A Brief Timeline of Dinosaur Discoveries
They lived millions of years ago and died millions of years ago. Apart from modern birds, humans have never really been face to face with dinosaurs, but still they fascinate us maybe more than any other animal alive today. Let’s take a look at how dinosaurs went from ruling the earth to being unearthed by palaeontologists today.
The Mesozoic era is a period of roughly 165 million years that contains the Triassic, Jurassic and Cretaceous periods. The Mesozoic era saw the rise and fall of dinosaurs.
231.4 million years ago
The first dinosaurs started roaming the Earth in the Triassic period about 231.4 million years ago. At the beginning of the Triassic age there was a mass extinction during which about two-thirds of land animals and 95 percent of sea-creatures died out. During these early days of the Triassic there were no real dinosaurs yet, but during the approximate 40 million years that followed dinosaurs like the 8 meters long Plateosaurus started populating the Earth.
Towards the end of the Triassic period volcanic eruptions, climate change and possibly even an asteroid impact triggered another mass extinction in which a lot of marine life died out as well as many amphibians and therapsids (which were the ancestors of mammals). About half of all species alive died out during this extinction event. This paved the way for dinosaurs to truly take over the planet.
201.3 million years ago
After the extinction event at the end of the Triassic period dinosaurs truly started to become the dominate species. The Jurassic period, thanks mostly to a certain movie, is easily the most well-known period in prehistoric times. During the Jurassic period the super-continent Pangaea split apart into Laurasia and Gondwana and giant sauropods like Apatosaurus and Diplodocus as well as theropods like Allosaurus stomped the lands.
66 million years ago
The Cretaceous period is the last period during which dinosaurs lived. Dinosaurs could be found everywhere during the Cretaceous period; they populated the seas, soared through the sky and dominated the land. The Cretaceous period also saw the first flowering plants, and “modern” insects like ants, grasshoppers and butterflies.
By the end of the Cretaceous period, about 66 million years ago, most dinosaurs went extinct in what looks like a single instant. We’ll look at what might have caused this extinction event later.
200,000 years ago
Humans first appeared about 200,000 years ago. Since dinosaurs have spent many millions of years roaming the Earth humans have always been finding dinosaur remains. Quite often these were regarded as mythical dragons or monsters rather than pre-historic animals.
The first time dinosaurs were called dinosaurs was in 1842. The term was coined by palaeontologist Richard Owen. Besides coming up with the name dinosaur, Richard Owen is the founder of the London Natural History Museum. Taking the natural history department of the British Museum (which at the time was closed off to the public) and making them available to everyone in one of the most beautiful museums in the world.
His career was riddled with controversy as he regularly claimed other people’s discoveries as his own. Even going as far as to rename dinosaurs that already had names.
In 1868 Thomas Henry Huxley suggested that maybe birds were direct descendants of dinosaurs. This idea did not get a foothold at the time and was ultimately abandoned. Prominently, the book “The Origin Of Birds” by Gerhard Heilmann from 1926 dismissed the idea due to the lack of a furcula (a wishbone) in dinosaurs. It wasn’t until the 1960’s that the idea was revisited by scientists. Today we can say with quite some certainty that birds are in fact dinosaurs.
After the discovery that dinosaur may have been warm-blooded rather than cold-blooded creatures palaeontology gained strongly in popularity. This rising interest in prehistoric animals is referred to as the “Dinosaur Renaissance”.
A dinosaur named Deinonychus Antirrhopus was discovered by John Ostrom. This dinosaur had all the hallmarks of a bird and caused palaeontologists to reinvestigate the idea the birds are direct descendants of dinosaurs. An idea that is now commonly accepted.
Father and son scientists Luis and Walter Alvarez suggested dinosaurs went extinct at the end of the Cretaceous period because of the impact of a large asteroid. The main reasoning behind this was the relatively large amount of iridium that can be found in the earth’s crust in between the Cretaceous layer and the Paleogene layer. Iridium being fairly rare on earth Luis and Walter suggested it might have come from a large asteroid.
While it is the most popular theory at the moment explaining the extinction of dinosaurs, it’s not without its opponents. The main problem with the theory is that at the end of the Cretaceous period only a selection of animals died out. Many species of mammals, for instance, lived on unaffected. This is why some scientists don’t think an asteroid impact was what killed the dinosaurs, but in stead point at climate change, the drifting apart of the continents, volcanic activity and rising competition from mammals.
In 1860 the fossil remains of Archaeopteryx was discovered in Germany. This fossil clearly showed the presence of feathers. It was considered to be a transitional animal showing elements from both reptiles and birds. However, just like the idea that birds are dinosaurs, the idea that many dinosaurs had feathers faded away. It made a comeback in the 1970’s, when the link between birds and dinosaurs had regained popularity and artists started depicting more dinosaurs with feathers. Evidence in the fossil record discovered in the 1990’s sealed the deal. We now know for certain that many species of dinosaurs had feathers.
When you ask people to name their favourite dinosaur (providing they have one) they will name dinosaurs like Tyrannosaurus rex, Brontosaurus, Velociraptor or Triceratops. Let’s get this out of the way first: Brontosaurus should be called Apatosaurus and most people think Velociraptors are man-sized monsters (like in the movies) when in reality they’re turkey sized feathery raptors. But in 2010 it turned out that one of the other popular dinosaurs might not be what we thought it was. The Triceratops, a three-horned truck sized dinosaur, turned out to be the young version of a Torosaurus according to palaeontologists John Scannella and Jack Horner. They studied a collection of fossils and concluded that during its life the Torosaurus’ skull changed remarkably, from a skull with three horns to a skull with just two.
Scannella’s and Horner’s hypothesis has since met with quite some criticism, like that of Nicholas Longrich and Daniel J. Field. They claim that Triceratops and Torosaurus should be considered to be two separate species.
Today our idea of dinosaurs is radically different from when mankind first found prehistoric remains, obviously. We no longer believe they belonged to demons or dragons. But even if you look at our knowledge on dinosaurs a century ago and now it is very different. We now know dinosaurs and birds are directly related. We know a lot of dinosaurs had feathers. One can only imagine what more amazing things we will discover about life on earth millions of years ago.
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Also on Trivial Discourse:
- Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy
- Archaeopteryx: The Transitional Fossil
- What Is the Triassic-Jurassic Extinction Event?
- Lecture 23 - The Impact Theory of Mass Extinction
- Thanks to the good folk over at the Paleontology subreddit for providing some very useful insights