Prehistoric Crocodile Evolution

Meet the Crocodiles of the Mesozoic Era

Nile crocodile emerging from Mara River.

Manoj Shah/Getty Images

Of the many species on earth today that can trace their ancestry back to prehistoric times, evolution has touched crocodiles perhaps least. Along with pterosaurs and dinosaurs, crocodiles were an offshoot of the archosaurs, the "ruling lizards" of the early-to-middle Triassic period of the Mesozoic Era. This epoch in history began about 251 million years ago and ended 65 million years ago.

What distinguished the first crocodiles from the first dinosaurs was the shape and musculature of their jaws, which tended to be much more prominent and powerful. But other physical traits of Triassic- and Jurassic-era crocodiles, such as bipedal postures and vegetarian diets, were quite distinctive. It was only during the late Cretaceous period of the Mesozoic Era that crocodiles evolved the distinguishing traits they still today: stubby legs, armored scales, and a preference for marine habitats.

The Triassic Period

Phytosaur skulls

Lee Ruk/Wikimedia Commons/CC BY-SA 2.0

At the beginning of the Mesozoic Era, known as the Triassic Period, there were no crocodiles, just dinosaurs. This period began about 237 million years ago and lasted about 37 million years. Archosaurs, the crocodile's oldest relative, were among the many plant-eating dinos that thrived during this period. Archosaurs looked very much like crocodiles, except that their nostrils were positioned on the tops of their heads rather than the tips of their snouts. These reptiles subsisted on marine organisms in freshwater lakes and rivers worldwide. Among the most noteworthy phytosaurs were Rutiodon and Mystriosuchus.

The Jurassic Period

A life restoration of Doswellia kaltenbachi,

Fanboyphilosopher (Neil Pezzoni)/Wikimedia Commons/CC BY-SA 4.0 

During the middle Mesozoic Era, called the Jurassic Period, some dinosaurs evolved into new species, including birds and crocodiles. This period began about 200 million years ago. The earliest crocs were small, terrestrial, two-legged sprinters, and many were vegetarian. Erpetosuchus and Doswellia are two leading candidates for the honorific of "first" crocodile, though the exact evolutionary relationships of these early archosaurs are still uncertain. Another likely choice is the Xilousuchus from early Triassic Asia, a sailed archosaur with some distinct crocodilian characteristics.

But as the era progressed, these proto-crocodiles began migrating to the sea, developing elongated bodies, splayed limbs, and narrow, flat, tooth-studded snouts with powerful jaws. There was still room for innovation, though: for example, paleontologists believe that Stomatosuchus subsisted on plankton and krill, like a modern grey whale.

The Cenozoic Period

terrestrisuchus

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0

The final part of the Mesozoic Era, the Cenozoic Period, began about 145 million years ago and lasted until about 65 million years ago. It was during this final epic that the modern crocodile, Crocodylidae, first appeared as a distinct species and flourished.

But the crocodile family tree also forked about 100 million years ago, with the appearance of the enormous Sarcosuchus, which measured about 40 feet long from head to tail and weighed about 10 tons. There was also the slightly smaller Deinosuchus, which was about 30 feet long. Despite their fearsome mass, these giant crocodiles probably subsisted on largely on snakes and turtles.

As the Cenozoic Period drew to a close, the number of crocodile species began to dwindle. Deinosuchus and its offspring grew smaller over the centuries, evolving into caimans and alligators. Crocodylidae evolved into the modern crocodile and spawned several species now extinct. Among these was the Australian quinkana, which was 9 feet long and weighed 500 pounds. These beasts died out about 40,000 BCE.

Aegisuchus

aegisuchus
Aegisuchus.

Charles P. Tsai/Wikimedia Commons/CC BY 2.5

  • Name: Aegisuchus (Greek for "shield crocodile"); pronounced AY-gih-SOO-kuss; also known as the ShieldCroc
  • Habitat: Rivers of northern Africa
  • Historical Period: Middle Cretaceous (100-95 million years ago)
  • Size and Weight: About 50 feet long and 10 tons
  • Diet: Fish and small dinosaurs
  • Distinguishing Characteristics: Large size; broad, flat snout

The latest in a long line of giant prehistoric "crocs," including SuperCroc (aka Sarcosuchus) and BoarCroc (aka Kaprosuchus), the ShieldCroc, also known as Aegisuchus, was a giant, river-dwelling crocodile of middle Cretaceous northern Africa. Judging by the size of its single, partial fossilized snout, Aegisuchus may have rivaled Sarcosuchus in size, full-grown adults measuring at least 50 feet from head to tail (and possibly as much as 70 feet, depending on whose estimates you rely on).

