Assertion: sea urchin | /r/AtLocation | the fossil record
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Source sentences:
text: The phylogenetic analyses and the order in which sea urchins occur in the fossil record are formalized beyond dispute: irregular sea urchins derived from regular sea urchins (therefore, note that the latter do not constitute a clade: they do indeed all have a common ancestor, but one which is not exclusive to them: that animal is also the ancestor of irregular sea urchins).