Catutosaurus, meaning “the lizard from Los Catutos”, was a small ichthyosaur which lived around Argentina during the late Jurassic Period 152-145 million years ago.
Fossils of this animal were found in the Vaca Muerta (“Dead Cow”) Formation, and the exact rock layer that the bones were embedded within was dated to the Tithonian Stage of the Jurassic Period, which lasted from 152-145 MYA. Phylogenic analysis shows that Catutosaurus was a basal member of the ichthyosaur family Ophthalmosauridae. Based upon the size of the remains and comparing them to the overall proportions of other ophthalmosaurid ichthyosaurs, Catutosaurus is believed to have measured just 2 meters (6 feet) in length.
In addition to the bones, the outlines of the body and the dorsal and pectoral fins are also faintly visible. These show that the body had a thick layer of muscle and blubber over the skeleton. In general, Catutosaurus’ body – or at least the front half of it – seems to have been similar in overall shape to the early-to-middle Jurassic ichthyosaur Stenopterygius. However, the shape of the dorsal fin was different. Catutosaurus’ dorsal fin seems to have been sharply angled backwards, indicating that the animal was optimized for great bursts of speed and wanted to reduce drag as much as possible. This dorsal fin shape is similar to that of the much larger early Jurassic ichthyosaur Temnodontosaurus. It is completely unknown what the rear half of the animal looked like, including the shape of the tail, so any reconstruction of Catutosaurus’ tail structure is guesswork at the moment. It’s possible that the caudal fin was also strongly forked with the flukes angled backwards like the dorsal fin, as is seen in the middle Jurassic ichthyosaur Baptanodon, but at the moment there’s no way to prove this.
Below is a reconstruction of Catutosaurus. The reconstruction is partially based upon the holotype specimen as well as on the bodies of Stenopterygius and Baptanodon.
Catutosaurus gaspariniae. © Jason R. Abdale (February 10, 2026).
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