There are few creatures more synonymous with the word ‘deadly’ than dinosaurs. As a group, dinosaurs pioneered many of the traits we associate with dangerous animals today – big teeth, large bodies, powerful jaws, and razor-sharp claws.
A lot of species took these traits to the extreme, evolving into some of the most ferocious, meat-eating monsters the world has ever seen, and probably ever will see.
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However, despite establishing one of, if not the most successful terrestrial dynasties of all time, dinosaurs (except for several groups of birds) ultimately faced extinction – their fates sealed by an approximately 15km-wide asteroid that collided with Earth some 66 million years ago. In a way, we can thank this asteroid for our own existence: without it, dinosaurs may have continued flourishing, becoming even more deadly and stopping our mammalian ancestors in their evolutionary tracks. Here are some of the deadliest dinosaurs that live up to their title of ‘monstrous lizard’...
Meet 10 of the deadliest dinosaurs
T-rex
There are more than 1,000 species of dinosaurs known to science, yet none are nearly as well known as Tyrannosaurus rex – the carnivorous poster child of the Mesozoic Era. T-rex’s popularity has made it the most studied dinosaur by far, yet there’s still so much we don’t know about it.
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It was one of the largest predators of all time (measuring approximately 12.5m [41 ft] in length and weighing in at around 8,000kg), and its estimated bite force is the strongest of any land animal ever (delivering up to six tons of pressure), but whether it was a hunter or scavenger, whether it could run fast enough to chase down its prey, and whether it was smart enough to outwit other predators, is still fiercely debated.
T-rex lived from 72 million years ago to 66 million years ago, making it one of only two dinosaurs on this list that were actually present on the ‘last day of the dinosaurs’. It lived in North America during a time when the continent was split in two by an inland sea known as the Western Interior Seaway.
Lots of T-rex fossils have been found on the western side of this split, sandwiched between layers of rock belonging to the famous Hell Creek Formation. This rock formation has also yielded fossils of T-rex’s favoured prey, Triceratops and Edmontosaurus, as well as several species of raptors.
What’s most interesting about the Hell Creek Formation is that, unlike a lot of other dinosaur-bearing rock formations, it only contains one large-bodied predator, T-rex. This alone epitomises T-rex’s deadliness and its status as the most dominant predator of the Late Cretaceous. It’s no surprise why it was given the name, ‘King of the Tyrant Lizards’.
Therizinosaurus
This dinosaur lived across Asia roughly 70 million years ago and sported the largest claws of any land animal ever known, measuring more than half a metre in length. These formidable claws are what give Therizinosaurus, or ‘Scythe Lizard’, its name.
Therizinosaurus was a bipedal dinosaur (meaning it walked on two legs) that stood almost 5m tall and weighed more than 5,000kg. It had a small, beaked head, a huge belly, and – according to some well-preserved fossils of its close relatives – patches of shaggy, hair-like feathers on its back, arms, and tail. Its claws, referred to as unguals by palaeontologists, were not only long but frighteningly-shaped too, resembling crowbars.
Despite having some of the most deadly-looking weaponry of any dinosaur, Therizinosaurus wasn’t an apex predator. In fact, it was a herbivore, and a pretty slow one at that. While most other theropods (a group of dinosaurs that includes both T-rex and raptors) ate meat and specialised as active or ambush predators, Therizinosaurus opted for a vegetarian lifestyle, using its height to its advantage as it plucked fruit, flowers, and leaves from the tops of trees.
Just what Therizinosaurus used its crowbar-like claws for is uncertain. Some think they may have been used for defence, while others see them as tools for raking vegetation into huge piles. Whatever it used its claws for, no dinosaur would have wanted to be on the receiving end of a slap from Therizinosaurus.
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Argentinosaurus
The dinosaurs were the largest animals to ever walk the Earth, and Argentinosaurus was the largest amongst them. This titan belongs to a group of dinosaurs known as sauropods, which includes other well-known, long-necked giants such as Brontosaurus, Brachiosaurus, and Diplodocus. While these other sauropods were giants of their time they would have been towered over by Argentinosaurus, which stood 20m (65 ft) tall, measured 40m (131 ft) in length, and weighed close to 80 tons. As an adult, its sheer size would have made it almost invincible and a real danger to any predator that may have been stupid enough to attack it.
Argentinosaurus lived in what is now Argentina during the Late Cretaceous, around 95 million years ago. It’s only known from fragmentary remains and there is some debate surrounding its title as the ‘largest dinosaur’, with other sauropods like Dreadnoughtus, Alamosaurus, and Paralititan all staking some kind of a claim.
