"Rauisuchia" is an informal grouping of large, predatory archosaurs that lived during the Triassic period. This group is the sister group to the group that gave rise to the modern-day crocodilians (crocodiles, alligators, caimans, and gharials).  This group includes Fasolasuchus, Ticinosuchus, Saurosuchus, Batrachotomus, Prestosuchus, Rauisuchus, Postosuchus, Teratosaurus, Arizonasaurus, Lotosaurus,  and Shuvosaurus. These animals were usually between 1 and 10 metres long and 0.5 to 3 metres tall. This group includes the largest non-dinosaurian land carnivore ever and some like Fasolasuchus tenax were so large that they could go head to head with T. rex and other large theropods like Saurophaganax and Torvosaurus. This group is like a sister clade to the group that gave rise to the crocodylomorphs so in an informal sense it is like the crocodilians uncles. They all share the trait that they have an erect gait and large heads and robust bodies which would be suited to their environment by having osteoderms on their backs and all being relatively slow walkers.


Left to Right: Saurosuchus, Batrachotomus, Postosuchus, and Arizonasaurus

They were all carnivorous and fed on small lizards and proto-mammals for their first years and would have gradually upgraded to larger animals like dicynodonts when their weapons started getting more lethal and deadly. The larger ones like Saurosuchus would have been the top predators in their environment wherever they went and would have dominated the landscape and inspired terror in the first mammals and dinosaurs of the late Triassic. Much like the dinosaurs that succeeded them, rauisuchians likely had warm-blooded metabolisms, which allowed them to evolve erect limbs and lead a successful niche as apex predators; this is also indicated by their bone histology, which is more similar to that of birds, mammals and dinosaurs than other reptiles. However, they gradually went extinct at the end of the late Triassic because they were not as specialized as early dinosaurs, and they were not well-adapted for hunting the faster, more agile dinosauriform herbivores that gradually replaced their usual slow prey. A list of the "rauisuchians" is shown below:

  • Arganasuchus
  • Fasolasuchus
  • Postosuchus
  • Prestosuchus
  • Saurosuchus
  • Sillosuchus
  • Arizonasaurus
  • Shuvosaurus
  • Arizonasaurus
  • Effigia
  • Stagonosuchus
  • Ticinosuchus
  • Batrachotomus
  • Tikisuchus
  • Teratosaurus
  • Bromsgroveia
  • Qianosuchus

Rauisuchians were very general in their eating habits in that they would have taken anything in their territorial range. Their teeth were usually thin, serrated and sharp so they could tear into flesh and pull out large chunks out of their prey so it would then die of blood loss or shock. The rauisuchians would have been able to rear up on their hind legs for a short amount of time because of their strong back legs and by using their tail as a counter balance. This would have been used to get a view of their area, scouting for enemies, looking for prey or to deliver the killing blow to their prey by using their big relative body weight. This wouldn't have applied for bipedal rauisuchians because they were able to do this naturally if not being able to do it by default. The bipedal rauisuchians are:

  • Postosuchus
  • Sillosuchus
  • Shuvosaurus
  • Effigia
  • Poposaurus

There was even a genus of sail-backed rauisuchian called Lotosaurus. This rauisuchian had a huge chest that tapered off to a slender tail, mainly because it was a herbivore, so its small head would have a strong base. This is the only example of a herbivorous rauisuchian, because all the other rauisuchians are medium to large carnivores that would have been nearly insatiable due to the lack of large prey items that could sustain them and the other prey being so small.

In the media[]

WWDBook Postosuchus

Postosuchus in Walking With Dinosaurs

A Postosuchus appeared in Walking With Dinosaurs episode One, New Blood, where it was at the top of the food chain, but at the end of the episode it was wounded and died of an infection.

It also appears in the british BBC show Primeval, where it killed a Eustreptospondylus.


Rauisuchians were the biggest land carnivores in the Triassic period and were the top predators when they first evolved.

They lived from Europe to North America to South America where they grew much larger, and became one of the biggest land carnivores ever.

They may look extremely similar to crocodiles, but they are only distantly related.