One odd fact about Aegisuchus is that it lived in a part of the world not generally known for its abundant wildlife. However, 100 million years ago, the stretch of northern Africa now dominated by the Sahara Desert was a green, lush landscape threaded with numerous rivers and populated by dinosaurs, crocodiles, pterosaurs and even small mammals. There's still a lot about Aegisuchus that we don't know, but it's reasonable to infer that it was a classic crocodilian "ambush predator" that subsisted on small dinosaurs as well as fish.

Anatosuchus

anatosuchus
Anatosuchus. University of Chicago
  • Name: Anatosuchus (Greek for "duck crocodile"); pronounced ah-NAT-oh-SOO-kuss
  • Habitat: Swamps of Africa
  • Historical Period: Early Cretaceous (120-115 million years ago)
  • Size and Weight: About two feet long and a few pounds
  • Diet: Probably insects and crustaceans
  • Distinguishing Characteristics: Small size; quadrupedal posture; broad, duck-like snout

Not literally a cross between a duck and a crocodile, Anatosuchus, the DuckCroc, was an unusually small (only about two feet from head to tail) ancestral crocodile equipped with a broad, flat snout--similar to those sported by the contemporary hadrosaurs (duck-billed dinosaurs) of its African habitat. Described in 2003 by the ubiquitous American paleontologist Paul Sereno, Anatosuchus probably kept well out of the way of the larger megafauna of its day, rousting small insects and crustaceans from the soil with its sensitive "bill."

Angistorhinus

angistorhinus
Angistorhinus.

Mitternacht90/Wikimedia Commons

  • Name: Angistorhinus (Greek for "narrow snout"); pronounced ANG-iss-toe-RYE-nuss
  • Habitat: Swamps of North America
  • Historical Period: Late Triassic (230-220 million years ago)
  • Size and Weight: About 20 feet long and half a ton
  • Diet: Small animals
  • Distinguishing Characteristics: Large size; long, narrow skull

Just how big was Angistorhinus? Well, one species has been dubbed A. megalodon, and the reference to the giant prehistoric shark Megalodon is no accident. This late Triassic phytosaur--a family of prehistoric reptiles that evolved to look uncannily like modern crocodiles--measured over 20 feet from head to tail and weighed about half a ton, making it one of the largest phytosaurs of its North American habitat. (Some paleontologists believe Angistorhinus was actually a species of Rutiodon, the giveaway being the position of the nostrils high up on these phytosaurs' snouts).

Araripesuchus

araripesuchus
Araripesuchus.

Gabriel Lio/Wikimedia Commons/CC BY 3.0

  • Name: Araripesuchus (Greek for "Araripe crocodile"); pronounced ah-RAH-ree-peh-SOO-kuss
  • Habitat: Riverbeds of Africa and South America
  • Historical Period: Middle Cretaceous (110-95 million years ago)
  • Size and Weight: About six feet long and 200 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Long legs and tail; short, blunt head

It wasn't the biggest prehistoric crocodile that ever lived, but to judge by its long, muscular legs and streamlined body, Araripesuchus must have been one of the most dangerous--especially to any small dinosaurs prowling the riverbeds of middle Cretaceous Africa and South America (the existence of species on both these continents is yet more proof for the existence of the giant southern continent Gondwana). In fact, Araripesuchus looks like a crocodile caught halfway along evolving into a theropod dinosaur--not a stretch of the imagination, since both dinosaurs and crocodiles evolved from the same archosaur stock tens of millions of years earlier.

Armadillosuchus

armadillosuchus
Armadillosuchus.

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0

  • Name: Armadillosuchus (Greek for "armadillo crocodile"); pronounced ARM-ah-dill-oh-SOO-kuss
  • Habitat: Rivers of South America
  • Historical Period: Late Cretaceous (95-85 million years ago)
  • Size and Weight: About seven feet long and 250-300 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Moderate size; thick, banded armor

Armadillosuchus, the "armadillo crocodile," comes by its name honestly: this late Cretaceous reptile had a crocodile-like build (albeit with longer legs than modern crocs), and the thick armor along its back was banded like that of an armadillo (unlike an armadillo, though, Armadillosuchus presumably couldn't curl up into an impenetrable ball when threatened by predators). Technically, Armadillosuchus has been classified as a distant crocodile cousin, a "sphagesaurid crocodylomorph," meaning it was closely related to the South American Sphagesaurus. We don't know much about how Armadillosuchus lived, but there are some tantalizing hints that it might have been a digging reptile, lying in wait for smaller animals that passed by its burrow.

Baurusuchus

Life restoration of Baurusuchus albertoi.

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0

  • Name: Baurusuchus (Greek for "Bauru crocodile"); pronounced BORE-oo-SOO-kuss
  • Habitat: Plains of South America
  • Historical Period: Late Cretaceous (95-85 million years ago)
  • Size and Weight: About 12 feet long and 500 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Long, doglike legs; powerful jaws

Prehistoric crocodiles weren't necessarily restricted to river environments; the fact is that these ancient reptiles could be every bit as diverse as their dinosaur cousins when it came to their habitats and lifestyles. Baurusuchus is an excellent example; this South American crocodile, which lived during the middle-to-late Cretaceous period, possessed long, dog-like legs and a heavy, powerful skull with the nostrils placed on the end, indications that it actively prowled the early pampas rather than snapping at prey from bodies of water. By the way, the similarity of Baurusuchus to another land-dwelling crocodile from Pakistan is further proof that the Indian subcontinent was once joined to the giant southern continent of Gondwana.

