Prehistoric Amphibian Pictures and Profiles

01
of 34

Meet the Amphibians of the Paleozoic and Cenozoic Eras

platyhystrix
Platyhystrix. Nobu Tamura

During the Carboniferous and Permian periods, prehistoric amphibians, and not reptiles, were the apex predators of the earth's continents. On the following slides, you'll find pictures and detailed profiles of over 30 prehistoric amphibians, ranging from Amphibamus to Westlothiana.

02
of 34

Amphibamus

amphibamus
Amphibamus. Alain Beneteau

Name:

Amphibamus (Greek for "equal legs"); pronounced AM-fih-BAY-muss

Habitat:

Swamps of North America and western Europe

Historical Period:

Late Carboniferous (300 million years ago)

Size and Weight:

About six inches long and a few ounces

Diet:

Probably insects

Distinguishing Characteristics:

Small size; salamander-like body

 

It's often the case that the genus that lends its name to a family of creatures is the least understood member of that family. In the case of Amphibamus, the story is a bit more complicated; the word "amphibian" was already in wide currency when the famous paleontologist Edward Drinker Cope bestowed this name on a fossil dating from the late Carboniferous period. Amphibamus seems to have been a much smaller version of the larger, crocodile-like "temnospondyl" amphibians (such as Eryops and Mastodonsaurus) that dominated terrestrial life at this time, but it might also have represented the point in evolutionary history when frogs and salamanders split off from the amphibian family tree. Whatever the case, Amphibamus was a small, inoffensive creature, only slightly more sophisticated than its recent tetrapod ancestors.

 

03
of 34

Archegosaurus

archegosaurus
Archegosaurus (Nobu Tamura).

Name:

Archegosaurus (Greek for "founding lizard"); pronounced ARE-keh-go-SORE-us

Habitat:

Swamps of western Europe

Historical Period:

Late Carboniferous-Early Permian (310-300 million years ago)

Size and Weight:

About 10 feet long and a few hundred pounds

Diet:

Fish

Distinguishing Characteristics:

Stubby legs; crocodile-like build

 

Considering how many complete and partial skulls of Archegosaurus have been discovered--almost 200, all of them from the same fossil site in Germany--this is still a relatively mysterious prehistoric amphibian. To judge from reconstructions, Archegosaurus was a large, crocodile-like carnivore that prowled the swamps of western Europe, feasting on small fish and (perhaps) smaller amphibians and tetrapods. By the way, there are a handful of even more obscure amphibians under the umbrella "archegosauridae," one of which bears the amusing name Collidosuchus.

 

 

04
of 34

Beelzebufo (Devil Frog)

beelzebufo
Beelzebufo (National Academy of Sciences).

The Cretaceous Beelzebufo was the biggest frog that ever lived, weighing about 10 pounds and measuring a foot and a half from head to tail. With ts unusually wide mouth, it probably feasted on the occasional baby dinosaur as well as its usual diet of large insects. See an in-depth profile of Beelzebufo

05
of 34

Branchiosaurus

branchiosaurus
Branchiosaurus. Nobu Tamura

Name:

Branchiosaurus (Greek for "gill lizard"); pronounced BRANK-ee-oh-SORE-us

Habitat:

Swamps of central Europe

Historical Period:

Late Carboniferous-Early Permian (310-290 million years ago)

Size and Weight:

About six inches long and a few ounces

Diet:

Probably insects

Distinguishing Characteristics:

Small size; oversized head; splayed limbs

 

It's amazing what a difference a single letter can make. Brachiosaurus was one of the largest dinosaurs ever to roam the earth, but Branchiosaurus (which lived 150 million years earlier) was one of the smallest of all the prehistoric amphibians. This six-inch-long creature was once thought to have represented the larval stage of larger "temnospondyl" amphibians (like Eryops), but an increasing number of paleontologists believe that it deserves its own genus. Whatever the case, Branchiosaurus possessed the anatomical features, in miniature, of its larger temonspondyl cousins, most notably an oversized, roughly triangular head.