Like other sauropods, Argentinosaurus was a herbivore and lived in large family groups. To support its huge size, Argentinosaurus would have had to eat around 850kg of plants per day. Such a large amount of food would have, understandably, produced a lot of waste – roughly 400kg a day according to some estimates. It might seem far-fetched, but a pooping Argentinosaurus was probably a deadly prospect for some smaller dinosaurs, particularly those unlucky enough to find themselves underneath one as it answered the call of nature.
Utahraptor
We can blame the Jurassic Park franchise for the mislabelling of Velociraptor as a large, deadly, and highly intelligent killer. While Velociraptor was certainly deadly to some degree, it was no bigger than a turkey and therefore pales in comparison to the largest – and deadliest – raptor that ever lived, Utahraptor.
Utahraptor looked a lot like the Velociraptors depicted in Steven Spielberg’s films, measuring around 7m (22 ft) in length, weighing in at nearly half a ton, and standing as tall as an average man (1.7m). Its jaws were lined with serrated teeth, but its deadliest weapons – 25cm-long, sickle-shaped claws – were fixed to its second toes. Utahraptor used these claws to tear open the bellies and necks of its prey, letting them bleed out before it moved in to feast. It wasn’t quite as fast as other, smaller raptors, but researchers think it was still capable of running at 25-35mph (40-56kph).
There’s a lot of debate surrounding raptors and whether they hunted in groups. Some suggest they hunted in tight-knit family groups, à la Blue and her brothers and sisters from Jurassic World, while others say it's more likely they hunted alone or in loose, uncoordinated rabbles like some crocodiles do today. Utahraptor, however it hunted, preyed on iguanodons and some smaller species of sauropods. These dinosaurs are known from the lower part of the Cedar Mountain Formation, located in the US state of Utah and dated to approximately 135 million years ago.
Tarchia
Its name might mean ‘brainy one’, but it wasn’t Tarchia’s brain power that made it one of the deadliest dinosaurs in Asia during the Late Cretaceous – rather its clubbed tail.
Tarchia belonged to a group of ironically dim-witted dinosaurs known as ankylosaurs. These slow-moving tanks were covered in thick, bony plates, known as osteoderms, and had huge, heavy clubs on the ends of their tails. Like other ankylosaurs, Tarchia used its club to protect itself from predators. Just one connection from this club may have been enough to break bones, which would have no doubt dissuaded a lot of dinosaurs from ever getting close to Tarchia. These clubs weren’t just used to ward off predators, however; a recent study published in 2022 suggests ankylosaurs’ tail clubs were used to primarily fight one another.
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Tarchia lived in Mongolia during the Late Cretaceous, from 75 million years ago to 70 million years ago. It was a relatively solitary herbivore that had a particular taste for easy-to-chew, succulent plants. Based on a fossilised Tarchia skull that shows bite marks from a close cousin of T-rex, Tarbosaurus, we know that some predators were brave enough (or perhaps desperate enough) to hunt this ankylosaur. Whether they came through such a hunt unscathed is another question.
Allosaurus
Before T-rex there was a smaller, yet faster and perhaps equally as ferocious, theropod known as Allosaurus. It measured 8.5m (27 ft) from tail to snout and weighed almost two tons. Like T-rex, it also had powerful jaws packed with dozens of sharp, serrated teeth designed for slicing through vast quantities of meat.
Allosaurus lived in North America between 155 million years ago and 145 million years ago, meaning it was long-dead and fossilised by the time T-rex took over its hunting grounds. Some Allosaurus made it as far as Portugal, Siberia, and Tanzania, suggesting they were incredibly widespread. They were numerous too; of the theropod remains found in the famous Morrison Formation of the western US, 75% belong to Allosaurus.
A lot of fossils belonging to Allosaurus have been found together, which some palaeontologists have interpreted as a sign they hunted in small groups. However, others suggest they were rather solitary hunters and that congregations of fossils are a result of individuals squabbling over the same carcasses.
Interestingly, Allosaurus coexisted with two other large theropods – Ceratosaurus and Torvosaurus. While they’re thought to have prowled along waterways and the margins of forests, Allosaurus is thought to have ruled over dry floodplains, hunting large herbivores such as Stegosaurus, Diplodocus, and Camptosaurus.
Qianzhousaurus
The affectionately nicknamed ‘Pinocchio Rex’ is a distant cousin of T-rex and actually lived at the same time, around 66 million years ago and just before the dinosaurs’ asteroid-induced destruction (although new research is questioning this long-held theory). Unlike others on this list, Qianzhousaurus was found relatively recently – in 2010 during the construction of an industrial park in Ganzhou, southern China.