Carnufex

carnufex
Carnufex. Jorge Gonzalez
  • Name: Carnufex (Greek for "butcher"); pronounced CAR-new-fex
  • Habitat: Swamps of North America
  • Historical Period: Middle Triassic (230 million years ago)
  • Size and Weight: About nine feet long and 500 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Large size; short front limbs; bipedal posture

During the middle Triassic period, about 230 million years ago, archosaurs started to branch off in three evolutionary directions: dinosaurs, pterosaurs, and ancestral crocodiles. Recently discovered in North Carolina, Carnufex was one of the largest "crocodylomorphs" of North America, and may well have been the apex predator of its ecosystem (the first true dinosaurs evolved in South America at about the same time, and tended to be much smaller; in any case, they didn't make it to what would become North America until millions of years later). Like most early crocodiles, Carnufex walked on its two hind legs, and probably feasted on small mammals as well as its fellow prehistoric reptiles.

Champsosaurus

champsosaurus
Champsosaurus. Canadian Museum of Nature
  • Name: Champsosaurus (Greek for "field lizard"); pronounced CHAMP-so-SORE-us
  • Habitat: Rivers of North America and western Europe
  • Historical Period: Late Cretaceous-Early Tertiary (70-50 million years ago)
  • Size and Weight: About five feet long and 25-50 pounds
  • Diet: Fish
  • Distinguishing Characteristics: Long, narrow body; long tail; narrow, tooth-studded snout

Appearances to the contrary, Champsosaurus wasn't a true prehistoric crocodile, but rather a member of an obscure breed of reptiles known as choristoderans (another example being the fully aquatic Hyphalosaurus). However, Champsosaurus lived alongside the genuine crocodiles of the late Cretaceous and early Tertiary periods (both families of reptiles managing to survive the intervening K/T Extinction that wiped out the dinosaurs), and it also behaved like a crocodile, spearing fish out of the rivers of North America and western Europe with its long, narrow, tooth-studded snout.

Culebrasuchus

culebrasuchus
Culebrasuchus. Danielle Byerley

Culebrasuchus, which lived in the northern part of Central America, had a lot in common with modern caimans--a hint that the ancestors of these caimans managed to traverse miles of ocean sometime between the Miocene and Pliocene epochs.

Dakosaurus

Life restoration of Dakosaurus maximus (breaching, center)

Dmitry Bogdanov/Wikimedia Commons/CC BY 3.0

Given its large head and leg-like rear flippers, it seems unlikely that the ocean-dwelling crocodile Dakosaurus was a particularly fast swimmer, though it was clearly speedy enough to prey on its fellow marine reptiles.

Deinosuchus

Fossil specimen in the Natural History Museum of Utah, Salt Lake City, Utah, USA.

Daderot/Wikimedia Commons/Public Domain 

Deinosuchus was one of the biggest prehistoric crocodiles that ever lived, growing to a whopping length of 33 feet from head to tail--but it was still dwarfed by the biggest crocodile ancestor of them all, the truly enormous Sarcosuchus.

Desmatosuchus

Desmatosuchus spurensis

Matteo De Stefano/MUSE/Wikimedia Commons/CC BY-SA 3.0

  • Name: Desmatosuchus (Greek for "link crocodile"); pronounced DEZ-mat-oh-SOO-kuss
  • Habitat: Forests of North America
  • Historical Period: Middle Triassic (230 million years ago)
  • Size and Weight: About 15 feet long and 500-1,000 pounds
  • Diet: Plants
  • Distinguishing Characteristics: Crocodile-like posture; splayed limbs; armored body with sharp spikes protruding from shoulders

The crocodile-like Desmatosuchus actually counted as an archosaur, the family of terrestrial reptiles that preceded the dinosaurs, and represented an evolutionary advance over other "ruling lizards" its kind such as Proterosuchus and Stagonolepis. Desmatosuchus was relatively large for middle Triassic North America, about 15 feet long and 500 to 1,000 pounds, and it was protected by an intimidating suit of natural armor that culminated in two long, dangerous spikes jutting out from its shoulders. Still, the head of this ancient reptile was somewhat comical by prehistoric standards, looking a bit like a pig's snout pasted onto a grumpy trout.

Why did Desmatosuchus evolve such an elaborate defensive armament? Like other plant-eating archosaurs, it was probably hunted by the carnivorous reptiles of the Triassic period (both its fellow archosaurs and the earliest dinosaurs that evolved from them) and needed a reliable means to keep these predators at bay. (Speaking of which, the fossils of Desmatosuchus have been found in association with the slightly larger meat-eating archosaur Postosuchus, a strong hint that these two animals had a predator/prey relationship.)

