Editor’s Note: Science has transformed our understanding of dinosaurs in the past two decades. Get caught up with what’s new in this five-part CNN series.
Defined by their disappearance dinosaurs might appear to be evolutionary failures. Not so.
Dinosaurs survived and thrived for 165 million years – far longer than the roughly 300,000 years modern humans have so far roamed the planet.
They lived on every continent, munched on plants, snapped their jaws at insects, itched from fleas, suffered from disease, got into fights, snoozed, performed elaborate courtship rituals and looked after their young. The creatures were much more diverse – and downright bizarre – than what we might recall from childhood books.
Were it not for an asteroid strike 66 million years ago, the ancient creatures still might have dominated our world. And they still are here, in the form of birds we see around us today.
Scientists have discovered more in the past two decades than they had in the prior 200 years about how dinosaurs behaved and evolved. Here’s what’s new and different about what is known of dinosaurs.
How many dinosaurs were there?
The short answer: Lots.
Take T. Rex, the predator with banana-sized teeth that is perhaps the best studied dinosaur. Scientists believe that each T. rex generation was 20,000 individuals, and this adds up to a total of 2.5 billion during the 2.4 million years they are thought to have lived.
While it’s only an estimate and relies on lots of assumptions, it’s a good reminder that the fossil record only captures a tiny fraction of ancient life. The same team of researchers purports that for every 80 million adult T. rexs, there is only one clearly identifiable specimen in a museum.
Scientists have definitively identified around 900 dinosaur species – although there are plenty more potential species for which paleontologists don’t quite have enough bones or the fossils aren’t well preserved enough to truly designate them as such. And there are about 50 new dinosaurs discovered each year, inspiring many scientists to think we’re experiencing a golden age of paleontology.
Many, many more species existed – one estimate suggests that there were between 50,000 and 500,000, but we might never find their fossil remains.
So many species could exist because they were highly specialized, meaning different types of dinosaurs had different sources of food and could live in the same habitats without competing. For example, with unusually large eyes and hair-trigger hearing, Shuuvia deserti, a tiny desert-dwelling dinosaur evolved to hunt at night, while Mononykus had perplexingly stunted forelimbs, each of which had only one functional finger and claw – perhaps to eat ants or termites.
It’s worth pointing out, of course, that many of the dinosaurs you might be familiar with did not live together as one community. Stegosaurus and T. rex never co-existed, separated by 80 million years of evolution. In fact, the time separating Stegosaurus and Tyrannosaurus is greater than the time separating T. rex and you.
What did they look like?
The first dinosaur discoveries, the earliest more than 150 years ago, focused on the sensational: The big bones and skulls we know from museum atriums.
But dinosaurs came in all shapes and sizes. In fact, some of the most exciting finds in recent years have been tiny. In 2016, a tail belonging to a sparrow-sized creature could have danced in the palm of your hand was found preserved in three dimensions in a chunk of amber.
New evidence has dramatically shifted the way researchers see and perceive dinosaurs. While some dinosaurs did have reptilian scaly skin, many did not and were a lot more bird-like.
In 1996, a fossil unearthed from Liaoning province in China by a farmer digging a well shook up the world of paleontology. It preserved some brown, furry stuff along the head, back and tail of Sinosauropteryx, as the fossilized creature became known. Paleontologists described them as primitive feathers – something that generated intense debate. But it’s now widely accepted that many dinosaurs had fur or feathers.
Since then, according to Xu Xing, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing who worked on some of the earliest feathered fossils, 50 feathered dinosaur species have been found, mostly – but by no means exclusively – in one of the three main dinosaurs lineages: therapods.
Therapods are two-legged dinosaurs that include familiar predators like Velociraptors and T. Rex, which quite likely had some kind of feathers. While many feathered dinosaurs were small, some, like Yutyrannus, were big: The 30-foot-long dinosaur was covered with wispy feathers. (We don’t know for certain whether all therapods were feathered.)
“Different feathers tell us different things about dinosaurs. Many dinosaurs use feathers for insulation; some dinosaurs use feathers for display; some use feathers for flight,” Xu said.
The first feathered fossil Xu studied was Beipiaosaurus, which was discovered in 1997 and was for a while the largest known feathered dinosaur. He said when he first saw it, he knew immediately it would be the biggest discovery of his career.
Thanks to these discoveries, scientists now believe that the birds that flap around in our backyards directly evolved from small, theropod dinosaurs.
They likely acquired bird-like characteristics piece by piece, shrinking, losing their sharp teeth and evolving beaks and the ability to fly over time. Their smaller size and ability to fly may have helped them survive the city-sized asteroid that struck off the coast of Mexico 66 million years ago and doomed most dinosaurs to extinction.
The feathers aren’t just an outfit change that popular culture representations of dinosaurs just haven’t come to grips with. They can reveal intriguing details about dinosaur coloring – something once thought impossible to know – and the habitats in which they lived.
In some fossils, tiny structures called melanosomes that once contained pigment are preserved. By comparing the melansomes with those of living birds, scientists can tell the possible original colors of the feathers. In the case of Sinosauropteryx, dark areas of the fossil were a rusty brown or ginger color, and the rest were thought to be white.
“If you have a black feather, the melanosomes are shaped like little sausages. Then, if you have ginger, or reddish brown hair, that obviously has a slightly different chemical composition. They are shaped like meatballs,” said Jakob Vinther, a senior lecturer in paleobiology and evolutionary biology at the University of Bristol in the UK.
“And whether you take a the chest of a European robin or the hair of a ginger person, (the melansomes) are shaped like meatballs,” he added.
In 2017, Vinther and his colleagues also found evidence of camouflage in Sinosauropteryx: a dark back and light underside, a striped tail and a “bandit mask” stripe running across its eyes. They believe it lived in an open habitat like a savannah because living animals in these environments sport sharp contrasts in their body markings.
Similar research on other dinosaurs has revealed they were surprisingly brightly colored: Microraptor, a bizarre dinosaur with four wings, for instance, had a glossy, iridescent sheen in its feathers, while Psittacosaurus had a dark back and lighter underbelly, but the muted and gradual contrast between the different colors suggested it lived in a closed habitat like a forest.
So why is there so much resistance to the idea of feathered, fluffy dinosaurs? Vinther blames the legacy of the “Jurassic Park” movie franchise and its depiction of fierce, reptilian killers.
“‘Jurassic Park’ was such an immense milestone. The story (is) so captivating and enthralling. You cannot mess with ‘Jurassic Park.’”
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