Dinosaurs were the largest species ever to walk the Earth. Some, like the sauropods, weighed around 90 tonnes (the equivalent of 15 adult elephants) and make fascinating examples of the extremities of biological engineering.
There is no uncontroversial explanation for their size, and scientists have numerous intriguing theories. The long necks of sauropods acted like giant rakes, constantly sweeping in food as they swung from side to side or helping to reach high up foliage.
Sauropods did not chew and had specialised teeth for swallowing mouthfuls of food, stripped from plants. Their bulky bodies housed factory-like stomachs for highly efficient, massive-scale digestion, which might have driven physiological shifts towards larger bodies.
Sauropod bones were also lightweight, hollowed out by numerous air sacs extending from the lungs, making a bigger body easier to support. Being huge also gave an advantage against the large theropod dinosaurs and could have been triggered by an evolutionary arms race against predators.
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