10 Facts About Megalosaurus

Megalosaurus holds a special place among paleontologists as the first dinosaur ever to be named — but, two hundred years down the road, it remains an extremely enigmatic and poorly understood meat-eater. On the following slides, you'll discover 10 essential Megalosaurus facts.

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Megalosaurus Was Named in 1824

Megalosaurus, Retro Look, illustration — MARK GARLICK/SCIENCE PHOTO LIBRARY/Getty Images

In 1824, the British naturalist William Buckland bestowed the name Megalosaurus — "great lizard" — on various fossil specimens that had been discovered in England over the past few decades. Megalosaurus, however, could not yet be identified as a dinosaur, because the word "dinosaur" wasn't invented until eighteen years later, by Richard Owen — to embrace not only Megalosaurus but also Iguanodon and the now-obscure armored reptile Hylaeosaurus.

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Megalosaurus Was Once Thought to Be a 50-Foot-Long, Quadrupedal Lizard

An early illustration of Megalosaurus (right) battling Iguanodon — Édouard Riou/Wikimedia Commons/Public Domain

Because Megalosaurus was discovered so early, it took quite a while for paleontologists to figure out what they were dealing with. This dinosaur was initially described as a 50-foot-long, four-footed lizard, like an iguana scaled up by a couple orders of magnitude. Richard Owen, in 1842, proposed a more reasonable length of 25 feet, but still subscribed to a quadrupedal posture. (For the record, Megalosaurus was about 20 feet long, weighed one ton, and walked on its two hind legs, like all meat-eating dinosaurs.)

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Megalosaurus Was Once Known as "Scrotum"

Megalosaurus may only have been named in 1824, but various fossils had been extant for over a century before then. One bone, discovered in Oxfordshire in 1676, was actually assigned the genus and species name Scrotum humanum in a book published in 1763 (for reasons you can probably guess, from the accompanying illustration). The specimen itself has been lost, but later naturalists were able to identify it (from its depiction in the book) as the lower half of a Megalosaurus thigh bone.

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Megalosaurus Lived During the Middle Jurassic Period

Megalosaurus dinosaur walking toward the ocean at sunset. — Stocktrek Images/Getty Images

One odd thing about Megalosaurus, which is not often stressed in popular accounts, is that this dinosaur lived during the middle Jurassic period, about 165 million years ago — a stretch of geologic time poorly represented in the fossil record. Thanks to the vagaries of the fossilization process, most of the world's best-known dinosaurs date to either the late Jurassic (about 150 million years ago), or early or late Cretaceous (130 to 120 million or 80 to 65 million years ago), making Megalosaurus a true outlier.

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There Were Once Dozens of Named Megalosaurus Species

megalosaurus skeleton — Christian Erich Hermann von Meyer/Wikimedia Commons/Public Domain

Megalosaurus is the classic "wastebasket taxon" — for over a century after it was identified, any dinosaur that even vaguely resembled it was assigned as a separate species. The result, heading into the early 20th century, was a baffling bestiary of presumed Megalosaurus species, ranging from M. horridus to M. hungaricus to M. incognitus. Not only did profusion of species generate an inordinate amount of confusion, but it also kept early paleontologists from firmly grasping the intricacies of theropod evolution.

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Megalosaurus Was One of the First Dinosaurs to Be Displayed to the Public

The Crystal Palace Megalosaurus — CGPGrey/Wikimedia Commons/CC BY 3.0

The Crystal Palace exhibition of 1851, in London, was one of the first "World Fairs" in the modern sense of the phrase. However, it was only after the Palace had moved to another part of London, in 1854, that visitors were able to behold the world's first full-sized dinosaur models, including Megalosaurus and Iguanodon. These reconstructions were fairly crude, based as they were on early, inaccurate theories about these dinosaurs; for example, Megalosaurus is on all fours and has a hump on its back!

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Megalosaurus Was Name-Dropped by Charles Dickens

Photograph of Charles Dickens writing at a desk. — Apic/RETIRED/Contributor/Getty Images

"It would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling like an elephantine lizard up Holborn Hill." That's a line from Charles Dickens' 1853 novel Bleak House, and the first prominent appearance of a dinosaur in a work of modern fiction. As you can tell from the completely inaccurate description, Dickens subscribed at the time to the "giant lizard" theory of Megalosaurus promulgated by Richard Owen and other English naturalists

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Megalosaurus Was Only One-Quarter the Size of T. Rex

The lower jaw of Megalosaurus — Ghedoghedo/Wikimedia Commons/CC BY-SA 3.0

For a dinosaur incorporating the Greek root "mega," Megalosaurus was a relative wimp compared to the meat-eaters of the later Mesozoic Era — only about half the length of Tyrannosaurus Rex and one-eighth of its weight. In fact, one wonders how early British naturalists might have reacted if they were confronted with a genuinely T. Rex-sized dinosaur — and how that might have affected their subsequent views of dinosaur evolution.

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Megalosaurus Was a Close Relative of Torvosaurus

Torvosaurus mounted cast — Etemenanki3/Wikimedia Commons/CC BY-SA 4.0

Now that (most) of the confusion has been sorted out pertaining to the dozens of named Megalosaurus species, it's possible to assign this dinosaur to its proper branch in the theropod family tree. For now, it appears that the closest relative of Megalosaurus was the comparably sized Torvosaurus, one of the few dinosaurs to be discovered in Portugal. (Ironically, Torvosaurus itself was never classified as a Megalosaurus species, perhaps because it was discovered in 1979.)

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Megalosaurus Is Still a Poorly Understood Dinosaur

megalosaurus bones in case — Ballista/Wikimedia Commons/CC BY-SA 3.0

You might think — given its rich history, numerous fossil remains, and a plethora of named and reassigned species — that Megalosaurus would be one of the world's best-attested and most popular dinosaurs. The fact is, though, that the Great Lizard never quite emerged from the mists that obscured it during the early 19th century; today, paleontologists are more comfortable investigating and discussing related genera (like Torvosaurus, Afrovenator, and Duriavenator) than Megalosaurus itself!

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Strauss, Bob. "10 Mazing Facts About Megalosaurus." ThoughtCo, Feb. 16, 2021, thoughtco.com/things-to-know-megalosaurus-1093810. Strauss, Bob. (2021, February 16). 10 Mazing Facts About Megalosaurus. Retrieved from https://www.thoughtco.com/things-to-know-megalosaurus-1093810 Strauss, Bob. "10 Mazing Facts About Megalosaurus." ThoughtCo. https://www.thoughtco.com/things-to-know-megalosaurus-1093810 (accessed June 8, 2023).