Eoraptor

Eoraptor was a miniature, bipedal dinosaur that lived during the Late Triassic period in what is now Argentina, about 230 million years ago. Measuring around one metre long and weighing roughly as much as a domestic cat, it was an agile ground runner with slender limbs. When first discovered in 1991, palaeontologists considered it an ancestral meat-eating theropod due to its lightly built skull and sharp claws. However, more detailed studies of its skeleton and heterodont teeth, which display both curved serrated edges and leaf-shaped crushing surfaces, indicate it was likely an omnivorous basal sauropodomorph. Its modest form offers crucial evidence of how the ancestors of colossal sauropods started out as nimble, generalist omnivores.

Initially hailed as the most primitive theropod, subsequent anatomical analyses reclassified it as an early ancestor of giant sauropods.

Where and when

Eoraptor lived in the Late Triassic, from 231.4 to 228 million years ago (Carnian age). Its remains come from Argentina, in the Ischigualasto Formation.

The numbers

Length 1.2 m (estimates run from 1 to 1.3 m). Mass about 7.1 kg. Hip height about 0.3 m. That is 0.7 human-lengths, or 0.11 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

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