An Asteroid Didn’t Kill All the Dinosaurs

According to the prevailing theory among scientists, some 66 million years ago, an asteroid we now call Chicxulub slammed into the coast off the Yucatan Peninsula, triggering Earth’s fifth mass extinction in its more than 4 billion-year-long history. The debris ejected into the atmosphere streaked through the sky, and the resulting friction superheated the atmosphere, causing forest fires around the globe. After a prolonged winter caused by a thick haze of ash blotting out the sun, some 75% of all living species on Earth went extinct. Although many of those species were land-dwelling dinosaurs, one group largely survived the devastation — beaked avian dinosaurs known today as birds.

The first avian dinosaur, archaeopteryx, popped up around 150 million years ago. This proto-bird had teeth, though through evolution, a subsect of these flying dinos dropped teeth for beaks instead. Some scientists theorize that these beaks gave birds a post-apocalyptic advantage, because they could more easily dine on the hearty nuts and seeds found throughout the world’s destroyed forests.

Science Is Still Debating the Existence of the Brontosaurus

Paleontologists have been debating the existence of the giant sauropod named brontosaurus for nearly 150 years. The story starts during the fast-and-loose “Bone Wars” period of paleontology in the late 19th century. During that time, a bitter rivalry developed between American paleontologists Edward Drinker Cope and Othniel Charles Marsh. It was Marsh who discovered the skeleton of a long-necked apatosaurus in 1877, but the fossil was missing its skull. Marsh incorrectly paired the body with the skull of another dinosaur (likely a camarasaurus). Two years later, when a more complete apatosaurus skeleton wound up in his possession, the specimen was unrecognizable compared to Marsh’s Frankenstein dino, so he instead created a whole new species — brontosaurus, meaning “thunder lizard.” Scientists spotted the mistake in 1903, but the name stuck in the public’s mind.

However, a century later, scientists examining more fossils determined that a close cousin of apatosaurus who had a thinner and less robust neck did exist, and resurrected the name brontosaurus to describe it. However, not all paleontologists accept the revived name for the genus — as beloved as it is.

Dinosaurs Didn’t Live in Water

Although many aquatic reptiles existed during the Age of the Dinosaurs, they were not dinosaurs. The most famous of these water-dwelling creatures was ichthyosaurus, which is actually a distinct marine vertebrate — not a dino. The term “dinosaur” instead mostly refers to terrestrial reptiles who walked with their legs under them (not to the side like crocodilians). Other factors such as foot and neck size also help define what is and isn’t a dinosaur.

Despite the fact that nearly all dinosaurs were terrestrial, a few lived a semi-aquatic existence. The spinosaurus, which lived 99 million to 93 million years ago, shows evidence of eating fish, and ankylosaurus lived near coastlines.
Similarly, species like the flying pterodactyls (also known as pterosaurs) — which could be as large as a fighter jet or as small as a paper airplane — are distant cousins of dinosaurs, not dinosaurs themselves, although media coverage frequently refers to them that way.

Dinosaurs and Mammals Coexisted

Mammals and dinosaurs coexisted during most of the Mesozoic Era (252 million to 66 million years ago). The first known mammal, called morganucodontids, appeared around 200 million years ago and was about the size of a shrew. During the Age of the Dinosaurs, mammals remained small, never really exceeding the size of a badger, and were a go-to food source for carnivorous dinos (though sometimes the opposite was also true).

Things changed when a giant asteroid smacked into Earth at the end of the Cretaceous period. Mammals’ small size meant they could burrow underground and escape scorching surface temperatures. As for food, mammals were perfectly content with eating insects and aquatic plant life (which also survived the asteroid’s impact), while large herbivorous dinosaurs went hungry. Over the next 25 million years, mammals underwent a drastic growth spurt as the Age of Mammals began to take shape.

The Film "Jurassic Park" Is a Bit of a Misnomer

The entry point for many into the world of dinosaurs is Steven Spielberg’s 1993 film Jurassic Park, which inspired an entire generation of paleontologists. Despite its outsized impact on the field, the film does get a few things wrong about dinosaurs. For one, dinosaurs are now thought to sport feathers, whereas Jurassic Park’s dinos represent the lizard-esque depiction popular in times past. Also, the film’s very name is a misnomer, as the dinosaurs that take up the most screen time — such as the Tyrannosaurus rex, velociraptor, and triceratops — all lived during the Cretaceous period (145 million to 66 million years ago).

This may seem like a small difference, but the Age of the Dinosaurs is surprisingly long. In fact, the T. rex lived closer to humans, separated by more than 60 million years, than to the stegosaurus, which lived in the Jurassic period some 80 million years before the “king of the tyrant lizards.”

We’re Living in a Golden Age of Dinosaur Discovery

Paleontology is far from a static field. Every year, an estimated 50 new dinosaur species are discovered — that’s basically a new dinosaur every week. Roughly half of those species are being discovered in China, a country that only recently opened up to paleontological pursuits. Technology has also upended the field, with CT scans able to examine the interiors of dino skulls, while other tomographic image techniques can render 3D recreations of bones. Dinosaurs may be a species buried in Earth’s geological past, but uncovering that past has a bright and exciting future.