Eoraptor
Despite the lack of certainty about its size, Fasolasuchus is still one of the larger rauisuchians and as such it would have been the apex predator of its ecosystem. This would have seen Fasolasuchus dominant over newly emerging predatory dinosaurs like Herrerasaurus that even at its maximum size estimate, would have been smaller, lighter and overall been less powerful predators than Fasolasuchus. However despite the advantages that Fasolasuchus had, it was a heavy quadrupedal predator that did not have speed on its side. This means that it would have had to focus upon hunting other reptile groups that were larger and slower, the disappearance of which at the end of the Triassic may have caused the disappearance of Fasolasuchus itself when it found it was too slow to catch the new and faster dinosaurs that were taking over the planet as the dominant creatures.
An interesting thing to note about Fasolasuchus is the single row of osteoderms that rand down its back. Usually rauisuchians had more than this so that they would have some form of defence against attacks from other rauisuchians as they tried to deliver bites to the neck and the spine. As one of the largest rauisuchians in its ecosystem however, Fasolasuchus may have only had to worry about conflict with others of its species, perhaps in contests of carcasses or mating.
Saurosuchus
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.
Tanystropheus
Taking up half of its total body length, Tanystropheus’s neck is almost inconceivable. Indeed, when Francesco Bassani discovered Tanystropheus remains in 1886 (although he named it Tribelesodon), he conceived the extra long neck vertebrae as the wing bones of a pterosaur. It was not until later that the mistake was realised and Tribelesodon became a synonym of Tanystropheus.
Analysis of Tanystropheus remains and the areas that they are recovered from strongly suggests a life spent on the Triassic shorelines. The teeth are adapted in a way that would enable them to easily snatch marine prey like fish, and the elongated neck would have given it significant each over and under the water. The legs however appear to be more suited for terrestrial locomotion. An interesting feature is that the front legs are shorter than the rear, suggesting that Tanystropheus may have pitched itself forward at the water’s edge for feeding.
For hunting strategy, it is possible that Tanystropheus visited tidal pools that would have been re-stocked with fresh prey items at high tide that would then in turn be trapped in the pools when the tide receded. This would provide a naturally trapped and easily sought out food supply.
In 2006 Dr. Silvio Renesto discovered a specimen in Switzerland that appears to display the impressions of soft tissue. One of the main discoveries here is a skin impression that shows Tanystropheus did not have overlapping scales. The other discovery is a dark impression that suggests that there was a significant development of muscle to the rear of Tanystropheus. This counter weight of muscle would have shifted the centre of mass back allowing the neck to move in a more balanced manner. It may have also had a secondary function of giving Tanystropheus great strength to grip onto shoreline rocks.
Utatsusaurus
Utatsusaurus is an important entry in the fossil record concerning marine reptiles as it is often considered one of the first ichthyosaurs and as such it is used by some as the bench mark for identifying basal (primitive) features in ichthyosaurs. This includes skeletal features similar to diapsid reptiles, today the group that includes lizards that dates back as least as far as the Carboniferous with the appearance of Petrolacosaurus. Utatsusaurus was not as well developed to aquatic life as later ichthyosaurs were as it lacked a dorsal fin, and had a tail that seems to have bent down to a larger lower lobe that resulted in an uneven caudal tail.
Utatsusaurus may not have been ‘the’ defining primitive form however as the fins have four toes instead of the usual five seen in other primitive ichthyosaurs. This suggests that Utatsusaurus was on the evolutionary line to transitionary ichthyosaurs such as Mixosaurus which had three toes indicative of advanced forms like Ichthyosaurus. For this reason alone Utatsusaurus remains an important entry when dealing with ichthyosaur evolution. The limelight has shifted away from Utatsuaurus somewhat since the 2015 naming of Cartorhynchus.
The skull of Utatsusaurus is quite broad in proportion when compared to other ichthyosaurs (especially narrow skulled ones like Shastasaurus), and is a feature that harks back to its terrestrial ancestors. Teeth in the jaws suggests that Utatsusaurus hunted for fish, although its plausible that Utatsusaurus may have taken other prey such as cephalopods and possibly even other smaller marine reptiles.
Eoraptor stands out not only for being one of the first dinosaurs to ever walk the Earth, but because palaeontologists cannot conclusively agree on where to place it in relation to other dinosaurs. Initially Eoraptor was classed as a theropod because of its bipedal stance and narrow build, but the sauropodomorphs (which would go on to evolve into giant quadrupedal dinosaurs like Apatosaurus and Brachiosaurus) were also bipedal with a similar body plan in their early stages of development. To confuse things further, Eoraptor had two main types of teeth, those of a carnivore and a herbivore. This is why Eoraptor has in the past been classed as a theropod by some and sauropodomorph by others, and why in 2011 it was classed again as a eusaurischid, a position that places it between these two groups.
The combination of the two types of teeth has been seen to suggest that Eoraptor was a generalist omnivore that adapted to the availability of different food and prey. Still, Eoraptor may have had a preference for one type of diet but still feeding upon another type to balance out nutritional deficiencies that were in the other. Eoraptor also lacked specialist carnivore adaptations such as a sliding jaw joint, which meant that Eoraptor would have been limited to small prey animals such as insects and lizards.
