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Description

Madhya Pradesh, India, 230 million years ago

A Tikisuchus romeri engages in a tug of war with a Colossosuchus techniensis over a Panthasaurus. Away from the commotion, a few Parasuchus hislopi, mere dwarfs compared to the colossal Colossosuchus, watch from a safe distance.

The two reptiles had chanced upon the amphibian aestivating in a burrow, and now neither party is willing to give up such an easy meal. As pseudosuchians, both predators have the same tenacity to bite and not let go as some of their future relatives, but Colossosuchus has a major size advantage. Eventually, the Tikisuchus may decide to let go of the carcass, rather than risk being dragged into the water.

Despite its crocodile-like appearance, Colossosuchus techniensis was not a crocodilian. Rather, it belonged to a lineage of Late Triassic, semi-aquatic reptiles called phytosaurs. As heavily armored, long snouted semi-aquatic reptiles, phytosaurs would've resembled modern crocodilians to a great degree in terms of appearance and possibly lifestyle, but they weren't particularly closely related, making these similarities a result of convergent evolution. Phytosaurs were essentially the crocodilians before crocodilians. However, there are some notable differences between the 2 groups.

Croc nostrils are located at the very tip of their snout, whereas phytosaur nostrils were located just in front of the eyes. This is why many phytosaurs had a very noticeable dome-shaped skull: their nostrils and eyes were located at the very top of the skull on an elevated part of the skull.

Additionally, phytosaurs were even more heavily armored than crocodilians; they had larger scutes/osteoderms and even their bellies were reinforced internally by gastralia. Their ankles were also much simpler in structure (croc ankles are more complex than you might think and are what help them switch between belly crawling like a lizard and doing the crocodilian " high walk"). Phytosaurs also seemed to have lacked a secondary palate, a bony structure seen in mammals and crocs, which allows crocs to breathe air even when their mouths are full of water. It is however possible that phytosaurs had a false palate made of soft tissue that doesn't fossilize.

Phytosaur taxonomy is a matter of debate. While they were originally classified as pseudosuchians (the archosaur lineage that gave rise to modern crocodilians), they were later classified as archosauriforms, meaning that they weren't exactly archosaurs but still more closely related to them than to any other reptile lineage. Later studies placed them within Archosauria as a basal member of the group, and the most recent studies recover them as a basal pseudosuchian lineage. Simply put, phytosaurs went from being pseudosuchians to pseudosuchians (because science). The Parasuchidae are a family of derived phytosaurs and arguably the best understood members of the group, due in no small part to the fact that many species are relatively well represented in the fossil record. The group is named after Parasuchus, a phytosaur known from India and possibly Poland and the US. At 2-2.5 m long, it was much smaller than Colossosuchus, but nonetheless appears to have been closely related.

Interestingly enough, Colossosuchus is known from not just one isolated fossil, but rather an entire bonebed comprising no fewer than 21 animals, mainly juveniles and subadults. The upper estimate of 8 m therefore is more or less just that, an estimate based on extrapolated measurements of individuals that weren't fully grown. Moreover, these measurements were made based mainly on skull length. Modern crocodilians have a fairly consistent head to body length ratio. Assuming that Colossosuchus had a head to body length ratio similar to that of a modern saltwater crocodile, it would mean that an adult would've been 9 m long. However, if its proportions were similar to those of more basal parasuchids like Parasuchus, it would mean it was perhaps just over 6 m (as big as a very large saltwater crocodile). However, Colossosuchus belonged to a more derived subfamily of parasuchids called the Mystriosuchinae, which includes another large phytosaur, Smilosuchus, that inhabited North America. Assuming Colossosuchus had Smilosuchus proportions, an upper estimate of 8 m was considered likely.

Like Smilosuchus but unlike Parasuchus and other basal parasuchids, Colossosuchus had teeth of different sizes and shapes, however, unlike its North American relative, it has a very distinctive hooked snout tip. This hooked tip was surrounded by 4 pairs of large teeth, reminiscent of the "tusk" like teeth seen in Smilosuchus. However, Colossosuchus had more teeth overall (upto 57).

As well as these derived characteristics, Colossosuchus also shows some basal traits. Similar to Parasuchus and some other basal parasuchids, the nasal septum (the "wall" that separates the 2 nostrils in the nose) is raised above the level of the eyes, which gave Colossosuchus a dome-shaped head. By comparison, more derived taxa like Smilosuchus had less domed heads as their nostrils were at eye level.

