Megalosaurus

Megalosaurus (meaning "great lizard", from Greek μέγας, megas, meaning 'big', 'tall' or 'great' and σαῦρος, sauros, meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic Epoch (Bathonian stage, 166 million years ago) of southern England. The earliest remains of Megalosaurus were described in the 17th century, but it was officially named in 1824 by William Buckland, making it the first dinosaur genus to be named. It played a key role in helping scientists recognize dinosaurs as a distinct group of ancient reptiles.

Megalosaurus was about 6 metres (20 ft) long and weighed around 700 kilograms (1,500 lb). It walked on two strong hind legs, with a balanced tail and shorter front legs. This dinosaur had a big head with long, curved teeth, making it a fearsome hunter. At the time it lived, Europe was made up of many islands, and Megalosaurus was probably the top predator on its island, sharing its home with other dinosaurs like the large plant-eater Cetiosaurus.

Discovery and naming

In 1699, Edward Lhuyd described what he believed was a fish tooth, later thought to be part of a belemnite. This tooth, known as specimen 1328 from the University of Oxford, was almost certainly from an unknown species of Megalosaurus. It was collected near Witney, Oxfordshire during the 17th century.

The earliest possible fossil of Megalosaurus was a piece of a femur found in Oxfordshire in 1676. It was first thought to be from a Roman war elephant or even a giant human, as described in the Bible. This bone was illustrated in 1676 by naturalist Robert Plot in his book about the natural history of Oxfordshire. Later, in 1763, Richard Brookes called it "Scrotum humanum", comparing its shape to human testicles. However, this name was not widely accepted.

In the early 1800s, more fossils were discovered. In 1815, John Kidd reported finding giant bones at a quarry in Stonesfield. These bones were studied by William Buckland, who, with help from Mary Morland and William Conybeare, identified them as belonging to a large lizard-like creature. In 1822, the name “Megalosaurus” was proposed, meaning “great lizard.” It was formally named by Buckland in 1824, making Megalosaurus the first non-avian dinosaur genus to be named.

Description

Since the first discovery of Megalosaurus, many more bones have been found, but no complete skeleton has ever been uncovered. Because of this, scientists are not completely sure about its exact appearance. However, a detailed study of all known bones was published in 2010 by a researcher named Benson.

Traditionally, Megalosaurus was thought to be about 30 feet (9 meters) long. But estimates have varied over time. Some scientists have suggested it was as short as 20 feet (6 meters). In general, Megalosaurus looked like a large meat-eating dinosaur. It walked on two legs, with a long tail for balance. Its hind legs were long and strong, while its front legs were shorter but very sturdy. It had sharp, knife-like teeth for catching and eating its prey.

Phylogeny

In 1824, the scientist Buckland placed Megalosaurus in a group called Sauria, thinking it was close to modern lizards. Later, in 1842, Owen included Megalosaurus among the first three dinosaurs ever identified. By 2012, scientists used a method called cladistics to show that Megalosaurus was closely related to another dinosaur called Torvosaurus. This helped scientists understand where Megalosaurus fit among other dinosaurs.

Main article: Megalosauridae
Main articles: Cladistics, List of dinosaurs

Paleobiology

Megalosaurus lived in what is now Europe during the Bathonian stage of the Middle Jurassic, around 166-168 million years ago. It was one of the largest predators in its habitat, likely hunting other dinosaurs such as stegosaurs and sauropods. Scientists believe Megalosaurus lived on an island made up of parts of southern Britain and nearby areas of northern France, the Netherlands, Belgium, and western Germany. This island was connected to a larger landmass, which may explain why the dinosaurs there did not shrink in size as expected for island animals.

One rib of Megalosaurus shows a healed fracture, suggesting that these dinosaurs could survive injuries. The area where Megalosaurus lived had many different kinds of plants, including conifers, ferns, and other ancient plants, creating a coastal environment that might have been dry at times and included mangroves.

Species and synonyms

During the 1800s, Megalosaurus was considered the typical carnivorous dinosaur. If fossils weren’t distinct enough to be their own genus, they were often classified under Megalosaurus. This led to Megalosaurus having more species than any other dinosaur genus, many of which were not well-defined.

In 1857, Joseph Leidy renamed Deinodon horridus into Megalosaurus horridus. In 1858, Friedrich August Quenstedt named Megalosaurus cloacinus based on a tooth. Many other scientists named new Megalosaurus species throughout the 1800s and early 1900s, often based on single teeth or small bone fragments. These species are now considered uncertain or reclassified into different genera.

Some notable examples include:

• Megalosaurus ingens, a large tooth from German East Africa, is now seen as a specimen of Torvosaurus.
• Megalosaurus poikilopleuron was renamed from Poekilopleuron bucklandii and is generally considered valid today.
• Megalosaurus wetherilli, based on a fairly complete skeleton from Arizona, was later made its own genus, Dilophosaurus.

Over time, many of these species were re-examined and either renamed or placed in different genera.