The largest known rauisuchian is Fasolasuchus tenax, which measured an estimated 8–10 metres.
It is both the largest rauisuchian known to science, and the largest non-dinosaurian terrestrial predator ever discovered. Fasolasuchus is an extinct genus of rauisuchid. Fossils have been found from Argentina that date back to the Rhaetian stage of the Late Triassic, making it one of the last rauisuchians to have existed before the order went extinct at the end of the Triassic.It is quite possibly the largest known member of Rauisuchia, with an estimated length of 8–10 meters (26.4–33 ft), even bigger than the prestosuchid Saurosuchus at 7 meters (23.1 ft) in length. This would make Fasolasuchus the largest terrestrial predator to have ever existed save for large theropods. Like Saurosuchus, it had only a single row of caudal osteoderms, unusual among rauisuchians.It also had a hyposphene-hypantrum articulation that gave the vertebral column extra rigidity. This feature is also seen in several other rauisuchians such as Postosuchus as well as saurischian dinosaurs.
Karamuru is an extict genus of prestosuchid rauisuchian, a clade of large predatory crurotarsan archosaurs distantly related to crocodilians that lived an active terrestrial lifestyle. It is based on remains that had been previously assigned to Prestosuchus chininiquensis, including a nearly complete skull. Its fossils have been found in Brazil and date back to Middle Triassic. This animal had a skull alone that was almost 1 meter in length and an overall length of 6-9 meters, as large as a medium-sized theropod dinosaur. It is one of the largest known member of Rauisuchia, with an estimated weight somewhere in the 700 - 2000 kg (1,500 - 4,500 lbs) range.
The 97 cm long skull was robust and equipped with 10 - 11 cm long serrated teeth and powerful biting jaws that would be a match for many later theropods. It was a quadrupedal that had strong fairly short limbs but which acquired a nimble upright non-sprawling stance thanks to a vertical femur in a strong hip joint and an ankle and foot design more advanced than in modern crocodiles. This is referred as the pillar-erect posture. The erect gait indicates that these animals were clearly active, agile predators, with locomotor superiority over their prey. The body was crossed by rows of dermal plates (osteoderms).
Saurosuchus (Lizard crocodile)
Unfortunately Saurosuchus is only known from incomplete remains, but those that are known indicate that it was big. Key to identifying the fossils as being those of a predator is the skull that has several classic predatory characteristics. One is the fact that the skull is wider at the back than at the snout which not only suggests housing for strong biting muscles but also eyes that were slightly angled forwards for depth perception. This would allow for easier prey location as well as timing of strikes so that Saurosuchus could more successfully deliver a mortal bite that would result in the death of the prey. The exact method of execution may have varied according to prey however, with small animals being killed outright by the teeth and crushing jaws, while large prey may have been bitten but then allowed to weaken by bleeding to death before the final kill. The back of the skull however features attachments for strong neck muscles which might suggest that Saurosuchus clamped its jaws and held onto prey as it struggled, something that would require strong neck muscles to support the skull so that the prey could not shake itself free.
The teeth of Saurosuchus are thought to have been replaced over the course of its life so that when a tooth became worn and lost, another would grow in to take its place. This would compensate for tooth loss caused by overly powerful attacks upon large animals that may have caused some teeth to be broken as they struggled while being bitten. Tooth replacement is also seen in modern crocodiles and also existed in the dinosaurs. Another similarity Saurosuchus shares with the crocodiles (as well as phtyosaurs) is that the maxillae and snout are pitted, although the pitting is not as well developed in Saurosuchus. These pits are attachment points for tissues, and the under developed pits of Saurosuchus suggest that its skulls soft tissues were not as strong or specially developed as the later phytosaurs and crocodiles. Such pitting of the skull is so far not known in other rauisuchian however, which might suggest that Saurosuchus was at a more advanced stage of development.
Like other rauisuchians, Saurosuchus is thought to have had a quadrupedal posture in order to support its larger size and weight. While slowing Saurosuchus down when compared to bipedal reptiles, it was probably not a hindrance as there were plenty of reptilian prey animals that would have been just as slow if not slower. A lower quadrupedal posture also explains the development of osteoderm armour along its back. While quadrupedal Saurosuchus would have been able to climb onto the back of another, and if two Saurosuchus came into conflict over territory or the right to feed from a kill, the armour may have helped protect Saurosuchus from being bitten on a critical area like the spine from another. This would allow for a weaker or more submissive individual to withdraw from a fight injured but still alive.
