Archosaur Pictures and Profiles

01
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These "Ruling Lizards" Preceded the Dinosaurs

silesaurus
Silesaurus. Wikimedia Commons

Archosaurs, "ruling lizards," were the dominant reptiles on earth until the rise of the dinosaurs, which evolved from a population of archosaurs during the late Triassic period. On the following slides, you'll find pictures and detailed profiles of over two dozen archosaurs, ranging from Arizonasaurus to Xilousuchus.

02
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Arizonasaurus

arizonasaurus
Arizonasaurus. Wikimedia Commons

Name:

Arizonasaurus (Greek for "Arizona lizard"); pronounced AH-rih-ZONE-ah-SORE-us

Habitat:

Woodlands of western North America

Historical Period:

Middle Triassic (240 million years ago)

Size and Weight:

About 20 feet long and 500 pounds

Diet:

Meat

Distinguishing Characteristics:

Large size; sail on back

 

Until 2000, the poorly understood Arizonasaurus languished in the back pages of paleontological history. Then, the discovery of a near-complete skeleton in 2002 revealed that this archosaur had a sailed back, like its distant relative of the Permian period, Dimetrodon. The anatomy of Arizonasaurus has led to speculation that birds and crocodiles split off from the archosaur family tree earlier than once thought, toward the middle rather than the end of the Triassic period. As for the purpose of this reptile's sail, it probably served both as a temperature-regulation device and a sexually selected characteristic (meaning males with bigger sails had the opportunity to mate with more females).

03
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Asilisaurus

asilisaurus
Asilisaurus. Field Museum of Natural History

Name:

Asilisaurus (Greek for "ancestor lizard"); pronounced ah-SILL-ah-SORE-us

Habitat:

Woodlands of Africa

Historical Period:

Middle Triassic (240 million years ago)

Size and Weight:

About six feet long and 30-40 pounds

Diet:

Possibly omnivorous

Distinguishing Characteristics:

Small size; theropod-like appearance

 

The most important thing about Asilisaurus--numerous fossils of which have been discovered in the African nation of Tanzania--is when it lived. This "silesaur," as it's technically known, dates to the middle Triassic period (about 240 million years ago), which has profound implications for the dinosaurs it was closely related to. You see, paleontologists believe that the earliest dinosaurs and the silesaurs branched off from a common archosaur ancestor, and the first dinosaurs (such as Herrerasaurus and Staurikosaurus) date from only 230 million years ago. What this means is that the dinosaur evolutionary line may be 10 million years older than anyone had thought!

Its evolutionary implications aside, what was Asilisaurus like? Well, this was a fairly small, mostly quadrupedal (though possibly occasionally bipedal) reptile that seems to have been well-adapted for an omnivorous diet. If Asilisaurus did munch on the occasional vegetable, this might shed light on the evolution of herbivory in early dinosaurs, which (as far as we know) started out as exclusive meat eaters.

04
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Batrachotomus

batrachotomus
Batrachotomus. Wikimedia Commons

Name:

Batrachotomus (Greek for "frog slicer"); pronounced bah-TRACK-oh-TOME-us

Habitat:

Swamps of western Europe

Historical Period:

Late Triassic (230 million years ago)

Size and Weight:

About 20 feet long and 500 pounds

Diet:

Meat

Distinguishing Characteristics:

Large size; plates on back; longer hind than front limbs

 

Batrachotomus is one of those ancient reptiles whose name sounds better in translation: it's Greek for "frog slicer," a reference to the remains of a prehistoric amphibian (Mastodonsaurus) on which it likely feasted. The sleek body and relatively long limbs of Batrachotomus made it look like a bit like a crocodile, and it also had bony plates, or "scutes," along its back, probably a form of defense against predators. For an archosaur, the legs of Batrachotomus were relatively erect (though not quite as "locked in" as the limbs of true dinosaurs), which made it a fast and agile hunter.

