A Brief History of Dinosaur Discoveries

The group of animals that we today call dinosaurs was first recognized scientifically during the 1840s. At this time, British anatomist Richard Owen proposed that three large fossil reptiles, all from southern England, shared features of the hip region lacking in other reptiles. The animals that possessed these unusual features were all large, and the key features that Owen regarded as important showed how their bodies and limbs were specialized to carry great weight. He essentially regarded them as ‘super-reptiles’ – as reptiles that, in contrast to the mostly small, sprawling reptiles of modern times, resembled giant mammals like elephants and rhinos. Owen named them dinosaurs, a name meaning something like ‘terrible reptiles’, but with ‘terrible’ intended to mean ‘awesome’.

The three animals that Owen regarded as founder members of the Dinosauria are the predatory theropod Megalosaurus and the planteaters Iguanodon and Hylaeosaurus. All had been discovered a few decades beforehand, but it hadn’t been realized that all three were close relatives. Indeed, a confusing number of large, ancient fossil reptiles were being documented by scientists at this time, and many were exciting, strange and without any obvious close relationship to modern turtles, snakes, lizards or crocodylians.

People had actually been finding and wondering about the fossil bones of dinosaurs and other long-extinct animals for centuries beforehand. Some of these people, including the ancient Greeks, Romans and Chinese, interpreted fossil bones as the remains of mythological heroes or monsters. Indeed, some experts have proposed that certain mythological creatures – most famously the griffin of central Asia – were invented as a result of people’s attempts to interpret the fossils of long-extinct animals.

Owen’s idea that dinosaurs were pachyderm-like animals was challenged by additional discoveries made in Europe during the latter half of the 19th century. Some of these fossils – namely the small, two-legged planteater Hypsilophodon in England, and the even smaller bipedal predators Compsognathus and Archaeopteryx in Germany – demonstrated a close evolutionary link between dinosaurs and birds. Archaeopteryx, famously preserved with feather impressions, was significant in showing that birds existed as long ago as the Late Jurassic, about 150 million years ago.

Europe continued to yield new dinosaurs throughout the rest of the 19th century and beyond, but it was North America that then became the centre of attention. Numerous spectacular dinosaur remains from the Late Jurassic and Late Cretaceous of Colorado, Montana and elsewhere resulted in a golden age of discovery as scientists, prospectors and professional fossil collectors found and excavated scores of new dinosaurs. The most familiar non-bird dinosaurs of all – Tyrannosaurus, Triceratops, Diplodocus, Apatosaurus and Stegosaurus among them – were found at this time, their skeletons transported to the great museums of the eastern USA.

After this phase of enormous interest, things quietened down substantially during the first few decades of the 1900s, so much so that research on dinosaurs had mostly ground to a halt by the 1930s. A long ‘quiet phase’ characterized the middle part of the 20th century. Work did continue during this time – Indian dinosaurs were discovered and described during the 1930s, and Russian expeditions went in search of Mongolian dinosaurs during the 1940s, for example – but it was much overshadowed by work on other animal groups. Indeed, during the ‘quiet phase’ it was generally thought that mammals (especially those belonging to modern groups, like rodents and horses) were more deserving of study than dinosaurs, and that dinosaurs were dead-ends, uninteresting with respect to our understanding of life on Earth as a whole, and generally not all that worthy of attention. By the 1950s and early 1960s, non-bird dinosaurs were often cast in a negative light – they were said to be failures destined for extinction, inferior to the mammals that replaced them, and only able to survive because the Mesozoic Earth was a vast tropical swampland.

It’s often assumed that this old-fashioned view of dinosaurs as failures developed directly from the ideas that scientists held during the 19th century. But this is not really true since it was actually a 20th-century invention that emerged from a phase of apathy about dinosaurs. If anything, the scientists who worked on dinosaurs during the late 1800s and early 1900s frequently imagined them as active creatures related to birds.

Whatever the cause of the ‘quiet phase’, it came to an end during the late 1960s when a handful of palaeontologists began to look at dinosaurs anew. In a way, they revived the more active view of non-bird dinosaurs and archaic birds that had existed during the 19th century. This event is termed the Dinosaur Renaissance and it involved equal amounts of careful, detailed science and rash, poorly supported speculation. Two scientists, both based in the USA, are most famously associated with the Renaissance. The first is John Ostrom of the Peabody Museum of Natural History at Yale University.

Ostrom’s early scientific work concerned the teeth and jaws of the duckbilled hadrosaurs and of horned dinosaurs like Triceratops, two important plant-eating groups of the Late Cretaceous. He argued that hadrosaurs were not swamp-dwellers as thought during the ‘quiet phase’, but land-living browsers that ate from conifers. He also saw evidence indicating that non-bird dinosaurs were more social and more complex in behaviour than thought. And he pointed to indications of fast growth and a more active, ‘warm-blooded’ physiology for non-bird dinosaurs than was considered likely during the ‘quiet phase’.

But outshining this work were his studies of the bird-like theropod Deinonychus (discovered in Montana in 1964) and the Jurassic bird Archaeopteryx. Not only did Ostrom describe the extraordinary anatomy of the sickle-clawed, highly agile Deinonychus, he was also able to document the many features shared by Deinonychus and Archaeopteryx – so many that they provided clear evidence of a close evolutionary relationship. Deinonychus is a Cretaceous fossil (dating to about 115 million years ago) while Archaeopteryx is a much older, Jurassic one (dating to about 150 million years ago), meaning that Deinonychus is surely a late-surviving relict of an earlier phase in evolution. Far older, smaller Deinonychus-like theropods awaited discovery, Ostrom proposed. This view has since been confirmed by numerous discoveries.

Ostrom’s ideas and observations received widespread coverage in magazines and TV shows. They were vigorously promoted even further by one of his students, the famously iconoclastic Robert Bakker. He argued that the microscopic structure of dinosaur bone revealed evidence for rapid growth similar to that present in mammals and birds, and that dinosaur trackways provided evidence for rapid walking and running speeds like those seen in living mammals and birds. He also looked at the pace of dinosaur evolution, their overall anatomy, and the ratio of dinosaur predators to herbivores. All these lines of evidence, Bakker said, provided strong support for the idea that dinosaurs were ‘warm-blooded’ animals whose bodies and organs worked more like those of birds and mammals than those of lizards and crocodylians. He also championed Ostrom’s work on bird origins, and argued that the traditional idea then prevalent – that non-bird dinosaurs were evolutionary failures, inferior to mammals – was wrong, and that dinosaurs were a phenomenal success story, superior in evolutionary terms to other animal groups.

Ostrom’s and Bakker’s ideas and publications encouraged other scientists to pay closer attention to what was going on in the world of non-bird dinosaur research. But it would be wrong to say that Ostrom and Bakker were the only ones generating interest in non-bird dinosaurs at this time. In fact, research programmes in Poland, Russia, China, South Africa, Argentina and elsewhere meant that scientists outside the USA were making spectacular discoveries at the same time. Some of this research was occurring as a consequence of postwar economic recovery, while much of it was the continuation of research that had started during the ‘quiet phase’ but had previously failed to win attention, or produce exciting results.

Whatever happened, the ideas and discoveries put forward by Ostrom and Bakker coincided with the announcement of amazing new dinosaurs from many places, including Deinocheirus from Mongolia (famous for its gargantuan arms), fang-toothed Heterodontosaurus from South Africa, the sail-backed plant-eater Ouranosaurus from Niger, and the enormous long-necked Supersaurus from Colorado. Add Deinonychus to this mix, and it seems that many things came together at just the right time, enough to capture the attention of journalists and the public alike. The Dinosaur Renaissance marked a shift in how much attention dinosaurs received relative to other fossil animal groups.

Since that time, an increasing number of scientists have been attracted to the study of dinosaurs. Ostrom’s hypothesis of bird origins is now so well supported that it can be considered one of the best supported hypotheses in the history of vertebrate evolution. The old idea that non-bird dinosaurs were evolutionary dead-ends is therefore woefully wrong. Indeed, an understanding of dinosaur biology and anatomy is crucial if we want to investigate how and where the many features of birds evolved.

The vast numbers of new dinosaurs that have been documented since the 1960s are equally exciting. New dinosaurs have of course been discovered ever since the first fossil dinosaur (Megalosaurus) was named in 1824, but an incredible surge in discoveries mean that more than 85% of recognized non-bird dinosaurs have been named since 1990.

The soft tissues of fossil dinosaurs – the structures that covered the outsides of their bodies – are becoming better known thanks to amazing discoveries. We now have substantial information on the feathers, filaments and other structures that grew from the skin of non-bird dinosaurs, and a few specimens even have muscles, guts and other internal organs preserved. These new ideas about dinosaur biology and evolution and the many new discoveries have, combined with technological advances, made the study of non-bird dinosaurs and archaic birds one of the most ground-breaking, active areas of palaeontology. The face of dinosaur science today is a world away from that which existed just a few decades ago.

This work on non-bird dinosaurs and archaic birds has also made it obvious that all too little research has been done on the anatomy of living animals, specifically on functional morphology. Work on dinosaurs has inspired palaeontologists to test many ideas about the patterns and trends of evolution using techniques originally devised to test ideas relevant to dinosaurs alone. Questions asked by palaeontologists have therefore driven an ‘anatomical revolution’ in which scientists have studied modern animals anew, including elephants, lizards, crocodiles and birds.

Read more in Dinosaurs: How They Lived and Evolved, which is available from Smithsonian Books. Visit Smithsonian Books’ website to learn more about its publications and a full list of titles. 

Excerpt from Dinosaurs © The Trustees of the Natural History Museum, London, 2016