Rauisuchians and Phytosaurs

Battles between big carnivores are a rarity in the fossil record. One find from Triassic rocks in New Mexico reveals something incredible. It is a life-and-death duel between two of the era’s most powerful hunters.

Rauisuchia

1. Teratosaurus 2. Ctenosauriscus 3. Arizonasaurus 4. Postosuchus 5. Prestosuchus
Rauisuchia is an order of diapsid reptiles that lived during the Triassic period. This group is the sister group to the group that gave rise to the modern-day crocodiles, alligators, caimans, and gharials.  This order 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.

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.

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 cere able to do this naturally if not being able to do it by default.
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.
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.

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 vorax

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.

Phytosauridae

1. Mystriosuchus 2. Phytosaurus 3. Angistorhinus 4. Nicrosaurus 5. Rutiodon
Phytosaurs are a basal group of reptiles that are the sister group to the archosaurs which includes the dinosaurs and crocodylomorphs. They evolved in the mid Triassic period and survived to the early Jurassic for unknown reasons. When Phytosaurus was first discovered in the early 1850"s. The scientist that discovered them saw that its teeth were blunt and serrated like plant eaters so he gave it the name Phytosaurus which means ""plant lizard"".
Phytosaurs were all carnivores that probably did not like plants very much. It would be unreasonable for it to be a plant eater when it was perfectly evolved to be a predator because its teeth were conical for biting fish, not blunt for crushing plants. it also was ot adapted for eating plants on the bottom of its river or lake because it would not be able to uproot them because of their long snouts. Their body was also not large to digest large quantities of plants and extract every possible nutrients from them. Instead they were developed for breaking down meat in the same way crocodilians are today.

They may seem similar to crocodiles in body shape, eating habits and overall looks but they are not the same thing and have quite a few differences if one looks close enough at them. Firstly modern crocodilians like the mugger have nostrils situated at the end of their snout but phytosaurs have their nostrils located on a crest-like protrusion above their head not dissimilar to the future brachiosaurs. This may be so they they can have their eyes above the surface of the water and their rostrum completely submerged and still be able to see AND breathe perfectly fine. This indicates a lifestyle highly evolved for water and for ambush! They also had a much more primitive ankle structure than crocodiles because they would have been mostly restricted to pushing themselves along the ground with their legs as crocodiles to today. There is one phytosaur that felt like this was not its thing. This one phytosaur left tracks or ichnofossils that suggested that it too high-walked like crocodiles do today when they are feeling mammalian. This genus was called Apatopus. This was one of the only phytosaurs that is known to have had an erect gait during its life suggesting that they were more evolved than we originally thought.
Phytosaurs first appeared during the Carnian age, evolving from an unknown crurotarsan ancestor. There are no clear intermediate forms, as even the earliest known phytosaurs are highly specialized aquatic animals, unlike most contemporary archosauriforms that were terrestrial. However, a recent study has suggested that Diandongosuchus is a basal phytosaur. If this is the case, this taxon offers more of a bridge between phytosaurs and earlier Archosauriformes.

The earliest phytosaurs are traditionally classified in the genus Paleorhinus, now thought to be polyphyletic. Parasuchus and related basal species were widely distributed, meaning that phytosaurs dispersed across Pangea early on and there were probably few geographical barriers for their distribution; only in the southernmost regions are they rare, possibly due to increased aridity.
A somewhat more advanced and larger form, Angistorhinus appears at the same time or soon after. Later in the Carnian, both these animals were replaced by more specialised forms like Rutiodon, Leptosuchus, and the huge Smilosuchus.The Carnian-Norian extinction meant that these animals died off, and the Early Norian sees new genera like Nicrosaurus and Pseudopalatus, both of which belong to the most derived clade of phytosaurs, the Pseudopalatinae. Later in the middle Norian the advanced and specialised fish-eater Mystriosuchus appears. Fossil remains of this widespread animal is known from Germany, northern Italy, and Thailand. Finally the large Redondasaurus in south-west North America and the long-snouted (altirostral) Angistorhinopsis ruetimeyeri in Europe continued the group into the Rhaetian. Phytosaur footprints (the ichnotaxon Apatopus) are also known from the latest Rhaetian of the East Coast of USA.This indicates that phytosaurs continued as successful animals until the very end of the Triassic, when, along with many other large crurotarsan reptiles, they were killed off by the end Triassic extinction event, about 200 Ma ago.
There have been reports of phytosaur remains found in lowermost Jurassic rocks. Several teeth from Early Jurassic deposits in France have been identified as phytosaur teeth, but other studies argue they have either been misidentified or were reworked from Late Triassic into Early Jurassic deposits. In 1951, a partial upper jaw was discovered in the Early Jurassic Lower Lufeng Series in China and described as a new genus of phytosaur, Pachysuchus, but a study in 2012 reinterpreted the fossil as a sauropodomorph dinosaur.
A fragment of a lower jaw from a longirostrine archosaur has been described from early Hettangian strata in the town of Watchet in Somerset, England. While teleosaurid thalattosuchians had similar longirostrine jaws to phytosaurs and were common in the Jurassic, they do not appear in the earliest Jurassic rocks. The mandible is more similar to those of known phytosaurs than to thalattosuchians, and likely belongs to a phytosaur closely related to the genus Mystriosuchus. The presence of phytosaurs in the earliest Jurassic may have prevented thalattosuchians from occupying similar ecological niches at that time.However, more recent work suggests that the jaw fragment came from a pre-Hettangian rock unit, and is therefore Late Triassic in age.

Redondasaurus

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.

Angistorhinus

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

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