Qianzhousaurus was a medium-sized tyrannosaur, measuring 7.5m (24 ft) in length and weighing in at just under a ton. Unlike other tyrannosaurs, it had a long, elongated snout with narrow, golf-tee-like teeth – rather than the deep-set jaws and thick teeth characteristic of T-rex. Its discovery in 2010 was monumental as it confirmed the existence of long-snouted tyrannosaurs, something that researchers had previously theorised based on some earlier, inconclusive fossils.
Qianzhousaurus lived in Asia, far from T-rex but alongside one of its closest relatives, Tarbosaurus. A study published in 2022 hypothesised that Qianzhousaurus was able to avoid competition with Tarbosaurus by carving out its own ecological niche – one where it used its speed and agility to hunt small, nimble prey, leaving the larger, slower herbivores for the stockier and more appropriately equipped Tarbosaurus.
Spinosaurus
It’s a mystery why this particular dinosaur is so recognisable, considering it has been reconstructed umpteen times since its discovery in the early 20th century. A big reason behind this constant reimagining of Spinosaurus is the fact that the original fossils used to describe it were lost when the Munich Museum was destroyed during a British bombing raid in 1944. Since then, finds of Spinosaurus fossils have been few and far between, creating a lot of mystery around this enigmatic theropod.
Nevertheless, Spinosaurus is considered a contender for the largest theropod ever – up there with the likes of T-rex and Giganotosaurus at around 15m (49 ft) in length and just over six tons in weight. Spinosaurus had several features that set it apart from these other, more ‘traditional’ theropods; chiefly its huge dorsal sail, but also its long, crocodile-like snout full of sharp, conical teeth.
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Spinosaurus is one of only a handful of dinosaurs that are thought to have been semi-aquatic. While it may have been able to hunt on land, researchers think it was a lot more comfortable in water and had a particular taste for large fish. How it hunted these fish is hotly debated, but there are two main hypotheses: it dived and pursued its prey underwater, or it stood on the shoreline and ‘fished’ for its dinner like today’s herons do.
Spinosaurus lived in what is now North Africa from 100 million years ago to 94 million years ago. This area was covered by huge tidal flats and mangrove forests at the time, which served as particularly fertile hunting grounds for Spinosaurus.
Diabloceratops
When it comes to horned dinosaurs, there are none more iconic than Triceratops – perhaps the largest ceratopsian of all time. That said, with a name that means ‘devil-horned face’, it’s hard to ignore its cousin Diablocertatops. This stocky, four-legged herbivore was only half the size (and weight) of Triceratops, yet its dazzling head decor would have made it just as, if not even more scary, to potential predators.
As well as having two horns above its eyes, Diabloceratops had two, even larger horns emanating from its bony frill. In life, these bony frills were covered in a thin layer of colourful, patterned skin that served as an advertising billboard, attracting mates while warning rivals and predators to not come any closer.
Diabloceratops lived in what is now the state of Utah, US, during the Late Cretaceous (approximately 81 million years ago). Like other ceratopsians, it’s thought it lived in large herds and relied on safety in numbers to protect itself from the apex predator in its environment – the medium-sized tyrannosaur Lythronax, or ‘Gore King’. Even if a lone Diabloceratops was isolated from its herd, it was armed enough to make Lythronax probably think twice before it attempted to move in for the kill.
Stenonychosaurus
For a long time, fossils belonging to Stenonychosaurus were assigned to a possibly dubious dinosaur known as Troodon. While Troodon is currently considered an invalid genus, Stenonychosaurus is recognised as a distinct and valid genus. It lived in Alberta, Canada, roughly 76 million years ago, where it roamed warm, coastal floodplains and scurried under the feet of larger predators like Daspletosaurus and Gorgosaurus.
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Stenonychosaurus, whose name means ‘narrow claw lizard’, is by far the smallest dinosaur on this list, measuring 2.5m (8 ft) in length and weighing in at just 35kg. However, what it lacked in size it more than made up for in brains. From studies of its skull, researchers have worked out that Stenonychosaurus had the largest brain of any dinosaur relative to its body size. While this means it was certainly smart by dinosaur standards, it likely had nothing on its closest living relatives, birds – the smartest of which, crows, are considered as intelligent as 7 year old children.
Thanks to its large brain, Stenonychosaurus had fantastic eyesight. It also had small yet deadly claws, leading researchers to believe it was probably a predator. That said, studies of its teeth have revealed that they were more suited to biting through tough plant material, suggesting Stenonychosaurus might have been an omnivore.
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