Megalosaurus: The First Dinosaur Ever Named

Two hundred years ago, the word “dinosaur” didn’t exist. But in a small English parish, a colossal jawbone and a few limb bones were about to change everything. That creature was Megalosaurus – the first dinosaur ever scientifically described. Revered as the “great lizard” by the pioneering geologist William Buckland in 1824, Megalosaurus opened the door to the lost world of the Mesozoic. In this comprehensive guide, we’ll explore the anatomy of this Middle Jurassic predator, the twisting path of its reconstruction, and how a collection of bones became the foundation of a new science.

From its discovery in the stone quarries of Oxfordshire to its place in the first dinosaur classification, we’ll cover everything about Megalosaurus bucklandii.

1. What is Megalosaurus?

Megalosaurus bucklandii is a genus of large theropod dinosaur from the Middle Jurassic (Bathonian stage, about 166 million years ago). It is the type genus of the family Megalosauridae and the first non‑avian dinosaur to be scientifically named. The name means “great lizard,” and the species epithet honors William Buckland, the Oxford professor who described it. Megalosaurus was a bipedal carnivore, related to later theropods like Torvosaurus and Eustreptospondylus. Its remains have been found primarily in the Taynton Limestone Formation (part of the Great Oolite Group) in Oxfordshire, England.

For over a century, Megalosaurus was a wastebasket taxon – any large theropod bone from Europe was often thrown into the genus. Today, paleontologists recognize a single valid species, M. bucklandii, based on its distinctive lower jaw and a handful of other diagnostic specimens.

2. Anatomy: Piecing Together a Predator

Because Megalosaurus was discovered so early – long before complete theropod skeletons were known – its anatomy was initially misunderstood. Today, comparisons with related megalosaurids give a clearer picture:

• Length: Estimated at 7–9 meters (23–30 ft) for the largest individuals.
• Weight: Around 1–1.5 metric tons (1.1–1.7 short tons).
• Skull and jaws: The lower jaw (dentary) was deep and robust, with large, serrated teeth. The premaxilla likely had a small crest or ridge.
• Teeth: Blade‑like and recurved, with fine serrations on both edges – typical of large carnivorous theropods.
• Posture: Bipedal, with a horizontal body balanced by a long, muscular tail. The hip structure is similar to that of Torvosaurus.
• Limbs: Relatively stout hind limbs and shorter, strong forelimbs with three fingers.

No complete skeleton exists; the diagnostic material includes the holotype dentary, a few vertebrae, ribs, limb bones, and isolated teeth. Therefore, reconstructions rely heavily on its close relatives from Europe and North America. Current thinking places Megalosaurus as a robust, medium‑sized theropod, equipped to tackle large prey in the dense coastal forests of Jurassic Britain.

3. The Discovery That Changed Everything

The first fragment of Megalosaurus – a portion of a thigh bone – was found as early as 1676 in a quarry near Chipping Norton, and was initially misidentified as the bone of a giant man (possibly a Roman or a biblical giant) by Robert Plot. It was not until the early 19th century that more bones came to light in the Stonesfield slate quarries.

Between 1815 and 1824, William Buckland gathered a collection of fossils: a lower jaw with teeth, vertebrae, ribs, and limb bones. In 1824, he presented his findings to the Geological Society of London, naming the genus Megalosaurus. Buckland recognized it as an enormous reptile, but its full form remained a mystery. In 1842, Richard Owen used Megalosaurus to help erect the Dinosauria, and the first life‑sized reconstructions – built as quadrupedal, lizard‑like beasts – appeared in the Crystal Palace Park in 1854. These early restorations were, of course, wrong, but they captured the public imagination.

It wasn’t until the late 19th and early 20th centuries, with the discovery of complete theropods in North America, that Megalosaurus was recognized as a bipedal predator. The modern understanding of Megalosaurus was solidified by Roger Benson’s detailed revision in 2008‑2010, which restricted the genus to the Stonesfield material and clarified its distinctive features.

4. Size and Proportions: From Giant Lizard to Theropod

Early estimates of Megalosaurus suggested a length of over 20 meters (66 ft), based on the gigantic scale of known bones compared to modern reptiles. As the bipedal theropod body plan became established, estimates shrank to a more reasonable 7–9 meters. Today’s understanding places Megalosaurus as a mid‑sized theropod, comparable in size to a large Allosaurus, but with a somewhat stockier build.

The size was not constant across individuals; fragments suggest variation, perhaps between 6 and 9 meters. The skull likely measured about 1–1.2 meters (3.3–4 ft). Despite the limited remains, the limb bones indicate a robust, powerfully built predator, not a slender runner like the later ornithomimids.

5. Habitat: Jurassic England and the Stonesfield Slate

The Stonesfield Slate, in particular, has produced a remarkable array of fossils: pterosaurs, marine crocodylomorphs, ichthyosaurs, plesiosaurs, and the early mammal Phascolotherium. On land, other dinosaurs such as the sauropod Cetiosaurus, the stegosaur Lexovisaurus, and the small ornithopod Yaverlandia shared the environment. Megalosaurus would have been the dominant land predator, hunting in coastal woodlands and perhaps scavenging along the shoreline.

The presence of abundant pterosaurs and small crocodilians suggests that Megalosaurus may have also fed on these coastal creatures, making the shoreline a fruitful hunting ground.

6. Diet and Feeding Ecology

With its robust skull and serrated teeth, Megalosaurus was built to kill and consume large prey. Potential prey species included:

• Cetiosaurus: A medium‑sized sauropod (up to 16 m long), likely a dangerous but rewarding target, especially juveniles or sick individuals.
• Stegosaurs and ornithopods: Armored dinosaurs like Lexovisaurus would have been tough prey, but small, unarmored ornithopods were easier meals.
• Marine reptiles: Carcasses of ichthyosaurs and plesiosaurs washed up on shore would have provided carrion.

Bite marks on some fossil bones from the same deposits have been attributed to large theropods, possibly Megalosaurus. Its teeth were not as laterally compressed as those of Allosaurus, suggesting a stronger bone‑crushing bite, useful for scavenging and handling large carcasses.

7. Megalosaurus in Culture and Science

As the first named dinosaur, Megalosaurus holds an unshakeable place in history. It appears in countless Victorian books and was one of the main attractions at Crystal Palace. In Charles Dickens’ Bleak House (1853), the opening paragraph famously imagines a Megalosaurus waddling up Holborn Hill – a direct reflection of how dinosaurs were viewed at the time.

In modern times, Megalosaurus may have been overshadowed by the likes of Tyrannosaurus and Velociraptor, but it continues to appear in documentaries and games as the archetypal “first dinosaur.” The 2024 bicentenary of its naming was celebrated worldwide with exhibitions and new research, reaffirming its status as the grand ancestor of all dinosaur science.

8. Megalosaurus Gallery

Walk with the great lizard

← Swipe or scroll →  |  Click any image to enlarge

Final Thoughts

Megalosaurus is far more than a dusty museum curiosity. It is the spark that ignited humanity’s fascination with dinosaurs. From a handful of broken bones to the towering, feathered theropods we reconstruct today, the journey of Megalosaurus reflects the entire history of paleontology. Every new study of its fossils teaches us not only about the animal itself, but about how science slowly uncovers the truth – one bone at a time. The “great lizard” will always remain the grandfather of the dinosaurs.