 Along with its close relative "Sclerocormus", "Cartorhynchus" was part of a diversification of marine reptiles that occurred suddenly (over about one million years) during the Spathian substage, soon after the devastating Permian-Triassic extinction event, but they were subsequently driven to extinction by volcanism and sea level changes by the Middle Triassic.Measuring about long, "Cartorhynchus" was small animal with a lizard-like body and a short torso; it probably swam in an eel-like manner at slow speeds.Its limbs bore extensive cartilage and could bend like flippers, which may have allowed it to walk on land.