If a two-valved animal is not a Bivalve... it could be a Brachiopod!

Don’t call them clams or scallops! Despite their similar shapes, brachiopods, real stars in the world of paleontology, are only distantly related to bivalves. Such similarity is not caused by blood, but by adaptive convergence! A boon to paleontologists, these organisms include over 12,000 fossil species, although only a few hundred survive today.