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Megalosaurus Dinosaur Facts

Megalosaurus is one of the most interesting dinosaurs since it has been known for a very long time and is therefore the basis of our knowledge of these animals. Its history goes back as far as 1676; in Oxfordshire, England, the lower part of a Megalosaurus femur was discovered. First assigned under the name Scrotum humanum in a naturalistic book published in 1763 because of its testicular appearance, the specimen was later lost but could be identified as belonging to a Megalosaurus through illustrations.

Scrotum humanum
Scrotum humanum

Since Megalosaurus was discovered at a time when dinosaur knowledge was almost non-existent, it took a long time before paleontologists realized what they were dealing with. It was initially thought to be a huge quadrupedal lizard measuring almost 50 feet long, a sort of iguana with massive proportions. Naturalist Sir Richard Owen proposed in 1842 that the Megalosaurus probably had a more modest length of 25 feet. We now know with current knowledge that Megalosaurus was a bipedal carnivore, a theropod measuring about 20 feet long for a weight of 1 ton. Megalosaurus was a runt compared to later Mesozoic theropods such as the Tyrannosaurus, of which it was only half the length and one-eighth the weight.


The name Megalosaurus, "Great Lizard", was officially granted in 1824 by the British naturalist William Buckland on the basis of numerous fossil remains discovered in England some decades ago. The term "Dinosauria" was invented only 18 years later (in 1842) by Richard Owen to accomodate three prehistoric reptiles considered at the time to be simple oversized lizards: Megalosaurus, Iguanodon and Hylaeosaurus. Owen saw them as active and dynamic animals, which prompted him to invent a new word to categorize them.

An exhibition at Crystal Palace

Crystal Palace - Megalosaurus
Crystal Palace - Megalosaurus

In the early 1850s, in London, the Crystal Palace was host to major exhibitions and world fairs of culture and industry. The events were organized by Prince Albert and many influential and famous people of the time attended. Thus, in 1854, after the Palace relocated to another part of London, it was now possible to admire the first life-size models of dinosaurs such as Megalosaurus and Iguanodon. These early reconstructions were, to say the least, crude and did not reflect reality; Megalosaurus was depicted as a quadrupedal bear-like creature with a camel's hump on its shoulders. This is far from the classic silhouette of the theropod family to which it belongs.

A middle Jurassic ghost

What makes Megalosaurus particularly interesting is the time at which it lived. Most of the dinosaurs known to date come almost exclusively from Upper Jurassic and Lower and Upper Cretaceous periods, with the possible exception of Dilophosaurus and some other rare specimens. Megalosaurus, meanwhile, lived about 165 million years ago during the Middle Jurassic, a very poorly represented time in terms of fossil discoveries.

Wastebasket taxon

For almost a century after its initial identification, all dinosaurs that resembled even vaguely Megalosaurus were automatically assigned as subspecies of it. Thus, at the beginning of the 20th century, paleontologists found themselves with a confusing assortment of Megalosaurus species that only helped further complicate the understanding of theropods evolution.

A poorly understood dinosaur

Even today and despite all the fossils discovered and modern knowledge that we have, the Megalosaurus remains a very poorly understood dinosaur. For this reason, paleontologists often prefer to discuss close relatives such as Torvosaurus (one of the rare dinosaurs discovered in Portugal) rather than Megalosaurus itself.

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