05
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Desmatosuchus

desmatosuchus
Desmatosuchus. Wikimedia Commons

Like other plant-eating archosaurs, Desmatosuchus was hunted by the carnivorous reptiles of the Triassic period, and probably evolved its sharp spikes as a means of keeping these hungry predators at bay. See an in-depth profile of Desmatosuchus

06
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Effigia

effigia
Effigia. Wikimedia Commons

Effigia was discovered in the 1940's, then promptly forgotten for the next 50 years, until the paleontologist Sterling Nesbitt re-examined the original fossil and concluded that it was a crocodile-like archosaur rather than a true dinosaur. See an in-depth profile of Effigia

07
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Erythrosuchus

erythrosuchus
Erythrosuchus. Dmitry Bogdanov

Name:

Erythrosuchus (Greek for "red crocodile"); pronounced eh-RITH-roe-SOO-kuss

Habitat:

Woodlands of southern Africa

Historical Period:

Early Triassic (240 million years ago)

Size and Weight:

About 15 feet long and half a ton

Diet:

Meat

Distinguishing Characteristics:

Large size; long, massive head with numerous teeth

 

Discovered by the famous paleontologist Robert Broom in 1905, Erythrosuchus was one of the largest land-dwelling archosaurs of its time, with a long, massive, muscular head suited to chomping down on the fauna of the early Triassic period. Despite its name--which means "red crocodile"--Erythrosuchus was only distantly related to early crocodiles, and there's no way of determining the true color of its skin. Erythrosuchus probably preyed on the numerous therapsids (mammal-like reptiles) of its southern African habitat, including the cow-sized Kannemeyeria.

08
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Euparkeria

euparkeria
Euparkeria. Taena Doman

Name:

Euparkeria (Greek for "Parker's original lizard"); pronounced YOU-par-CARE-ee-ah

Habitat:

Woodlands of South Africa

Historical Period:

Middle Triassic (235 million years ago)

Size and Weight:

About two feet long and 5-10 pounds

Diet:

Meat

Distinguishing Characteristics:

Tiny size; long hind legs

 

If you saw a picture of Euparkeria without any reference to scale, you might be forgiven for thinking it was one of the most dreaded predators of the Triassic period. However, as fierce as this archosaur looked close up, in reality it was only about two feet long and 10 pounds, not much of a threat to the bigger animals of its day. Because of its light weight and long hind legs (compared to its front limbs), paleontologists believe Euparkeria was a relatively fast critter, flitting across the forest floor to chase down smaller prey and avoid being eaten by larger reptiles. It's even conceivable that this primitive reptile (which closely resembled, and was probably directly ancestral to, the earliest theropod dinosaurs) built up enough speed to skip across water!

09
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Hyperodapedon

hyperodapedon
Hyperodapedon. Wikimedia Commons

Name:

Hyperodapedon (Greek for "best pestle tooth"); pronounced HIGH-per-oh-DAP-eh-don

Habitat:

Swamps of South America, western Europe and central Asia

Historical Period:

Late Triassic (220 million years ago)

Size and Weight:

About four feet long and 10-20 pounds

Diet:

Plants

Distinguishing Characteristics:

Beaked snout; tube-shaped body; quadrupedal posture

 

Almost certainly not the brainiest reptile of the late Triassic period, Hyperodapedon was a particularly widespread type of archosaur-like reptile known as a "rhynchosaur." Fossils of this ancient, dog-sized beast have been unearthed all over what used to be the supercontinent Pangaea, including western Europe, South America and eastern Asia. As common (and small) as it was, Hyperodapedon was probably a primary food source for late Triassic predators like Saurosuchus; notably, it was one of the few rhynchosaurs to survive past the Permian/Triassic boundary.

10
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Lotosaurus

lotosaurus
Lotosaurus. Wikimedia Commons

Name:

Lotosaurus (Greek for "lotus lizard"); pronounced LOW-toe-SORE-us

Habitat:

Swamps of Asia

Historical Period:

Middle Triassic (240 million years ago)

Size and Weight:

About eight feet long and a few hundred pounds

Diet:

Plants

Distinguishing Characteristics:

Squat trunk; short sail on back

 

Not the most prepossessing of archosaurs, the family of reptiles that preceded the dinosaurs, the deceptively named Lotosaurus ("lotus lizard") was a squat, ungainly looking creature; it even had a squat sail, at least compared with showier and more distantly related reptiles like Dimetrodon and Edaphosaurus (which were actually pelycosaurs rather than archosaurs). Judging from its toothless jaws, Lotosaurus was a devoted vegetarian, though it's also possible that it crushed shellfish with its beaked snout (especially since it lived in the often-flooded lowlands of Asia).

