Life on land during the Age of Dinosaurs had never been so spectacularly huge ever before, nor has it been since. Animals like Torosaurus, T-rex and Argentinosaurus were truly giants among giants, the biggest of the big!
What is the biggest dinosaur?
Dinosaurs come in a huge variety of sizes, from the 1.4-meter (4.6 ft) Compsognathus to the 40-meter (130 ft) Supersaurus, and from the 2-gram Bee Hummingbird to the possibly 80-tonne (88 US tons) Argentinosaurus. But if there is one thing about dinosaurs that has historically captivated people, it’s how big some of them could get. Even in scientific circles, bigger dinosaurs tend to garner more attention than small ones.
Here we present the biggest dinosaurs from several major dinosaur groups and we will explore what allowed to them to grow to their gargantuan proportions.
Defining “Big”
First things first, just what does “big” mean? “Big” is not an especially scientific or precise term, and can refer height, length, or mass. These often go hand in hand. A longer animal is often more massive than a short animal. A taller animal is often longer and heavier than a shorter animal. But dinosaurs came in a great variety of shapes and proportions, so those measurements don’t always line up. An especially lanky dinosaur may have superior length, yet a shorter but stockier dinosaur might have the greater mass. Typically, when we say a dinosaur is bigger than another, we are referring to its mass, and as we explore the biggest of the big, mass/weight is what we will use to determine who is biggest.
What is the biggest thyreophoran?
Thyreophora is the clade of ornithischian (bird-hipped) dinosaurs which includes both Stegosauria (dinosaurs with decorative dorsal plates) and Ankylosauria (armored dinosaurs). They were common in the Jurassic and Cretaceous, with stegosaurs hitting their stride in the Jurassic and ankylosaurs having their heyday in the Cretaceous.
Stegosaurus takes the title for largest stegosaur. But for Thyreophora overall, the title of Biggest is taken by Ankylosaurus. Both animals can reach up to 26 ft in length, but the stout, stocky, and extremely heavily armored Ankylosaurus weighs roughly twice as much as its stegosaur competition! At about 8 tons, Ankylosaurus weighs more than a modern bull elephant!
Winner: Ankylosaurus!
What is the biggest ceratopsian?
Ceratopsians are another group of ornithischians, notable for their beaked jaws, neck frills, and in many species, horned faces. Ceratopsia were relative latecomers to the dinosaur lineup only appearing in the Late Jurassic, with their most famous subgroup, the family Ceratopsidae (those are the ones with the horns) only appearing in the Late Cretaceous.
There are two contenders for the Biggest in this group, and both of them lived in Laramidia (western North America) at the tail end of the Cretaceous. These were Torosaurus and the ever-famous Triceratops. Both of these animals are thought to have been about the same size. Triceratops measured about 8-9 meters (26-30 ft) in length and weighed between 6 and 10 tonnes (6.6-11 US tons). Torosaurus on the other hand measured 7.5-9 meters (25-30 ft) and is estimated to have weighed in at 6-11 tonnes (6.6-12.1 US tons). These animals mostly overlapped in size, and both had the mass of one to two elephants, but based purely on the published estimates, Torosaurus’s maximum weight slightly edges out Triceratops. Torosaurus also holds the record for Longest Dinosaur Skull, thanks to its elongated neck frill. The longest Torosaurus skull is one nicknamed “Adam” on display at the Museum of Evolution at the Knuthenborg Safaripark in Bandholm, Denmark, measuring a whopping 3 meters (9.8 ft) long!
Winner: Torosaurus! (But maybe also Triceratops)
What is the biggest hadrosaur?
Hadrosaurs, often called duckbilled dinosaurs, were among the most common herbivores across North America during the Late Cretaceous. And while they weren’t known for being especially gargantuan, there was a handful which got truly massive. A few reached lengths of over 12 meters (40 ft), including Edmontosaurus and Saurolophus. But there was one that dwarfed the rest: Shantungosaurus of Late Cretaceous China, 77.3-73.5 million years ago, which measured 15-17 meters (49-56 ft) in length and weighed in at 13-16 tonnes (14-18 US tons). It could weigh almost as much as three modern elephants and even surpassed some sauropods in size!
Winner: Shantungosaurus!
What is the biggest theropod?
“What is the biggest theropod” is one of the most oft debated topics in paleontology fan circles. The names most commonly put forward are T-rex, Spinosaurus, and Giganotosaurus. But based on all the paleontological evidence to date, there is only one answer, the “King of the Dinosaurs” itself, Tyrannosaurus rex! Now to be fair, the title for Longest Theropod does belong to Spinosaurus, which measured upwards of 14-15 meters (46-49 ft) in length. But its 7.4-tonne (8.2 US ton) maximum weight is trounced by T-rex’s 8.87-tonne (9.78 US ton) maximum, despite T-rex’s maximum known length coming in about a meter short of Spinosaurus at 13 meters (43 ft). T-rex also narrowly beats out Giganotosaurus. Giga’s maximum weight estimate is 43 ft, equal to the maximum for T-rex, but at 8.2 tonnes (9 US tonnes), it still falls short of T-rex’s impressive bulk. What’s more, Giganotosaurus is known from incomplete material, and some authors suggest that the size estimates for this animal may be exaggerated, thus there may actually be a larger size gap between Rex and Giga. Either way, as the science currently stands, T-rex is still the king. And not only is it the largest theropod, but it also wielded the strongest bite force, not only of any dinosaur, but of any land animal in Earth’s history, upwards of 12,000 lb of pressure!
Winner: Tyrannosaurus rex!
What is the biggest sauropod?
