© Getty Images

Where did they come from? - The earliest dinosaurs reportedly originated in what is now South America, then diverged and spread across the globe when the continents were an enormous landmass called Pangaea.

© Shutterstock

Eggs -

Upon discovering fossilized nests, scientists can learn about a dinosaur’s egg-laying and parenting strategy from the number of eggs and the way they are arranged.

© Reuters

Footprints - The footprints reveal the size of the animal and how it walked, using how many legs, and the length of the stride can be used to calculate how fast the dinosaur was moving.

© iStock

Poo -

Yes, even fossilized dinosaur poo, called coprolite, has helped shape our knowledge of the species! They sometimes contain evidence of the animal’s past meal. Dark bits are pieces of plant, indicating that the dinosaur was likely a herbivore.

© Getty Images

Other clues - There are preserved gut contents, skin impressions, living animals to compare with, and, of course, the skeletons we love to see in museums.

© Reuters

Skeletons -

Detailed examination of skeletons can show how bones fit and moved together, with paleontologists sometimes extrapolating knowledge of anatomy and other species to put separate pieces together.

© Getty Images

Skeletons - If they're lucky, paleontologists find the fossilized remains preserved in the position the dinosaur died in, so they can see which bones were next to each other and how the joints worked. From this, they can reconstruct it and see how they moved.

© Shutterstock

Inferring muscles - Rough patches and marks on bone can also be used to locate the positions of muscles, cartilage, and ligaments.

© Shutterstock

Diet -

A dinosaur's teeth shape can reveal their diet, and analysis under a microscope may reveal wear marks and scratches that give further clues to what the dinosaur ate and how.

© Shutterstock

Modern technology lets us see more -

Particularly the use of computed tomographic (CT) scanning, which uses rotating X-rays to build a 3D model of both internal and external anatomy. With dinosaur bones, it can reveal features of the skeleton like the shape of the brain and the presence of air-filled sacs that ran through many dinosaur bones.

© Reuters

The benefits of CT scans -

They can produce virtual models of the bones, which can then be tested in ways real fossils would never be allowed to. The virtual models are imported into different computer programs, clothed in muscle, and subjected to forces ranging from walking to destruction.

© Shutterstock

Dinosaurs grew really fast - Like tree rings, by carefully cutting thin sections through dinosaur bones and putting them under the microscope, we can count growth lines in the bone walls to age dinosaurs and work out how fast they grew to adulthood.

© Shutterstock

Dinosaurs sort of hit puberty -

Even the largest species, such as the Tyrannosaurus, reaches full size in no more than 30 years, and, like humans, dinosaurs reportedly have a teenage growth spurt.

© Shutterstock

Their appearance -

Some dinosaur fossils, if well-preserved, include evidence of soft tissues like skin, muscle, and internal organs, giving vital clues on dinosaur biology and appearance.

© Reuters

Some had built-in armor - Fossilized skin remains show that some dinosaurs had pebbly plate-like armor set into their leathery skin.

© Shutterstock

Some had feathers -

Some fossils (pictured is the Caudipteryx) show that many meat-eating dinosaurs were covered in thick coats of feathers, which leads to a strange fact...

© Reuters

Birds are dinosaurs -

The idea that birds are nothing more than small, meat-eating dinosaurs that gained feathers and learned how to fly has actually been proven in the last 20 years!

© Reuters

Once again -

Birds are dinosaurs! They're only one small branch of the dinosaur family tree, but they carry a direct genetic legacy, meaning that their genes are dinosaur genes.

© Reuters

'Jurassic Park' wasn’t actually that far off -

Scientists have figured out that birds today contain dormant genes for forming teeth, and some are attempting to switch on these genes in living birds. There's also the possibility of transforming bird beaks into more dinosaur-like snouts, and possibly re-introducing the long tails, too!

© Reuters

But how did it end for them? -

Dinosaurs went extinct 66 million years ago, but they roamed Earth for at least 160 million years prior to that. For reference, humans’ ancestors have been traced back six million years, and modern homo sapiens only evolved about 200,000 years ago.

© Getty Images

Mysterious mass extinction - As the Cretaceous period yielded to the Paleogene, a mass extinction event claimed three quarters of life on Earth, but paleontologists have struggled for years with finding out what that event was. They have two strong theories...

© iStock

First theory: Deathly meteor -

One of the most well-known theories is credited to father-son scientists Luis and Walter Alvarez, who in 1980 proposed the notion that a meteor the size of a mountain slammed into Earth 66 million years ago, filling the atmosphere with gas, dust, and debris that drastically altered the climate.

© Reuters

The reasoning -

The main evidence is an oddly high amount of the metal iridium—rare on Earth but common in meteorites—in the geologic boundary that appears to cap any known rock layers containing dinosaur fossils.

© Reuters

More evidence -

Scientists were also able to link the extinction event to a huge impact crater—the approximately 93-mile (150-km) wide Chicxulub crater seen in a faint dark green arc on the upper left—along the coast of Mexico’s Yucatán Peninsula.

© Getty Images

It was a deadly event -

After examining deep inside the crater, scientists deduced the impact would have been powerful enough to send huge amounts of vaporized rock and gases into the atmosphere, which later rained down tiny glass bits called tektites. These were found with the dinosaur fossils.

© Getty Images

Second theory: Earth’s own doing -

Other scientists don't think the meteor is conclusive, and hypothesize that a volcanic eruption is more likely, especially since the ancient lava flows in India, known as the Deccan Traps, match up with the end of the Cretaceous period, releasing huge amounts of lava between 60 and 65 million years ago.

© Reuters

Similar release of deadly gases -

Today, the resulting volcanic rock covers nearly 200,000 sq miles (518,000 sq km) in layers that can be more than 6,000 feet (1,828 m) thick. Such an eruptive event would have released enormous amounts of harmful gases that would have also dramatically changed Earth’s climate.

© Reuters

More evidence -

Some studies show that Earth’s temperature was changing before the cataclysmic meteor, and that dinosaurs had already been slowly declining before they disappeared. Ongoing eruptions are also much more common than giant meteor strikes.

© iStock

Could be a combination of the two -

Dinosaurs had no chance of surviving that double slam.

Sources: (NBC News) (National Geographic)

See also: Where in the world to see dinosaur tracks

© Getty Images