11
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Malerisaurus

malerisaurus
Malerisaurus. Nobu Tamura

Name

Malerisaurus (after the Lower Maleri Formation in India); pronouned mah-LAIR-ee-SORE-us

Habitat

Swamps of North America and Eurasia

Historical Period

Late Triassic (230-210 million years ago)

Size and Weight

About three feet long and five pounds

Diet

Probably insects

Distinguishing Characteristics

Small size; slender build

 

It was a reptile-eat-reptile world during the late Triassic period, when mammals were still thin on the ground and birds had yet to evolve. Witness the discovery of Malerisaurus, the two type specimens of which were extracted from the stomachs of two fossilized phytosaurs (a breed of ancient reptiles that resembled crocodiles). The small, skittery Malerisaurus was probably an all-purpose archosaur, climbing trees and paddling across swamps, though it clearly wasn't agile enough to avoid larger predators. This close relative of Protorosaurus was once believed to be restricted to India, but the discovery of an additional species in Colorado indicates a much wider distribution.

12
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Marasuchus

marasuchus
Marasuchus. Wikimedia Commons

Name:

Marasuchus (Greek for "Mara crocodile"); pronounced MAH-rah-SOO-kuss

Habitat:

Woodlands of South America

Historical Period:

Middle Triassic (230 million years ago)

Size and Weight:

About 18 inches long and a few pounds

Diet:

Small animals

Distinguishing Characteristics:

Small size; long legs and tail

 

First things first: the genus names Marasuchus and Lagosuchus are often used interchangeably. The more popular of the two, Lagosuchus ("rabbit crocodile"), was "diagnosed" from scattered remains, while Marasuchus (named after the mara, a rabbit-like creature from South America) is much better attested. For all intents and purposes, Marasuchus and Lagosuchus are considered to be identical by paleontologists, though there's a slight chance that they may represent two species of the same genus.

Now that that's out of the way, Marasuchus was a very "advanced" archosaur, to the extent that it's possible to view this tiny reptile as counting among the first true dinosaurs. Marasuchus had a bipedal posture, with long legs, a long tail and much shorter arms, and it differed only in size (and a few odd anatomical details) from the very first theropod dinosaurs like Herrerasaurus. There's even a possibility that Marasuchus hopped like a rabbit (or a mara), but the evidence for this is inconclusive.

13
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Ornithosuchus

ornithosuchus
Ornithosuchus. Sergey Krasovskiy

Name:

Ornithosuchus (Greek for "bird crocodile"); pronounced ORN-ith-oh-SOO-kuss

Habitat:

Swamps of western Europe

Historical Period:

Late Triassic (210 million years ago)

Size and Weight:

About 12 feet long and a few hundred pounds

Diet:

Small animals

Distinguishing Characteristics:

Long tail; bipedal posture; shorter front than hind limbs

 

As if the name Ornithosuchus ("bird crocodile") weren't deceptive enough, this ancient reptile was once thought to be a true dinosaur, until further analysis showed that it belonged in the archosaur camp (to be fair, though, the archosaurs of the Triassic period, when Ornithosuchus lived, did evolve into the first dinosaurs). Ornithosuchus had a mix of characteristics common to both early crocodiles and dinosaurs; for example, it was capable of rearing up on its hind legs, and it had a long, powerful, crocodile-like snout. As for how that "bird" reference crept into its name, well, that's a bit of a mystery!

14
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Poposaurus

poposaurus
Poposaurus. Wikimedia Commons

Name:

Poposaurus; pronounced POP-oh-SORE-us

Habitat:

Woodlands of western North America

Historical Period:

Late Triassic (210 million years ago)

Size and Weight:

About 5-10 feet long and a few hundred pounds

Diet:

Small animals

Distinguishing Characteristics:

Low-slung body; longer hind than front legs

 

As obscure as it is, Poposaurus has given its name to a sub-family of archosaurs known (you guessed it) as "poposaurs," the most famous member of which is probably Effigia. Poposaurus was a low-slung, crocodile-like reptile that preyed on the small animals of late Triassic North America; it was very similar to early theropods like Coelophysis, but betrayed some distinctly primitive (if obscure) anatomical traits that have consigned it firmly to the archosaur camp. In light of its longer hind than front limbs, it may have run occasionally on two legs.