Further remains of teeth and skull fragments from the Chinle Formation of Arizona were attributed to the genus in 2002, but today these remains are considered to be too indeterminate for classification. Unless more complete material is found at a later date, the geographic distribution of Saurosuchus will remain restricted to Argentina.
Being one of the largest known rauisuchian in the fossil record, Saurosuchus was the apex predator of its day. Saurosuchus lived in an ecosystem that saw the steady rise of the early dinosaurs such as Eoraptor and Herrerasaurus. Saurosuchus was probably too slow for active predation of the early dinosaurs, although its larger size meant that the early dinosaurs would almost certainly have given way to it rather than risk being its next meal. Saurosuchus was instead probably a predator of other large and slower animals such as the rhynchosaur Hyperodapedon.
Despites its large size Saurosuchus may not have been the largest rauisuchian as another named Fasolasuchus has been estimated at being between eight and ten meters long.
Postosuchus (Crocodile from Post) was a basal archosaur which lived in what is now North America during the middle to the late Triassic. It was not a dinosaur, having a closer relationship to crocodiles, and was even at a higher level on the food chain than the dinosaurs it lived near and preyed on.
Postosuchus was one of the largest carnivorous reptiles of the Triassic, reaching 5-7 meters (16-23 ft) long 2 to 3.5 meters tall and weighed 300–600 kg (550-660 lbs). It had a massively built skull, bearing powerful jaws and dagger like teeth that can easily kill its quarry by cutting through its flesh and ripping off pieces. Rows of protective osteoderms covering its back formed a defensive shield, protecting it from other predators and dangerous prey.
Postosuchus's forelimbs were over half the size of its hind legs, this characteristic of short forelimbs can usually be seen in bipedal reptiles. Chatterjee suggested that Postosuchus could walk in an erect stance, since the short forelimbs were used probably only during slow moving locomotion. However, in 1995, Robert Long and Phillip A. Murry claimed that Postosuchus was a stocky quadruped. There is a debate over whether Postosuchus was either a biped or a quadruped as scientists aren't sure yet. However, some paleontologists suggested that Postosuchus was probably a facultative biped, meaning that it altered between bipedally and quadrupedally.
Prestosuchus (fast Crocodile)
There appears to be some confusion regarding the full size of Prestosuchus. Earlier fossil discoveries seemed to point at a total length of around five hundred centimetres for an adult Prestosuchus. However an almost complete specimen reported in 2010 was stated as being the equivalent of about six hundred and seventy centimetres long. If this is correct, then Prestosuchus would represent one of the largest rauisuchian predators that we know about, with only the genus Saurosuchus being larger.
Regardless of what the adult size of Prestosuchus was, it was without doubt an apex predator that would have targeted other reasonably large animals. Rauisuchians like Prestosuchus are usually seen as ambush predators, rearing up and delivering a strong bite to the back of a target animal. Evidence does actually support his, as the aforementioned 2010 specimen of Prestosuchus was found in sedimentary rock that has been perceived to have been a watering hole for local wildlife. Ambush predators are known to haunt such locations as inevitably prey species will come to them in order to drink.
The key thing about the 2010 specimen of Prestosuchus is that it included a remarkably well preserved rear leg, so much so that paleontologists were able to accurately reconstruct the muscle groups of the leg, and allowing for a more accurate general reconstruction of the animal. In Prestosuchus the strongest and best developed muscles of the rear leg were for limb rotation, not back and forth movement, which indicates that Prestosuchus had a primarily quadrupedal posture. It should be pointed out however that other types of rauisuchian such as poposaurids like Poposaurus, seem to have been primarily bipedal.
