Your Daily Fossil

Apr 7


Mounted specimen from Ischigualasto Provincial Park, San Juan, Argentina

Reconstructed model from the Titanes de Ischigualasto (Titans of Ischigualasto) exhibit while at the Museo Argentino de Ciencias Naturales in Buenos Aires, Argentina. 

When: Late Triassic (~231 to 226 million years ago)

Where: Argentina

What: Saurosuchus is a very large basal member of the crocodile lineage within the Archosauria. It lived in what is now Argentina during the late Triassic, where it was a dominante apex predator, reaching lengths of up to 23 feet (~7 meters).  A good deal of this length was its massive skull filled with pointy recurving teeth. Saurosuchus is a member of the Rauisuchia, one of the first branches to come off of the Crurotarsi (crocodile line archosaurs) lineage.  Like other rauisuchians Saurosuchus had an erect leg posture, you can see this in the model above, it looks very much like a large crocodile (albiet with more dinosaur looking like head on), but its legs are directly underneath its body, not sprawling out like in modern crocodiles. This posture is the same as in mammals and dinosaurs, but was accomplished in a different way. Mammals and dinosaurs modify the femur itself for erect posture, but in rauisuchians it was the pelvis that was transformed. Saurosuchus was a fully terrestrial creature capable of fast speeds as it hunted its prey (including the much smaller dinosaurs) in the ancient flood plane. 

Saurosuchus fossils are from the Ischigualasto formation (and national park!) in Argentina. This area is open to the public and is more popularly called the Valle de la Luna (Valley of the Moon).  Not only do basal crocodile line archosaurs come from this formation, but some of the oldest dinosaurs as well. These animals, which would go on to dominate later in the Mesozoic, were a minor part of the fauna. The Triassic here was dominated by rhynchosaurs and cynodonts, these groups would both suffer great losses during the end Triassic extinction event.