15
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Postosuchus

postosuchus
Postosuchus. Wikimedia Commons

Name:

Postosuchus (Greek for "Post crocodile"); pronounced POST-oh-SOO-kuss

Habitat:

Woodlands of North America

Historical Period:

Middle-Late Triassic (230-200 million years ago)

Size and Weight:

About 10-15 feet long and 1,000-1,500 pounds

Diet:

Meat

Distinguishing Characteristics:

Large size; tyrannosaur-like head

 

Before we discuss Postosuchus, a short primer in evolution is in order. Starting in the middle Triassic period--about 230 million years ago--the prehistoric reptiles known as the archosaurs ("ruling lizards") began to evolve in three separate directions: pterosaurs, prehistoric crocodiles and the first dinosaurs. In fact, for tens of millions of years, large, dinosaur-like archosaurs coexisted with two-legged crocodiles, which themselves bore an uncanny resemblance to the first true theropod dinosaurs--and if you think this sounds confusing, just place yourself in the shoes of a paleontologist trying to sort out the mess.

A true archosaur--despite its marked resemblance to the large theropod dinosaurs of the Jurassic period, and also despite the fact that the last part of its name is Greek for "crocodile"--Postosuchus was the apex predator of middle to late Triassic North America. In fact, when its fossils were first discovered, Postosuchus was assumed to be a theropod dinosaur, but closer analysis of its ankle bones (not to mention the very un-dinosaur-like plates along its back) revealed its true place on the reptile family tree. This large "rauisuchian," as it's known, preyed on the prehistoric crocodiles and small dinosaurs it so much resembled, and was doubtless preyed on by them in return (assuming they were smart enough to team up for the kill!)

16
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Prestosuchus

prestosuchus
Prestosuchus. Wikimedia Commons

To judge by its sleek trunk and narrow, sharp-toothed snout, Prestosuchus was a fearsome archosaur of Triassic South America, feasting on small reptiles, amphibians, and its fellow "ruling lizards." See an in-depth profile of Prestosuchus

17
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Proterosuchus

proterosuchus
Proterosuchus. Wikimedia Commons

Name:

Proterosuchus (Greek for "early crocodile"); pronounced PRO-teh-roe-SOO-kuss

Habitat:

Riverbanks of Asia and South Africa

Historical Period:

Early Triassic (250 million years ago)

Size and Weight:

About seven feet long and 100-200 pounds

Diet:

Fish and small reptiles

Distinguishing Characteristics:

Long snout; sprawled feet; crocodile-like posture

 

Once known as Chasmatosaurus, Proterosuchus was one of the oldest known archosaurs, the reptilian ancestors of dinosaurs characterized by their splay-footed, rather than upright, postures. Dating to the early Triassic period, about 250 million years ago, the 200-pound Chasmatosaurus was already one of the largest land-dwelling animals of its time (with a couple of exceptions, gigantic reptiles didn't come into style until the sauropods and tyrannosaurs of the later Jurassic and Cretaceous periods). Like modern crocodiles, to which it was distantly related, Proterosuchus was probably an ambush predator, lurking by lakes and riverbeds and snapping up slow-moving prey (one candidate being the ubiquitous Lystrosaurus).

18
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Protorosaurus

protorosaurus
Protorosaurus. Wikimedia Commons

Name:

Protorosaurus (Greek for "first lizard"); pronounced PRO-tore-oh-SORE-us

Habitat:

Swamps of western Europe

Historical Period:

Late Permian (260 million years ago)

Size and Weight:

About six feet long and 10-20 pounds

Diet:

Probably insects

Distinguishing Characteristics:

Long neck; low-slung build

 

Not a whole lot is known about Protorosaurus, partial fossils of which have been found in late Permian sediments in England and Germany. This was a fairly slender, low-slung reptile that probably fed on insects, and was ancestral to the more robust archosaurs that dominated the first half of the Triassic period and gradually evolved into the first true dinosaurs. (By the way, Protorosaurus was the original name of the ceratopsian dinosaur Chasmosaurus, until the famous paleontologist Lawrence M. Lambe discovered that it had been assigned to this obscure archosaur.)