 

06
of 34

Cacops

cacops
Cacops (Field Museum of Natural History).

Name:

Cacops (Greek for "blind face"); pronounced CAY-cops

Habitat:

Swamps of North America

Historical Period:

Early Permian (290 million years ago)

Size and Weight:

About 18 inches long and a few pounds

Diet:

Insects and small animals

Distinguishing Characteristics:

Squat trunk; thick legs; bony plates along back

 

One of the more reptile-like of the earliest amphibians, Cacops was a squat, cat-sized creature possessing stubby legs, a short tail, and a lightly armored back. There's some evidence that this prehistoric amphibian had relatively advanced eardrums (a necessary adaptation for life on land), and there's also some speculation that Cacops may have hunted at night, to avoid the larger predators of its early Permian North American habitat (as well as the parching heat of the sun).

 

07
of 34

Colosteus

colosteus
Colosteus (Nobu Tamura).

Name

Colosteus; pronounced coe-LOSS-tee-uss

Habitat

Lakes and rivers of North America

Historical Period

Late Carboniferous (305 million years ago)

Size and Weight

About three feet long and one pound

Diet

Small marine organisms

Distinguishing Characteristics

Long, slim body; stubby legs

 

Hundreds of millions of years ago, during the Carboniferous period, it could be very difficult to distinguish between advanced lobe-finned fish, the first, land-venturing tetrapods, and the most primitive amphibians. Colosteus, the remains of which are plentiful in the state of Ohio, is often described as a tetrapod, but most paleontologists are more comfortable classifying this creature as a "colosteid" amphibian. Suffice it to say that Colosteus was about three feet long, with extremely stunted (which is not to say useless) legs, and a flat, pointy head equipped with two not-very-threatening tusks. It probably spent most of its time in the water, where it fed on small marine animals.

08
of 34

Cyclotosaurus

cyclotosaurus
Cyclotosaurus. Nobu Tamura

Name:

Cyclotosaurus (Greek for "round-eared lizard"); pronounced SIE-clo-toe-SORE-us

Habitat:

Swamps of Europe, Greenland and Asia

Historical Period:

Middle-Late Triassic (225-200 million years ago)

Size and Weight:

About 10 to 15 feet long and 200 to 500 pounds

Diet:

Marine organisms

Distinguishing Characteristics:

Large size; unusually large, flat head

 

The golden age of amphibians was ushered in by the "temnospondyls," a family of massive swamp-dwellers typified by the amusingly named Mastodonsaurus. The remains of Cyclotosaurus, a close Mastodonsaurus relative, have been discovered across an unusually wide geographical span, ranging from western Europe to Greenland to Thailand, and as far as we know it was one of the last of the temnospondyls. (Amphibians started to dwindle in population by the start of the Jurassic period, a downward spiral that continues today.)

As with Mastodonsaurus, the most notable feature of Cyclotosaurus was its large, flat, alligator-like head, which looked vaguely whimsical when attached to its relatively puny amphibian trunk. Like other amphibians of its day, Cyclotosaurus probably made its living by prowling the shoreline snapping up various marine organisms (fish, mollusks, etc.) as well as the occasional small lizard or mammal.

 

09
of 34

Diplocaulus

diplocaulus
Diplocaulus (Wikimedia Commons).

Name:

Diplocaulus (Greek for "double stalk"); pronounced DIP-low-CALL-us

Habitat:

Swamps of North America

Historical Period:

Late Permian (260-250 million years ago)

Size and Weight:

About three feet long and 5-10 pounds

Diet:

Fish

Distinguishing Characteristics:

Small size; large, boomerang-shaped skull

 

Diplocaulus is one of those ancient amphibians that looks like it was put together wrong out of the box: a relatively flat, unremarkable trunk attached to a hugely oversized head ornamented with boomerang-shaped bony protrusions on each side. Why did Diplocaulus have such an unusual skull? There are two possible explanations: its V-shaped noggin may have helped this amphibian to navigate strong ocean or river currents, and/or its huge head may have made it unappetizing to the larger marine predators of the late Permian period, which spurned it for more easily swallowed prey.

 

10
of 34

Eocaecilia

eocaecilia
Eocaecilia. Nobu Tamura

Name:

Eocaecilia (Greek for "dawn caecilian"); pronounced EE-oh-say-SILL-yah

Habitat:

Swamps of North America

Historical Period:

Early Jurassic (200 million years ago)

Size and Weight:

About six inches long and one ounce

Diet:

Insects

Distinguishing Characteristics:

Worm-like body; vestigial legs

 

When asked to name the three main families of amphibians, most people will easily come up with frogs and salamanders, but not many will think of caecilians--small, earthworm-like creatures that are mostly confined to dense, hot, tropical rain forests. Eocaecilia is the earliest caecilian yet identified in the fossil record; in fact, this genus was so "basal" that it still retained small, vestigial legs (much like the earliest prehistoric snakes of the Cretaceous period). As to which (fully legged) prehistoric amphibian Eocaecilia evolved from, that remains a mystery.

 

11
of 34

Eogyrinus

eogyrinus
Eogyrinus. Nobu Tamura

Name:

Eogyrinus (Greek for "dawn tadpole"); pronounced EE-oh-jih-RYE-nuss

Habitat:

Swamps of western Europe

Historical Period:

Late Carboniferous (310 million years ago)

Size and Weight:

About 15 feet long and 100-200 pounds

Diet:

Fish

Distinguishing Characteristics:

Large size; stubby legs; long tail

 

If you saw Eogyrinus without your glasses on, you might have mistaken this prehistoric amphibian for a good-sized snake; like a snake, it was covered with scales (a direct inheritance from its fish ancestors), which helped protect it as it twisted its way through the swamps of the late Carboniferous period. Eogyrinus did have a set of short, stumpy legs, and this early amphibian seems to have pursued a semi-aquatic, crocodile-like lifestyle, snapping up small fish from shallow waters.

 

12
of 34

Eryops

eryops
Eryops. Wikimedia Commons

Name:

Eryops (Greek for "long face"); pronounced EH-ree-ops

Habitat:

Swamps of North America and western Europe

Historical Period:

Early Permian (295 million years ago)

Size and Weight:

About six feet long and 200 pounds

Diet:

Fish

Distinguishing Characteristics:

Broad, flat skull; crocodile-like body

 

One of the best-known prehistoric amphibians of the early Permian period, Eryops had the broad outlines of a crocodile, with its low-slung trunk, splayed legs and massive head. One of the biggest land animals of its time, Eryops wasn't all that tremendous compared to the true reptiles that followed it, only about 6 feet long and 200 pounds. It probably hunted like the crocodiles it resembled, floating just below the surface of shallow swamps and snapping up any fish that swam too near.

 

13
of 34

Fedexia

fedexia
Fedexia (Carnegie Museum of Natural History).

Name:

Fedexia (after the company Federal Express); pronounced fed-EX-ee-ah

Habitat:

Swamps of North America

Historical Period:

Late Carboniferous (300 million years ago)

Size and Weight:

About two feet long and 5-10 pounds

Diet:

Small animals

Distinguishing Characteristics:

Moderate size; salamander-like appearance

 

Fedexia wasn't named under the rubric of some corporate sponsorship program; rather, the fossil of this 300-million-year-old amphibian was unearthed near the Federal Express Ground headquarters at Pittsburgh International Airport. Other than its distinctive name, though, Fedexia seems to have been a plain-vanilla type of prehistoric amphibian, vaguely reminiscent of an overgrown salamander and (judging by the size and shape of its teeth) subsisting on the small bugs and land animals of the late Carboniferous period.

 

14
of 34

Gastric-Brooding Frog

gastric-brooding frog
The Gastric-Brooding Frog. Wikimedia Commons

As its name implies, the Gastric-Brooding Frog had an odd method for gestating its young: the females swallowed their newly fertilized eggs, which developed in the safety of their stomachs before the tadpoles climbed out via the esophagus. See an in-depth profile of the Gastric-Brooding Frog

15
of 34

Gerobatrachus

gerobatrachus
Gerobatrachus, the Frogamander (Wikimedia Commons).

Name:

Gerobatrachus (Greek for "ancient frog"); pronounced GEH-roe-bah-TRACK-us

Habitat:

Swamps of North America

Historical Period:

Late Permian (290 million years ago)

Size and Weight:

About five inches long and a few ounces

Diet:

Insects

Distinguishing Characteristics:

Frog-like head; salamander-like body

 

It's amazing how a single, incomplete fossil of a 290-million-year-old creature can shake up the world of paleontology. When it made its debut in 2008, Gerobatrachus was widely touted as a "frogamander," the last common ancestor of both frogs and salamanders, the two most populous families of modern amphibians. (To be fair, the large, frog-like skull of Gerobatrachus, combined with its relatively slender, salamander-like body, would set any scientist to thinking.) What this implies is that frogs and salamanders went their separate ways millions of years after Gerobatrachus' time, which would vastly accelerate the known rate of amphibian evolution.

 

16
of 34

Gerrothorax

gerrothorax
Gerrothorax (Wikimedia Commons).

Name:

Gerrothorax (Greek for "plated chest"); pronounced GEH-roe-THOR-ax

Habitat:

Swamps of the northern Atlantic

Historical Period:

Late Triassic (210 million years ago)

Size and Weight:

About three feet long and 5-10 pounds

Diet:

Fish

Distinguishing Characteristics:

External gills; football-shaped head

 

One of the most distinctive of all prehistoric amphibians, Gerrothorax possessed a flat, football-shaped head with eyes fixed on top, as well as external, feathery gills jutting out from its neck. These adaptations are a sure clue that Gerrothorax spent most (if not all) of its time in the water, and that this amphibian may have had a unique hunting strategy, hovering on the surface of swamps and simply waiting as unsuspecting fish swam into its broad mouth. Probably as a form of protection against other marine predators, the late Triassic Gerrothorax also had lightly armored skin along the top and bottom of its body.

 

17
of 34

The Golden Toad

golden toad
The Golden Toad. U.S. Fish and Wildlife Service

Last seen in the wild in 1989--and presumed to be extinct, unless some individuals are miraculously discovered elsewhere in Costa Rica--the Golden Toad has become the poster genus for the mysterious worldwide decline in amphibian populations. See an in-depth profile of the Golden Toad

18
of 34

Karaurus

karaurus
Karaurus (Wikimedia Commons).

Name:

Karaurus; pronounced kah-ROAR-us

Habitat:

Swamps of central Asia

Historical Period:

Late Jurassic (150 million years ago)

Size and Weight:

About eight inches long and a few ounces

Diet:

Insects

Distinguishing Characteristics:

Small size; triangular head with upward-pointing eyes

 

Considered by paleontologists to be the first true salamander (or at least, the first true salamander the fossils of which have been discovered), Karaurus appeared relatively late in amphibian evolution, toward the end of the Jurassic period. It's possible that future fossil finds will fill in the gaps concerning the development of this tiny creature from its larger, scarier ancestors of the Permian and Triassic periods.

 

19
of 34

Koolasuchus

koolasuchus
Koolasuchus. Wikimedia Commons

Name:

Koolasuchus (Greek for "Kool's crocodile"); pronounced COOL-ah-SOO-kuss

Habitat:

Swamps of Australia

Historical Period:

Middle Cretaceous (110-100 million years ago)

Size and Weight:

About 15 feet long and 500 pounds

Diet:

Fish and shellfish

Distinguishing Characteristics:

Large size; broad, flat head

 

The most remarkable thing about Koolasuchus is when this Australian amphibian lived: the middle Cretaceous period, or about a hundred million years after its more famous "temnospondyl" ancestors like Mastodonsaurus had gone extinct in the northern hemisphere. Koolasuchus adhered to the basic, crocodile-like temnospondyl body plan--oversized head and long trunk with squat limbs--and it seems to have subsisted on both fish and shellfish. How did Koolasuchus prosper so long after its northern relatives vanished off the face of the earth? Perhaps the cool climate of Cretaceous Australia had something to do with it, allowing Koolasuchus to hibernate for long periods of time and avoid predation.

 

20
of 34

Mastodonsaurus

mastodonsaurus
Mastodonsaurus. Dmitri Bogdanov

Name:

Mastodonsaurus (Greek for "nipple-toothed lizard"); pronounces MASS-toe-don-SORE-us

Habitat:

Swamps of western Europe

Historical Period:

Late Triassic (210 million years ago)

Size and Weight:

About 20 feet long and 500-1,000 pounds

Diet:

Fish and small animals

Distinguishing Characteristics:

Huge, flat head; stubby legs

 

Granted, "Mastodonsaurus" is a cool-sounding name, but you might be less impressed if you knew that "Mastodon" is Greek for "nipple-tooth" (and yes, that applies to the Ice Age Mastodon as well). Now that that's out of the way, Mastodonsaurus was one of the biggest prehistoric amphibians that ever lived, a bizarrely proportioned creature with a huge, elongated, flattened head that was almost half the length of its entire body. Considering its large, ungainly trunk and stubby legs, it's unclear if the late Triassic Mastodonsaurus spent all of its time in the water, or ventured occasionally onto dry land for a tasty snack.

 

21
of 34

Megalocephalus

megalocephalus
Megalocephalus. Dmitri Bogdanov

Name:

Megalocephalus (Greek for "giant head"); pronounced MEG-ah-low-SEFF-ah-luss

Habitat:

Swamps of Europe and North America

Historical Period:

Late Carboniferous (300 million years ago)

Size and Weight:

About six feet long and 50-75 pounds

Diet:

Small animals

Distinguishing Characteristics:

Large skull; crocodile-like build

 

As impressive as its name (Greek for "giant head") is, Megalocephalus remains a relatively obscure prehistoric amphibian of the late Carboniferous period; pretty much all we know about it is that it had a, well, giant head. Still, paleontologists can infer that Megalocephalus possessed a crocodile-like build, and it probably behaved like a prehistoric crocodile as well, prowling lakeshores and riverbeds on its stubby legs and snapping up any smaller creatures wandering nearby.

 

22
of 34

Metoposaurus

metoposaurus
Metoposaurus (Wikimedia Commons).

Name:

Metoposaurus (Greek for "front lizard"); pronounced meh-TOE-poe-SORE-us

Habitat:

Swamps of North America and western Europe

Historical Period:

Late Triassic (220 million years ago)

Size and Weight:

About 10 feet long and 1,000 pounds

Diet:

Fish

Distinguishing Characteristics:

Broad, flat skull; splayed legs; long tail

 

During long stretches of the Carboniferous and Permian periods, giant amphibians were the dominant land animals on earth, but their long reign came to an end by the end of the Triassic period, 200 million years ago. A typical example of the breed was Metoposaurus, a crocodile-like predator possessing a bizarrely oversized, flat head and a long, fishlike tail. Given its quadrupedal posture (at least when on land) and relatively weak limbs, Metoposaurus wouldn't have posed much of a threat to the earliest dinosaurs with which it coexisted, feasting instead on fish in the shallow swamps and lakes of North America and western Europe (and probably other parts of the world as well).

With its strange anatomy, Metoposaurus must clearly have pursued a specialized lifestyle, the exact details of which are still a source of controversy. One theory has it that this half-ton amphibian swam close to the surface of shallow lakes, then, as these bodies of water dried up, burrowed into the moist soil and bided its time until the return of the wet season. (The trouble with this hypothesis is that most other burrowing animals of the late Triassic period were a fraction of Metoposaurus' size.) As big as it was, too, Metoposaurus wouldn't have been immune to predation, and may have been targeted by phytosaurs, a family of crocodile-like reptiles that also led a semiaquatic existence.

 

23
of 34

Microbrachis

microbrachis
Microbrachis. Nobu Tamura

Name:

Microbrachis (Greek for "little branch"); pronounced MY-crow-BRACK-iss

Habitat:

Swamps of eastern Europe

Historical Period:

Early Permian (300 million years ago)

Size and Weight:

About one foot long and less than a pound

Diet:

Plankton and small aquatic animals

Distinguishing Characteristics:

Small size; salamander-like body

 

Microbrachis is the most notable genus of the family of prehistoric amphibians known as "microsaurs," which were characterized by, you guessed it, their tiny size. For an amphibian, Microbrachis retained many characteristics of its fish and tetrapod ancestors, such as its slender, eel-like body and puny limbs. Judging from its anatomy, Microbrachis seems to have spent most, if not all, of its time immersed in the swamps that covered large areas of Europe during the early Permian period.

 

24
of 34

Ophiderpeton

ophiderpeton
Ophiderpeton (Alain Beneteau).

Name:

Ophiderpeton (Greek for "snake amphibian"); pronounced OH-fee-DUR-pet-on

Habitat:

Swamps of North America and western Europe

Historical Period:

Carboniferous (360-300 million years ago)

Size and Weight:

About two feet long and less than a pound

Diet:

Insects

Distinguishing Characteristics:

Large number of vertebrae; snake-like appearance

 

If we didn't know that snakes evolved tens of millions of years later, it would be easy to mistake Ophiderpeton for one of these hissing, coiling creatures. A prehistoric amphibian rather than a true reptile, Ophiderpeton and its "aistopod" relatives seem to have branched off from their fellow amphibians at a very early date (about 360 million years ago), and have left no living descendants. This genus was characterized by its elongated backbone (which consisted of over 200 vertebrae) and its blunt skull with forward-facing eyes, an adaptation that helped it home in on the small insects of its Carboniferous habitat.

 

25
of 34

Pelorocephalus

pelorocephalus
Pelorocephalus (Wikimedia Commons).

Name:

Pelorocephalus (Greek for "monstrous head"); pronounced PELL-or-oh-SEFF-ah-luss

Habitat:

Swamps of South America

Historical Period:

Late Triassic (230 million years ago)

Size and Weight:

About three feet long and a few pounds

Diet:

Fish

Distinguishing Characteristics:

Short limbs; large, flat head

 

Despite its name--Greek for "monstrous head"--Pelorocephalus was actually fairly small, but at three feet long this was still one of the biggest prehistoric amphibians of late Triassic South America (at a time when this region was spawning the very first dinosaurs). The true importance of Pelorocephalus is that it was a "chigutisaur," one of the few amphibian families to survive the end-Triassic extinction and persist into the Jurassic and Cretaceous periods; its later Mesozoic descendants grew to impressively crocodile-like proportions.

 

26
of 34

Phlegethontia

phlegethontia
Phlegethontia. Wikimedia Commons

Name:

Phlegethontia; pronounced FLEG-eh-THON-tee-ah

Habitat:

Swamps of North America and western Europe

Historical Period:

Late Carboniferous-Early Permian (300 million years ago)

Size and Weight:

About three feet long and one pound

Diet:

Small animals

Distinguishing Characteristics:

Long, snake-like body; openings in skull

 

To the untrained eye, the snake-like prehistoric amphibian Phlegethontia might seem indistinguishable from Ophiderpeton, which also resembled a small (albeit slimy) snake. However, the late Carboniferous Phlegethontia set itself apart from the amphibian pack not only with its lack of limbs, but with its unusual, lightweight skull, which was similar to those of modern snakes (a feature most likely explained by convergent evolution).

 

27
of 34

Platyhystrix

platyhystrix
Platyhystrix (Nobu Tamura).

Name:

Platyhystrix (Greek for "flat porcupine"); pronounced PLATT-ee-HISS-trix

Habitat:

Swamps of North America

Historical Period:

Early Permian (290 million years ago)

Size and Weight:

About three feet long and 5-10 pounds

Diet:

Small animals

Distinguishing Characteristics:

Small size; sail on back

 

An otherwise unremarkable prehistoric amphibian of the early Permian period, Platyhystrix stood out because of the Dimetrodon-like sail on its back, which (as with other sailed creatures) probably served double duty as a temperature-regulation device and a sexually selected characteristic. Beyond that striking feature, Platyhystrix seems to have spent most of its time on the land rather than in the swamps of southwestern North America, subsisting on insects and small animals.

 

28
of 34

Prionosuchus

prionosuchus
Prionosuchus (Dmitry Bogdanov).

Name:

Prionosuchus; pronounced PRE-on-oh-SOO-kuss

Habitat:

Swamps of South America

Historical Period:

Late Permian (270 million years ago)

Size and Weight:

About 30 feet long and 1-2 tons

Diet:

Small animals

Distinguishing Characteristics:

Large size; crocodile-like build

 

First things first: not everyone agrees that Prionosuchus deserves its own genus; some paleontologists maintain that this huge (about 30 foot long) prehistoric amphibian was actually a species of Platyoposaurus. That said, Prionosuchus was a true monster among amphibians, which has inspired its inclusion in many imaginary "Who would win? Prionosuchus vs. [insert large animal here]" discussions on the internet. If you managed to get close enough--and you wouldn't want to--Prionosuchus would probably have been indistinguishable from the large crocodiles that evolved tens of millions of years later, and were true reptiles rather than amphibians.

 

29
of 34

Proterogyrinus

proterogyrinus
Proterogyrinus (Nobu Tamura).

Name:

Proterogyrinus (Greek for "early tadpole"); pronounced PRO-teh-roe-jih-RYE-nuss

Habitat:

Swamps of North America and western Europe

Historical Period:

Late Carboniferous (325 million years ago)

Size and Weight:

About three feet long and 5-10 pounds

Diet:

Fish

Distinguishing Characteristics:

Narrow snout; long, paddle-like tail

 

As unlikely as it may seem, considering the dinosaurs that followed in its wake a hundred million years later, the three-foot-long Proterogyrinus was the apex predator of late Carboniferous Eurasia and North America, when the earth's continents were just beginning to be populated by air-breathing prehistoric amphibians. Proterogyrinus bore some evolutionary traces of its tetrapod ancestors, most notably in its broad, fish-like tail, which was nearly the length of the rest of its slender body.

 

30
of 34

Seymouria

seymouria
Seymouria (Wikimedia Commons).

Name:

Seymouria ("from Seymour"); pronounced see-MORE-ee-ah

Habitat:

Swamps of North America and western Europe

Historical Period:

Early Permian (280 million years ago)

Size and Weight:

About two feet long and a few pounds

Diet:

Fish and small animals

Distinguishing Characteristics:

Small size; robust backbone; powerful legs

 

Seymouria was a distinctly un-amphibious looking prehistoric amphibian; this tiny creature's robust legs, well-muscled back and (presumably) dry skin prompted paleontologists of the 1940's to classify it as a true reptile, after which it reverted back to the amphibian camp, where it belongs. Named after the town in Texas where its remains were discovered, Seymouria appears to have been an opportunistic hunter of the early Permian period, about 280 million years ago, roving over dry land and murky swamps in search of insects, fish and other small amphibians.

Why did Seymouria have scaly rather than slimy skin? Well, at the time it lived, this part of North America was unusually hot and dry, so your typical moist-skinned amphibian would have shriveled up and died in no time flat, geologically speaking. (Interestingly, Seymouria may have possessed another reptile-like characteristic, the ability to excrete excess salt from a gland in its snout.) Seymouria may even have been able to survive for extended amounts of time away from the water, though, like any true amphibian, it had to return to water in order to lay its eggs.

A few years ago, Seymouria made a cameo appearance on the BBC series Walking with Monsters, lurking by a clutch of Dimetrodon eggs in the hopes of scoring a tasty meal. Perhaps more suited to an R-rated episode of this show would be the discovery of the "Tambach lovers" in Germany: a pair of Seymouria adults, one male, one female, lying side by side after death. Of course, we don't really know if this duo died after (or even during) the act of mating, but it sure would make for interesting TV!

 

31
of 34

Solenodonsaurus

solenodonsaurus
Solenodonsaurus. Dmitri Bogdanov

Name:

Solenodonsaurus (Greek for "single-toothed lizard"); pronounced so-LEE-no-don-SORE-us

Habitat:

Swamps of central Europe

Historical Period:

Middle Carboniferous (325 million years ago)

Size and Weight:

About 2-3 feet long and five pounds

Diet:

Probably insects

Distinguishing Characteristics:

Flat skull; long tail; scales on belly

 

There wasn't a sharp dividing line that separated the most advanced amphibians from the earliest true reptiles--and, even more confusingly, these amphibians continued to coexist with their "more evolved" cousins. That, in a nutshell, is what makes Solenodonsaurus so confusing: this proto-lizard lived too late to be the direct ancestor of reptiles, yet it seems to belong (provisionally) in the amphibian camp. For example, Solenodonsaurus had a very amphibian-like backbone, yet its teeth and inner-ear structure were uncharacteristic of its water-dwelling cousins; its closest relative seems to have been the much better-understood Diadectes.

 

32
of 34

Triadobatrachus

triadobatrachus
Triadobatrachus. Wikimedia Commons

Name:

Triadobatrachus (Greek for "triple frog"); pronounced TREE-ah-doe-bah-TRACK-us

Habitat:

Swamps of Madagascar

Historical Period:

Early Triassic (250 million years ago)

Size and Weight:

About four inches long and a few ounces

Diet:

Insects

Distinguishing Characteristics:

Small size; frog-like appearance

 

Although older candidates may eventually be discovered, for now, Triadobatrachus is the earliest prehistoric amphibian known to have lived near the trunk of the frog and toad family tree. This small creature differed from modern frogs in the number of its vertebrae (fourteen, compared to half that for modern genera), some of which formed a short tail. Otherwise, though, the early Triassic Triadobatrachus would have presented a distinctly frog-like profile with its slimy skin and strong hind legs, which it probably used to kick rather than to jump.

 

33
of 34

Vieraella

vieraella
Vieraella. Nobu Tamura

Name:

Vieraella (derivation uncertain); pronounced VEE-eh-rye-ELL-ah

Habitat:

Woodlands of South America

Historical Period:

Early Jurassic (200 million years ago)

Size and Weight:

About one inch long and less than an ounce

Diet:

Insects

Distinguishing Characteristics:

Small size; muscular legs

 

To date, Vieraella's claim to fame is that it's the earliest true frog in the fossil record, albeit an extremely tiny one at a little over an inch long and less than an ounce (paleontologists have identified an even earlier frog ancestor, the "triple frog" Triadobatrachus, which differed in important anatomical respects from modern frogs). Dating to the early Jurassic period, Vieraella possessed a classically frog-like head with big eyes, and its tiny, muscular legs could power some impressive jumps.

 

34
of 34

Westlothiana

westlothiana
Westlothiana. Nobu Tamura

Name:

Westlothiana (after West Lothian in Scotland)); pronounced WEST-low-thee-ANN-ah

Habitat:

Swamps of western Europe

Historical Period:

Early Carboniferous (350 million years ago)

Size and Weight:

About one foot long and less than a pound

Diet:

Insects

Distinguishing Characteristics:

Long, thin body; splayed legs

 

It's a bit of an oversimplification to say that the most advanced prehistoric amphibians evolved directly into the least advanced prehistoric reptiles; there was also an intermediate group known as the "amniotes," which laid leathery rather than hard eggs (and thus weren't restricted to bodies of water). The early Carboniferous Westlothiana was once believed to be the earliest true reptile (an honor now bestowed on Hylonomus), until paleontologists noted the amphibian-like structure of its wrists, vertebrae and skull. Today, no one is quite sure how to classify this creature, except for the unenlightening statement that Westlothiana was more primitive than the true reptiles that succeeded it!