By Will Dunham
(Reuters) – On February 20, 1824, English naturalist and theologian William Buckland addressed the Geological Society of London, describing enormous jaw and limb bones unearthed from a slate quarry in the village of Stonesfield near Oxford.
Buckland recognized that these fossils belonged to a huge, bygone reptile, and gave it a formal scientific name: Megalosaurus, meaning “great lizard.” This officially recognized the first dinosaur, although the actual word dinosaur would not be coined until the 1840s.
“It was the beginning of our fascination with dinosaurs,” said paleontologist Steve Brusatte of the University of Edinburgh. “His announcement opened the floodgates and started a fossil rush, and people started looking for other giant bones in England and beyond.”
In the intervening 200 years, dinosaur science has blossomed, providing insight into what these creatures looked like, how they lived, how they evolved, and what made them tick. Dinosaurs entered the planet from about 231 million years ago to 66 million years ago during the Mesozoic Era. Their bird descendants remain with us today.
“Our understanding of dinosaurs has changed significantly since the 19th century,” says paleontologist Emma Nicholls of the Oxford University Museum of Natural History, home to the Megalosaurus fossils Buckland studied.
“Buckland and other gentlemen naturalists of the early 19th century would be amazed at how much we now know about dinosaurs,” Brusatte added.
Megalosaurus is an example of this. Buckland thought it was a lizard about twenty meters long, which walked on four legs and could live on land or in water. Scientists now know that it was neither a quadruped nor a lizard, but belonged to the theropod group of carnivorous dinosaurs such as Tyrannosaurus and Spinosaurus, and that it was about 9 meters long.
“It ran around on its hind legs, chasing its prey and using its clawed hands and wide jaws to subdue its victims,” Brusatte said.
Buckland, like others at the time, did not understand how long ago dinosaurs lived, believing that the Earth was only a few thousand years old. Scientists now know that the Earth is about 4.5 billion years old. Megalosaurus lived about 165 million years ago.
‘It took decades for geologists to understand that the Earth was really old, and that life evolved over vast periods of time. Dinosaurs and the other fossils that were discovered were a huge impetus for this enormous change in people’s understanding of their place in the Earth. world,” said Brusatte.
English naturalist Richard Owen recognized that fossils found in southern England of Megalosaurus and two other large land-dwelling reptiles, Iguanodon and Hylaeosaurus, formed a common group and named them “Dinosauria” in an 1841 lecture and a publication the following year .
The subsequent discovery of Hadrosaurus and Dryptosaurus fossils in the US state of New Jersey showed that at least some dinosaurs were bipedal, changing the perception that they resembled reptilian rhinos. Beginning in about the 1870s, the first complete large dinosaur skeletons – first in the American West, then in Belgium and elsewhere – demonstrated the distinctive anatomy and diversity of dinosaurs.
In the 1960s, the identification of the small carnivorous dinosaur Deinonychus shook up dinosaur science, ushering in a period of research dubbed the “Dinosaur Renaissance.” It showed that dinosaurs could be small and agile. Some were anatomically remarkably similar to early birds like Archeopteryx, confirming how birds evolved from small, feathered dinosaurs. It also sparked a debate over whether dinosaurs were warm-blooded like birds, contradicting the long-standing view that they were slow, lumbering and cold-blooded.
‘In the decades since, increasing work has been done on dinosaur growth, on the use of CT scans, on analytical methods for the reconstruction of evolutionary relationships, and on biomechanical function, all of which have helped create a more dynamic and biological view of dinosaurs as living beings. ,” said paleontologist Thomas Holtz of the University of Maryland.
Paleontologists put skull fossils into CT scanners to build digital models of dinosaur brains and ears, giving them a better understanding of dinosaurs’ senses such as sight, hearing and smell. Researchers can now also determine the color of dinosaurs if their skin or feathers are sufficiently well preserved to retain microscopic melanosome bubbles that hold pigment in the cells.
There are now more than 2,000 known dinosaur species and paleontology is a vibrant, international science. Remarkable fossil finds have been made in China, Argentina, Brazil, South Africa and Mongolia, among others.
“In terms of discoveries about dinosaurs in recent decades, the most important in my opinion is the discovery that at least the carnivorous dinosaurs, theropods, had feathers instead of scales, and that some had really well-developed feathers on their arms, even though they were. unable to fly for various reasons,” says paleontologist Hans-Dieter Sues of the Smithsonian Institution’s National Museum of Natural History in Washington.
“Presumably these feathers, which were often colorful, provided insulation for the body and were displayed in some species,” Sues added.
THE DEADLIEST ASTEROID
The extinction of the dinosaurs has long puzzled scientists, with various hypotheses ranging from plausible to ridiculous. Some even claimed that the mammals of that time, the size of a shrew, ate the dinosaur eggs.
In 1980, researchers identified a sediment layer dating from the very end of the dinosaur age that contained high concentrations of iridium, an element common in meteorites, indicating that a huge space rock had struck Earth. The Chicxulub crater on Mexico’s Yucatán Peninsula – 180 kilometers wide – was subsequently identified as the impact site of the asteroid that wiped out three-quarters of Earth’s species, including the dinosaurs.
If that asteroid had missed Earth, would dinosaurs still rule, instead of the mammals — eventually including humans — who inherited a shattered world?
“Almost certainly,” Holtz said. “Mammals emerged not long after the first dinosaurs, but spent many tens of millions of years in their shadows. Mesozoic mammals were very successful and diverse, but only with smaller body sizes.”
“The dinosaurs would have faced the eventual drying and cooling of the world, and with it the reduction of forests and their replacement by grasslands,” Holtz added. “But these changes appear to have been so gradual that the dinosaurs would have had a chance to adapt to the new conditions, just as large mammals did.”
Scientists have evaluated dinosaur metabolism using a formula based on body mass, as evidenced by the bulk of their femurs, and growth rate, as evidenced by growth rings in fossil bones that resemble those in trees. The research suggested that dinosaurs were an intermediate to today’s warm-blooded and cold-blooded animals.
Scientists have also refined their assessment of the size of several dinosaurs, including the sauropod group that was among the largest land animals in Earth’s history. In a 2023 study based on limb bone dimensions, the Argentinosaurus, which was about 35 meters long, was crowned the heavyweight champion at about 76 tons.
Even after two centuries, the research is far from finished.
“Outside the realm of new technology, there are still many badlands in various corners of the world that are largely unexplored paleontologically,” Holtz said. “These regions will reveal new species from the dinosaur age. There are almost certainly entire groups of dinosaurs that we currently know nothing about, waiting to be discovered.”
(Reporting by Will Dunham in Washington, Editing by Rosalba O’Brien)