Now we get to the sauropods, the giant “long-necks” of the Jurassic and Cretaceous. Some of these were surpassed by especially large members of other groups, like the hadrosaur Shantungosaurus. But most sauropods were quite a bit larger. For reference, Apatosaurus, which is a fairly “standard” sauropod, achieved masses of around 20-33 tonnes (22-36 US tons). And the largest sauropods were truly spectacular, even mind-boggling, and boarder-line physics-defying!
So, what was the biggest sauropod? There have been several contenders, a few with some truly extraordinary measurements. The Late Jurassic Maaripunisaurus, discovered by E.D. Cope in Colorado, is one such contender, being estimated at 32 meters (105 ft) long and 122.4 tonnes (134.9 US tons). The Late Cretaceous Indian titanosaur Bruhathkayosaurus may have been even bigger and has been estimated at 45 meters (148 ft) in length, with an estimated mass of 110–170 tonnes (120–190 short tons), rivalling even today’s blue whales (the record-holder for largest animal of all time with a maximum mass of 190 tonnes/210 US tons)! However, both Maaripunisaurus and Bruhathkayosaurus are known only from fragmentary remains, so the size estimates may not be entirely reliable. Additionally, the remains of both have since disintegrated and no longer exist, making the estimates not only suspect, but also completely unverifiable.
Thus, the title of Biggest Sauropod, is typically given to a more verifiable animal. And that animal is – drumroll please – Argentinosaurus! Argentinosaurus was a titanic titanosaur (an aptly named group) which lived in Argentina around 96-92 million years ago. And while it didn’t meet the purported proportions of Maaripunisaurus or Bruhathkayosaurus, it nevertheless came in at a very respectable and still mind-boggling 30–35 m (98–115 ft) in length with a mass of 65–80 tonnes (72–88 short tons), the equivalent of about 11-15 elephants! Fellow titanosaurs Patagotitan, also from Argentina, and Alamosaurus from the American southwest, have been touted as potentially similar in size to Argentinosaurus, and the diplodocid Supersaurus from the western United States in the Late Jurassic currently holds the record for Longest Sauropod, at over 40 meters (131 ft) in length (though it was much less heavy), but as the science currently stands, Argentinosaurus is the record-holder for (verifiable) Biggest Sauropod, and by extension Biggest Dinosaur and Biggest Land Animal, known to science!
Winner: Argentinosaurus!
How did dinosaurs get so big?
Dinosaurs, particularly the sauropods tend to dwarf the large land mammals which arose after them. The largest land mammals in Earth’s history were the giant hornless rhinoceros Paraceratherium and the giant elephant Paleoloxodon namadicus, reaching masses of 15-20 tonnes and 13-22 tonnes, respectively. While these colossal beasts certainly dwarf our modern land giants, they fall conspicuously short of the largest dinosaurs, failing to equal even the average sauropods, let alone the super-giants. So, what’s so different between mammals and dinosaurs that dinosaurs could get so much bigger?
In short, paleontologists are still working on that. There is still much we don’t fully understand. But there have been several ideas put forward, some better, some worse. In the past, some have speculated that dinosaurs got so big thanks to the Earth having less gravity than it does now or that and higher oxygen levels allowed them to get bigger, as has been suggested for the giant bugs of the Carboniferous Period. However, both of these theories have been debunked. For one, gravity is based on mass, and the Earth’s mass has not changed significantly for the last few billion years. As for the oxygen idea, arthropods have completely different respiratory systems and physiologies from vertebrates and thus have different oxygen constraints. So while a hyper-oxygenated atmosphere may support larger insects and arachnids, vertebrates are not size-limited by oxygen availability. What’s more, oxygen levels in the Mesozoic Era (“The Age of Dinosaurs”) varied greatly, with some periods of time having oxygen levels much lower than today, and other times having oxygen levels much higher.
Dinosaurs are now thought to have grown so large due to a combination of ecological factors and bird-like physiology. Abundant ecosystems fueled by warm climate conditions may have contributed to dinosaurs getting bigger, as generally, more food is required to support bigger animals. But other factors may have also been at play. Sauropods seem to have favored seasonal climates, and their large size may have evolved in part to help them store energy and water so as to go long periods without food or water during migrations or droughts. Much of the food which sauropods ate, ferns and conifers, was also rather nutrient poor, and evolving larger size would have helped them have a larger gut, which they used as huge vats of fermentation in order to better squeeze as much energy and nutrition out of their food as possible. And furthermore, being so big would have helped protect them from predators.
Of course, sauropods weren’t the only giants. Other herbivores and carnivores reached sizes a good deal larger than their modern mammalian counterparts. And these other dinosaurs may have gotten big in part to keep up with the sauropods and each other. Other herbivores may have gotten bigger so as to compete in the sauropods’ world, and the predators got bigger so as to not be completely outclassed by their prey or by other predators. Part of the reason for the giant dinosaurs may essentially be runaway size competition.
However, while these may be reasons WHY dinosaurs got so big, it still doesn’t answer the question of HOW they could get so big where mammals cannot. As previously mentioned, climate could have something to do with it, but the biggest reason is probably physiological. Dinosaurs, including birds, have a much more efficient respiratory system than mammals, allowing them to better oxygenate their bodies, regardless of how much oxygen is in the atmosphere. And these respiratory systems include numerous air sacs which invade the bones and help lighten the skeleton. In essence, while dinosaurs could get heavier than mammals, they were also less dense than mammals, helping them to essentially carry their weight better.
And now you know about the biggest dinosaurs and a bit about what made them tick. New discoveries are constantly being made in the world of paleontology, and new discoveries could change some of these answers one day. But one thing is unlikely to ever change, and that is that life on land during the Age of Dinosaurs had never been so spectacularly huge ever before, nor has it been since. Animals like Torosaurus, T-rex and Argentinosaurus were truly giants among giants, the biggest of the big!