Prehistoric giants: The biggest dinosaurs to ever exist

It’s somewhat frightening to imagine what it must have been like to wander around the plains of Africa and Argentina 100 million years ago. Whereas today you’d be hard-pressed to encounter a beast any bigger than yourself, back then you’d be running for your life as bus-sized creatures roamed free, some remaining largely peaceful and distant, others full of aggression.

The biggest land-based animal alive today is the African bush elephant, with the largest weighing a measly 13.5 tons and measuring 10.6m (34.8ft) long and 4.2m (13.8ft) high. Argentinosaurus, the current official record-holder for largest dinosaur of them all, would have been at least four times the size.

It was a sauropod, dinosaurs of the Jurassic and Cretaceous period that were mostly herbivores and known for being very large. Indeed, many other types of sauropod would have stood tall above the African bush elephant, as would carnivores, raptors and pterosaurs (‘flying dinosaurs’).

Of course, the dinosaurs inhabited the Earth for much longer than any modern animal, from 251 to 65 million years ago, allowing plenty of time for certain species to develop into the giant hulks of flesh we now so revere. The biggest dinosaurs discovered to date have largely been determined to live in the Late Cretaceous period, 99.6-65.5 million years ago, before they faced extinction.

For a long time, though, palaeontologists have wondered why dinosaurs grew to be so large.

While impressive, size can also be a hindrance. Not only does a large animal need a much higher rate of metabolism, but it must also develop much stronger bones and skeletal structures to be able to hold itself upright.

Many of these gigantic animals were also cumbersome and slow, leaving themselves open to attack from large predators.

Why did dinosaurs continue to grow for millions of years, then?

One train of thought is that there was a huge surplus of carbon dioxide in the atmosphere during the age of the dinosaurs. This meant that vegetation flourished, and herbivores such as the sauropods simply had an over-abundance of nourishment available to eat.

While somewhat of a burden in terms of manoeuvrability, their size would certainly have helped to some extent when fending off smaller carnivores. This leads to another proposal from palaeontologists, namely that some dinosaurs grew in size over millions of years as a form of self-defence.

However, others think that these giant dinosaurs were cold-blooded, which was directly responsible for their size. Indeed, warm-blooded animals simply wouldn’t be able to sustain such mammoth sizes, somewhat backed up by the lack of mammals larger than a few tons today.

Huge cold-blooded sauropods, weighing in at up to 100 tons, would have been almost self-sustainable, as they could store heat throughout the day for the colder nights, maintaining a fairly unchanged body temperature and prolonging their survival.

Biggest overall



Top stats:

  • Weight: >100 tons
  • Length: <45m (148ft)
  • Height: 21m (70ft)
  • Date: Late Cretaceous (99.6-65.6 Ma)
  • Group: Sauropodomorphs
  • Bigger than: A basketball court

Argentinosaurus is the largest-known dinosaur to have ever lived, based on fossilised evidence. Weighing in at over 100 tons and measuring as much as 45 metres (148 feet) in length, this herbivore was wider and longer than a basketball court and was as heavy as a fuel-less jumbo jet.

The vertebrae of the argentinosaurus were very broad, with small peg-and-socket articulations above the spinal cord that kept the backbones of these animals sturdy and rigid. In addition, the ribs of the argentinosaurus were hollow, possibly allowing for greater manoeuvrability.

Although the skull, neck and tail of an argentinonsaurus have never been found, measurements made from a shinbone can estimate the size of the various features of this colossal creature. Each hind limb of the argentinosaurus would have been about 4.5 metres (15 feet) long.

Biggest carnivore



Top stats:

  • Weight: 12 tons
  • Length: 16m (52ft)
  • Date: Late Cretaceous (99.6-65.6 Ma)
  • Group: Theropods
  • Bigger than: A double-decker bus

The spinosaurus is often overlooked as the largest carnivorous dinosaur in favour of its more famous cousin, the tyrannosaurus rex.

However, the spinosaurus would have dwarfed the popular movie star, measuring 16m (52ft) in length compared to 12m (39ft) for a T-rex. That being said, the characteristic features of the spinosaurus – namely its fin-like spinal protrusion – make it one of the most recognisable theropods.

In the late-Cretaceous period, this 12-ton creature would have been fairly common, with its sail-like spine adding to a fearsome display and possibly helping to regulate its body temperature.

Biggest pterosaur



Top stats:

  • Weight: <250kg
  • Wingspan: 12m (39ft)
  • Date: Late Cretaceous (99.6-65.6 Ma)
  • Group: Pterosaurs
  • Bigger than: A small plane

Although not technically regarded as ‘dinosaurs’, pterosaurs were around at a similar time and are often (somewhat incorrectly) referred to as ‘flying dinosaurs’, much to the ire of some palaeontologists.

Nevertheless they were impressive creatures, and none more so than quetzalcoatlus, the largest flying animal of all time. Its huge 2.5m (8ft) skull housed an elongated mouth that was used to hunt land animals including dinosaurs and other vertebrates.

Despite its size quetzalcoatlus was comparatively light as its bones were comprised of a series of air sacs, a useful feature for such a colossal creature aiming to take to the skies. While most other pterosaurs fed on fish, quetzalcoatlus was somewhat unique in its hunting of land animals, no doubt useful nutrition to fuel its giant metabolic needs.

Best of the rest

Liopleurodon: A 25-ton sea-dweller, the liopleurodon reached lengths of up to 15m (49ft) when it ruled the waters in the late Jurassic Period

Shantungosaurus: A dinosaur of the hadrosaur genus, this duck-billed herbivore was very common in the late- Cretaceous period. It was

about 15m (50 feet) long and weighed up to 50 tons.

Utahraptor: Weighing in at a sizeable 680kg (1,499lb) and measuring 6m (20ft) in length, the utahraptor was the biggest raptor of all time.

For more amazing dinosaur facts, pick up the Issue 73 of How It Works magazine. Order it in print, download the digital version or subscribe today to ensure you never miss an issue!

How It Works cover issue 73