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What Did Dinosaurs Eat and How Big Were They?

Part of Dinosaur Week

Dinosaurs ate lots of different things, and it changed depending on where they lived and how big they were.

Enormous sauropods like Brachiosaurus, Dreadnoughtus, and Titanosaur, were herbivores, that is, they ate plants. Because they were so big, they had to eat thousands of kilograms worth of food every day! There is a bit of a debate, though, about how they were able to digest their food. Most did not have the teeth to chew, only to pull leaves from branches. Some scientists believe they will have swallowed rocks like some birds do to grind up their food in their stomachs; whereas, other scientists believe they may have had lots of microbes in their bellies to digest their food for them. Recently, research suggests that they did not have stones in their stomachs, but that they held on to their food for very long periods to digest it.

Ornithischians like triceratops, ankylosaurs, and hadrosaurs are also well-known to have been herbivores, but they were much smaller than the sauropods, meaning they ate plant material closer to the ground. These dinosaurs had an extra bony tip on their lower jaw, and many rows of teeth in their jaws, as well as powerful cheek teeth for grinding their food.

Perhaps the most interesting is that theropods, those we typically think of as being predatory carnivores, weren’t all exclusively carnivorous! Some of these dinosaurs ate plants as well, making them omnivores! At least 44 species of theropods (specifically coelurasaurs) did eat plants! Of course, tyrannosaurs and raptors were among the strict carnivore groups, but this means that dinosaurs who only ate meat were the odd ones out!

So how big were these animals? In modern times, the largest animal on Earth is the Antarctic Blue Whale. It can reach 30 m in length (approximately 3 buses end to end) and weighs up to 400,000 pounds (33 elephants!).

The largest sauropod we know of was the Argentinosaurus. Scientists estimate this dinosaur to have been somewhere between 37 and 40 m long and would have weighed around 90-100 metric tonnes (about 18 elephants). Not only would it have been 1/3 longer than the Blue Whale, but it would have been about 21-24 m tall – as tall as a 6-story building. Most sauropods were about 15-20 m in length.

Ornithisician dinosaurs vary quite a lot in size – some being as small as a dog, and others growing to 15 m in length! Most seemed to fall in the range of 2-8 m, however.

Theropods, however, varied the most in size. The smallest theropods were only about 34 cm in length (almost as long as a laptop), and the largest – Spinosaurus aegyptiacus – was around 15 m in length. Until recently, the T-Rex was believed to be the largest theropod at around 12-13 m long.

Try out the activity below to compare some of these dinosaurs' sizes to things in your home!

Dinosaur Footprints Activity Sheet (PDF) (The Geological Society)
How do we know what dinosaurs and other extinct animals ate?
Argentinosaurus Eating (BBC’s Planet Dinosaurs)

This page is part of the Dinosaur Week information.

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