Dibothrosuchus

dibothrosuchus
Dibothrosuchus.

Nobu Tamura/Wikimedia Commons/CC BY 3.0

  • Name: Dibothrosuchus (Greek for "twice-excavated crocodile"); pronounced die-BOTH-roe-SOO-kuss
  • Habitat: Rivers of eastern Asia
  • Historical Period: Early Jurassic (200-180 million years ago)
  • Size and Weight: About four feet long and 20-30 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Moderate size; long legs; armor plating along back

If you crossed a dog with a crocodile, you might wind up with something like the early Jurassic Dibothrosuchus, a distant crocodile ancestor that spent its entire life on land, had exceptionally sharp hearing, and trotted around on four (and occasionally two) very canine-like legs. Dibothrosuchus is technically classified as a "sphenosuchid crocodylomorph," not directly ancestral to modern crocodiles but more like a second cousin a few times removed; its closest relative seems to have been the even tinier Terrestrisuchus of late Triassic Europe, which may itself have been a juvenile of Saltoposuchus.

Diplocynodon

Diplocynodon darwini

Kuebi/Armin Kübelbeck/Wikimedia Commons/CC BY-SA 3.0

  • Name: Diplocynodon (Greek for "double dog tooth"); pronounced DIP-low-SIGH-no-don
  • Habitat: Rivers of western Europe
  • Historical Epoch: Late Eocene-Miocene (40-20 million years ago)
  • Size and Weight: About 10 feet long and 300 pounds
  • Diet: Omnivorous
  • Distinguishing Characteristics: Moderate length; tough armor plating

Few things in natural history are as obscure as the difference between crocodiles and alligators; suffice it to say that modern alligators (technically a sub-family of crocodiles) are restricted to North America, and are characterized by their blunter snouts. The importance of Diplocynodon is that it was one of the few prehistoric alligators to be native to Europe, where it prospered for millions of years before going extinct sometime during the Miocene epoch. Beyond the shape of its snout, the moderately sized (only about 10 feet long) Diplocynodon was characterized by the tough, knobby body armor that covered not only its neck and back, but its belly as well.

Erpetosuchus

Erpetosuchus

Mojcaj/Wikimedia Commons/CC BY-SA 3.0 

  • Name: Erpetosuchus (Greek for "crawling crocodile"); pronounced ER-pet-oh-SOO-kuss
  • Habitat: Swamps of North America and western Europe
  • Historical Period: Late Triassic (200 million years ago)
  • Size and Weight: About one foot long and a few pounds
  • Diet: Insects
  • Distinguishing Characteristics: Small size; possibly bipedal posture

It's a common theme in evolution that large, fierce creatures descend from tiny, meek forebears. That's certainly the case with crocodiles, which can trace their lineage back 200 million years to Erpetosuchus, a tiny, foot-long archosaur that prowled the swamps of North America and Europe during the late Triassic and early Jurassic periods. Aside from the shape of its head, though, Erpetosuchus didn't much resemble modern crocodiles in either appearance or behavior; it may have run quickly on its two hind feet (rather than crawling on all fours like modern crocodiles), and probably subsisted on insects rather than red meat.

Geosaurus

Life reconstruction showing the maximum body length for Geosaurus giganteus.

PLOS/Wikimedia Commons/CC BY 4.0

  • Name: Geosaurus (Greek for "earth reptile"); pronounced GEE-oh-SORE-us
  • Habitat: Oceans worldwide
  • Historical Period: Middle-late Jurassic (175-155 million years ago)
  • Size and Weight: About 10 feet long and 250 pounds
  • Diet: Fish
  • Distinguishing Characteristics: Slim body; long, pointed snout

Geosaurus is the most inaccurately named marine reptile of the Mesozoic Era: this so-called "earth lizard" probably spent most, if not all, of its life in the sea (you can blame the famous paleontologist Eberhard Fraas, who also named the dinosaur Efraasia, for this spectacular misunderstanding). A remote ancestor of modern crocodiles, Geosaurus was a different creature entirely from the contemporary (and mostly bigger) marine reptiles of the middle to late Jurassic period, the plesiosaurs and ichthyosaurs, though it seems to have made its living in the exact same way, by hunting down and eating smaller fish. Its closest relative was another sea-going crocodile, Metriorhynchus.

