Thanks to decades of movies, comic books and less-than-accurate TV documentaries, many people continue to hold mistaken notions about Dinosaurs. Here are some things you thought you knew about dinosaurs that aren’t actually true.
1. All Dinosaurs are extinct
The vast majority of scientists now believe birds are dinosaurs. More specifically, they’re avian Coelurosaurs (avian means powered flight). Coelurosaurs (see-LOOR-oh-SORES) are advanced Theropod dinosaurs that include tyrannosaurs, small bird-like dinosaurs, and birds themselves. Coelurosaur features include an enlarged brain, long arms and a bowed lower arm bone; a hinged ankle joint; a long sacrum; and a long, stiff tail (although birds have lost their long, bony tails).
To separate birds from other dinosaurs we now use a definition based on ancestry – birds are all the descendants of the common ancestor of Archaeopteryx and modern birds. Birds can be called ‘avian dinosaurs’ but it is still correct to use the term ‘bird’ when talking about the feathered animals we see today. Dinosaurs that are not birds are often called ‘non-avian (meaning non-bird) dinosaurs’.
2. Dinosaurs all lived at the same time.
The first dinosaurs appeared in the Middle Triassic about 230 million years ago. The last non-avian (or non-bird) dinosaurs died out 66 million years ago. As the life span for most animal species is only about 2 to 5 million years, there was a continuing evolution and extinction (from events such as climate change, competition, or volcanic activity) of dinosaurs throughout the Mesozoic Era (251 to 66 million years ago). Those dinosaurs living at the end of the Mesozoic looked very different from those that appeared at the beginning. In addition, different species lived in different locations and different continents, so wouldn’t have even met those that they did share the Earth with. So T. rex, who lived about 66 million years ago, would never have met the iconic Stegosaurus, who lived about 150 million years ago!
3. Humans and Dinosaurs coexisted.
This myth has been muddied a little since scientists have classified birds as a group of small theropod dinosaurs. So, while humans have definitely shared the Earth with avian (bird) Dinosaurs, we have definitely not shared it with non-avian dinosaurs.
The latter is known as the Flintstones fallacy – there is a 63 million year gap between the extinction of non-avian dinosaurs and the appearance of humans. The last of the non-avian dinosaurs died about 66 million years ago during the end-Mesozoic extinction, whereas the earliest humans (Homo genus) appeared about 2.5 million years ago.
4. Brontosaurus was a species of dinosaur.
Unfortunately for Brontosaurus, this name never truly existed! Back in 1877, American fossil collector Othniel Charles Marsh gave the name Apatosaurus to a fossilised partial dinosaur skeleton, although it was missing the skull. In 1879, he named a new fossilised skeleton Brontosaurus, it too was missing the skull,. Both sets of fossils were re-examined by Elmer Riggs, and in 1905 he announced that they were the same species. As Apatosaurus was named first, this was deemed the correct species name. Despite Brontosaurus losing its validity as a name all the way back in 1905, the name stayed around for many more decades, and is even mistakenly used now. When the fossil skeleton found in 1879 was first displayed back in 1905, in Yale’s Peabody Museum, it used the skull from another set of remains. It was also incorrectly labelled as a Brontosaurus, so perpetuating the myth. In 1970 it was shown that this skull was from another species of sauropod, called Camarasaurus. Poor old Brontosaurus was losing out on all sides.
5. Pterosaurs, plesiosaurs and mosasaurs were dinosaurs
No, they were marine and flying reptiles that also lived during the Mesozoic Era, alongside dinosaurs. The name ‘dinosaur’ applies only to a group of terrestrial (land-dwelling) reptiles with a set of physical features that are different from those of all other reptiles. They include extinct animals we know from fossils and the birds we see today.
6. All dinosaurs were apex predators
It is estimated that carnivores, or predators, made up only about one per cent of the dinosaur population. The vast majority were plant-eaters. This figure is typical of similar ecosystems today. Many meat-eating dinosaurs, or theropods, were relatively small and preyed on insects, small mammals and reptiles, and other dinosaurs. In turn, these smaller dinosaurs were preyed upon by pterosaurs, marine reptiles, crocodiles and even mammals.
7. All dinosaurs were covered in green scales
Feathers, bright skin colours and decorative head crests are now accepted covers for these prehistoric animals. It is now widely believed that most coelurosaur theropods were covered with feathers at some stage of their life cycles, most probably when juveniles. Other theropods have also been found with protofeathers and feathers, so this covering may have been widespread amongst the meat-eaters.