19
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Saurosuchus

saurosuchus
Saurosuchus. Wikimedia Commons

Name:

Saurosuchus (Greek for "lizard crocodile"); pronounced SORE-oh-SOO-kuss

Habitat:

Swamps of South America

Historical Period:

Middle Triassic (230 million years ago)

Size and Weight:

About 20 feet long and 500-1,000 pounds

Diet:

Meat

Distinguishing Characteristics:

Large size; slender trunk; short legs

 

"Saurosuchus" is an impressive, but not entirely accurate, name. First off, its Greek translation, "lizard crocodile," is a bit redundant, since all crocodiles are lizards. And second, Saurosuchus wasn't even a true crocodile, but a type of archosaur known as a rauisuchian (you have to admit, though, "crocodile" is a lot easier to pronounce). Nomenclature issues aside, Saurosuchus was probably one of the apex predators of late Triassic South America, a speedy, low-slung carnivore that would have had little trouble chasing down the smaller archosaurs of its ecosystem. Among this creature's notable features were its differently shaped teeth, which kept regenerating throughout its lifetime as old ones succumbed to wear or injury.

20
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Sharovipteryx

sharovipteryx
Sharovipteryx. Vladimir Nikolov

Name:

Sharovipteryx (Greek for "Sharov's wing"); pronounced SHA-roe-VIP-teh-rix

Habitat:

Woodlands of central Asia

Historical Period:

Late Triassic (230 million years ago)

Size and Weight:

About one foot long and one pound

Diet:

Insects

Distinguishing Characteristics:

Small size; long tail; flaps of skin along limbs

 

Given its overall appearance--especially its long tail and the flaps of skin along its hind and (possibly) front limbs--it would be tempting to assume that the late Triassic Sharovipteryx lay at the root of pterosaur evolution. However, this is far from a universally accepted conclusion; for example, this archosaur wasn't capable of powered flight, merely gliding from tree to tree, an adaptation that has arisen numerous times in the animal kingdom (and not only among reptiles, as witness the flying squirrel). This tiny creature also seems to have spent a fair amount of its time walking, judging by its relatively long legs.

21
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Silesaurus

silesaurus
Silesaurus. Wikimedia Commons

Name:

Silesaurus (Greek for "Silesian lizard"); pronounced SIGH-leh-SORE-us

Habitat:

Woodlands of central Europe

Historical Period:

Late Triassic (230 million years ago)

Size and Weight:

About six feet long and 30-40 pounds

Diet:

Plants

Distinguishing Characteristics:

Small size; beaked snout; bipedal posture

 

Silesaurus appeared on the scene suddenly in 2003, after a whopping 20 more-or-less complete fossils were discovered in a Polish lakebed. From a dinosaur perspective, this is one of those "almost, but not quite" reptiles, classified by most paleontologists as a dinosaur-like archosaur (or "dinosauriform") rather than a true early dinosaur, which breed appeared toward the middle Triassic period. However, some scientists place Silesaurus at the root of the ornithischian family tree, one of the branches of which includes the early ornithopods Silesaurus so resembled.

22
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Smok

smok
Smok. Wikimedia Commons

Some paleontologists believe the Triassic archosaur Smok was a "rauisuchian," the problem being that other members of this family were an order of magnitude smaller, while others peg it as a "crurotarsan," and thus more closely related to crocodiles than to dinosaurs. See an in-depth profile of Smok

23
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Stagonolepis

stagonolepis
Stagonolepis. Wikimedia Commons

Name:

Stagonolepis (Greek for "ornamented scale"); pronounced STAG-oh-no-LEP-iss

Habitat:

Forests of Western Europe

Historical Period:

Middle Triassic (235-225 million years ago)

Size and Weight:

About eight feet long and 400 pounds

Diet:

Plants

Distinguishing Characteristics:

Unusually small head; body covered by bony plates

 

A type of archosaur--the family of terrestrial reptiles that preceded, and evolved into, the first dinosaurs--Stagonolepis cut a very crocodile-like profile, with two main differences: its teeth were peglike rather than sharp, and it subsisted on plants rather than meat. Clearly, the bony plates lining this reptile's back and belly were meant to ward off the carnivorous archosaurs and therapsids ("mammal-like reptiles") of its middle Triassic habitat. (In case you find the image of a vegetarian crocodile hilarious, bear in mind that Stagonolepis was far from the only salad-eating croc of the Triassic period!)

