Shonisaurus

Name:
Shonisaurus (Greek for "Shoshone mountain reptile"); pronounced show-nih-SORE-us
Habitat:
Oceans worldwide
Historical Period:
Late Triassic (225-208 million years ago)
Size and Weight:
About 50 feet long and 30 tons
Diet:
Fish, squid and cephalopods
Distinguishing Characteristics:
Large, thick trunk; large eyes; sharp teeth
About Shonisaurus:

Shonisaurus was among the strangest of all ichthyosaurs ("fish lizards"), looking a bit like a cross between a dolphin and a whale with its thick, round body, long, narrow front and rear flippers, pointed mouth with teeth only on the front end, and double-pronged tail. At upwards of 50 feet long and 30 tons, this was one of the biggest animals on the planet during the late Triassic period, matched in size only by the giant marine reptiles and fish that lived tens of millions of years later, notably Liopleurodon and Leedsichthys.

Like other ichthyosaurs, Shonisaurus is believed to have evolved from land-dwelling lizards that returned to an aquatic lifestyle during the early Triassic period. That makes this family of marine reptiles roughly analogous to modern dolphins and whales, which also evolved from smaller, land-dwelling ancestors. (By the way, Shonisaurus is the state fossil of land-locked Nevada, which was submerged beneath a shallow body of water during much of the Mesozoic Era.)

Moschops

Name:
Moschops (Greek for "calf face"); pronounced MOE-shops
Habitat:
Forests of South Africa
Historical Period:
Late Permian (255 million years ago)
Size and Weight:
About 16 feet long and one ton
Diet:
Plants
Distinguishing Characteristics:
Thick skull; short tail; front legs longer than hind legs
About Moschops:

Moschops is a case study in how evolution produces roughly the same forms to occupy the same ecological niches. Although it was a therapsid (mammal-like reptile) rather than a true dinosaur, Moschops was markedly similar to later ornithopods and hadrosaurs like Iguanodon and Maiasaura: thick-set, medium-sized, and built close to the ground, the better to browse on low-lying vegetation. In an important sense, though, Moschops was the less "evolved" reptile, since it had a classic, splay-footed reptilian posture and (if it was possible) an even tinier brain. (By the way, the family of mammal-like reptiles to which Moschops belong went on to spawn the earliest true mammals during the Triassic period.

It may seem hard to believe, but Moschops was the star of a short-lived kids' TV show back in 1983, though it's unclear whether the producers knew that it technically wasn't a dinosaur. Granted, that wasn't the only scientific inaccuracy: for example, Moschops shared a cave with his best friend, an Allosaurus, and his grandfather was a Diplodocus. Perhaps it was a good thing that Moschops only lasted for 13 episodes before fading into pop-culture obscurity.

Quetzalcoatlus

Name:
Quetzalcoatlus (named after the Aztec god Quetzalcoatl); pronounced KWET-zal-co-AT-lus
Habitat:
Skies of North America
Historical Period:
Late Cretaceous (80-65 million years ago)
Size and Weight:
Wingspan of 30 feet and 200 pounds
Diet:
Fish and meat
Distinguishing Characteristics:
Large size; narrow wings; long, pointed beak
About Quetzalcoatlus:

Almost certainly the largest creature--whether bird, insect, mammal or reptile--ever to take to the air, Quetzalcoatlus did credit to the fearsome Aztec god after which it was named. The most impressive species of this giant pterosaur attained wingspans of over 30 feet, and must have been greatly feared by terrestrial critters when they soared down from the sky in search of food. Right? Well, maybe not: a recent analyis of Quetzalcoatlus' anatomy hints that this pterosaur may have led a completely terrestrial existence, stalking its prey on two legs like the contemporary raptors and tyrannosaurs of the late Cretaceous period. (See a gallery of Quetzalcoatlus pictures.)

The fact is, paleontologists are still trying to piece together exactly how Quetzalcoatlus lived. It's generally agreed that, if this reptile indeed flew, it glided rather than flapped its wings, which given its size and presumed cold-blooded metabolism would likely have been an anatomical impossibility. Even less certain is how Quetzaloatlus fed; it may have scavenged already-dead carcasses like a vulture, gobbled down fish like a stork, or plucked out unfortunate fish, plesiosaurs and mosasaurs as it skimmed close to the North American shoreline.

As big as it was, Quetzalcoatlus wasn't the only plus-sized pterosaur of the Mesozoic Era, though it vastly outweighed its nearest relatives. The next biggest pterosaur on the block was probably Ornithocheirus, and a pair of genera from South America, Tapejara and Tupuxuara, also cut impressive profiles (and were probably brightly colored as well; we know virtually nothing about how Quetzalcoatlus might have looked at the height of the mating season).