Goniopholis

Goniopholis

Ghedoghedo/Wikimedia Commons/CC BY-SA 3.0

  • Name: Goniopholis (Greek for "angled scale"); pronounced GO-nee-AH-foe-liss
  • Habitat: Swamps of North America and Eurasia
  • Historical Period: Late Jurassic-Early Cretaceous (150-140 million years ago)
  • Size and Weight: About 10 feet long and 300 pounds
  • Diet: Omnivorous
  • Distinguishing Characteristics: Strong, narrow skull; quadrupedal posture; distinctively patterned body armor

Unlike some more exotic members of the crocodylian breed, Goniopholis was a fairly direct ancestor of modern crocodiles and alligators. This relatively small, unassuming-looking prehistoric crocodile had a widespread distribution across late Jurassic and early Cretaceous North America and Eurasia (it's represented by no less than eight separate species), and it led an opportunistic lifestyle, feeding on both small animals and plants. Its name, Greek for "angled scale," derives from the distinctive pattern of its body armor.

Gracilisuchus

Skeleton of Gracilisiirhiis stipanicicoiiini, restored

Internet Archive Book Images/Flickr 

  • Name: Gracilisuchus (Greek for "graceful crocodile"); pronounced GRASS-ill-ih-SOO-kuss
  • Habitat: Swamps of South America
  • Historical Period: Middle Triassic (235-225 million years ago)
  • Size and Weight: About one foot long and a few pounds
  • Diet: Insects and small animals
  • Distinguishing Characteristics: Small size; short snout; bipedal posture

When it was discovered in South America in the 1970's, Gracilisuchus was thought be an early dinosaur--after all, it was clearly a fast, two-legged carnivore (though it often walked on all fours), and its long tail and relatively short snout bore a distinctly dinosaur-like profile. On further analysis, though, paleontologists realized they were looking at a (very early) crocodile, based on subtle anatomical features of Gracilisuchus' skull, spine and ankles. Long story short, Gracilisuchus provides further evidence that the big, slow, plodding crocodiles of the present day are the descendants of fast, two-legged reptiles of the Triassic period..

Kaprosuchus

A reconstruction showing the head of Kaprosuchus

PaleoEquii/Wikimedia Commons/CC BY-SA 4.0

  • Name: Kaprosuchus (Greek for "boar crocodile"); pronounced CAP-roe-SOO-kuss; also known as the BoarCroc
  • Habitat: Plains of Africa
  • Historical Period: Middle Cretaceous (100-95 million years ago)
  • Size and Weight: About 20 feet long and 1,000-2,000 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Large, boar-like tusks in upper and lower jaws; long legs

Kaprosuchus is known by only a single skull, discovered in Africa in 2009 by the globetrotting University of Chicago paleontologist Paul Sereno, but what a skull it is: this prehistoric crocodile had oversized tusks embedded toward the front of its upper and lower jaws, inspiring Sereno's affectionate nickname, the BoarCroc. Like many crocodiles of the Cretaceous period, Kaprosuchus wasn't restricted to river ecosystems; to judge by its long limbs and impressive dentition, this four-legged reptile roamed the plains of Africa much in the style of a big cat. In fact, with its big tusks, powerful jaws and 20-foot length, Kaprosuchus may have been capable of taking down comparably sized plant-eating (or even meat-eating) dinosaurs, possibly even including juvenile Spinosaurus.

Metriorhynchus

Metriorhynchus

Daderot/Wikimedia Commons/Public Domain 

  • Name: Metriorhynchus (Greek for "moderate snout"); pronounced MEH-tree-oh-RINK-us
  • Habitat: Shores of western Europe and possibly South America
  • Historical Period: Late Jurassic (155-145 million years ago)
  • Size and Weight: About 10 feet long and 500 pounds
  • Diet: Fish, crustaceans and marine reptiles
  • Distinguishing Characteristics: Lack of scales; light, porous skull; tooth-studded snout

The prehistoric crocodile Metriorhynchus comprised about a dozen known species, making it one of the most common marine reptiles of late Jurassic Europe and South America (though the fossil evidence for this latter continent is sketchy). This ancient predator was characterized by its un-crocodile-like lack of armor (its smooth skin probably resembled that of its fellow marine reptiles, the ichthyosaurs, to which it was only distantly related) and its lightweight, porous skull, which presumably enabled it to poke its head out of the surface of the water while the rest of its body floated underneath at a 45-degree angle. All of these adaptations point to a varied diet, which probably included fish, hard-shelled crustaceans, and even larger plesiosaurs and pliosaurs, the corpses of which would have been ripe for scavenging.

One of the odd things about Metriorhynchus (Greek for "moderate snout") is that it seems to have possessed relatively advanced salt glands, a feature of certain marine creatures that allows them to "drink" salt water as well as eat unusually salty prey without dehydrating; in this (and in certain other) respects Metriorhynchus was similar to another famous sea-going crocodile of the Jurassic period, Geosaurus. Unusually for such a widespread and well-known crocodile, paleontologists have adduced no fossil evidence of Metriorhynchus nests or hatchlings, so it's unknown whether this reptile gave birth at sea to live young or returned laboriously to land to lay its eggs, like a marine turtle.

Mystriosuchus

mystriosuchus
The skull of Mystriosuchus.

