How Many Dinosaurs Are There?

Dinosaurs, the giant reptiles that ruled the earth for over 160 million years, continue to capture our imagination. Their massive size, strange features, and mysterious extinction have made them cultural icons. But exactly how many species of dinosaurs existed?

Estimating the total number of dinosaurs that lived on Earth is challenging. The fossil record is incomplete, and new species are still being discovered. However, scientists have made educated guesses based on available evidence.

How Many Extinct Non-Avian Dinosaurs Are There?

When most people think of dinosaurs, they are picturing non-avian dinosaurs – the extinct, non-bird members of the dinosaur clade. This includes famous dinosaurs like Tyrannosaurus rex, Triceratops, Brachiosaurus and more.

Estimates vary, but in terms of extinct non-avian dinosaurs, about 300 valid genera and roughly 700 valid species have been discovered and named. However, given that the fossil record is incomplete, these numbers do not reflect the true diversity of extinct dinosaurs.

Over 900 non-avian dinosaur genera have been identified with certainty as of 2018, and the total number of genera preserved in the fossil record has been estimated at around 1850, nearly 75% of which remain to be discovered, and 1124 species by 2016.

In 2016, the estimated number of dinosaur species that existed in the Mesozoic was 1,543–2,468.

The Challenges of Estimating Extinct Dinosaur Diversity

Estimating the total diversity of extinct dinosaurs is difficult for several reasons:

Incomplete fossil record – Fossilization is a rare event. Many dinosaurs likely lived and died without leaving any fossils behind. Even for known species, few complete skeletons exist.
Specimen fragmentation – Many dinosaurs are only known from partial or disarticulated remains, making confident identification difficult.
Geographic bias – Most discoveries have been made in North America and Europe, potentially missing diversity elsewhere.
Synonyms – The same species may have been named multiple times by different paleontologists. Determining which names are valid is an ongoing process.
Invalid species – Some named species turn out to be juveniles or geographic variants rather than distinct species. These need to be re-evaluated.
Yet to be discovered – New dinosaurs are still being found every year, especially in previously unexplored regions. Many likely remain undiscovered.

Estimating Total Dinosaur Diversity

Given these challenges, coming up with an accurate total for how many dinosaur species existed is impossible. However, scientists have made some educated guesses:

In 2016, Baron et al. published a study attempting to estimate global dinosaur diversity. They came up with a range of 1443–2468 species for non-avian dinosaurs.
Upchurch et al. (2011) estimated that we have fossil evidence for only 20–30% of dinosaur genera that existed. If around 1850 genera are known, the actual number may have been 6,000-9,500.
Wang and Dodson (2006) estimated 700 valid dinosaur species globally based on available fossils. They then used statistical methods to estimate the total prehistoric diversity may have been 1258-2247 species.
Chapman et al. (1994) concluded we have likely only sampled around 7% of existing dinosaur species in the fossil record. If around 500 species were known at the time, the total number could be over 7,000.

So while estimates vary, most paleontologists think that between 1000-2500 non-avian dinosaur species likely existed. But the actual number could be far higher when accounting for incomplete sampling.

Estimating Total Dinosaur Diversity

The picture gets more complex when considering that birds are living dinosaurs. The approximately 10,000 living species of birds must be added to any total dinosaur estimate.

In 2016, Brusatte et al. published a large-scale analysis attempting to estimate total dinosaur diversity including avian dinosaurs. They came up with a range of 1443-3045 species for non-avian dinosaurs, and 15,845–24,900 total dinosaur species once Mesozoic birds were added.

However, the researchers stressed this was a conservative estimate given limitations in the fossil record. They concluded that over 50,000 distinct dinosaur species may have existed, and possibly over 500,000 when uncertainties in the fossil record are accounted for.

Estimating Extinct Dinosaur Diversity Through Time

The number of dinosaur species that existed fluctuated over the ~160 million years dinosaurs dominated the planet:

Dinosaur diversity increased through the Triassic and early Jurassic as they diversified into empty ecological niches.
Diversity peaked in the mid-Jurassic around 167 million years ago, with an estimated 600-1000 species existing globally.
Extinction events like that at the Jurassic-Cretaceous (J-K) boundary ~145 million years ago reduced diversity.
Diversity recovered through the mid-Cretaceous, with another peak in the late Cretaceous ~70 million years ago.
The extinction that killed all non-avian dinosaurs 66 million years ago rapidly reduced diversity to zero.

So while 1000+ non-avian dinosaurs are known from fossils, far more species likely lived that we will never discover. And with over 10,000 living avian dinosaurs, the total number of dinosaur species that existed likely numbers in the tens or hundreds of thousands.

How Many Valid Dinosaur Species Are There?

The actual number of dinosaur species changes over time as new discoveries are made and old ones are re-evaluated. This process of refining dinosaur taxonomy is ongoing. Some trends include:

New species discovered – On average ~50 new non-avian dinosaur species are named each year as new fossils are found.
Synonyms – As more fossils are found, some species are determined to be synonyms – different names for the same dinosaur species.
Invalid species – Some named species turn out to be juveniles or geographic variants rather than distinct species. These are then declared nomina dubia (dubious names) and considered invalid.
Splitting and lumping – Analysis of variations within a species can lead to it being split into multiple species. But sometimes multiple named species are lumped together into one.
Extinction of avian dinosaurs – Extinctions of birds like the Dodo and Passenger Pigeon have also reduced total dinosaur diversity over time.

So while the number of discovered non-avian dinosaurs has increased over time, the actual valid total fluctuates up and down with new research. The percentage of named dinosaurs considered valid has actually decreased from about 80% in the 1990s to 60% today.

In their 2016 estimate, Baron et al. concluded that of 1031 non-avian dinosaur species named, approximately 700 were still considered taxonomically valid at the time of publication.

Why Estimating Dinosaur Diversity Matters

While we may never know exactly how many species of dinosaurs inhabited prehistoric Earth, refining our estimates is an important scientific pursuit because it can:

Improve understanding of dinosaur evolution and paleobiology. More accurate diversity estimates lead to new insights into dinosaur origins, adaptation, ecology and extinction.
Refine knowledge of ancient environments and ecosystems. Dinosaur diversity correlates to climate, geography and food web structure through time.
Provide context for modern conservation. Estimating prehistoric biodiversity allows comparison to modern ecosystem diversity and health.
Guide future fossil exploration. Identifying gaps in the fossil record focuses new exploration in underrepresented habitats and regions.
Refine statistical methods for estimating prehistoric biodiversity more broadly. Dinosaurs provide a well-studied test case.

So while arriving at a final total remains elusive, estimating just how many dinosaurs once flourished across our planet is a compelling scientific endeavor. As new research and fossil discoveries continue to refine our knowledge, a clearer picture emerges of dinosaur diversity across time and geography. While we may never know exactly how many species existed, uncovering clues to just how numerous and varied dinosaurs once were remains an exciting adventure.

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