Saurosuchus

*Saurosuchus galilei*

***Saurosuchus*** (meaning "lizard crocodile") is a genus of large carnivorous paracrocodylomorph that grew to over 7 metres (23 ft) long. It was the second largest rauisuchian, ever only behind the less well known *Fasolasuchus*, as it is larger than its North American cousin *Postosuchus*. Like most of the other rauisuchians, *Saurosuchus* walked on four erect legs like the later dinosaurs and mammals. It was at the top of the food chain of its area, in Argentina during the late Triassic period. It was one of the largest South American predators of the Triassic so it could have killed nearly anything in its area.

*Saurosuchus* did not have legs that were that strong so it would have been restricted to a pace that was around the same as a human's. It would have been able to accelerate for only a short amount of time due to its weight, cold bloodedness and having legs that were not too good at running. This would have enabled it to grow to bigger sizes however because animals that don't need to move fast do not need to be light and fragile like cheetahs. This slow paced lifestyle would have allowed it to get weighted body parts and limbs so it might not have been fast but it would have been sturdy.

*Saurosuchus* massive neck supported a head that would be very similar to a scaled down *T. rex* skull. This would have given it a tremendous bite force that would be comparable to today's big biters like alligators. Its tail was long, sturdy and weighted which might have supported it when it reared up to face rivals or deliver a killing blow to it prey. It had rows of osteoderms running down its back from its head to the very tip of its tail which would have given it some protection from dangerous prey or other *Saurosuchus*. Unlike most future Crocodylomorphs, *Saurosuchus* had a laterally compressed skull and large conical teeth. Another Crocodylomorphs with a skull like this is called *Sebecus* which had a very similar laterally compressed skull.

*Saurosuchus* only enemies would have been others of its' species. It might have engaged in combat similar to today's large carnivores like bears, lions and crocodiles. Seeing as it had small limbs and could not rear up for very long, it would have primarily used its massive jaws to fight other predators or other members of its own species. This would not have resulted in death since it was protected by its armour and most modern carnivores do not fight to the death including its close relatives the crocodilians.

Its lifespan would have been fairly long considering it was cold blooded and its modern relatives the crocodilians live over 100 years. This would have meant that *Saurosuchus* would have learnt skills and got experience that younger *Saurosuchus* did not have so it might have been able to tackle tricky prey like large dicynodonts and maybe smaller carnivores. This would have also resulted in it accumulating lots or scars and wounds over the years.

## Discovery and naming

*Saurosuchus* is known from several partial skeletons collected from the Ischigualasto Formation of Argentina. The holotype specimen consists of a complete but deformed skull, dorsal vertebrae, dorsal osteoderms, and parts of the pelvis. The hind limbs, tail, neck, and scapulae are also represented in several other skeletons. The type species *S. galilei* was named in 1959. *Saurosuchus* was also reported from the Chinle Formation of Arizona in 2002 on the basis of isolated teeth and small skull fragments. The diagnostic value of these bones has been questioned in later studies, which considered them to be from an indeterminate species of rauisuchian.

## Description

*Saurosuchus* is one of the largest rauisuchians. The complete skeleton is not known and size estimates range from around 6 to 9 metres (20 to 30 ft) in total body length. Dorsal osteoderms run along the back of *Saurosuchus*. There are two rows to either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it.

### Skull

It has a deep, laterally compressed skull. The teeth are large, recurved, and serrated. The skull is wide at its back and narrows in front of the eyes. The skull roof and maxilla are somewhat pitted, a distinguishing feature not seen in any other rauisuchian. Pitting is also seen in aquatic phytosaurs and crocodilians, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The frontal bones, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in other rauisuchians, a small rod projects down from the lacrimal bone in front of the eye, but it does not attach firmly to the jugal bone below it. Ridges along the upper surface of the supraoccipital bone at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck.

## Classification

*Saurosuchus* was considered a member of the Rauisuchia, although now it is considered part of the more basal Loricata, a clade comprising both Rauisuchia and the true crocodylians. Below is the cladogram of the Loricata conducted by Nesbitt 2011:

## Paleoecology

*Saurosuchus* was unearthed in the Cancha de Bochas Member from the Ischigualasto Formation, being the major predator on its environment. The Ischigualasto Formation was dominated by fluvial and floodplain environments with strongly seasonal rainfalls. Interlayered volcanic ash layers above the base and below the top of the formation provide chronostratigraphic control and have yielded ages of 231.4 ± 0.3 Ma and 227 ± 0.9 Ma respectively.

### Contemporaneous fauna

Animals that lived alongside included numerous nondinosaurian tetrapods and basal dinosauromorphs. Notable paleofauna that were contemporaneous with *Saurosuchus* in the Cancha de Bochas Member include: *Hyperodapedon*, *Exaeretodon*, *Herrerasaurus*, *Sillosuchus*, *Eoraptor*, *Trialestes*, *Aetosauroides*, and *Ischigualastia*. *Herrerasaurus* and *Saurosuchus* are some of the most common predators in the formation, with numerous specimens and remains.

## References

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