EEMB 131 Lecture Notes - Lecture 17: Ediacaran, Cambrian Stage 2, Body Plan
8 Mar 2018
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Exceptions to agm: origin of phyla, mass extinctions. 4 major fossil deposits span the vendian/ cambrian boundary (543 mya) See major increase in morphological complexity and taxonomic diversity. Occurred at the level of major novelties in body plans-> new classes and phyla. Deposits contain sponges and embryos (64 stages) of other taxa. Predates the evolution of shells and skeletons. At the time, continents were spread out and span along the equator. So fossil records are found in canada, australia, cyberia. Have organisms with radial, bipolar, unipolar growth. Most are poorly reserved in the sand. In order to be preserved in the sand, these organisms must have hard shells and skeletons to not be compressed. Illustrates the full range of body plans present in a single site soon after the cambrian diversity explosion. Arthropods has segmented body plan, 3 pairs of appendages on each segmented body part. 4 persistent classes: trilobites, insects, crustaceans, chelicerates.