All things considered, Colossosuchus shows a mix of basal and derived traits, and the hooked snout is certainly a distinctive feature. Similar to modern crocs, phytosaur snout shape gives an idea of their ecology and diet. Some taxa had long, thin snouts full of teeth of equal size reminiscent of modern gharials, and were likely piscivores, with Parasuchus being an example of this. Others had shorter but more robust snouts with teeth of varying size and shape, similar to large modern crocs such as Nile and saltwater crocodiles, and we're likely ambush hunters that hunted large prey. One species of Smilosuchus appears to fit this description. Colossosuchus had a long snout, but it wasn't quite as narrow as that of Parasuchus, and the hooked tip and large tusk-like teeth may have aided in gripping larger prey.

Considering all this, I'm inclined to believe that Colossosuchus was a generalist with an extremely broad diet, similar to the modern false gharial (which has a narrow snout slightly broader than a gharial's but a very broad diet consisting of everything from fish and amphibians to small ungulates and monkeys) and certain crocodiles like the critically endangered Orinoco crocodile.

For some background, Colossosuchus techniensis was described less than 2 months ago at the time of this upload (Datta & Ray, 2023 ). This basically makes this only my third time illustrating a prehistoric animal in the same year it was discovered (first 2 being these ). Some of you might have noticed that, unlike many other paleoartists who love riding the hype train that follows every new discovery, I avoid illustrating recently discovered taxa; what I wrote above is more or less why. Similar to paleo-enthusiasts hyping about recently described taxa, scientists too take a strong interest, and recent discoveries are often subject to serious re-analysis, rebuttals, commentary etc. (remember Oculudentavis ? Once thought to be a bird but later turned out to be a lizard, and was obtained from Burmese amber, which many paleontologists and many respectable paleoartists have pledged to boycott researching/illustrating for ethical reasons), and sometimes several unethical aspects of their discoveries only come to light long after (remember the Ubirajara fiasco and the blatant racism involved? Or the guy who described the Tanis site and starred in a David Attenborough documentary but later turned out to have stolen and falsified data?). Because of this I usually avoid illustrating new taxa until I have either read the papers describing them or learned through respectable sources that there was no foul play involved. That said though, a finding from my home country and that too one like this is a big one, and considering the abysmally low coverage and attention the overwhelming majority of paleo-discoveries from India get (the last one that had any impact was Shringasaurus back in 2017), I figured I’d do one quickly in some attempt to draw more attention to it before it fades into obscurity (see examples below). The only other reconstruction I’ve seen of Colossosuchus so far is this one . This is no doubt the first one on DA (though I would be very happy to be corrected).

Tikisuchus romeri was a species of rauisuchid pseudosuchian known from the Tiki Formation, the same locality as Colossosuchus. Tikisuchus is especially noteworthy in that it's the first rauisuchid known from Asia. Unfortunately, beyond the original paper, there appears to be no other information on this taxon. I couldn't even find a reliable size estimate, and considering the original description is from 1987, following which the Rauisuchidae has undergone some major taxonomic reshuffling, I'm not sure if it's even considered part of the group now.

Rauisuchids were a clade of Triassic pseudosuchians that were essentially the dinosaurs before dinosaurs. The most famous member of this group is Postosuchus from Walking With Dinosaurs. They were built similar to later large theropods and filled a similar niche as apex predators in their respective ecosystems. Nonetheless, they did have some croc-like features, most notably croc-like ankles and osteoderms on their backs. But this is where Tikisuchus shows a notable departure from other rauisuchids. Other rauisuchids had non-overlapping, leaf-shaped osteoderms, but Tikisuchus had rectangular osteoderms that did overlap slightly.

Although previously considered to be quadrupedal animals that only reared up occasionally, recent studies of rauisuchids (including Postosuchus) indicate that they may have been obligate bipeds, similar to theropods. This is because their forelimbs were a lot shorter than their hindlimbs, making quadrupedal locomotion very difficult.
However, the forelimbs do show some weight-bearing adaptations, so perhaps rauisuchids were bipeds that only using their forelimbs for support when crouching, such as when bending down to drink, eat, or (in this case) playing tug of war. As Tikisuchus may or not belong to this group and considering it shows some differences from other rauisuchids, I decided to show it here with moderately long forelimbs that would've been more useful than those of theropods for balance/support. While I couldn't find a reliable size estimate, I decided to make this one around 5 m long, slightly on the smaller side of Postosuchus and a fairly typical size for rauisuchids as a whole.

