in earlier reconstructions. A complex suite of digestive, respiratory, and locomotory characters are revealed in the posterior body region, including a differentiated foregut and hindgut, a midgut with paired glands, setal blades that are gill-like, and evidence of muscle bundles and struts that are presumed to have supported the swimming movement of the body flaps. A central blade is included in the tail fan, which is in addition to the 3 pairs of lateral blades that were previously described. According to the authors¹ some of these structures have not previously been identified in other anomalocaridids, which the authors¹ say makes Anomalocaris critical for understanding the morphology of the group as a whole and corroboration of its arthropod affinities.

  Sources & Further reading

1. Daley, Allison C., and Gregory D. Edgecombe. "Morphology of Anomalocaris Canadensis from the Burgess Shale." Journal of Paleontology 88, no. 1 (January 1, 2014 2014): 68-91.