Complex sentence: The hinge teeth (dentition) or lack of them is an important feature of bivalve shells because the teeth are generally similar within major groups, and have historically provided a convenient means upon which to base classification schemes and the phylogenetic order.
Split into simpler sentences: The hinge teeth (dentition) or lack of them is an important feature of bivalve shells. They are generally conservative within major groups, and have historically provided a convenient means upon which to base classification schemes and the phylogenetic order.