Spinosaurus

Name:
Spinosaurus (Greek for "spine lizard"); pronounced SPINE-oh-SORE-us
Habitat:
Swamps of North Africa
Historical Period:
Middle Cretaceous (95 million years ago)
Size and Weight:
About 50 feet long and 7 tons
Diet:
Meat and fish
Distinguishing Characteristics:
Long, spiky protuberances from vertebrae supporting a "sail" of skin
About Spinosaurus:

If it weren't for one tell-all feature, Spinosaurus might have been indistinguishable from any other large theropod stalking the swamps of the Cretaceous period. That feature, of course, was the extensive, fin-shaped sail on its back, a thin flap of skin supported by sharp needles of bone that protruded from Spinosaurus' vertebrae. (See more facts, figures and news about Spinosaurus, 10 Facts About Spinosaurus and a gallery of Spinosaurus pictures.)

Why did Spinosaurus have this strange-looking sail? The most likely explanation is that this structure evolved for cooling purposes in the hot northern African climate in which Spinosaurus lived (a bit like the big, floppy ears of African elephants). It may also, as a byproduct, have been a sexually selected characteristic--perhaps male Spinosaurus with bigger sails had more success mating with females.

By the way, paleontologists now believe that Spinosaurus was the largest carnivore that ever lived--outclassing even Tyrannosaurus Rex by one or two tons. Fortunately--or unfortunately, if you happen to be a movie producer--these two dinosaurs didn't share the same time or territory, T. Rex living tens of millions of years later in North, rather than South, America.

Albertosaurus

Name:
Albertosaurus (Greek for "Alberta lizard"); pronounced al-BERT-oh-SORE-us
Habitat:
Forests of western North America
Historical Epoch:
Late Cretaceous (75 million years ago)
Size and Weight:
About 30 feet long and 3 tons
Diet:
Herbivorous dinosaurs
Distinguishing Characteristics:
Large head with numerous teeth; powerful hind legs; short arms
About Albertosaurus:

As carnivorous dinosaurs go, Albertosaurus is fairly well known, with multiple, more-or-less complete fossils of this famous tyrannosaur having been dug up in North America (many in the Canadian province of Alberta, after which the genus is named).

For all intents and purposes, Albertosaurus can be considered a slightly smaller version of Tyrannosaurus Rex, "only" about three tons (compared to more than twice that for the largest T. Rex individuals) but every bit as dangerous. This tyrannosaur made its living by hunting the numerous herbivorous dinosaurs of the late Cretaceous period, probably making a specialty out of slow-witted hadrosaurs.

Scarily, paleontologists have found traces of evidence that Albertosaurus may have hunted in packs. If this is true, then it's likely that not even the armored, full-grown herbivores of Cretaceous North America (such as Triceratops) were truly safe from being turned into a quick lunch.

Colepiocephale

Name:
Colepiocephale (Greek for "knucklehead"); pronounced co-LEE-pee-oh-SEF-ah-lee
Habitat:
Woodlands of North America
Historical Period:
Late Cretaceous (75-70 million years ago)
Size and Weight:
About 3 feet long and 10-15 pounds
Diet:
Plants
Distinguishing Characteristics:
Small size; flat, sloped skull
About Colepiocephale:

There's one thing you can say about the paleontologist who discovered Colepiocephale: he or she had a good sense of humor. In true Three Stooges style, this tiny herbivore's name is Greek for "knucklehead," as befits your typical pachycephalosaur (or bone-headed dinosaur).

Its odd name aside, Colepiocephale is important for being one of the earliest boneheads discovered to date in North America (Asian pachycephalosaurs, such as Goyocephale, appear to have predated their American cousins by a few million years). Colepiocephale also had an unusual skull compared to other dinosaurs of its kind; it wasn't domed or especially thick, but flat, sloped and roughly triangular.

Titanophoneus

Name:
Titanophoneus (Greek for "titanic murderer"); pronounced tie-TAN-oh-PHONE-ee-us
Habitat:
Woodlands of central Asia
Historical Period:
Late Permian (255-250 million years ago)
Size and Weight:
About 8 feet long and 200 pounds
Diet:
Meat
Distinguishing Characteristics:
Long tail and head; short, sprawling legs
About Titanophoneus:

As therapsids, or mammal-like reptiles, go, Titanophoneus has been a bit oversold by paleontologists. True, this "titanic murderer" was probably dangerous to other therapsids of the late Permian period, but it must have been positively harmless compared to the bigger raptors and tyrannosaurs that lived almost 200 million years later.

Probably the most advanced feature of Titanophoneus was its teeth: two dagger-like canines in front, accompanied by sharp incisors and flat molars in back for grinding up flesh. As with other mammal-like reptiles--which went on to spawn the first true mammals of the late Triassic period--it's possible that Titanophoneus was covered in fur and had a warm-blooded metabolism, though we may never know for sure.