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Question on glide reflections in Ediacaran biota
I've seen that many Ediacaran biota are described as having a glide reflection
(Spriggina, Pteridinium, Dickinsonia for example) - yet the pictures I see of
the fossils are (in my opinion) inconclusive.
Can anyone comment on this or provide clear photographs conclusively showing
I am unsure how to interpret this. If these disparate forms all share glide
reflections, then it seems that one should conclude they are monophyletic.
Spriggina has been compared to a proto-worm-arthropod - yet I can't see how it
fits in with this if it really does have a glide reflection symmetry.
Perhaps "glide-reflection" forms later evolved true bilateral symmetry? but
If you have Kimberella as a Mollusk, and Arkarua as a echinoderm (assuming
these are valid), then bilateria was already around for a while by this point,
and it seems unlikely that a creature such as Sprigginia with glide-reflection
independently evolved true bilateral symmetry before leading to the ecdysozoa
clade. (this would also imply that bilateral symmetry in Deuterostomes was
independently evolved, which isn't so hard to believe, but we'd also need to
postulate it independently evolved in Lophotrochozoa)
- Or we coud just write off Sprigginia as a dead end, but then we'd be missing
a precambrian antecedent to the arthropods in the cambrian.
It would simplify things if this "glide reflection" stuff could be discounted
(and also make the Cambrian explosion look like less of an explosion).
Ok, its not dino related, but I assume anything Paleontology related goes,