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Megalosaurus

Megalaosaurus, meaning “Great Lizard”, from Greek megalo, meaning ‘big’ or ‘tall’ and sauros, meaning “lizard”, is a genus of large and meat-eating theropod dinosaurs of the Middle Jurassic period of Europe. It’s significant as the first genus of dinosaur, outside of birds, to be described and named.

Megalosaurus might have been the first dinosaur to be described in scientific literature. Part of a bone was recovered from a limestone quarry at Cornwell by Chipping Norton, Oxfordshire, England in 1776. The piece was sent to Robert Plot, Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum, who published a description in his Natural History of Oxfordshire in the year 1676. He acceptably identified the bone as the lower end of the femur of a sizable animal and he recognized that it was too large to belong to any species that are known. The therefore concluded it to be a thigh bone of a giant human, such as those that were mentioned in the Bible. The bone has been lost since then but the illustration is detailed enough that some have since identified it as one of Megalosaurus.

The Cornwell bone was described again by Richard Brookes in the year 1763. He called it “Scrotum humanum”, whilst comparing its appearance to a pair of testicles of a human. The label was not considered to be a proper Linnaean “name” for the animal at the time, and was not used in subsequent writing. The name was technically published, though, after the advent of binomial nomenclature, and so it was truly intended to be representation of the establishment of a new genus it would have priority over Megalosaurus.

More discoveries were made, starting in the year 1815, again at the Stonesfield quarry. They were acquired by William Buckland, Professor of Geology at the University of Oxford and dean of Christ Church. He didn’t know what animal the bones belonged to, but in 1818, after the Napoleonic Wars, the French comparative anatomist Georges Cuvier visited Buckland in Oxford and realized that the bones belonged to a giant creature resembling a lizard. Buckland then published descriptions of the bones in Transactions of the Geological Society, in the year 1824.

By 1824, Buckland acquired a piece of a lower jaw with teeth, fragments of a pelvis, some vertebrae, scapula and hind limbs, most likely not all from the same individual. He identified the organism as being a giant animal related to the Sauria, which means lizards, and he placed it in the new genus Megalosaurus, estimating that animal to be around 12 meters long in life. In the year 1826, Ferdinand von Ritgen gave this dinosaur a complete binomial, Megalosaurus conybeari, which was not used by later authors and isn’t considered to be a noman oblitum. A year later, in 1827, Gideon Mantell included Megalosaurus in his geological survey of southeastern England, and assigned the species its present binomial name, Megalosaurus bucklandii. It wouldn’t be until 1842 that Richard Owen coined the term ‘dinosaur’.

In the year 1997, a well-known group of fossilized footprints, called ichnites, was found in a limestone quarry at Ardley, which is 20 km Northeast of Oxford, England. They were thought to have been made by Megalosaurus and possibly also some left by Cetiosaurus. There are models of some of these footprints, set across the lawn of Oxford University Museum of Natural History.

Since those initial finds, many other Megalosaurus bones have been recovered but still no complete skeletons have been found. Therefore, the details of its physical traits cannot be certain. However, a full description of all known material was recently published.

In 1852, Benjamin Waterhouse Hawkins was commissioned to construct a replica of Megalosaurus for the exhibition of dinosaurs at the Crystal Palace in Sydenham, where it has remained to this day. Early paleontologists, never having seen such a creature before, reconstructed it like the dragons of some popular mythology, with an enormous head and walking on all four limbs. The hump on the back of the sculpture in Crystal Palace and other restorations from the 1800s was based on the material that is now referred to as Becklespinax. It wasn’t until the middle of the 19th century, when other theropods started to be discovered in North America, that a more correct picture was developed. Some confusion still exists, for at one time, all theropods from Europe were given the title of Megalosaurus. Since that time, these have mostly been reclassified. For further confusion, the most reproduced anatomy diagram of a Megalosaurus skeleton was provided before any vertebrae had been recovered. While drawing it, Friedrich von Huene of the University of Tubingen, Germany, instead used the backbones of Altispinax, a mysterious and large theropod know from high-spined dorsal vertebrae and at times listed as a spinosaur. Hence, many later drawings based on his original one, show Megalosaurus with a deep spinal ridge, or even a small sail much like that of Spinosaurus.

Megalosaurus had a comparatively large sized head and its teeth were those of a carnivore. However, the tail was long and would have balanced the body and head and so Megalosaurus is now restored as bipedal – like all other theropods – about 9 meters in length. The structure of the cervical vertebrae suggests that the neck would have been very flexible. To support its weight of about 1 ton, the legs were sizable and muscular. Like most theropods, it had three toes that faced forward and a hallux. Its forelimbs were small, although not proportionally as small as those of some later theropods like Tyrannosaurus, and probably had three or four digits.

Living in what is now Europe, during the Jurassic Period, which was 181 to 169 million years ago, Megalosaurus might have hunted stegosaurs and sauropods. Repeated descriptions of Megalosaurus hunting Iguanodon through the forests that then covered the continent are most likely incorrect, due to Iguanodon skeletons being commonly found in much younger Early Cretaceous formations. No fossils that are assignable to Megalosaurus have been recovered in Africa, contrary to some outdated dinosaur books.

The Oxford University Museum of Natural History include a descriptive display of Megalosaurus and of the history of its discovery.

For decades after the discovery, Megalosaurus was viewed by many researchers as a definitive or typical largely sized carnivorous dinosaur. It has also historically been a Wastebasket taxon, and many sizable carnivorous dinosaurs from Europe and elsewhere were referred to the genus without any justification. This started to change in the 20th century, when scientists much like con Huene proposed that the genus should be restricted to the fossils found in the original Stonesfield Slate quarry, and this was followed by most later researchers. However, even further taxonomic revision began in the late 20th and early 21st centuries, in which researchers such as Allain and Chure showed that the Stonesfield Slate fossils most likely belonged to several, possibly unrelated, species of theropod dinosaur. Further research established this hypothesis, and the genus Megalosaurus and species M. bucklandii became generally regarded as applying only to the type specimen, specifically to the species that provided the lower jaw. Furthermore, several researchers failed to find any traits in the jaw that could be used to distinguish Megalosaurus from its relatives, and many started to regard it as a nomen dubium.

However, a complete study by Benson and colleagues in the year 2008, and several related analyses published in following years, upturned the previous compromise by identifying several apomorphies, meaning distinguishing characteristics, in the lower jaw that could be used to separate Megalosaurus from other megalosaurids.

A Megalosaurus rib figured in 1856 and 1884 by Sir Richard Owen has a pathological inflamed area near the base of its capitular process.

Megalosaurus has the honor of being the first dinosaur to appear in any popular media.

Image Caption: Megalosaurus skeleton, World Museum Liverpool, England. Found in southern England. Credit: Rept0n1x/Wikipedia (CC BY-SA 3.0)

Megalosaurus


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