Cartorhynchus

Cartorhynchus (meaning "shortened snout") is an extinct genus of early ichthyosauriform marine reptile that lived during the Early Triassic epoch, about 248 million years ago. The genus contains a single species, Cartorhynchus lenticarpus, named in 2014 by Ryosuke Motani and colleagues from a single nearly-complete skeleton found near Chaohu, Anhui Province, China. 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 a 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. The most distinctive features of Cartorhynchus were its short, constricted snout, and its multiple rows of molar-like teeth which grew on the inside surface of its jaw bones. These teeth were not discovered until the specimen was subjected to CT scanning. Cartorhynchus likely preyed on hard-shelled invertebrates using suction feeding, although how it exactly used its inward-directed teeth is not yet known. It was one of up to five independent acquisitions of molar-like teeth among ichthyosauriforms. In 2011, the only known specimen of Cartorhynchus was discovered in Bed 633 from the second level of the Majiashan Quarry near downtown Chaohu, Anhui Province, China; the rock strata in this quarry belong to the Upper Member of the Nanlinghu Formation. The specimen consists of a nearly-complete skeleton missing only part of the tail and some of the bones from the left part of the rear skull. The specimen's preservation likely resulted from it having been deposited in sediment right side down, thus leaving the left side exposed to the elements.