Paleontologists Are Still Unraveling the Mystery of the First Dinosaur

Two hundred years after it was first named, scientists are just beginning to reveal the secrets of Megalosaurus

Paleontologists are still investigating what the carnivorous dinosaur Megalosaurus looked like. De Agostini via Getty Images

The reptilian giant found in England’s Stonesfield quarry needed a name. Throughout the 18th century and into the 19th, European naturalists in had been pondering strange and giant bones of long-dead creatures uncovered in quarries and sent to them through the tendrils of colonialism. For even longer, Indigenous peoples and others around the world had been wondering over similar remains of animals that clearly did not roam the planet anymore. But in the beginning of the 19th century, as science set about naming and describing fossilized creatures through its own language and standards, the curious bones needed proper titles. Among these early efforts, in 1824, University of Oxford geologist William Buckland dubbed the collection of skeletal pieces from Stonesfield Megalosaurus, the first dinosaur to receive a scientific name.

Buckland didn’t know that Megalosaurus was a dinosaur. That’s because the word “dinosaur” would not be coined for another 18 years. He was working during a time when the sciences of geology and paleontology were still very new, when the identity and broader significance of fossilized creatures were only just beginning to be understood. After all, it had only been in 1799 that naturalists finally accepted that extinction was a reality and Earth’s rocks were full of strange, bygone species. Megalosaurus was one such creature.

Working through the science of comparative anatomy, Buckland was sure that Megalosaurus was a giant reptile. “Buckland himself recognized that the bones he described as Megalosaurus must have come from several different individuals of various ages and sizes, but were all from the same kind of animal,” says University of Oxford paleontologist Eliza Howlett. Those pieces represented a creature not quite like any known reptile. Even though the leg bones indicated an animal with upright, column-like legs, like most mammals, the details of the teeth were clearly reptilian. He envisioned the animal as crocodile-like in nature. “The megalosaurus itself was probably an amphibious animal,” he wrote in his paper. Fossils of crocodile teeth and turtle shells found in the same quarry seemed to bolster the idea.

Iguanodon Versus Megalosaurus
An 1863 depiction of Iguanodon battling Megalosaurus Édouard Riou / Public Domain

Two centuries later, we have a very different image of Megalosaurus, whose full name is Megalosaurus bucklandii in the Oxford geologist’s honor. Paleontologists have gone back to the original bones, as well as the dinosaur’s paper trail through the history of science, to reintroduce us to Megalosaurus as a bipedal predator that wandered along the Jurassic coastline. The dinosaur roamed what’s now England about 166 million years ago, a fairly large carnivore of its time at an adult length of more than 20 feet. Stalking about on two legs, the flesh-eater had a long and low skull of curved teeth and likely had short, stout arms tipped in large claws like its later relative Torvosaurus.

To this day, however, no one has ever found anything near a complete skeleton of Megalosaurus. The task of reconstructing the form of such a dinosaur is like trying to put together a puzzle when you have a pile of pieces from different sets, but no box. In addition to the bones Buckland originally described, experts attributed other fossils from England and elsewhere to Megalosaurus because they seemed roughly similar. On top of that, some pieces of Megalosaurus have gone missing. American Museum of Natural History paleontologist Roger Benson notes that some Megalosaurus fossils that had been illustrated in the scientific literature, such as a jaw with teeth and the end of a femur that was infamously illustrated in the 1700s with the label “scrotum humanum” for its resemblance to a human body part, are not in any museum’s collections, and their whereabouts are unknown. All of this uncertainty has led to widely varying interpretations of Megalosaurus over time.

Scrotum Humanum
An illustration of a femur that was dubbed “scrotum humanum” for its resemblance to a human body part Public Domain

Megalosaurus started getting makeovers soon after the animal got a name. In 1842, in a paper that coined the word “dinosaur,” the English anatomist Richard Owen not only identified Megalosaurus as a dinosaur but refashioned its image into something between reptile and mammal. Owen advised artist Benjamin Waterhouse Hawkins on creating a sculpture of his vision of Megalosaurus, as well as depictions of other dinosaurs, that was placed at London’s Sydenham Hill in 1853. The dinosaur was almost mammal-like, standing on all fours with a hump on its back, fitting Owen’s idea that dinosaurs were advanced reptiles unlike today’s lizards and crocodiles. But as new finds in North America were unearthed in the 1850s and ’60s, such as the carnivorous Dryptosaurus, paleontologists revised dinosaurs yet again. Dryptosaurus and other new finds were bipedal, bird-like predators, and Megalosaurus was again adjusted to fit the new consensus.

Year by year and find by find, Megalosaurus was overshadowed. No complete skeleton appeared to reveal the dinosaur’s full form, and the fact that it was named based on isolated parts made it easy for experts to attribute other isolated bones and footprints to Megalosaurus. The dinosaur had become what experts often call a “wastebasket taxon,” or a biological category that researchers attribute various specimens to because they don’t seem to fit anything else. Eventually Megalosaurus was relegated to accounts of dinosaur history and was not especially relevant to new studies of how dinosaurs lived and evolved.

In the early 21st century, however, Benson took on the arduous task of disentangling the megalosaur mess and providing the dinosaur with a modern description as a doctoral project. “I was always really motivated to understand how different groups of dinosaurs were related to each other,” Benson says, and to do that for Megalosaurus required going back to the dinosaur’s historic record.

Some bones attributed to Megalosaurus turned out to belong to other dinosaurs. In 2009, for example, Benson named the theropod Cruxicheiros from historic Jurassic bones that had been labeled Megalosaurus and overlooked since their discovery. Likewise, Benson found that a toothy jaw fragment once thought to belong to Megalosaurus really represented a new dinosaur he named Duriavenator. For Megalosaurus itself, Benson recognized parts of the jaw, skull, forelimbs, hindlimbs, ribs and vertebrate that could confidently be deemed Megalosaurus, providing at least a rough look at the dinosaur’s skeleton. Incomplete as the skeleton seemed, experts could now be confident about which remains truly belonged to Megalosaurus when comparing similar dinosaurs and working out the shape of the dinosaur family tree.

Benson still hopes that more Megalosaurus fossils are out there awaiting discovery. Any new bones could offer important hints about the animal. “If we were looking for a wish list of what I would like to know about Megalosaurus,” says University of Oxford paleontologist Emma Nicholls, “then the answer would be: everything.” How Megalosaurus moved, how large it got and perhaps even how the dinosaur reproduced can only be guessed at by looking at related animals. “There are so many questions about Megalosaurus that it would be fantastic to have definitive answers for,” Nicholls says, and that curiosity is what drives paleontologists to keep going back to the rocks to search for more fossils.

Even so, experts have been showing more interest in the dinosaur than they did for most of the past century. “Scientists would often write that Megalosaurus was a generalized theropod,” Benson says, “but that’s a bit like saying, ‘We don’t know much about it, so let’s assume it’s kind of average.’” The reality is that Megalosaurus was probably more unusual than paleontologists expected.

Megalosaurus was not amphibious, as Buckland thought, but it seems that the dinosaur really did live along Jurassic waterways. The bones of Megalosaurus, Benson says, come from rocks that formed in coastal habitats where the remains of terrestrial plants and animals were being washed into shallow water and preserved there, suggesting that the dinosaur lived nearby. Given that Megalosaurus is related to the fish-eating spinosaurs, and spinosaurs themselves are categorized under the broader umbrella of megalosaurs, Megalosaurus may have been a fish-eater, too, representing the sort of dinosaur that gave rise to the specialized spinosaurs.

When Megalosaurus was first found, scientists hadn’t imagined such a creature could have existed. Makeover after makeover, the dinosaur kept changing. Now, 200 years after its name first appeared in print, we are truly just getting to know the first dinosaur, a Jurassic reptile that might have been more unusual than we ever knew. A hundred years from now, perhaps we’ll finally be able to envision Megalosaurus as more than a historic puzzle waiting to be completed.

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