Monster Crocodiles, Part 3: Crocodile vs. Dinosaur

by guest writer and artist Hodari Nundu

Kaprosuchus sizing up their prey

Go to the beginning of this series

Most books tell us that dinosaurs dominated the world with an iron claw during 160 million years or so. They were so big, so fierce and so powerful that all other animals had to flee from them (becoming flyers, like pterosaurs, or aquatic like crocodiles) or become so small and insignificant that dinosaurs wouldn´t even pay any attention to them (like mammals).

Kaprosuchus, the Boar Croc, is only one of many newly discovered creatures that seem to challenge this idea. Here we have a dinosaur-eating, sabertoothed crocodile that coexisted and probably competed with some of the largest meat-eating dinosaurs known.

And that's not all; the remains of a similarly-sized land crocodile, Pissarrachampsa, were found in Brazil in 2011, suggesting that this lineage of dinosaur-eaters may have been more widely distributed than previously thought.

Some scientists have even noted that where land crocodiles were abundant, meat-eating dinosaurs were scarce.

Not all land crocodiles were big game hunters, however. In 2010, the fossils of a strange little land crocodile were found. It had a short snout, long slender legs, and teeth incredibly similar to those of a mammal.

In fact, it looked a lot like the reptilian version of a small feline, hence the name it was given: Pakasuchus, the cat-croc.

At 50 cm long, it was certainly the size of a house cat and probably behaved in a similar way. It may have been nocturnal, hunting for small mammals, reptiles and baby dinosaurs and killing them with its canine-like front teeth. In order to become more agile, it had lost most of its body armor, but it retained it on its tail. It is possible that its heavy armored tail was its main defense against predators.

Even stranger was Simosuchus, whose remains were found in Madagascar. This creature measured less than one meter long, had a short tail and a blunt snout, and its maple-leaf-shaped teeth suggest it was herbivorous.

Its robust, erect limbs suggest it didn´t swim, and it may instead have been a burrower. Simosuchus is therefore the most extreme example of crocodylomorph diversification; it would never be mistaken for a crocodile in our times.

Other Cretaceous crocs were more typical in appearance. Perhaps the most famous of all is Deinosuchus, which many of us knew first as Phobosuchus in popular books. Either way, the name means "frightening" or "terrifying" crocodile, and the name fits it perfectly.

Although technically an alligator relative, Deinosuchus looked like a scaled up crocodile, measuring at least 12 meters long.

It lived in what is today North America, including Mexico, where scutes from its armor have been found, as well as bite marks in the bones of its dinosaur prey.

Deinosuchus is often depicted as coexisting with Tyrannosaurus rex; this, however, is inaccurate, as the giant crocodilian disappeared millions of years before the rise of the "king of dinosaurs". In fact, for as long as Deinosuchus existed, no carnivorous dinosaur grew to particularly large size. The monstrous crocodilian had monopolized the top of the food chain.

Not satisfied with ruling the swamps and rivers of its time, Deinosuchus, like modern day saltwater crocodiles, seems to have lived in marine habitats as well, and there's good evidence that it swam across the Western Interior Sea, the shallow body of water that divided North America in half.

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At the end of the Cretaceous, 65 million years ago, a series of catastrophic events caused a great number of species to die out. The most famous casualties of this mass extinction were of course dinosaurs (except for birds and perhaps a few large species that faded into oblivion over the course of the next millennia).

Many unique crocodiles, like the aforementioned Simosuchus, disappeared as well. Some, however, survived, and found themselves in a silent world in which large meat eating dinosaurs were gone. Without competitors, crocodilians quickly started to diversify again, ready to take over the vacant niches left by their distant cousins.

If it hadn´t been for mammals, which also diversified at the time, it is possible that crocodiles would've given rise to the dominant lineages of future times. They were certainly adaptable enough.

Mammals, however, had some advantages over them. One of them was warm-bloodedness, which allowed mammals to conquer habitats and regions that crocodiles could not. Eventually, mammals secured their place as the dinosaur's successors. But even then, they had to be alert; crocodilians started evolving into monstrous and deadly forms. One of them, the three meter long Pristichampsus, had large, blunt toenails, more like hooves than claws, and was able to run at high speed. Not even early horses were safe from this land crocodile, able to walk either bipedally or on all fours.