Panthasaurus was a genus of metoposaurid temnospondyl amphibians that lived during the Late Triassic of India. One species, Panthasaurus maleriensis, has been described from the Lower Maleri Formation of Andhra Pradesh in southern India, which is south of and of similar age as the Tiki Formation. Moreover, as the 2 do share a good degree of faunal overlap, and at least one metoposaurid (assigned to the genus Metoposaurus) has been found in the Tiki Formation, I figured this genus would have also lived in the region. Panthasaurus was originally classified as Metoposaurus, but was later moved to a separate genus. However, it was similar enough that the 2 could've been closely related. Because I couldn't find much information on this genus, I decided to borrow traits from Metoposaurus (assuming the 2 genera are similar).

One notable aspect of Metoposaurus is that numerous individuals have been found in what appear to be mass bonebeds. This indicates that a large number of animals may have died in the same spot due to drought. Metoposaurus appears to have lived in ephemeral lakes that would've filled with water during the wet season and dried out during the dry season. Its limbs were well adapted for swimming, but not so much for walking, so it's believed to have used its large, shovel-like head like an actual shovel to burrow into the ground and aestivate when its habitat dried up. This is a behavior seen in many modern vertebrates from frogs and salamanders to crocodilians, so it's not at all surprising that a prehistoric amphibian would've shown similar behavior. Considering how big this animal could get, it's unlikely it could've finished growing within a year, and Metoposaurus bones do show evidence of periods of arrested development. In other words, this animal likely took years to reach full size, as it would've grown very little (if at all) during the unfavorable dry season.

More importantly, Metoposaurus fossils from bonebeds do show evidence of phytosaur predation, so it's likely that these crocs before crocs occasionally got lucky and stumbled upon large aestivating amphibians too dazed to put up much resistance. Bad for the amphibians, but good for the phytosaurs.

Description

Madhya Pradesh, India, 230 million years ago

A Tikisuchus romeri engages in a tug of war with a Colossosuchus techniensis over a Panthasaurus. Away from the commotion, a few Parasuchus hislopi, mere dwarfs compared to the colossal Colossosuchus, watch from a safe distance.

The two reptiles had chanced upon the amphibian aestivating in a burrow, and now neither party is willing to give up such an easy meal. As pseudosuchians, both predators have the same tenacity to bite and not let go as some of their future relatives, but Colossosuchus has a major size advantage. Eventually, the Tikisuchus may decide to let go of the carcass, rather than risk being dragged into the water.

Despite its crocodile-like appearance, Colossosuchus techniensis was not a crocodilian. Rather, it belonged to a lineage of Late Triassic, semi-aquatic reptiles called phytosaurs. As heavily armored, long snouted semi-aquatic reptiles, phytosaurs would've resembled modern crocodilians to a great degree in terms of appearance and possibly lifestyle, but they weren't particularly closely related, making these similarities a result of convergent evolution. Phytosaurs were essentially the crocodilians before crocodilians. However, there are some notable differences between the 2 groups.

Croc nostrils are located at the very tip of their snout, whereas phytosaur nostrils were located just in front of the eyes. This is why many phytosaurs had a very noticeable dome-shaped skull: their nostrils and eyes were located at the very top of the skull on an elevated part of the skull.

Additionally, phytosaurs were even more heavily armored than crocodilians; they had larger scutes/osteoderms and even their bellies were reinforced internally by gastralia. Their ankles were also much simpler in structure (croc ankles are more complex than you might think and are what help them switch between belly crawling like a lizard and doing the crocodilian " high walk"). Phytosaurs also seemed to have lacked a secondary palate, a bony structure seen in mammals and crocs, which allows crocs to breathe air even when their mouths are full of water. It is however possible that phytosaurs had a false palate made of soft tissue that doesn't fossilize.