Ghedoghedo/Wikimedia Commons/CC BY-SA 3.0

The pointy, tooth-studded snout of Mystriosuchus bears a remarkable resemblance to the modern gharial of central and southern Asia--and like the gharial, Mystriosuchus is believed to have been an especially good swimmer.

Neptunidraco

neptunidraco
Neptunidraco.

Nobu Tamura/Wikimedia Commons/CC BY-SA 3.0

  • Name: Neptunidraco (Greek for "Neptune's dragon"); pronounced NEP-tune-ih-DRAY-coe
  • Habitat: Shores of southern Europe
  • Historical Period: Middle Jurassic (170-165 million years ago)
  • Size and Weight: Undisclosed
  • Diet: Fish and squids
  • Distinguishing Characteristics: Sleek body; long, narrow jaws

Often, the "wow factor" of a prehistoric creature's name is inversely proportional to how much we actually know about it. As marine reptiles go, you can't ask for a better name than Neptunidraco ("Neptune's dragon"), but otherwise there has not been a lot published about this middle Jurassic predator. We do know that Neptunidraco was a "metriorhynchid," a line of marine reptiles distantly related to modern crocodiles, the signature genus of which is Metriorhynchus (to which the type fossil of Neptunidraco was once referred), and that it also seems to have been an unusually fast and agile swimmer. Following the announcement of Neptunidraco in 2011, a species of another marine reptile, Steneosaurus, was reassigned to this newer genus.

Notosuchus

notosuchus
Notosuchus.

Gabriel Lio/Wikimedia Commons/CC BY-SA 3.0

  • Name: Notosuchus (Greek for "southern crocodile"); pronounced NO-toe-SOO-kuss
  • Habitat: Riverbeds of South America
  • Historical Period: Late Cretaceous (85 million years ago)
  • Size and Weight: About three feet long and 5-10 pounds
  • Diet: Probably plants
  • Distinguishing Characteristics: Small size; possible pig-like snout

Paleontologists have known about Notosuchus for over a hundred years, but this prehistoric crocodile didn't garner much attention until a new study published in 2008 proposed an astonishing hypothesis: that Notosuchus possessed a sensitive, prehensile, pig-like snout that it used to sniff out plants from beneath the soil. On the face of it (sorry), there's no reason to doubt this conclusion: after all, convergent evolution--the tendency of different animals to evolve the same features when they occupy the same habitats--is a common theme in the history of life on earth. Still, since soft tissue doesn't preserve well in the fossil record, Notosuchus' pig-like proboscis is far from a done deal!

Pakasuchus

Life restoration of Pakasuchus kapilimai.

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0

Animals that pursue the same lifestyles tend to evolve the same features--and since Cretaceous southern Africa lacked both mammals and feathered dinosaurs, the prehistoric crocodile Pakasuchus adapted to fit the bill.

Pholidosaurus

Pholidosaurus meyeri fossil at the Museum für Naturkunde, Berlin.

FunkMonk/Wikimedia Commons/CC BY-SA 3.0

  • Name: Pholidosaurus (Greek for "scaly lizard"); pronounced FOE-lih-doh-SORE-us
  • Habitat: Swamps of western Europe
  • Historical Period: Early Cretaceous (145-140 million years ago)
  • Size and Weight: About 20 feet long and 500-1,000 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Moderate size; long, narrow skull

Like many extinct animals that were discovered and named in the early 19th century, Pholidosaurus is a true taxonomic nightmare. Ever since its excavation in Germany, in 1841, this early Cretaceous proto-crocodile has gone under various genus and species names (Macrorhynchus is one notable example), and its exact place in the crocodile family tree has been a matter of ongoing dispute. To show how little the experts agree, Pholidosaurus has been adduced as a close relative of both Thalattosaurus, an obscure marine reptile of the Triassic period, and Sarcosuchus, the largest crocodile that ever lived!

Protosuchus

The skull of Protosuchus richardsoni, part of a fossil cast (specimen AMNH 3024) in the American Museum of Natural History.

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0 

  • Name: Protosuchus (Greek for "first crocodile"); pronounced PRO-toe-SOO-kuss
  • Habitat: Riverbeds of North America
  • Historical Period: Late Triassic-Early Jurassic (155-140 million years ago)
  • Size and Weight: About three feet long and 10-20 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Small size; occasional bipedal posture; armor plates on back

It's one of the ironies of paleontology that the earliest reptile to be conclusively identified as a prehistoric crocodile lived not in the water, but on the land. What puts Protosuchus firmly in the crocodile category are its well-muscled jaws and sharp teeth, which interlocked firmly when its mouth was closed. Otherwise, though, this sleek reptile seems to have led a terrestrial, predatory lifestyle very similar to that of the earliest dinosaurs, which began to flourish during the same late Triassic time frame.

