They would have terrified each other (and us!) but did dinosaurs have a softer side? Like most birds and reptiles, dinosaurs laid eggs. Parents made nests and some incubated and protected their offspring before hatching.
Were dinosaurs good parents?
But after birth, baby dinosaurs soon had to fend for themselves. When parents did look after their young, as commonly occurs in mammals, it likely wasn’t for very long.
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Parental care can be inferred by finding dinosaur bones and eggs in close proximity. This sometimes causes naturalists to jump to conclusions, however, as illustrated by a famous case that gave one species an undeserved reputation.
In the 1920s, explorer Roy Chapman Andrews (an inspiration for Indiana Jones) went to Mongolia and discovered eggs next to a theropod – a group whose members are often predators.
The eggs were thought to belong to a herbivore, Protoceratops (‘first horned face’), leading the American Museum of Natural History (AMNH) to picture scenes where ceratopsian parents protected their nest of eggs from the theropod, which was named Oviraptor (‘egg thief’).
That interpretation was incorrect. In 1995, palaeontologists from AMNH found new Mongolian fossils of the predator’s close relative sitting on a nest of so-called Protoceratops eggs. Oviraptor had been given a bad rap and may even have been a good parent.
Many dinosaurs were massive. How could they have incubated eggs without crushing them? Heavy groups like sauropods didn’t sit on their eggs, but lighter ones might have done, just like birds – a parent (typically the mother) gently lowers themselves and uses tail feathers to reposition eggs, then keep them warm.
Larger species may have used a heating system similar to that of crocodilians – piling plant matter on top of eggs to create a compost heap to generate warmth as the vegetation decays. Although we often picture nests as cosy places, many dinosaur nests were little more than holes in the ground, like those made by living reptiles and avians such as seabirds.
Fossils offer the most direct evidence that dinosaurs cared for their newborns. The best example is the hadrosaur Maiasaura (‘good mother lizard’). In 1979, Jack Horner (the model for the character Dr Alan Grant in Jurassic Park) discovered adult skeletons near babies, which suggests that parents brought food to offspring and guarded nests from predators.
The clutches of Maiasaura eggs were spread apart, meaning that the dinosaur nested in colonies. These nesting grounds were preserved in successive layers, meaning that parents returned to the same grounds to mate, possibly every year like many birds today. Ornithologists call this ‘nest site fidelity’. Sauropods did the same thing – at one site in Argentina, there are six layers of nests containing hundreds of eggs.
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