How did dinosaurs grow so big?

Dinosaurs are reptiles that lived in what is known as the Mesozoic era, and their bones can be seen in almost every natural history museum in the world. And for good reason: they were discovered in the 18th century and have since dominated the natural world with their interesting history and their massive size.

But how did they grow so big? And why have there been no other species that could match their size? Click through the following gallery to find all those answers and more.

A long time ago

Dinosaurs lived in a stretch of time known as the Mesozoic era, which occurred from about 230 million years ago until about 60 million years ago. During this time, many dinosaurs of varying sizes roamed the planet.

Bird of a feather

The smallest known (and also the smallest living) dinosaur in all of history is the hummingbird. This contrasts massively to theropods, a group of reptiles that includes famous species like the Tyrannosaurus rex.

Fossilized records

While scientists can never be truly certain about which dinosaurs were the biggest, some of their fossils have provided a bit of insight into what the world was like back then, and what contributed to their massive size.

Stomachs and size

Titanosaurs in particular also had unique features, including wide hips, which provided stability and space for their large stomachs. This enabled them to consume and digest large amounts of food, which was crucial for sustaining their massive bodies and helped them grow.

Sauropods

Sauropods are a sub-group of titanosaurs (which includes Argentinosaurus), and they achieved gigantism through a combination of physiological and ecological adaptations, such as long necks for reaching high vegetation and efficient respiratory systems.

Oxygen

Dinosaurs (particularly sauropods) had bird-like breathing systems, which included air sacs in their bones, that allowed them to take in oxygen continuously, even while exhaling. This facilitated their large size by ensuring efficient oxygen supply.

Predators

Another reason why dinosaurs grew so large is because gigantism was actually a great defense mechanism against predators. Larger dinosaurs were more formidable and less likely to be preyed upon, which increased their chances of survival and reproduction.

Necks

The long necks of sauropods also allowed them to feed over a wide area without moving much, which conserved energy and encouraged their growth.

Seasons

Paleontologists have suggested that seasonal fluctuations in the availability of resources may have influenced the evolution of large body sizes in dinosaurs. These reptiles stored energy during times of abundance (which added to their size) so that they were biologically prepared for when resources became scarce.

Social behavior

Herding behavior in some dinosaur species could have supported the evolution of large body sizes. By being in a herd, dinosaurs were more protected against predators, and so they were able to acquire resources and food more easily.

Metabolism

Sauropods had a highly efficient metabolism that slowed down as they grew older, which reduced the amount of food they needed to get energy. This allowed them to thrive on less food compared to mammals of similar sizes.

Plant evolution

Much like the predator-prey coevolution, herbivorous dinosaurs and their gigantism may have influenced the evolution of plants as well, leading to larger and more nutritious vegetation. This mutualistic relationship benefited both the dinosaurs and the plant species they fed on.

Mating

Large body sizes in some dinosaurs could have been the result of sexual selection, where bigger size was favored for mating purposes. Larger males might have been more attractive to females, which led to the evolution of larger sizes.

Sauropod plateau

During the Late Jurassic period, sauropods reached a size plateau and maintained constant gigantism afterward. Studies have suggested that they had optimized their size for their ecological roles and had no need to grow bigger.