Despite potentially carnivorous aspects of its diet, Eoraptor was not the dominant hunter of its day, and may itself have been prey to the larger Herrerasaurus that is also known from the same time and formation.
Fasolasuchus
Fasolasuchus was not only one of the last but it was possibly the largest of the rauisuchians. Unfortunately however incomplete remains mean that only a range estimate of between eight and ten meters is possible. The next largest rauisuchian is Saurosuchus which is also from Argentina and is estimated at seven meters long, however, Saurosuchus is also known only from incomplete remains, and analysis of these has yielded an upper estimate of up to nine meters long. This means that there is an outside chance that Saurosuchus is actually larger than Fasolasuchus although without more complete material for either one it remains impossible to be certain.Despite the lack of certainty about its size, Fasolasuchus is still one of the larger rauisuchians and as such it would have been the apex predator of its ecosystem. This would have seen Fasolasuchus dominant over newly emerging predatory dinosaurs like Herrerasaurus that even at its maximum size estimate, would have been smaller, lighter and overall been less powerful predators than Fasolasuchus. However despite the advantages that Fasolasuchus had, it was a heavy quadrupedal predator that did not have speed on its side. This means that it would have had to focus upon hunting other reptile groups that were larger and slower, the disappearance of which at the end of the Triassic may have caused the disappearance of Fasolasuchus itself when it found it was too slow to catch the new and faster dinosaurs that were taking over the planet as the dominant creatures.
An interesting thing to note about Fasolasuchus is the single row of osteoderms that rand down its back. Usually rauisuchians had more than this so that they would have some form of defence against attacks from other rauisuchians as they tried to deliver bites to the neck and the spine. As one of the largest rauisuchians in its ecosystem however, Fasolasuchus may have only had to worry about conflict with others of its species, perhaps in contests of carcasses or mating.
Saurosuchus
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.
Tanystropheus
Taking up half of its total body length, Tanystropheus’s neck is almost inconceivable. Indeed, when Francesco Bassani discovered Tanystropheus remains in 1886 (although he named it Tribelesodon), he conceived the extra long neck vertebrae as the wing bones of a pterosaur. It was not until later that the mistake was realised and Tribelesodon became a synonym of Tanystropheus.
Analysis of Tanystropheus remains and the areas that they are recovered from strongly suggests a life spent on the Triassic shorelines. The teeth are adapted in a way that would enable them to easily snatch marine prey like fish, and the elongated neck would have given it significant each over and under the water. The legs however appear to be more suited for terrestrial locomotion. An interesting feature is that the front legs are shorter than the rear, suggesting that Tanystropheus may have pitched itself forward at the water’s edge for feeding.
For hunting strategy, it is possible that Tanystropheus visited tidal pools that would have been re-stocked with fresh prey items at high tide that would then in turn be trapped in the pools when the tide receded. This would provide a naturally trapped and easily sought out food supply.
In 2006 Dr. Silvio Renesto discovered a specimen in Switzerland that appears to display the impressions of soft tissue. One of the main discoveries here is a skin impression that shows Tanystropheus did not have overlapping scales. The other discovery is a dark impression that suggests that there was a significant development of muscle to the rear of Tanystropheus. This counter weight of muscle would have shifted the centre of mass back allowing the neck to move in a more balanced manner. It may have also had a secondary function of giving Tanystropheus great strength to grip onto shoreline rocks.
Utatsusaurus
Utatsusaurus is an important entry in the fossil record concerning marine reptiles as it is often considered one of the first ichthyosaurs and as such it is used by some as the bench mark for identifying basal (primitive) features in ichthyosaurs. This includes skeletal features similar to diapsid reptiles, today the group that includes lizards that dates back as least as far as the Carboniferous with the appearance of Petrolacosaurus. Utatsusaurus was not as well developed to aquatic life as later ichthyosaurs were as it lacked a dorsal fin, and had a tail that seems to have bent down to a larger lower lobe that resulted in an uneven caudal tail.
Utatsusaurus may not have been ‘the’ defining primitive form however as the fins have four toes instead of the usual five seen in other primitive ichthyosaurs. This suggests that Utatsusaurus was on the evolutionary line to transitionary ichthyosaurs such as Mixosaurus which had three toes indicative of advanced forms like Ichthyosaurus. For this reason alone Utatsusaurus remains an important entry when dealing with ichthyosaur evolution. The limelight has shifted away from Utatsuaurus somewhat since the 2015 naming of Cartorhynchus.
The skull of Utatsusaurus is quite broad in proportion when compared to other ichthyosaurs (especially narrow skulled ones like Shastasaurus), and is a feature that harks back to its terrestrial ancestors. Teeth in the jaws suggests that Utatsusaurus hunted for fish, although its plausible that Utatsusaurus may have taken other prey such as cephalopods and possibly even other smaller marine reptiles.
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