Megalosaurus

*Megalosaurus bucklandi*

* Timothy Bradley Artwork
* Robert F Walters Artwork

***Megalosaurus*** (meaning "Great Lizard") is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period (Bathonian stage, 166 million years ago) of Southern England. Although fossils from other areas have been assigned to the genus, the only certain remains of *Megalosaurus* come from the late Middle Jurassic of the Oxfordshire.

The earliest possible fossils of the genus came from the Taynton Limestone Formation. One of these was the lower part of a femur, discovered in the 17th century. It was originally described by Robert Plot as a thighbone of a Roman war elephant, and then as a biblical giant. The first scientific name given for it, in the 18th century, was *Scrotum humanum*, created by Richard Brookes as a caption; however, this is not considered valid today.

*Megalosaurus* was, in 1824, the first genus of non-avian dinosaur to be validly named. The type species is *Megalosaurus bucklandii*, named in 1827. In 1842, *Megalosaurus* was one of three genera on which Richard Owen based his Dinosauria. On Owen's directions a model was made as one of the Crystal Palace Dinosaurs, which greatly increased the public interest for prehistoric reptiles. Subsequently, over fifty other species would be classified under the genus, originally because dinosaurs were not well known, but even during the 20th century after many dinosaurs had been discovered. Today it is understood these additional species were not directly related to *M. bucklandii*, which is the only true *Megalosaurus* species. Because a complete skeleton of it has never been found, much is still unclear about its build.

The first naturalists who investigated *Megalosaurus* mistook it for a gigantic lizard of twenty metres length. In 1842, Owen concluded that it was no longer than nine metres, standing on upright legs. He still thought it was a quadruped, though. Modern scientists, by comparing *Megalosaurus* with its direct relatives in the Megalosauridae, were able to obtain a more accurate picture. *Megalosaurus* was about seven metres long, weighing about 1.1 tonnes. It was bipedal, walking on stout hindlimbs, its horizontal torso balanced by a horizontal tail. Its forelimbs were short, though very robust. *Megalosaurus* had a rather large head, equipped with long curved teeth. It was generally a robust and heavily muscled animal.

## Description

***Megalosaurus*** was a larger theropod for its day, reaching between 23 and 30 feet (7 to 9 meters) long, and weighing 1.5 to 2 tons, it one of the largest predator in its area of occurrence. A femur even suggests a size of 11.36 m and 4.6 tonnes. It had somewhat short, but strong arms with sharp, hooklike claws on three fingers, perfectly designed for gripping onto prey and slashing at it. It also had long, powerful hindlegs, good for chasing down prey. Its tail, like most other theropods, was built to help balance it while moving. It had a long, narrow skull with sharp, bladelike teeth for slicing through the flesh of other creatures.
But, its bite wasn't weaker than *Allosaurus'*, despite the skull being much more flattened. That's because it had a very thick, neck, helping the predator to bite its prey with great force. Its tail is very heavy and stiff, helping *Megalosaurus* to balance; it presents half of the *Megalosaurus'* weight. It was a close relative of the larger *Torvosaurus* of North America. *Megalosaurus* for a long time was thought to have been a carnosaur, but closer analysis of the bones proved it was its own genus. The newer version of *Megalosaurus* looks much different than the old-fashioned version of dinosaurs, which looked like large, lumbering lizards instead of large, upright, birdlike reptiles. It used to be pictured looking closely like a large Komodo Dragon, walking on four stout, sprawled legs with its tail dragging on the ground.

## Discovery

*Megalosaurus* may have been the first dinosaur to be described in the scientific literature. Part of a bone was recovered from the Taynton Limestone Formation of Stonesfield limestone quarry, Oxfordshire in 1676. Sir Thomas Pennyson gave the fragment to Robert Plot, Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum, who published a description and illustration in his Natural History of Oxfordshire in 1676. It was the first illustration of a dinosaur bone published. Plot correctly identified the bone as the lower extremity of the thighbone or femur of a large animal and he recognized that it was too large to belong to any species known to be living in England. He therefore at first concluded it to be the thighbone of a Roman war elephant and later that of a giant human, such as those mentioned in the Bible. The bone has since been lost, but the illustration is detailed enough that some have since identified it as that of *Megalosaurus.*

