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Australia: The Land Where Time Began |
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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material that was previously unpublished, were examined with the aim of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.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |