The 20 Smallest Dinosaurs and Prehistoric Animals

Sergio Perez

In a way, it's much more difficult to identify the smallest dinosaurs (and prehistoric animals) than the biggest ones—after all, a tiny, foot-long reptile might easily have been the juvenile of a much larger species, but there's no mistaking the evidence for a 100-ton behemoth. Below, you'll find a list of the 20 smallest dinosaurs and prehistoric animals, according to our current state of knowledge. (Just how small were these ancient creatures? Compare them to the 20 Biggest Dinosaurs and Prehistoric Reptiles and the 20 Biggest Prehistoric Mammals.)  

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Smallest Raptor - Microraptor (Two Pounds)

Microraptor (Emily Willoughby).

With its feathers and four, count 'em, four primitive wings (one pair each on its forearms and hind legs), the early Cretaceous Microraptor might easily have been mistaken for a bizarrely mutated pigeon. This was, however, a genuine raptor, in the same family as Velociraptor and Deinonychus, albeit one that only measured about two feet from head to tail and weighed a few pounds soaking wet. Befitting its tiny size, paleontologists believe that Microraptor subsisted on a diet of insects.

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Smallest Tyrannosaur - Dilong (25 Pounds)

Dilong (Sergey Krasovskiy).

The king of the dinosaurs, Tyrannosaurus Rex, measured 40 feet from head to tail and weighed 7 or 8 tons—but its fellow tyrannosaur Dilong, which lived over 60 million years earlier, tipped the scales at 25 pounds, max, an object lesson in how plus-sized creatures tend to evolve from wee ancestors. Even more remarkably, the eastern Asian Dilong was covered with feathers—a hint that even the mighty T. Rex may have sported plumage at some stage of its life cycle.

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Smallest Sauropod - Europasaurus (2,000 Pounds)

Europasaurus (Gerhard Boeggeman).

When most people think of sauropods, they picture huge, house-sized plant-eaters like Diplodocus and Apatosaurus, some of which approached 100 tons in weight and stretched 50 yards from head to tail. Europasaurus, though, wasn't much bigger than a modern ox, only about 10 feet long and less than 2,000 pounds. The explanation is that this late Jurassic dinosaur lived on a small island cut off from the European mainland, like its equally shrimpy titanosaur cousin Magyarosaurus (see slide #9).  

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Smallest Horned, Frilled Dinosaur - Aquilops (Three Pounds)

Aquilops (Brian Engh).

The three-pound Aquilops was a true outlier on the ceratopsian family tree: whereas most ancestral horned and frilled dinosaurs hailed from Asia, Aquilops was discovered in North America, in sediments dating to the middle Cretaceous period (about 110 million years ago). You wouldn't know to look at it, but the the descendants of Aquilops, millions of years down the line, were multi-ton plant-eaters like Triceratops and Styracosaurus that could successfully fend off an attack by a hungry T. Rex.

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Smallest Armored Dinosaur - Minmi (500 Pounds)

Minmi (Wikimedia Commons).

You couldn't ask for a better name for a tiny dinosaur than Minmi—even if this early Cretaceous ankylosaur was named after Australia's Minmi Crossing, and not the adorable"Mini-Me" from the Austin Powers movies. The 500-pound Minmi may not seem especially small until you compare it to later, multi-ton ankylosaurs like Ankylosaurus and Euoplocephalus—and judging by the wee size of its brain cavity, it was every bit as dumb as (or even dumber than) its more famous descendants.

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Smallest Duck-Billed Dinosaur - Tethyshadros (800 Pounds)

Tethyshadros (Nobu Tamura).

The second example on this list of "insular dwarfism"—that is, the tendency of animals confined to island habitats to evolve to modest proportions—the 800-pound Tethyshadros was a fraction of the size of most hadrosaurs, or duck-billed dinosaurs, which usually weighed two or three tons. On an unrelated note, Tethyshadros is only the second dinosaur ever to be discovered in modern-day Italy, much of which was submerged under the Tethys Sea during the late Cretaceous period.

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Smallest Ornithopod Dinosaur - Gasparinisaura (25 Pounds)

Gasparinisaura (Wikimedia Commons).

Since many ornithopods—the two-legged, plant-eating dinosaurs ancestral to hadrosaurs—were slight in stature, it can be a tricky matter to identify the smallest member of the breed. But a good candidate would be the 25-pound Gasparinisaura, one of the few ornithopods to have lived in South America, where either scant plant life or the exigencies of predator-prey relationships downscaled its body plan. (By the way, Gasparinisaura is also one of the few dinosaurs to be named after the female of the species.)

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Smallest Titanosaur Dinosaur - Magyarosaurus (2,000 Pounds)

Magyarosaurus (Getty Images).

Ready for yet another insular dinosaur? Technically, Magyarosaurus is classified as a titanosaur—the family of lightly armored sauropods best represented by 100-ton monstrosities like Argentinosaurus and Futalognkosaurus. Because it was restricted to an island habitat, though, Magyarosaurus weighed only a single ton, and indulged in some odd dietary habits (some paleontologists believe this titanosaur plunged its neck under the surface of swamps and fed on aquatic vegetation!)

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Smallest Living Dinosaur - The Hummingbird (Less Than an Ounce)

A typical Hummingbird (Wikimedia Commons).

From the perspective of evolutionary biologists, dinosaurs never went extinct: they simply evolved into the first prehistoric birds (or, at least, the small, feathered, theropod dinosaurs of the later Mesozoic Era evolved into the first true birds, while their plant-eating sauropod, ornithopod and ceratopsian cousins went kaput). Based on this reasoning, the smallest theropod dinosaur that ever lived is the modern hummingbird, various species of which weigh as little as one-tenth of an ounce!  

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Smallest Pterosaur - Nemicolopterus (A Few Ounces)

Nemicolopterus (Nobu Tamura).

Only a few years ago, it seemed as if the remains of new pterosaurs were being dug up in China every week. In February of 2008, paleontologists discovered the type fossil of Nemicolopterus, the tiniest flying reptile yet identified, with a wingspan of only 10 inches and a weight of a few ounces. Oddly enough, this pigeon-sized pterosaur may have occupied the same branch of evolution that gave rise to the enormous Quetzalcoatlus 50 million years later!

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Smallest Marine Reptile - Cartorhynchus (Five Pounds)

Cartorhynchus (Nobu Tamura).

A few million years after the Permian-Triassic extinction—the deadliest mass extinction in the history of life on earth—marine life had yet to fully recover. Exhibit A is Cartorhynchus: this basal ichthyosaur ("fish lizard") only weighed five pounds, yet it was still one of the largest  marine reptiles of the early Triassic period. You wouldn't have known to look at it, but the descendants of Cartorhynchus, millions of years down the line, included the enormous, 30-ton ichthyosaur Shonisaurus.

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Smallest Prehistoric Crocodile - Bernissartia (10 Pounds)

Bernissartia (Wikimedia Commons).

Crocodiles—which evolved from the same archosaurs that spawned the dinosaurs--were thick on the ground during the Mesozoic Era, making it difficult to identify the smallest member of the breed. But a good candidate would be Bernissartia, an early Cretaceous croc about the size of a house cat. As tiny as it was, Bernissartia sported all the classic crocodilian features (narrow snout, knobby armor, etc.), making it looked like a scaled-down version of later behemoths like Sarcosuchus.

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Smallest Prehistoric Shark - Falcatus (One Pound)

Falcatus (Wikimedia Commons).

Sharks have a deep evolutionary history, predating mammals, dinosaurs, and pretty much all terrestrial vertebrates. To date, the smallest identified prehistoric shark is Falcatus, a tiny, bug-eyed menace the males of which were equipped with sharp spines jutting out of their heads (which seem to have been used, rather painfully, for mating purposes). Needless to say, Falcatus was a far cry from true undersea giants like Megalodon, which it preceded by a whopping 300 million years.

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Smallest Prehistoric Amphibian - Triadobatrachus (A Few Ounces)

Triadobatrachus (Wikimedia Commons).

Believe it or not, shortly after they evolved hundreds of millions of years ago, amphibians were the largest land-dwelling animals on earth—until their pride of place was usurped by even bigger prehistoric reptiles. One of the smallest amphibians yet identified, a mere tadpole compared to giants like Mastodonsaurus, was Triadobatrachus, the "triple frog," which inhabited the swamps of Madagascar during the early Triassic period and likely lay at the root of the frog and toad evolutionary tree.

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Smallest Prehistoric Bird - Ibermesornis (A Few Ounces)

Iberomesornis (Wikimedia Commons).

Pound for pound, the birds of the Cretaceous period weren't any bigger than their modern counterparts (for the simple reason that a dinosaur-sized pigeon would immediately plummet out of the sky). Even by this standard, though, Iberomesornis was unusually small, only about the size of a finch or sparrow—and you'd have to take a close look at this bird to discern its basal anatomy, including a single claw on each wing and a set of jagged teeth embedded in its tiny jaws.

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Smallest Prehistoric Mammal - Hadrocodium (Two Grams)

Hadrocodium (BBC).

As a general rule, the mammals of the Mesozoic Era were some of the smallest vertebrates on earth—the better to keep out of the way of the giant dinosaurs, pterosaurs and crocodiles with which they shared their habitat. Not only was the early Jurassic Hadrocodium incredibly tiny—only about an inch long and two grams—but it's represented in the fossil record by a single, exquisitely preserved skull, which hints (ironically) at a bigger-than-usual brain compared to the size of its body.

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Smallest Prehistoric Elephant - The Dwarf Elephant (500 Pounds)

dwarf elephant
A typical Dwarf Elephant (Wikimedia Commons).

Remember those "insular" dinosaurs we described in previous slides, Europasaurus, Magyarosaurus and Tethyshadros? Well, the same principle applies to the mammals of the Cenozoic Era, some of which found themselves trapped in island habitats and forced to adjust, evolutionarily speaking. What we call the Dwarf Elephant included scaled-down, quarter-ton species of Mammoths, Mastodons and modern elephants, all of which lived on various Mediterranean islands during the Pleistocene epoch.

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Smallest Prehistoric Marsupial - The Pig-Footed Bandicoot (A Few Ounces)

pig-footed bandicoot
The Pig-Footed Bandicoot (John Gould).

One faces a true "eeny-meeny-miney-moe" situation when it comes to identifying the smallest prehistoric marsupial: for every Australian behemoth like the Giant Wombat or the Giant Short-Faced Kangaroo, there were a bewildering variety of tiny, hyphenated pouched mammals. Our vote goes to the Pig-Footed Bandicoot, a long-nosed, spindly-legged, two-ounce furball that hopped across the plains of Australia until the modern era, when it was crowded out by the arrival of European settlers and their pets.

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Smallest Prehistoric Dog - Leptocyon (Five Pounds)


The evolutionary lineage of modern canines goes back 40 million years, including both plus-sized breeds (like Borophagus and the Dire Wolf) and comparatively runty genera like Leptocyon, the "slender dog." The amazing thing about the five-pound Leptocyon is that various species of this canid persisted for almost 25 million years, making it one of the most successful predatory mammals of Oligocene and Miocene North America. (And what did it prey on? Most likely, deer-sized prehistoric horses.)

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Smallest Prehistoric Primate - Archicebus (A Few Ounces)

Archicebus (Wikimedia Commons).

As with many other animals on this list, it's not a straightforward matter to identify the smallest prehistoric primate: after all, the vast majority of Mesozoic and early Cenozoic mammals were quivering and mouse-sized. Archicebus, though, is as good a choice as any: this tiny, tree-dwelling primate only weighed a few ounces, and it seems to have been ancestral to modern apes, monkeys, lemurs and humans (though some paleontologists, touting their own primates of choice, disagree).