The Discovery of Dinosaurs

In 1811 Joseph Anning found the skull of an ichthyosaur in the cliffs at Lyme Regis, and his sister Mary Anning uncovered the rest of the skeleton in the following months. The fossil, formally described in 1814, showed a large marine reptile unlike any living animal. Mary Anning's fossil work supported the emerging science of geology, though credit and payment for her discoveries were long denied to her. The specimen was sold to a private collector and described by the anatomist Everard Home, while the Anning family sold fossils to visitors to make their living. Mary Anning went on to find a plesiosaur in 1823 and a pterosaur in 1828, training the eye of a generation of English geologists. The ichthyosaur showed Victorian naturalists that the ancient seas had held reptiles of a scale and strangeness no living animal matched.

Location: Lyme Regis, Dorset, England

In 1822 Mary Ann Mantell found unusual fossil teeth in Sussex, which her husband Gideon Mantell identified in 1825 as belonging to a giant plant-eating reptile he named Iguanodon. The teeth resembled those of a modern iguana but were the size of a human fist. The discovery established that giant herbivorous reptiles had once lived in Europe. Mantell compared the teeth to the dentition of a modern iguana, hence the name Iguanodon, meaning iguana tooth, and estimated a giant herbivore from the resemblance. Together with Megalosaurus the find gave European science its first evidence of large extinct plant-eating reptiles. The Mantell collection, one of the great private cabinets of the nineteenth century, is now held by the Natural History Museum in London.

Location: Sussex, England

On 20 February 1824 the geologist William Buckland described Megalosaurus from a large jaw and limb bones found in Oxfordshire, the first dinosaur genus to be scientifically named. He estimated the animal at about 6 meters (20 feet) long. The find showed that Britain had once been home to reptiles of enormous size. Buckland described the find to the Geological Society of London in February 1824, making Megalosaurus the first dinosaur genus to be scientifically named. The bones had been known as curiosities in Oxfordshire quarries for decades before he recognized what they were. His estimate of the animal's size, around 20 feet, is remarkably close to modern reconstructions.

Location: Oxford, England

In August 1841 the anatomist Richard Owen told the British Association for the Advancement of Science that Megalosaurus, Iguanodon and Hylaeosaurus formed a distinct group of large fossil reptiles, which he named Dinosauria in 1842. The name, meaning "terrible lizards", gave the scattered discoveries a scientific identity. Owen later disputed the link between dinosaurs and birds championed by Thomas Henry Huxley. Owen's name drew a formal line between these fossil reptiles and all living animals, a claim about extinction that Victorian science was still absorbing. He became the driving force behind the founding of the Natural History Museum in London. His rejection of the link between dinosaurs and birds later put him on the wrong side of the debate his own classification had opened.

Location: Plymouth, England

In 1854 life-size models of dinosaurs and other prehistoric animals, built with Owen's advice by Benjamin Waterhouse Hawkins, opened to the public at the Crystal Palace grounds at Sydenham. The reconstructions gave Victorian audiences their first images of extinct giant reptiles. Some details, such as the Iguanodon's horn, were later found to be wrong. The models were the world's first life-size dinosaur reconstructions and a Victorian sensation, shaping how the public imagined extinct animals for generations. The Iguanodon's thumb spike was mounted as a nose horn, an error later corrected by Louis Dollo's work at Bernissart. Restored in recent decades, the models remain on public display in the park at Crystal Palace.

Location: Sydenham, London, England

In 1861, a year after a fossil feather was found, a complete skeleton from the Bavarian limestone of Solnhofen was described by Hermann von Meyer as Archaeopteryx, a bird with teeth and clawed wings. Huxley used such fossils to argue that birds descended from dinosaurs, a view Owen opposed and that most paleontologists rejected for a century. The fossil remains key evidence for the dinosaur-bird link. The Solnhofen limestone preserves the skeleton in fine detail including the impressions of its feathers, a rare assemblage of ash-lime deposits of the late Jurassic. Huxley's arguments for the dinosaur-bird link were largely abandoned in the early twentieth century before Ostrom's work revived them. The specimen remains one of the most famous fossils in the world and the icon of evolutionary transition.

Location: Solnhofen, Bavaria

From 1877 the American paleontologists Othniel Charles Marsh and Edward Drinker Cope competed to find and name dinosaurs in the American West, their rivalry escalating into bribery, theft of fossils and the destruction of specimens. Between them they named well over 100 new species from the Morrison Formation, including Stegosaurus, Triceratops and Diplodocus. The feud greatly expanded the fossil record while damaging their reputations and collections. The rivalry, fed by survey funding and personal fortunes, left many specimens smashed or burned in the rush to name them first. Together Cope and Marsh described well over a hundred species from the Morrison Formation, many still valid and others later synonymized. The feud made American paleontology front-page news and filled the museums of the eastern cities with the skeletons that defined the public image of dinosaurs.

Location: Western United States

In 1878 coal miners at Bernissart in Belgium found the remains of at least 29 Iguanodon skeletons at a depth of about 322 meters (1,056 feet). Louis Dollo reconstructed the animals and mounted them for display in Brussels, an upright pose later revised. The find gave science its first large sample of a single dinosaur species and fixed the public image of the plant-eater. The skeletons, preserved in a flooded coal seam, gave Louis Dollo the material to reconstruct Iguanodon in an upright kangaroo-like pose, later revised to a horizontal, four-legged stance. The deposit remains one of the richest single dinosaur graveyards ever found. The mounted skeletons still stand in the Royal Belgian Institute of Natural Sciences in Brussels.

Location: Bernissart, Belgium

In 1964 John Ostrom's team excavated Deinonychus, a predator about 3.4 meters (11 feet) long whose anatomy implied an active, agile hunter. Ostrom's work, with the arguments of his student Robert Bakker, overturned the Victorian image of dinosaurs as sluggish swamp-dwellers and revived the dinosaur-bird link. The reinterpretation, known as the dinosaur renaissance, reshaped the field from the 1970s onward. Ostrom's 1969 monograph argued that Deinonychus was an active, agile predator with a stiffened tail and a retractable sickle claw, and his student Robert Bakker popularized the warm-blooded, fast-moving dinosaur. The reinterpretation, known as the dinosaur renaissance, overturned the Victorian image of sluggish swamp-dwellers. It culminated in the cladistic revival of the dinosaur-bird link and the feathered fossils of the 1990s.

Location: Montana, United States

In 1980 a team led by Luis and Walter Alvarez reported a worldwide layer of iridium at the Cretaceous-Paleogene boundary and proposed that an asteroid impact killed the non-avian dinosaurs 66 million years ago. Many paleontologists resisted a catastrophic explanation at first, favoring gradual climate change. Evidence from the Chicxulub crater in the 1990s largely settled the debate in favor of the impact. The iridium anomaly, rare in Earth's crust but common in asteroids, was first found in boundary clays in Italy and Denmark. The Chicxulub crater on the Yucatán peninsula was identified as the impact site in the early 1990s, largely settling the debate. The asteroid hypothesis is now the mainstream explanation for the end-Cretaceous extinction, alongside the Deccan volcanism that many researchers treat as a contributing factor.

Location: Global

In 1996 scientists described Sinosauropteryx from Liaoning, China, a small predator preserved with a filamentous covering interpreted as primitive feathers. The find, and later discoveries from the same deposits, supplied direct evidence for feathers on non-avian dinosaurs. Feathered fossils from China became central to studies of how flight evolved. The filaments preserved along its tail and body were recognized as primitive feathers, the first evidence of feathers outside birds and a direct support for the dinosaur-bird link. Later studies of melanosomes in the filaments even suggested the animal's colour pattern. The Jehol Biota of Liaoning has since produced dozens of feathered dinosaur species, making China central to the study of how flight evolved.

Location: Liaoning, China

In 2005 Mary Schweitzer and colleagues reported structures resembling blood vessels and cells inside a Tyrannosaurus rex leg bone, a find considered impossible by most researchers because proteins should not survive 68 million years. Some scientists challenged the interpretation, arguing the structures were contamination or microbial in origin. The debate opened new questions about molecular survival in the fossil record. The claim, published in Science, provoked a decade of replication attempts and sharp criticism over sample handling and contamination. Subsequent work has reported collagen sequences and other proteins from dinosaur bone, extending the range of surviving biomolecules. If confirmed, such finds would open new questions about preservation and about the molecular distance between dinosaurs and their living relatives, the birds.

Location: Montana, United States