Cartorhynchus
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Cartorhynchus Temporal range: Early Triassic, 248 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | †Ichthyosauromorpha |
| Clade: | †Ichthyosauriformes |
| Clade: | †Nasorostra |
| Genus: |
†Cartorhynchus Motani et al., 2014 |
| Species: | †C. lenticarpus |
| Binomial name | |
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Cartorhynchus lenticarpus Motani et al., 2014 |
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Cartorhynchus is an extinct genus of basal ichthyosauriform marine reptile that lived during the early Triassic period. Fossils have been found in eastern China and were unearthed from rocks in 2011. Those rocks were laid down as marine sediments about 248 million years ago. The only well-preserved fossil is quite complete, with only a portion of the tail missing. When alive, the creature was probably about 40 cm (16 in) long — about the size of a large lizard — and weighed about 2 kg (4.4 lb).
The name of the only described species of the genus, Cartorhynchus lenticarpus, comes from the Greek words for “short snout” (a feature of the fossil) and Latin words for “flexible wrist.”
The vertebrae and ribs are thick-walled and well mineralized, so the creature was probably an adult when it died. But most bones in the forelimbs were small and widely separated, a sign that the forelimbs were likely cartilage-filled flippers and not legs. The creature’s hindlimbs were reduced in size, another adaptation for life at sea. The creature’s heavy bones, like a scuba diver’s weight belt, counteracted natural buoyancy and probably enabled it to forage in shallow coastal waters. Yet Cartorhynchus could probably get around well on land using its flippers, just as seals and sea lions do today.
Unlike the more derived ichthyosaurs, Cartorhynchus was probably a suction feeder, basically vacuuming up soft-bodied prey. A lack of fossilized prey near the specimen supports this theory, since soft-bodied animals are not preserved in rock.
The origin of ichthyosaurs has been a mystery for centuries. Even the oldest known genera were already strongly aquatic. However, Cartorhynchus lenticarpus is considered to be close to the ancestry of the Ichthyopterygia, the ichthyosaurs and their immediate relations, and may shed light on the origin of this enigmatic clade of marine reptiles. Naming author Ryosuke Motani suggested the clade Ichthyosauriformes consisting of the Ichthyopterygia and the more basal Cartorhynchus. Cartorhynchus also indicates that the enigmatic Hupehsuchia were closely related. Motani combined the Ichthyosauriformes and the Hupehsuchia into the Ichthyosauromorpha.
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