Phytosaur taxonomy is a matter of debate. While they were originally classified as pseudosuchians (the archosaur lineage that gave rise to modern crocodilians), they were later classified as archosauriforms, meaning that they weren't exactly archosaurs but still more closely related to them than to any other reptile lineage. Later studies placed them within Archosauria as a basal member of the group, and the most recent studies recover them as a basal pseudosuchian lineage. Simply put, phytosaurs went from being pseudosuchians to pseudosuchians (because science). The Parasuchidae are a family of derived phytosaurs and arguably the best understood members of the group, due in no small part to the fact that many species are relatively well represented in the fossil record. The group is named after Parasuchus, a phytosaur known from India and possibly Poland and the US. At 2-2.5 m long, it was much smaller than Colossosuchus, but nonetheless appears to have been closely related.

Interestingly enough, Colossosuchus is known from not just one isolated fossil, but rather an entire bonebed comprising no fewer than 21 animals, mainly juveniles and subadults. The upper estimate of 8 m therefore is more or less just that, an estimate based on extrapolated measurements of individuals that weren't fully grown. Moreover, these measurements were made based mainly on skull length. Modern crocodilians have a fairly consistent head to body length ratio. Assuming that Colossosuchus had a head to body length ratio similar to that of a modern saltwater crocodile, it would mean that an adult would've been 9 m long. However, if its proportions were similar to those of more basal parasuchids like Parasuchus, it would mean it was perhaps just over 6 m (as big as a very large saltwater crocodile). However, Colossosuchus belonged to a more derived subfamily of parasuchids called the Mystriosuchinae, which includes another large phytosaur, Smilosuchus, that inhabited North America. Assuming Colossosuchus had Smilosuchus proportions, an upper estimate of 8 m was considered likely.

Like Smilosuchus but unlike Parasuchus and other basal parasuchids, Colossosuchus had teeth of different sizes and shapes, however, unlike its North American relative, it has a very distinctive hooked snout tip. This hooked tip was surrounded by 4 pairs of large teeth, reminiscent of the "tusk" like teeth seen in Smilosuchus. However, Colossosuchus had more teeth overall (upto 57).

As well as these derived characteristics, Colossosuchus also shows some basal traits. Similar to Parasuchus and some other basal parasuchids, the nasal septum (the "wall" that separates the 2 nostrils in the nose) is raised above the level of the eyes, which gave Colossosuchus a dome-shaped head. By comparison, more derived taxa like Smilosuchus had less domed heads as their nostrils were at eye level.

All things considered, Colossosuchus shows a mix of basal and derived traits, and the hooked snout is certainly a distinctive feature. Similar to modern crocs, phytosaur snout shape gives an idea of their ecology and diet. Some taxa had long, thin snouts full of teeth of equal size reminiscent of modern gharials, and were likely piscivores, with Parasuchus being an example of this. Others had shorter but more robust snouts with teeth of varying size and shape, similar to large modern crocs such as Nile and saltwater crocodiles, and we're likely ambush hunters that hunted large prey. One species of Smilosuchus appears to fit this description. Colossosuchus had a long snout, but it wasn't quite as narrow as that of Parasuchus, and the hooked tip and large tusk-like teeth may have aided in gripping larger prey.

Considering all this, I'm inclined to believe that Colossosuchus was a generalist with an extremely broad diet, similar to the modern false gharial (which has a narrow snout slightly broader than a gharial's but a very broad diet consisting of everything from fish and amphibians to small ungulates and monkeys) and certain crocodiles like the critically endangered Orinoco crocodile.

For some background, Colossosuchus techniensis was described less than 2 months ago at the time of this upload (Datta & Ray, 2023 ). This basically makes this only my third time illustrating a prehistoric animal in the same year it was discovered (first 2 being these ). Some of you might have noticed that, unlike many other paleoartists who love riding the hype train that follows every new discovery, I avoid illustrating recently discovered taxa; what I wrote above is more or less why. Similar to paleo-enthusiasts hyping about recently described taxa, scientists too take a strong interest, and recent discoveries are often subject to serious re-analysis, rebuttals, commentary etc. (remember Oculudentavis ? Once thought to be a bird but later turned out to be a lizard, and was obtained from Burmese amber, which many paleontologists and many respectable paleoartists have pledged to boycott researching/illustrating for ethical reasons), and sometimes several unethical aspects of their discoveries only come to light long after (remember the Ubirajara fiasco and the blatant racism involved? Or the guy who described the Tanis site and starred in a David Attenborough documentary but later turned out to have stolen and falsified data?). Because of this I usually avoid illustrating new taxa until I have either read the papers describing them or learned through respectable sources that there was no foul play involved. That said though, a finding from my home country and that too one like this is a big one, and considering the abysmally low coverage and attention the overwhelming majority of paleo-discoveries from India get (the last one that had any impact was Shringasaurus back in 2017), I figured I’d do one quickly in some attempt to draw more attention to it before it fades into obscurity (see examples below). The only other reconstruction I’ve seen of Colossosuchus so far is this one . This is no doubt the first one on DA (though I would be very happy to be corrected).

