Fish lizard discovered 'half a seal and a half tadpole'

The 248 million-year-old fossil of Cartorhynchus lenticarpus reveals features never before seen in fish or lizard (Ichthyosaur).

With a body length of only 30 cm, C. lenticarpus is known as the smallest Ichthyosaur that ever existed on Earth. In a new study published today in Scientific Reports , paleontologists describe it as having been shaped like a hybrid between a seal and a tadpole (which has grown in all four legs) , rather than The dolphin shape is as long as most relatives.

Figure simulating fish lizard Cartorhynchus lenticarpus. (Photo: Stefano Broccoli).

This tiny fish lizard has a seal-like head with an unusually short snout. Fossil CT scans also showed that they possessed smooth, round teeth like pebbles, probably used to crush bivalve shellfish, such as clams, shellfish and snails. This helps to shed light on the role of the first Ichthyosaurs in the Three Gorges ecosystem, 251–200 million years ago.

The pebble-like teeth of C. lenticarpus. (Photo: Ryosuke Motani et al).

"We still do not know the exact origin of the fish lizard. They are reptiles related to the lizard group, which means more kinship with crocodiles, dinosaurs and birds than lizards." band and snake, " said lead researcher Olivier Rieppel, paleontologist and evolutionary biologist at Field Museum in Chicago, USA. "By studying the unique teeth of this ancient Ichthyosaur, we can better understand how they lived and evolved."

C. lenticarpus is thought to live in shallow coastal waters, where they easily find invertebrates for food. The flexible ankles also allow them to leave the water and move on land, though quite as difficult as seals today.

The only fossil of C. lenticarpus was discovered in China. (Photo: Ryosuke Motani).

So far only one fossil of C. lenticarpus has been found and recovered. In the next phase of the study, Rieppel wants to unearth more fossils to shed light on the evolutionary origins of the Ichthyosaur.

1. Discover the extinct fish lizard 25 years ago
2. Dog sniffs see ancient fish lizard fossils