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What were the biggest dinosaurs?

Dinosaurs are mostly known for being three things: old, dead and big.

Let's take a look at that last one. Here we're going to look at the biggest dinosaurs of each type to ever exist!

A size chart of some of the biggest dinosaurs compared to a human
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Dinosaurs are a group of creatures which have reached a level of diversity matched by very few groups, in ecological niches, body plans and, of course, size. Size is, however, a very broad word, as discussed in post the exploring how big an organism can get. What do we mean by big? Is it the tallest? The longest? The heaviest? Well, there's no official, objective definition for the word 'size' (at least when discussing the physical dimensions of organisms).

Instead, why don't we look at the biggest members of each group? This way, we can see how they're the 'biggest' and what is an impressive size for that group (also I can make this post a bit longer than a sentence...tell no one.)

Non-Dromaeosaur Theropods

Let's start with the more divisive one. This is on where the question of 'what does 'big' mean?' comes into play. We have four contenders for the largest theropod. The first of them is one we all know of.

T.rex was an animal that inhabited the 'Hell Creek' area of North America during the Maastrichtian stage of the late Cretaceous, meaning it was around when the meteor struck. T.rex was an apex predator (yes, I said predator, I explain why here) within this environment, since there was simply nothing large enough to take down a fully grown adult. T.rex was around 12.3–12.4 m (40.4–40.7 ft) in length, 3.66–3.96 m (12–13 ft) tall and 8.87 metric tons in weight. Despite being the big bad boss of Hell Creek, across time and space existed some contenders for 'the biggest'.

A mounted T.rex skeleton

The first contender is Giganotosaurus carolinii. Hailing from Argentina and discovered in 1995, Giganotosaurus's size estimates measures in at 12 to 13 m (39 to 43 ft) long, 3.5-4 m (11.5-13 ft) tall and 6.5-8.2 metric tons.

A mounted Giganotosaurus

Closely related to Giganotosaurus is Carcharodontosaurus saharicus. This guy comes from North Africa and has actually been seen in the fossil record to have interacted with the next contender. Carcharodontosaurus's estimates are between 12–12.5 metres (39–41 ft) long, 3-3.5 m (10-11.5 ft) and 6–8 metric tons.

An artist's reconstruction of a Carcharodontosaurus
Art belongs to Fred Weirum

Spinosaurus aegyptiacus is a dinosaur that came from the same rock formation as the aformentioned Carcharodontosaurus. Spinosaurus is a dinosaur that has rooted itself in pop culture, mostly due to the mystery and weirdness of the animal (the full story of which will be in a post soon!). Spinosaurus measures in at approximately 14 m (46 ft) long, 4.5 m (14.7 ft) tall and 7.4 metric tons.

A mounted skeleton of a Spinosaurus

Hopefully you can see the problems we now bump into. Not only are the above measurements only approximate estimates, but each one is the 'biggest' in their own right. Carcharodontosaurus and Giganotosaurus are in competition with eachother in terms of length, T.rex was potentially slightly taller than the formers and most definitely the heaviest of the four and Spinosaurus was the easily the longest, tallest (thanks to those spines) but also potentially the lightest.

To be honest, it all depends on which estimates you choose to believe and what you consider 'big'.

A size chart comparing the largest theropods (carnivorous dinosaurs) to a human
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Ah, the famous Dromaeosaurs. Don't think that's a famous name? You might know them better as the sickle-clawed 'raptors'. The dromaeosaurs have long had a reputation as swift, cunning killers, further helped by the inclusion of Velociraptor in Jurassic Park. Velociraptor sp. was not quite as big as the film led you to believe, though. Only actually standing as high as your average turkey, the dinosaur we see in the films were actually more based on Deinonychus which, at the time, was thought to be the biggest member of this family.

Times change though...

Since then, other dromaeosaurs have been found globally, some of them being much larger than the now meek looking Deinonychus, such as Atrociraptor and Dakotaraptor. Whilst these beasts stood at around () in height, paleontologists estimate that one member of this family, whilst around the same height, definitely counted as the biggest since weight was also on its side. Utahraptor ostrommaysi was an dinosaur hailing from (you guessed it) Utah during the early cretaceous.

A mounted skeleton of a Utahraptor

This beast measured in at 4.9–5.5 m (16–18 ft) long and weighing 280–300 kg (620–660 lb)!

A size chart comparing Utahraptor specimens to a human
Image credit:

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Fondly referred to as the 'cows of the Cretaceous', ornithopods were the (likely) herd grazing dinosaurs that included the likes of Iguanodon and the hadrosaurs, or the 'duck-billed' dinosaurs. As far as dinosaur standards go, these guys were somewhat modest in size, with most averaging from 7-9 metres (23-30 feet) in length (again, modest for a dinosaur).

Some of the biggest ornithopods have cropped up all over the world, from Edmontosaurus annectens in North America to Charonosaurus jiayinensis in China to Iguanodon bernissartensis from good ol' England, all of which could have reached up to 13 metres (43 feet) in length!