Redondasaurus is a genus of phytosaur from the Late Triassic of North America. The name means "Redonda lizard," referring to the Redonda Formation of east-central New Mexico, USA where fossils have been found. It was first named by Hunt & Lucas in 1993, and contains one species, R. gregorii. It is the youngest and most evolutionarily-advanced of the phytosaurs. Redondasaurus was a carnivore and measured from 10 to 12 meters in length, 1.5 meters of which made up the length of the head, and 1.5 meters in height. They could reach a weight of up to 26,000 lbs. It likely spent most of its time in lakes and rivers, and ambushed its prey, which consisted of fish, small reptiles, and possibly dinosaurs. There is little columnar enamel in the teeth of Redondasaurus. A recent phylogenetic analysis found that the genera Pseudopalatus, Mystriosuchus, Redondasaurus and Nicrosaurus were pseudopalatines.
Redondasaurus was a predator of large vertebrates, perhaps lurking in Late Triassic waters and jumping out at other creatures as they came to the water to drink. Redondasaurus was among the last phytosaurs known to have lived, and features several adaptations that make it notably more advanced than other phytosaurs.
With skulls measuring about one hundred and twenty centimetres long, Angistorhinus was easily amongst the largest phytosaurs, crocodile-like reptiles that hunted in Triassic waterways. The jaws of Angistorhinus were long and thin, more akin to those of a gharial, perhaps indicating that Angistorhinus was more of a fish hunter. The nostrils of Angistorhinus were situated further back on the skull, a feature that is not just indicative of a more advanced phytosaur form, but also kept the nostrils free from the water when the snout was dipped underneath. This was a more specialized condition that characterized all late phytosaurs. Angisthorhinus was a huge animal by any standards; the skull length was generally about 120 cm; estimated overall length to 8 meters, more in A. megalodon, a very large, short and heavy-muzzled form sometimes given its own genus (Brachysuchus), and which far exceeded in size any living crocodile
Angistorhinus has in the past been considered as a synonym to the genus Rutiodon, but later studies have continued to retain Angistorhinus as a distinct genus. One sometimes mentioned species of Angistorhinus, A. megalodon, is more often credited as the genus Brachysuchus. Fossils from Morocco have been tentatively place in the genus as a new species, A. talainti.
Smilosuchus (meaning "chisel crocodile") is an extinct genus of leptosuchomorph phytosaurid from the Late Triassic of North America. The type species was first described in 1995 as a replacement generic name for Leptosuchus gregorii.Because of the large rostral crest it possessed, it was considered to be distinct enough from other species of Leptosuchus (all of which had smaller and more restricted crests) to be within its own genus. Some studies seem to suggest that Smilosuchus is congeneric with Leptosuchus, as the enlarged crest could have been independently developed in Leptosuchus.However, newer studies support the idea that Smilosuchus is distinct from the type species of Leptosuchus, Leptosuchus crosbiensis. Phylogenetic analyses suggest that Smilosuchus is more closely related to pseudopalatines than to Leptosuchus species.
Machaeroprosopus is an extinct genus of pseudopalatine phytosaurid from the Late Triassic of the southwestern United States. M. validus, once thought to be the type species of Machaeroprosopus, was named in 1916 on the basis of three complete skulls from Chinle Formation, Arizona. The skulls have been lost since the 1950s, and a line drawing in the original 1916 description is the only visual record of the specimen. Another species, M. andersoni, was named in 1922 from New Mexico, and the species M. adamanensis, M. gregorii, M. lithodendrorum, M. tenuis, and M. zunii were named in 1930. Most species have been reassigned to the genera Smilosuchus,Rutiodon, Pseudopalatus, or Phytosaurus. Until recently, M. validus was considered to be the only species that has not been reassigned. Thus, Machaeroprosopus was considered to be a nomen dubium or "doubtful name" because of the lack of diagnostic specimens that can support its distinction from other phytosaur genera. However, a taxonomic revision of Machaeroprosopus, conducted by Parker et al. (in press), revealed that UW 3807, the holotype of M. validus, is not the holotype of Machaeroprosopus, while the previously named species Pseudopalatus buceros has priority as the type species of the genus. Therefore, the name Pseudopalatus must be considered a junior synonym of Machaeroprosopus, and all species of the former must be reassigned to the later. This revised taxonomy was already accepted in several studies, including Stocker and Butler (2013). Stocker and Butler (2013) also treated M. andersoni as a valid species and not a junior synonym of Machaeroprosopus buceros as was previously suggested by Long and Murry