The Quinkana

Quinkana timara skull

Mark Marathon/Wikimedia Commons/CC BY-SA 4.0

  • Name: Quinkana (aboriginal for "native spirit"); pronounced quin-KAHN-ah
  • Habitat: Swamps of Australia
  • Historical Epoch: Miocene-Pleistocene (23 million-40,000 years ago)
  • Size and Weight: About nine feet long and 500 pounds
  • Diet: Meat
  • Distinguishing Characteristics: Long legs; long, curved teeth

In certain respects, the Quinkana was a throwback to the prehistoric crocodiles that preceded, and coexisted with, the dinosaurs of the Mesozoic Era: this crocodile possessed relatively long, agile legs, very different from the splayed limbs of modern species, and its teeth were curved and sharp, like those of a tyrannosaur. Based on its distinctive anatomy, it's clear that the Quinkana spent most of its time on land, ambushing its prey from the cover of woodlands (one of its favorite meals may have been Diprotodon, the Giant Wombat). This fearsome crocodile went extinct about 40,000 years ago, along with most of the mammalian megafauna of Pleistocene Australia; the Quinkana may have been hunted to extinction by the first Australian aborigines, which it probably preyed on every chance it got.

Rhamphosuchus

Fossil of Rhamphosuchus, an extinct reptile at Musee d'Histoire Naturelle, Paris

Ghedoghedo/Wikimedia Commons/CC BY-SA 3.0

  • Name: Rhamphosuchus (Greek for "beak crocodile"); pronounced RAM-foe-SOO-kuss
  • Habitat: Swamps of India
  • Historical Epoch: Late Miocene-Pliocene (5-2 million years ago)
  • Size and Weight: About 35 feet long and 2-3 tons
  • Diet: Meat
  • Distinguishing Characteristics: Large size; long, pointed snout with sharp teeth

Unlike most prehistoric crocodiles, Rhamphosuchus wasn't directly ancestral to today's mainstream crocodiles and alligators, but rather to the modern False Gharial of the Malaysian peninsula. More notably, Rhamphosuchus was once believed to have been the biggest crocodile that ever lived, measuring 50 to 60 feet from head to tail and weighing over 20 tons--estimates that were drastically downgraded upon closer examination of the fossil evidence, to a still hefty, but not quite as impressive, 35 feet long and 2 to 3 tons. Today, Rhamphosuchus' place in the spotlight has been usurped by truly gigantic prehistoric crocodiles like Sarcosuchus and Deinosuchus, and this genus has faded into relative obscurity.

Rutiodon

Rutiodon life restoration

Frank Vincentz/Wikimedia Commons/CC BY-SA 3.0 

  • Name: Rutiodon (Greek for "wrinkled tooth"); pronounced roo-TIE-oh-don
  • Habitat: Swamps of North America
  • Historical Period: Late Triassic (225-215 million years ago)
  • Size and Weight: About eight feet long and 200-300 pounds
  • Diet: Fish
  • Distinguishing Characteristics: Crocodile-like body; nostrils on top of head

Although it's technically classified as a phytosaur rather than a prehistoric crocodile, Rutiodon cut a distinctive crocodilian profile, with its long, low-slung body, sprawling legs, and narrow, pointed snout. What set the phytosaurs (an offshoot of the archosaurs that preceded the dinosaurs) apart from early crocodiles was the position of their nostrils, which were located on the tops of their heads rather than on the ends of their snouts (there were also some subtle anatomical differences between these two types of reptiles, which only a paleontologist would be much concerned with).

Sarcosuchus

Scale diagram of crocodyliforms 10 metres or more in length

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0

Dubbed "SuperCroc" by the media, Sarcosuchus looked and behaved like a modern crocodile, but it was a whole lot bigger--about the length of a city bus and the weight of a small whale!

Simosuchus

Life restoration of Simosuchus clarki.

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0 

Simosuchus didn't look much like a crocodile, given its short, blunt head and vegetarian diet, but anatomical evidence points to its having been a distant crocodile ancestor of late Cretaceous Madagascar.

Smilosuchus

Smilosuchus adamanensis

Credit Dr. Jeff Martz/NPS/Wikimedia Commons/CC BY 2.0

  • Name: Smilosuchus (Greek for "saber crocodile"); pronounced SMILE-oh-SOO-kuss
  • Habitat: Rivers of southwest North America
  • Historical Period: Late Triassic (230 million years ago)
  • Size and Weight: Up to 40 feet long and 3-4 tons
  • Diet: Meat
  • Distinguishing Characteristics: Large size; crocodile-like appearance

The name Smilosuchus partakes of the same Greek root as Smilodon, better known as the Saber-Tooth Tiger--never mind that this prehistoric reptile's teeth weren't particularly impressive. Technically classified as a phytosaur, and thus only distantly related to modern crocodiles, the late Triassic Smilosuchus would have given true prehistoric crocodiles like Sarcosuchus and Deinosuchus (which lived tens of millions of years later) a run for their money. Clearly, Smilosuchus was the apex predator of its North American ecosystem, likely preying on smaller, plant-eating pelycosaurs and therapsids.