8. All dinosaurs were big
Dinosaurs were a diverse group of reptiles ranging in size from a chicken to many buses in length. They majority were actually fairly small, however some reached the largest proportions ever known for land animals.
Some statistics:
The smallest?
Compsognathus longipes (Europe): 60 cm long and 4-6 kg
Microraptor zhaoianus (China): 40 cm long and 2-4 kg
The largest? Titanosaur sauropods
Argentinosaurus huinculensis (Argentina): 35-40 m long and 80 tonnes
Puertasaurus reuili (Argentina): 35-40 m long and 80 tonnes
Paralititan stromeri (Egypt): 32 m long and 65-80 tonnes
The tallest? Sauropods
Brachiosaurus altithorax (USA): 12 m tall
Sauroposeidon proteles (USA): 12 m or taller
The largest meat-eater?
Mapusaurus rosaea (Argentina): 14 m long and 7–8 tonnes
Giganotosaurus carolinii (Argentina): 13–14 m long and 7 tonnes
Spinosaurus aegyptiacus (Egypt): 15 m long and 5–7 tonnes
Tyrannosaurus rex (North America): 12–13 m long and 7 tonnes
9. All dinosaurs lived in lush rainforest, swampy habitats.
Dinosaur fossils have been found in all parts of the world, including the Arctic and Antarctic circles. Although these regions were not covered in ice like today, temperatures were cool, particularly in winter, and there were long periods of darkness. Conditions were far below the level most living reptiles can tolerate. So, like animals today, we know different species were adapted to live in a diverse range of environments – from arid regions, and rainforests, to wide open plains and cold dark regions.
10. Plant-eating dinosaurs ate grass
Only a very few plant-eating dinosaurs would have had the pleasure of a meal of grass. The earliest fossil evidence for grass is only 66 million years old – so we know this plant only appeared right at the end of the Mesozoic Era, the ‘Age of the Dinosaurs’.
11. Large sauropods had 2 brains, one in their hip
Not true, although it makes good sense considering the distance from head to tail in some of these massive plant-eating dinosaurs. However, scientists did discover that some had enlarged nerve clusters at the base of their spine that helped pass on messages from the brain.
12. Dinosaurs were the first reptiles to rule the earth
The first reptiles evolved from their amphibian forebears during the late Carboniferous period, over 300 million years ago, while the first true dinosaurs didn’t appear until well into the Triassic period (about 230 million years ago). In between, the Earth was dominated by various families of prehistoric reptiles, including therapsids, pelycosaurs and archosaurs (the last of which included the ancestors of pterosaurs, crocodiles and dinosaurs).
Even when dinosaurs first appeared they were not the dominate type of reptile – they were simply another group of small reptiles in a world full of reptiles. By the end of the Triassic they dominated life on land and would for another 140 million years, till the close of the Mesozoic. Their rise was due to a combination of chance, superiority and physical features. A ‘well-timed’ extinction event early in the Late Triassic wiped out most of their competition, clearing the way for dinosaurs. We are not sure why they then thrived. Perhaps they were better adapted to the arid, dry conditions than other animals were or their more efficient, upright way of running gave them an advantage.
13. Dinosaurs were incinerated by the end-Mesozoic meteor impact
About 66 million years ago, a meteor or comet about 10 kilometres wide smashed into Mexico’s Yucatan Peninsula. It created fire storms and tsunamis, and raised a cloud of dust and ash that spread around the world, blotting out the sun and causing plants to die. The popular perception is that dinosaurs (along with pterosaurs and marine reptiles and 70 per cent of all life forms) were killed within hours by this explosion, but in fact, it may have taken tens of thousands of years for the last non-avian dinosaurs to die out. The fossil record is only so accurate!
Not all scientists believe this impact caused the mass extinction event. The fossil record shows many families of dinosaurs were already in decline at the end of the Cretaceous period. These scientists blame climate change or massive volcanic eruptions that turned Earth in to a hostile place to live. Most scientists, however, believe that the extinction event was the result of a combination of these deadly causes.
14. Mammals only evolved after dinosaurs died out
Tiny primitive mammals appeared in the Late Triassic about 225 million years ago. They lived in the shadow of the dinosaurs for the next 150 million years, mainly occupying ecological niches as small, nocturnal animals. They were also relatively small, with some weighing as little as 2 grams but others growing to the size of badgers. The end-Mesozoic extinction 66 million years ago, which included the demise of the non-avian dinosaurs, left a mass of niches for larger mammals to evolve and fill. Most of the types of mammals we know today evolved after this time
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