It has also been argued that this possible *Megalosaurus* bone was given the very first species name ever applied to an extinct dinosaur. Plot's engraving of the Cornwell bone was again used in a book by Richard Brookes in 1763. Brookes, in a caption, called it "Scrotum Humanum," apparently comparing its appearance to a pair of "human testicles". In 1970, paleontologist Lambert Beverly Halstead pointed out that the similarity of Scrotum humanum to a modern species name, a so-called Linnaean "binomen" that has two parts, was not a coincidence. Linnaeus, the founder of modern taxonomy, had in the eighteenth century not merely devised a system for naming living creatures, but also for classifying geological objects. The book by Brookes was all about applying this latter system to curious stones found in England. According to Halstead, Brookes thus had deliberately used binomial nomenclature, and had in fact indicated the possible type specimen of a new biological genus. According to the rules of the International Code of Zoological Nomenclature (ICZN), the name Scrotum humanum in principle had priority over *Megalosaurus* because it was published first. That Brookes understood that the stone did not actually represent a pair of petrified testicles was irrelevant. Merely the fact that the name had not been used in subsequent literature meant that it could be removed from competition for priority, because the ICZN states that if a name has never been considered valid after 1899, it can be made a nomen oblitum, an invalid "forgotten name".

In 1993, after the death of Halstead, his friend William A.S. Sarjeant submitted a petition to the International Commission on Zoological Nomenclature to formally suppress the name Scrotum in favour of Megalosaurus. He wrote that the supposed junior synonym Megalosaurus bucklandii should be made a conserved name to ensure its priority. However, the Executive Secretary of the ICZN at the time, Philip K. Tubbs, did not consider the petition to be admissible, concluding that the term "Scrotum humanum", published merely as a label for an illustration, did not constitute the valid creation of a new name, and stated that there was no evidence it was ever intended as such. Furthermore, the partial femur was too incomplete to definitely be referred to Megalosaurus and not a different, contemporary theropod.

## JPInstitute.com Description

*Megalosaurus* was the first dinosaur ever named. *Megalosaurus* was found in England in the year 1822 by a geologist named William Buckland. He found the teeth and knew it was from a really big animal. The word 'dinosaur' did not yet exist. In fact, this dinosaur was a typical two legged meat-eater, but people back then knew so little about it that they thought it walked on four legs like a big lizard. It wasn't until 20 years later, in 1842, that Sir Richard Owen came up with the word 'dinosaur' to describe these spectacular fossil creatures which were being discovered.

Since so little of Megalosaurus was originally discovered, it was depicted as a large, quadrupedal lizard with a head like a crocodile. This image of the first dinosaurs lasted some years until more complete specimens were discovered.

*Megalosaurus* was a common carnivore of the Jurassic - species of this genus have been found on several continents. As common as it was, it exhibits only a few of the technical characteristics associated with other therapods.

## Dinosaur Field Guide Description

*Megalosaurus* ("giant lizard") was the first Mesozoic dinosaur to be H named. For centuries, fragments of meat-eating dinosaurs had been found, but scientists thought these came from giant human beings (!) or elephants. Then around 1815, Reverend William Buckland, a scientist at the University of Oxford, came across the remains of a jawbone with teeth, leg bones, and other parts of a skeleton. The teeth reminded Buckland of those of the monitor lizards, meat-eating lizards of the modern world. But these teeth and bones came from a reptile far larger than any monitor lizard! In 1822, this new creature was given the name *Megalosaurus.* Buckland did not call his creature a dinosaur. That word would not be invented until 1842. No complete *Megalosaurus* skeleton has yet been found. However, we can compare the bones we have found to more complete theropods and see that *Megalosaurus* was a two-legged predator with short but powerful arms. It seems to have been the largest meat-eater on land in Europe during the Middle Jurassic Period.

### Fun Facts

The book Bleak House by Charles Dickens (published in 1853) begins with the author imagining a 40-foot-long Megalosaurus "waddling like an elephantine lizard" up a muddy street in London.

### Trivia

In the early days of paleontology, any meat-eating dinosaur fossils were considered to come from Megalosaurus however, as more and better skeletons were found, scientists realized how diverge the meat-eating dinosaurs truly were.

## Links

http://web.archive.org/web/20040214075058fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_megal.html