Irritator

Irritator was a mid-sized spinosaurid theropod that lived during the Early Cretaceous in what is now northeastern Brazil. The genus was discovered through illegal fossil dealing and purchased by a museum; its name stems from the extensive frustration palaeontologists experienced while removing plaster and automotive filler that collectors had used to artificially extend the snout. Recent biomechanical investigations into its well-preserved braincase and jaws suggest that Irritator possessed a kinetic lower jaw that could spread outward, allowing it to swallow sizeable prey whole. It lived alongside abundant pterosaurs and fish in a coastal lagoon environment. Although primarily known from its skull, Irritator is estimated to have measured up to eight metres in total length, walking on strong hind legs while patrolling shorelines for prey.

Palaeontologists named it after the irritation felt when undoing amateur plaster alterations to the skull.

Where and when

Irritator lived in the Early Cretaceous, from 113 to 108 million years ago (Albian age). Its remains come from Brazil, in the Romualdo Formation.

The numbers

Length 7.3 m (estimates run from 6.5 to 8 m). Mass about 1.4 t. Hip height about 2 m. That is 4.3 human-lengths, or 0.65 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

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