Tikisuchus romeri was a species of rauisuchid pseudosuchian known from the Tiki Formation, the same locality as Colossosuchus. Tikisuchus is especially noteworthy in that it's the first rauisuchid known from Asia. Unfortunately, beyond the original paper, there appears to be no other information on this taxon. I couldn't even find a reliable size estimate, and considering the original description is from 1987, following which the Rauisuchidae has undergone some major taxonomic reshuffling, I'm not sure if it's even considered part of the group now.

Rauisuchids were a clade of Triassic pseudosuchians that were essentially the dinosaurs before dinosaurs. The most famous member of this group is Postosuchus from Walking With Dinosaurs. They were built similar to later large theropods and filled a similar niche as apex predators in their respective ecosystems. Nonetheless, they did have some croc-like features, most notably croc-like ankles and osteoderms on their backs. But this is where Tikisuchus shows a notable departure from other rauisuchids. Other rauisuchids had non-overlapping, leaf-shaped osteoderms, but Tikisuchus had rectangular osteoderms that did overlap slightly.

Although previously considered to be quadrupedal animals that only reared up occasionally, recent studies of rauisuchids (including Postosuchus) indicate that they may have been obligate bipeds, similar to theropods. This is because their forelimbs were a lot shorter than their hindlimbs, making quadrupedal locomotion very difficult.
However, the forelimbs do show some weight-bearing adaptations, so perhaps rauisuchids were bipeds that only using their forelimbs for support when crouching, such as when bending down to drink, eat, or (in this case) playing tug of war. As Tikisuchus may or not belong to this group and considering it shows some differences from other rauisuchids, I decided to show it here with moderately long forelimbs that would've been more useful than those of theropods for balance/support. While I couldn't find a reliable size estimate, I decided to make this one around 5 m long, slightly on the smaller side of Postosuchus and a fairly typical size for rauisuchids as a whole.

Panthasaurus was a genus of metoposaurid temnospondyl amphibians that lived during the Late Triassic of India. One species, Panthasaurus maleriensis, has been described from the Lower Maleri Formation of Andhra Pradesh in southern India, which is south of and of similar age as the Tiki Formation. Moreover, as the 2 do share a good degree of faunal overlap, and at least one metoposaurid (assigned to the genus Metoposaurus) has been found in the Tiki Formation, I figured this genus would have also lived in the region. Panthasaurus was originally classified as Metoposaurus, but was later moved to a separate genus. However, it was similar enough that the 2 could've been closely related. Because I couldn't find much information on this genus, I decided to borrow traits from Metoposaurus (assuming the 2 genera are similar).

One notable aspect of Metoposaurus is that numerous individuals have been found in what appear to be mass bonebeds. This indicates that a large number of animals may have died in the same spot due to drought. Metoposaurus appears to have lived in ephemeral lakes that would've filled with water during the wet season and dried out during the dry season. Its limbs were well adapted for swimming, but not so much for walking, so it's believed to have used its large, shovel-like head like an actual shovel to burrow into the ground and aestivate when its habitat dried up. This is a behavior seen in many modern vertebrates from frogs and salamanders to crocodilians, so it's not at all surprising that a prehistoric amphibian would've shown similar behavior. Considering how big this animal could get, it's unlikely it could've finished growing within a year, and Metoposaurus bones do show evidence of periods of arrested development. In other words, this animal likely took years to reach full size, as it would've grown very little (if at all) during the unfavorable dry season.

More importantly, Metoposaurus fossils from bonebeds do show evidence of phytosaur predation, so it's likely that these crocs before crocs occasionally got lucky and stumbled upon large aestivating amphibians too dazed to put up much resistance. Bad for the amphibians, but good for the phytosaurs.