How Many Kinds of Dinosaurs Were There?

Despite the fact we take the existence of dinosaurs for granted, our knowledge of their existence is relatively new. Although dinosaur bones had been discovered prior, it wasn't until the mid-19th century that the concept of dinosaurs was solidified. Before this time, discoveries of fossilized bones were poorly understood with some even thinking they belonged to mythical creatures such as dragons or even giant humans.

Since the term dinosaur (meaning ‘giant lizard’) was first coined in 1841, new species have continued to be discovered. Such discoveries have been made with varying degrees of regularity, including a so-called ‘dinosaur Renaissance’ which began around the 1970s and seemingly continues to this day.

Since the first discovery, dinosaurs have caused astonishment, especially due to their great size. This doesn't mean that all dinosaur species were large. Part of the fascination around dinosaurs is their great diversity. Some are thought to have been as small as a hummingbird^[1], with the largest known dinosaur species weighing up to 100 metric tons (this being the Argentinosaurus)^[2].

To know how many types of dinosaurs existed, we need to learn more about what a dinosaur is. Since lizard is in their name, it can be a little confusing to understand that birds are also considered a type of dinosaur. This is because birds existed at the same time and are the only dinosaurs known to have survived the extinction event which lead to their demise. For this reason dinosaurs can be categorized as either:

• Avian dinosaurs: essentially, birds.
• Non-avian dinosaurs: the remaining species which are all dinosaurs except birds.

This is not to say that there are only two distinct lineages of dinosaurs. Birds are important as they are the only known surviving dinosaurs, but they confuse the question of how many dinosaurs are there by the fact they are now included as dinosaurs. Since there are over 10,000 extant living bird species, we need to be more specific.

As we stated above, there are thousands of extant bird species (over 10,700), but this does not mean that these birds lived at the same time as non-avian dinosaurs. Although they share a common ancestor, there has been great diversity in evolutionary terms since then.

With this in mind, we can say there are around 1000 species of non-avian dinosaurs known to science. If we include birds, this would mean there are around 11,7000 known dinosaur species, but this will depend on your definition.

We also know that many dinosaur species are yet to be discovered and our overall understanding is still limited. Paleontologists and other dinosaur experts have been able to make an estimation of how many dinosaurs are yet to be discovered. We actually discover a new dinosaur species at a rate of around 1 every 2 weeks, although this may change. Some suggest that the majority of dinosaur species have yet to be discovered^[3].

We have already explained that there are two main groups of dinosaurs, specifically avian and non-avian dinosaurs. These categorizations are explained further by the following taxonomic groups which are distinguished mainly by the structure of their hip bones:

Saurischians

Saurischians or lizard-hipped dinosaurs are those that had hip bones similar to the hip bones of modern reptiles. These include lizards and crocodiles. It is estimated that the species of this group of dinosaurs inhabited the Earth during the Mesozoic era. More precisely, they appeared during the Late Triassic (approximately 230 million years ago) and diversified during the Jurassic and Cretaceous.

Within the diversification of the saurischians we can find two subdivisions. The first is a group known as theropods. They were characterized by their carnivorous diet and their extremities ending in 3 digits. The second is the group known as sauropods, quadruped dinosaurs whose diet was herbivorous.

Ornithischians

The ornithischians or bird-hipped dinosaurs had a disposition of the hip bones similar to the hip bones of modern birds. Like the saurischians, they inhabited the Earth during the Mesozoic era, from the Late Triassic (approximately 230 million years ago) to the Cretaceous (approximately 65 million years ago). All ornithischians were herbivores and some of them lived in herds.

These categories of dinosaur are not the same as avian and non-avian dinosaurs. Current-day birds cannot be directly delineated from these dinosaurs, even if they share a common ancestor.

Learn more about how we know information about dinosaurs with our article on types of fozzilization.

It is difficult to say what are the most important dinosaurs since we have not yet discovered them all. However, we can say that certain dinosaurs have been more significant to paleontologists than others. These individual species have helped us to understand more about these prehistoric animals in general.

Tyrannosaurus rex

The Tyrannosaurus rex is possibly the most well-known dinosaur. It is a species belonging to the group of saurischians that inhabited North America. It was a large carnivorous species that exceeded 10 meters in length and weighed more than 5 tons.

Triceratops spp.

The genus Triceratops belongs to the group of ornithischians. It is made up of two known species: T. horridus and T. prorsus. Both species were herbivorous and distinguished by their large horned heads that were proportionally larger than those of other terrestrial animals. Fossils of these species have been found in Canada and the United States.

Velociraptor mongoliensis

In the history of dinosaurs, the velociraptor was the fastest of all dinosaurs, being able to run at a speed of 65 kilometers per hour thanks to its powerful hind legs. This quality made them a great hunter, something important for carnivorous animal. Fossils of this species have been found in Central Asia.

Archeopteryx spp.

Archeopteryx is a genus of dinosaurs that is considered the evolutionary transition between dinosaurs and modern birds. It had characteristics typical of dinosaurs such as jaws with strong teeth and a bony tail, but also characteristics of birds such as a small body size and large wings that allowed it to travel certain distances. Their fossils have been found in North America.

Patagotitan mayorum

Although not one of the best-known species, Patagotitan mayorum is the largest dinosaur ever found. It is estimated that it measured approximately 40 meters in length and could reach a weight of 70 tons. It was discovered in the province of Chubut, in Argentine Patagonia.

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