Based on well-preserved material from the Sinemurian of the western Carpathians, the new subgenus Terquemia (Dentiterquemia) is proposed, which is presently represented only by its type species T. (Dentiterquemia) eudesdeslongchampsi n. sp. Dentiterquemia is separated from Terquemia sensu stricto by a series of denticles along the hinge margin and corresponding, chevronlike ridges on the ligament area. The combination of hinge teeth with a cementing habit is interpreted as a defense strategy inhibiting torsion of the valves as well as manipulation of the animal as a whole. Whereas different kinds of articulating hinge structures evolved independently in several clades of early Mesozoic cementing bivalves, Paleozoic cementing bivalves generally lack such structures. It is proposed that this difference reflects an early Mesozoic proliferation of durophagous predators and therefore points to a beginning of the “Mesozoic marine revolution” soon after the end-Permian mass extinction.

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