Steneosaurus

Steneosaurus

Yinan Chen/Wikimedia Commons/CC-zero

  • Name: Steneosaurus (Greek for "narrow lizard"); pronounced STEN-ee-oh-SORE-us
  • Habitat: Shores of western Europe and northern Africa
  • Historical Period: Early Jurassic-Early Cretaceous (180-140 million years ago)
  • Size and Weight: Up to 12 feet long and 200-300 pounds
  • Diet: Fish
  • Distinguishing Characteristics: Long, narrow snout; armor plating

Although it's not quite as popular as other prehistoric crocodiles, Steneosaurus is well-represented in the fossil record, with over a dozen named species ranging from western Europe to northern Africa. This ocean-going crocodile was characterized by its long, narrow, tooth-studded snout, relatively stubby arms and legs, and the tough armor plating along its back--which must have been an effective form of defense, since the various species of Steneosaurus span a full 40 million years, from the early Jurassic to the early Cretaceous periods.

Stomatosuchus

Stomatosuchus inermis

Dmitry Bogdanov/Wikimedia Commons/CC BY 3.0 

  • Name: Stomatosuchus (Greek for "mouth crocodile"); pronounced stow-MAT-oh-SOO-kuss
  • Habitat: Swamps of northern Africa
  • Historical Period: Middle Cretaceous (100-95 million years ago)
  • Size and Weight: About 36 feet long and 10 tons
  • Diet: Plankton and krill
  • Distinguishing Characteristics: Huge size; pelican-like lower jaw

Although World War II ended over 60 years ago, paleontologists are still feeling the effects today. For example, the only known fossil specimen of the prehistoric crocodile Stomatosuchus was destroyed by an allied bombing raid on Munich in 1944. If those bones had been preserved, experts may, by now, have conclusively solved the riddle of this crocodile's diet: it seems that Stomatosuchus fed on tiny plankton and krill, much like a baleen whale, rather than on the land and river animals that populated Africa during the middle Cretaceous period.

Why would a crocodile that grew to lengths of a dozen yards (its head alone was over six feet long) have subsisted on microscopic creatures? Well, evolution works in mysterious ways--in this case, it seems that other dinosaurs and crocodiles must have cornered the market on fish and carrion, forcing Stomatosuchus to focus on smaller fry. (In any case, Stomatosuchus was far from the largest crocodile that ever lived: it was about the size of Deinosuchus, but way outclassed by the truly enormous Sarcosuchus.)

Terrestrisuchus

Terrestrisuchus

Apokryltaros/Wikimedia Commons/CC BY 2.5

  • Name: Terrestrisuchus (Greek for "earth crocodile"); pronounced teh-REST-rih-SOO-kuss
  • Habitat: Woodlands of western Europe
  • Historical Period: Late Triassic (215-200 million years ago)
  • Size and Weight: About 18 inches long and a few pounds
  • Diet: Insects and small animals
  • Distinguishing Characteristics: Slender body; long legs and tail

Since both dinosaurs and crocodiles evolved from archosaurs, it makes sense that the earliest prehistoric crocodiles looked uncannily like the first theropod dinosaurs. A good example is Terrestrisuchus, a tiny, long-limbed crocodile ancestor that may well have spent much of its time running on two or four legs (hence its informal nickname, the greyhound of the Triassic period). Unfortunately, while it has the more impressive name, Terrestrisuchus may wind up being assigned as a juvenile of another genus of Triassic crocodile, Saltoposuchus, which attained more impressive lengths of three to five feet.

Tyrannoneustes

tyrannoneustes
Tyrannoneustes.

Dmitry Bogdanov/Wikimedia Commons/CC BY 4.0

  • Name: Tyrannoneustes (Greek for "tyrant swimmer"); pronounced tih-RAN-oh-NOY-steez
  • Habitat: Shores of western Europe
  • Historical Period: Late Jurassic (160 million years ago)
  • Size and Weight: About 10 feet long and 500-1,000 pounds
  • Diet: Fish and marine reptiles
  • Distinguishing Characteristics: Large flippers; crocodile-like snout

Modern paleontologists have made an excellent living venturing into the dusty basements of far-flung museums and identifying long-forgotten fossils. The latest example of this trend is Tyrannoneustes, which was "diagnosed" from a 100-year-old museum specimen that had previously been identified as a plain-vanilla "metriorhynchid" (a breed of marine reptiles distantly related to crocodiles). The most notable thing about Tyrannoneustes is that it was adapted to eating extra-large prey, with unusually wide-opening jaws studded with interlocking teeth. In fact, Tyrannoneustes might have given the slightly later Dakosaurus--long reputed to be the most dangerous metriorhynchid--a run for its Jurassic money!

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