None of them quite reached the size of one known dinosaur from China though...

Shantungosaurus giganteus from the Late Cretaceous is a hadrosaur that reached up to 15 metres (49 feet) in length and weighed 12-20 tons! This absolute monster of a grazer had a skull with a length the same height as your average professional basketball player (6'6" if you wanted to know), so you can imagine the size of this behemoth. Still struggling to imagine? Here you go:

A mounted skeleton of a Shantungosaurus
Image credit:

What more needs to be said?

A size chart comparing the largest ornithopods to a human
Image credit:


For the ceratopsians, the largest member was an animal known as Eotriceratops xerinsularis. Originally from the late Cretaceous of South Alberta, Canada, this dinosaur has caused some debates as to whether it should be considered a member of the Triceratops genus. Since this hasn't been concluded though, we all still call it Eotriceratops.

The skull alone of this dinosaur was around 3 m (9.8 ft) in length. This isn't extraordinary for a ceratopsian, since this group had massive heads anyway (the guinness world record for largest skull of a land animal actually belongs to a smaller ceratopsian!), but the overall dimensions of Eotriceratops was 8.5–9 m (28–30 ft) in length, 3.5-4 m (11.5-13 ft) in height and 10 metric tons.

A size chart comparing the largest ceratopsians to a human
Image credit:


The next 3 groups will be slighlty anti-climactic, seeing as the largest members of each group are its namesake.

Ankylosaurus magniventris is not only the most famous ankylosaur, but also the largest! Measuring in at 8 m (26.2 ft) long, 1.8-2.2 m (5.9-7.2 ft) tall and 4.8-8 metric tons, this all natural cretaceous tank from the same rock unit as T.rex and Triceratops would have been a barbarian to reckon with!

A mounted Ankylosaurus skull


Again, the largest member of this group is its namesake, which is Pachycephalosaurus wyomingensis from the Hell Creek formation (a lot of big dinosaurs were there, eh?). Size is an interesting thing to discuss here, mostly because of the controversy surrounding this dinosaur ontogeny (a name given to the process in which an animal's anatomy changes with age). I have covered this in my Jurassic Park dinosaur accuracy: part 3 post, but several genera of smaller Pachycephalosaurs have actually been attributed to being much younger members of this particular species, despite the different skull shapes.

With regards to Pachycephalosaurus itself, this animal has been estimated to be around 4.5-5 m (14.8-16.4 ft) long and weighing in at 370–450 kg (820–990 lb). Height, however, is much more ranged, since hind limb material is scant for a fully grown adult, but estimates are anywhere between 1.3-2.2 m (4.3-7.2 ft) tall.

A mounted skeleton of a Pachycephalosaurus


You guessed it: Stegosaurus! Specifically, Stegosaurus ungulatus. This dinosaur came form the Morrison formation, a rock unit in a similar place to where T.rex came from, but was around 80 million years earlier, meaning Stegosaurus would have had to conted with the likes of Allosaurus.

Including all the thagomizers and back plates, Stegosaurus ungulatus measured in at around 8.5-9.5 m (27.8-31 ft) in length, 3-3.5 m (9.8-11.4 ft) in height and 3.8 metric tons.

Sally the Stegosaurus


Now, this is the heavyweight bout of the ages!

Again, we have two contenders sandwiching a hot debate about what was the biggest land animal to ever exist in our planet's history. The two contenders are Patagotitan mayorum and Argentinosaurus huinculensis, both of which hail from Argentina and are extraordinarily closely related.

Patagotitan mayorum was a sauropod from the early-mid Cretaceous of Patagonia, Argentina. Formally described in 2017, Patagotitan was originally described with estimates of 37 m (121 ft) long, 12.5-13 m (41-42.6 ft) in height and an approximate weight of 69 metric tonnes. However, since then other experts have given slightly more modest dimension estimates of 31 m (102 ft) in length, () in height and 50–55 metric tonnes. These weight estimations in particular have been hot points of contention, with a range of 42.5 to way up to 96.5 tonnes! Whilst the original researchers stated that the animal likely would have been the largest land animal in history, given it has the longest femur, Other experts have cautioned that other comparative bones are larger in Patagotitan's rival...

A size chart comparing a Patagotitan to a human man and woman
Image credit:

Argentinosaurus huinculensis also came from Patagonia and lived during the late Cretaceous. Discovered in 1987, size estimates of Argentinosaurus have (surprise surprise) been debated over the years due to fragmentary remains, but the final numbers fall between 30–35 metres (98–115 ft) in length and 60–75 tonnes.

A mounted skeleton of Argentinosaurus surrounded by café chairs and tables

A mounted skeleton of Argentinosaurus

So, once again, which one you think is the larger really depends on which experts you believe. Maybe one day we will have a definitive answer, but I'm sure if you were face to face with both of them, you wouldn't notice the difference of a few would just see two friggin' massive dinosaurs...

A painting of two Patagotitans at dawn
Art belongs to PaleoEquii

Until next time!

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