Today's post is from my History of the Earth Perpetual Calendar for March 4.
The diversity and abundance of trilobites during Ordovician time was similar to that of the Cambrian. Together with brachiopods, trilobites were the dominant (or most numerous) marine animals in Ordovician seas. Ordovician trilobites seem to have had better developed eyes than their Cambrian ancestors.
The trilobites here are Triarthrus becki (left) and Bumastus trentonensis (right).
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