10 Facts About Allosaurus

 The much later Tyrannosaurus Rex gets all the press, but pound for pound, the 30-foot-long, one-ton Allosaurus may have been the most fearsome meat-eating dinosaur of Mesozoic North America.

01
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Allosaurus Used to be Known as Antrodemus

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An early depiction of Allosaurus (Charles R. Knight).

Like many early dinosaur discoveries, Allosaurus bounced around a bit in the classification bins after its "type fossil" was excavated in the American west, in the late 19th century. This dinosaur was initially named Antrodemus (Greek for "body cavity") by the famous American paleontologist Joseph Leidy, and was only systematically referred to as Allosaurus ("different lizard") starting in the mid-1970's. (See more about the discovery and naming of Allosaurus.)

02
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Allosaurus Liked to Lunch on Stegosaurus

allosaurus
Alain Beneteau.

Paleontologists have unearthed solid evidence that Allosaurus preyed on (or at least occasionally tussled with) Stegosaurus: an Allosaurus vertebra with a puncture wound that matches the size and shape of a Stegosaurus tail spike (or "thagomizer"), and a Stegosaurus neck bone bearing an Allosaurus-shaped bite mark. (For a blow-by-blow description of this late Jurassic cage match, see Allosaurus vs. Stegosaurus - Who Wins?

03
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Allosaurus Was Constantly Shedding and Replacing its Teeth

allosaurus
Oklahoma Museum of Natural History.

Like many predatory dinosaurs of the Mesozoic Era (not to mention modern crocodiles), Allosaurus constantly grew, shed and replaced its teeth, some of which averaged three or four inches in length. (Surprisingly, though, this dinosaur only had about 32 teeth, 16 apiece in its upper and lower jaws, at any given time.)  Because there are so many Allosaurus fossil specimens, it's possible to buy genuine Allosaurus teeth for reasonable prices--only a few hundred dollars each!

04
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The Typical Allosaurus Lived for About 25 Years

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An elderly Allosaurus specimen (Wikimedia Commons).

Estimating the life span of any given dinosaur is always a tricky matter, but based on the voluminous fossil evidence, paleontologists believe Allosaurus attained its full adult size by the age of 15 or so (at which point it was no longer vulnerable to predation by other large theropods, or other hungry Allosaurus adults). Barring disease, starvation or thagomizer wounds inflicted by angry stegosaurs, this dinosaur may have been capable of living and hunting for another 10 or 15 years.

05
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Allosaurus Comprised at Least Seven Separate Species

allosaurus
Wikimedia Commons.

The early history of Allosaurus is littered with supposedly "new" genera of theropod dinosaurs (such as the now-discarded Creosaurus, Labrosaurus, and Epanterias) that turned out, on further examination, to be separate Allosaurus species. To date, there are three widely accepted species of Allosaurus: A. fragilis (designated in 1877 by the famous American paleontologist Othniel C. Marsh), A. europaeus (erected in 2006), and A. lucasi (erected in 2014).

06
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The Most Famous Allosaurus Fossil is "Big Al"

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"Big Al" the Allosaurus (Museum of the Rockies).

In 1991--after a full century of Allosaurus discoveries--researchers in Wyoming unearthed an exquisitely preserved, near-complete fossil specimen, which they promptly dubbed "Big Al." Unfortunately, Big Al didn't live a very happy life: analysis of its skeleton revealed numerous fractures and bacterial infections, which doomed this 26-foot-long teenaged dinosaur to a relatively early (and painful) death. (There's also "Big Al Two," an even more complete Allosaurus unearthed in the same general vicinity five years later.)

07
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Allosaurus Was One of the Instigators of the "Bone Wars"

othniel marsh
Othniel C. Marsh (back, center) and an excavation team (Wikimedia Commons).

In their endless zeal to one-up one another, the 19th-century paleontologists Othniel C. Marsh and Edward Drinker Cope often "diagnosed" new dinosaurs based on too-scanty fossil evidence, leading to decades of confusion. Although Marsh had the honor of coining the name Allosaurus in the midst of the so-called Bone Wars, both he and Cope went on to erect other, supposedly new genera of theropods that (on further examination) turned out to be separate Allosaurus species.

08
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There's No Evidence that Allosaurus Hunted in Packs

allosaurus
Denver Museum of Nature and Science.

Paleontologists have long speculated that the only way Allosaurus could have preyed on the huge, 25-to-50 ton sauropods of its day (even if it only targeted juvenile, aged, or sick individuals) was if this dinosaur hunted in cooperative packs. It's a compelling scenario, and it would make for a great Hollywood movie, but the fact is that modern big cats don't team up to bring down full-grown elephants--so Allosaurus individuals probably hunted smaller (or comparably sized) prey all on their lonesome.

09
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Allosaurus Was Probably the Same Dinosaur as Saurophaganax

saurophaganax
Saurophaganax (Wikimedia Commons).

Saurophaganax (Greek for "greatest lizard eater") was a 40-foot-long, two-ton theropod dinosaur that lived alongside the slightly smaller, one-ton Allosaurus in late Jurassic North America. Pending further fossil discoveries, paleontologists haven't yet conclusively decided whether this allusively named dinosaur deserves its own genus, or is more properly classified as a giant new Allosaurus species, A. maximus

10
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Allosaurus Was One of the First Dinosaur Movie Stars

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The Lost World, starring Allosaurus (Wikimedia Commons).

The Lost World, produced in 1925, was the first full-length dinosaur movie--and it starred not Tyrannosaurus Rex but Allosaurus (with guest appearances by Pteranodon and Brontosaurus, the dinosaur later renamed Apatosaurus). Less than a decade later, though, Allosaurus was permanently relegated to second-string Hollywood status by T. Rex's convincing cameo in the 1933 blockbuster King Kong--and pushed out of the spotlight entirely by Jurassic Park's focus on T. Rex and Velociraptor.