Australia: The Land Where Time Began |
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Cambrian Explosion Fossils – “Radiate”
Metazoan Body Plans The fossil record of Radiata (Cnidaria and
Ctenophora) is equivocal prior to the Cambrian; though it is suggested
by molecular clock evidence that the phyla comprising Radiata branched
from sponges about 780 Ma. In the latest Ediacaran there are a number of
organisms of probable diploblastic grade that are known. Among the
Cambrian
SSFs there are a number of tube-like forms, such as
anabaritids, protoconularids, as well as others from Stage 1 of the
Cambrian that have collectively been called cnidariomorphs (Kouchinsky
et al., 2012). As with the
spicule gap there is a “Radiata gap”, that is less severe but just as
troubling, between the probable clade origin and the first known fossil
representatives. As usual, small body size and lack of hard parts
imposes hurdles that may be sufficient to account for much of the gap.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |