Absolutely everything you want to know about dinosaurs
But seriously, what actually killed the dinosaurs? When did they exist in the first place? And how do scientists really know what they look like?
Dinosaurs: be it the fearsome Tyrannosaurus Rex, gigantic Brachiosaurus or the curiously pot-bellied Nothronychus, you definitely have a favourite.
However, while everyone can point to their number one dino, most non-palaeontologists probably have several reasonable questions about these prehistoric animals.
From when dinosaurs actually existed in the first place, to what made them extinct and how we know what they look like, and the lastest discoveries here’s everything worth knowing.
The latest Dinosaur discoveries and news
If you know anything about Protoceratops – 1.8m-long dinosaurs that lived more than 70 million years ago – it's that they evolved to have “huge” neck frills. However, while many previously theorised that these bony frills served as protection and helped regulate body temperature, scientists now believe they served another purpose: attracting mates.
Using 3D scans of Protoceratop skulls, researchers at the Natural History Museum determined that the frills grew more quickly than the rest of the body, indicating they were a sexually selected feature.
Sexual selection is the idea that certain traits in animals are favoured by members of the opposite sex, so in time, these characteristics become more dominant in the creatures. For example, the elaborate feathered display of peacocks are thought to be a result of sexual selection.
What killed the dinosaurs? When did they go extinct?
It’s believed dinosaurs were killed off by an asteroid. Although some scientists theorised a flurry of volcanic activity wiped out the reptiles, research now points to a major impact off the coast of modern-day Mexico about 66 million years ago.
Just how big was the asteroid that killed the dinosaurs? The impact left behind a crater off the coast of Mexico’s Yucatan Peninsula that measures 150km across and 20km deep. It is thought to have triggered tsunamis, earthquakes and volcanic eruptions that not only led to the demise of the dinosaurs but to almost three-quarters of all plant and animal life on Earth.
After blasting into the Earth, scientists say the asteroid would have released particles and gases, which blocked out the Sun and caused a lengthy winter. While this caused the extinction of many dinosaurs, many species that later evolved into birds survived.
In a 2021 study, researchers at Harvard University claimed that the Chicxulub comet may have originated from the Oort cloud, an extended shell of icy debris located at the edge of the Solar System.
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When did dinosaurs live?
Most dinosaurs lived in what’s called the Mesozoic Era, a time roughly 245 to 66 million years ago. Scientists generally divide this period into three separate ages:
- Triassic Period (252 to 201 million years ago) The era when reptiles first evolved into creatures we know as dinosaurs. However, the Earth they lived on was different from today's. Almost all animals lived on Earth’s one extremely hot and dry landmass, Pangaea.
- Jurassic Period (201 to 145 million years ago) In this period, temperatures on Earth fell, leading to more water, plants and dinosaurs. It’s in time period species such as the Brachiosaurus first emerged.
- Cretaceous Period (145 to 66 million years ago) With more continents forming around the globe, more dinosaurs started evolving independently, which led to more dino diversity. Despite what a certain Jeff Goldblum movie might suggest, the Tyrannosaurus Rex and Velociraptor first actually appeared in this Cretaceous Period, not the Jurassic.
Why were dinosaurs so big?
We don’t yet know why the dinosaurs survived the end-Triassic extinction while crocs were almost wiped out, reduced to a few lineages that produced today’s alligators and crocodiles. What we do know is that in the ensuing Jurassic Period the dinosaurs spread around the world and got much larger.
The sauropod dinosaurs like Brontosaurus, Diplodocus and Brachiosaurus were the heavyweights of the time. These were the largest animals to ever live on land, some of them exceeding 80 tonnes in mass – more than the take-off weight of a Boeing 737.
Why were they able to get so big? Their ultra-efficient lungs were probably key. These bird-style lungs were connected to air sacs, which stored extra oxygen-rich air, allowing these dinosaurs to take in more oxygen per breath than a mammal like us. – Professor Steve Brusatte
What were the first dinosaurs like?
Dinosaurs evolved in the Triassic, which began around 252 million years ago, after the most severe mass extinction in Earth’s history. Massive volcanic eruptions in Siberia led to runaway global warming, which killed up to 95 per cent of all species. Among the survivors were small, cat-sized reptiles that could run fast.
These dinosauromorphs were the ancestors of dinosaurs. Around 230 million years ago, they gave rise to true dinosaurs, which are distinguished by their upright legs that fit into a window-like opening in the pelvis, which is attached to the backbone by extra vertebrae. These features allowed the first dinosaurs – like Eoraptor and Herrerasaurus – to run faster, cover larger distances, and expend less energy than most other animals of the time.
These first dinosaurs diversified and split into the three fundamental divisions of the dinosaur family tree: the carnivorous theropods, long-necked sauropods, and beaked, plant-munching ornithischians. – SB
What came before dinosaurs?
No, not aliens. The answer to what dinosaurs evolved from is simple: more reptiles – just ones a lot smaller than a T-Rex. Known as dinosauromorphs, they were the size of house cats and flourished around 242 to 244 million years ago.
They were animals by no means at the top of the food chain, but they were speedy enough to outpace most attackers.
How did the earliest dinosaurs beat their rivals?
The first dinosaurs didn’t take over the world right away. Rather, it took them more than 30 million years to assert their dominance. They were evolving in a world very different from today, as all land was joined into the supercontinent Pangea, which stretched from pole to pole.
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Sharing this landmass were early crocodiles and their relatives, which were the main competitors of the early dinosaurs. For most of the Triassic, the crocs were pulling ahead of the dinosaurs: there were more species of them, they had a greater richness of body sizes, diets and behaviours, and they lived across a broader range of Pangea.
But just when it looked like the crocs were poised to defeat the dinosaurs, Pangea began to split, around 200 million years ago. Volcanoes erupted with gusto, spewing out greenhouse gases, causing global warming and another mass extinction. The crocs were decimated, but the dinosaurs survived nearly unscathed. – SB
How successful were the dinosaurs?
By every objective measure, dinosaurs were hugely successful. During much of the Mesozoic Era (252-66 million years ago), they dominated ecosystems on land, living in every conceivable environment from the poles to the equator, and from the seashore to the river valleys to the deep mountains.
They diversified into thousands of species, ranging in size from feisty carnivores like Microraptor (about the size of a crow) to behemoth plant-eaters like Brontosaurus, with the heft of a jet aeroplane. Some were specialised runners, others diggers, and some even glided and flew.
Some species were covered in armour and spikes, others had endless varieties of horns and crests for display, many lived in groups and had big brains and keen senses, and it seems like many dinosaurs – if not all of them – were covered in some type of feather. Indeed, today’s birds evolved from dinosaurs, meaning that 10,000-plus species live on, continuing dinosaur success to the present day. –SB
When were dinosaurs discovered?
The short answer: in 1842, when British scientist Richard Owen coined the term Dinosauria, literally meaning “terrible lizard” in Greek. Owen is often credited as the first person to place dinosaur in their own category of creature after examining a particularly large dino bone.
However, Owen is by no means the first to find dinosaur remains. For instance, many were unearthed in ancient China, but were treated as dragon bones.
Many historians have also noted how many dinosaur bones in Europe were believed to be the remains of biblical creatures. Even as late as 1763, British physician Richard Brookes believed a broken dinosaur femur was actually a fossilised giant's testicle.
How do we know what dinosaurs looked like?
Scientists can estimate the appearance of dinosaurs with some very clever detective work. Not only can experts piece together the size of these creatures from their remains, but tiny details on each bone can offer big clues.
For instance, many fossilised bones have tiny scars that indicate how dinosaur muscles connected to their bones, also illuminating how they moved. In recent years, palaeontologists have also used 3D computer modelling to test exactly how dinosaurs could have moved, and thus looked.
For a full explainer, you can read our full guide to how we know what dinosaurs looked like.
How did dinosaurs learn how to fly?
Not all dinosaurs were enormous. One group, the paravian theropods, went in the opposite direction. Like most dinosaurs, the first paravians sported simple, hair-like feathers, which probably helped to keep them warm.
As the paravians got smaller over time, the feathers on their bodies became larger and more packed together. Then they began to line up their feathers on their arms, to form wings. These first wings were too small to keep these dinosaurs aloft; instead, they were probably used for display.
At some point, though, a threshold was crossed. The wings became big enough that, when flapped, they could provide a bit of lift and thrust, and keep these paravians airborne. Flight had evolved! From these flapping ancestors arose today’s birds.
In other words, birds are dinosaurs! So while Triceratops, T. rex and the other famous dinosaurs went extinct 66 million years ago, some dinosaurs live on. – SB
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Thomas is a Staff Writer at BBC Science Focus and looks after all things Q&A. Writing about everything from cosmology to anthropology, he specialises in the latest psychology and neuroscience discoveries. Thomas has a Masters degree (distinction) in Magazine Journalism from the University of Sheffield and has written for Men’s Health, Vice and Radio Times. He has been shortlisted as the New Digital Talent of the Year at the national magazine Professional Publishers Association (PPA) awards.