Barinasuchus

Even more formidable were the sebecids, a group of short snouted land crocodiles with blade-like, flesh-slicing teeth like carnivorous dinosaurs. The largest sebecid, Barinasuchus, was a nine meter long monster that roamed the forests of what would become South America.

It was not only the largest land crocodile of all times, but also the largest post-Cretaceous land predator known. To the hapless mammals that lived in these Eocene forests, it was as if dinosaurs had never disappeared.

As time went on, mammals became more and more successful. Many forests disappeared, and many herbivores became adapted to open plains. Being cold blooded, crocodiles, even the land-based ones, were limited as to how fast they could run, and for how long. When the warm-blooded mammals evolved into lightning fast runners, only other mammals (and the legendary, towering “terror birds”) could keep up with them. Felines, canines and other carnivorans appeared, and land crocodiles started to become a thing of the past.

By the Middle Miocene, the sebecids (the lineage of land crocodiles to which Barinasuchus belonged), had disappeared. Crocodiles simply couldn´t compete with the warm-blooded killers that were evolving-- bears, sabertoothed tigers, giant hyenas. In most of the world, crocodiles became restricted to the habitats we relate them to nowadays: rivers, lakes, swamps.

The very last land crocodiles survived as relicts in Australia and nearby islands, where the most formidable predatory mammals were absent. Early aborigines probably encountered one of the most formidable when they arrived to Australia 40,000 years ago: Quinkana was the size of the largest saltwater crocodiles and had dinosaur-like flesh-slicing teeth. It probably tore a few humans apart before being exterminated itself.

Australia had also been home to a strange, probably tree-dwelling crocodilian named Trilophosuchus during the Miocene epoch. This creature measured about 1.5 meters long and held its head high when walking, like a monitor lizard and unlike most crocodilians today.

The Miocene also saw some of the most terrifyingly large crocodilians ever to have evolved.

8 million years ago, the region known today as the Amazon basin was a huge inland sea, the Pebas sea.

Purussaurus meets its prehistoric rivals

All sorts of strange creatures, from cetaceans to gharials to giant turtles lived in this sea, and all of them were food for the monstrous reptile that sat at the top of the food chain: Purussaurus, a giant caiman measuring up to 13 meters long, perhaps more. Unlike the long, slender snout of Sarcosuchus or Machimosaurus, the skull of Purussaurus was broad and massive, like that of the modern day broad-snouted caiman. Its teeth were small and blunt, especially adapted to crush any unfortunate animal it could catch, including turtles the size of dining room tables, whose fossil skeletons show proof of the caiman's terrible appetite; many of them lack huge portions of their shell or even entire limbs due to Purussaurus' attentions.

Also from the Miocene, the enormous Rhamphosuchus looked a lot like a gharial, although its closest living relative is actually the false gharial. Its fossilized remains, found in India, suggest a length of at least 11 meters long, although some estimates have suggested a much larger size. If, as some believe, Rhamphosuchus could grow up to 18 meters long, it would be as long as the longest carnivorous dinosaur, and likely much heavier. Unfortunately, since its remains are not complete, it is impossible to know if this colossal fish-eater is, as has been suggested, the largest crocodilian of all time.

Spinosaurus meets Stomatosuchus

Ironically, it is possible that in the end this title will be claimed by a docile creature, a monster only in size but not in temperament. Just as crocodiles gave rise to ferocious dinosaur hunters and sea monsters, they also produced some species that, although gigantic, would probably pose no threat to humans if they existed today. These animals are the stomatosuchids and the aegyptosuchids.

Found mostly in Africa, these Cretaceous crocodiles had flat heads with diminutive teeth, and large gular sacs. Some scientists believe they were filter-feeders that spent most, if not all of their time in the water, feeding on very small fish and other similar prey.

Some of them, like Stomatosuchus, grew to 12 meters long, being as large as the fearsome Sarcosuchus. Others, like the recently discovered Aegisuchus, may have been even larger. With an estimate length of 22 meters, Aegisuchus may have been the crocodilian equivalent of a whale- proving that the history of crocodilians was every bit as complex, fantastic and successful as that of dinosaurs or mammals.

That crocodiles today are all similar in shape and behavior may suggest to some that their lineage is finally over, and that eventually, these last remnants of a once glorious dynasty will fall into darkness.

But let's not underestimate them. Remember that all crocodylomorphs evolved from a few small, agile terrestrial hunters that also looked very similar to each other. Who knows what modern day crocs may give rise to one day, provided they survive past the age of men.