24
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Tanystropheus

tanystropheus
Tanystropheus. Wikimedia Commons

Why did Tanystropheus have such a cartoonishly long neck? This is still a matter of some debate, but most paleontologists believe that this late Triassic archosaur perched alongside riverbeds and shorelines and used its narrow neck as a kind of fishing line. See an in-depth profile of Tanystropheus

25
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Ticinosuchus

ticinosuchus
Ticinosuchus. Wikimedia Commons

Name:

Ticinosuchus (Greek for "Tessin River crocodile"); pronounced tih-SEEN-oh-SOO-kuss

Habitat:

Swamps of western Europe

Historical Period:

Middle Triassic (240 million years ago)

Size and Weight:

About eight feet long and 100 pounds

Diet:

Small animals

Distinguishing Characteristics:

Sleek body; quadrupedal posture; armored plates along back

 

Ticinosuchus was one of the smallest members of the family of predatory archosaurs known as rauisuchians, other members of which included the North American Arizonasaurus and the South American Saurosuchus. This sleek, dog-sized creature prowled the swamps of middle Triassic western Europe, feasting on smaller reptiles (and possible fish and shellfish). Judging by its fossil remains, Ticinosuchus appears to have been exceptionally well-muscled, with a heel structure that lent itself to sudden leaps on unsuspecting prey.

26
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Trilophosaurus

trilophosaurus
Trilophosaurus. Wikimedia Commons

Name:

Trilophosaurus (Greek for "three-crested lizard"); pronounced TRY-low-foe-SORE-us

Habitat:

Swamps of western North America

Historical Period:

Late Triassic (220 million years ago)

Size and Weight:

About eight feet long and 15-20 pounds

Diet:

Plants

Distinguishing Characteristics:

Long tail; splayed legs; toothless jaws

 

Although its sounds similar, the late Triassic Trilophosaurus was literally eons away from its more famous dinosaur relatives, Monolophosaurus and Dilophosaurus, which lived tens of millions of years later. This archosaur (which was named after the three small crests on its skull) has proven difficult to classify, with some experts proposing its assignment to the family of prehistoric reptiles known as rhynchosaurs, best typified by Hyperodapedon. There's some speculation that Trilophosaurus may have climbed trees in search of food, though the evidence for this is slim at best.

27
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Turfanosuchus

turfanosuchus
Turfanosuchus. Nobu Tamura

Name

Turfanosuchus (Greek for "Turfan crocodile"); pronounced TUR-fan-oh-SOO-kuss

Habitat

Plains of eastern Asia

Historical Period

Middle Triassic (235 million years ago)

Size and Weight

About three feet long and 5-10 pounds

Diet

Unknown

Distinguishing Characteristics

Slender build; long neck

 

Small, skittering archosaurs--the predecessors of dinosaurs, pterosaurs and crocodiles--were thick on the ground during the middle Triassic period, about 235 million years ago. As a result, archosaur classification can be a tricky business, as witness Turfanosuchus, which was initially pegged as a close relative of Euparkeria but was later assigned to a family (the aetosaurs) that made it closer kin to prehistoric reptiles like Stagonolepis and Desmatosuchus. Despite the "-suchus" at the end of its name, Turfanosuchus was not a true crocodile, lying completely outside the "crurotarsi" family to which ancestral crocodiles belonged.

28
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Vancleavea

vancleavea
Vancleavea. Wikimedia Commons

Name:

Vancleavea (after paleontologist Philip van Cleave); pronounced VAN-clay-AH-vee-ah

Habitat:

Swamps of North America

Historical Period:

Late Triassic (220-200 million years ago)

Size and Weight:

About three feet long and 10 pounds

Diet:

Probably fish

Distinguishing Characteristics:

Long, eel-like body; armor plating; prominent fangs

 

When most people think about archosaurs--the diverse family of reptiles that preceded the dinosaurs--they picture either early crocodiles or swift, two-legged scramblers closely resembling basal theropods like Herrerasaurus. Vancleavea doesn't fit comfortably into either of these categories; this archosaur looked like a cross between an eel and an early tetrapod, with its long, sleek body and its prominent rear fin (we won't even mention its bizarre armor plating and prominent, cat-like fangs). As you might guess, no one is quite sure what to make of this semi-aquatic reptile, or how it was related to the more "classic" archosaurs of late Triassic North America.

29
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Xilousuchus

xilousuchus
Xilousuchus. Rachel Simon

The significance of the recently discovered Xilousuchus is that it dates to the very beginning of the Triassic period, about 250 million years ago, and it also seems to have been one of the earliest crocodilian archosaurs. See an in-depth profile of Xilousuchus