Falcarius

Falcarius is a transitional theropod from the Early Cretaceous Cedar Mountain Formation of Utah. Known from an expansive mass-death quarry containing hundreds of individual animals, it offers an unprecedented look at how meat-eating coelurosaurs evolved into pot-bellied plant eaters. Roughly four metres in length, Falcarius retains the slender running legs and moderately agile frame of its predatory ancestors, but displays unmistakable herbivorous adaptations. Its teeth were small, closely spaced, and coarsely serrated for slicing plant fibres, while its pelvis had begun to flare outward to accommodate an enlarged digestive tract. Its hand claws were elongated and curved, though not nearly as extreme as those seen in later therizinosaurs like Nothronychus. This wealth of bonebed material makes Falcarius one of the clearest fossil examples of an evolutionary dietary shift.

Thousands of bones from a single bonebed document an evolutionary transition from carnivory towards herbivory.

Where and when

Falcarius lived in the Early Cretaceous, from 130 to 125 million years ago (Barremian age). Its remains come from United States, in the Cedar Mountain Formation.

The numbers

Length 3.8 m (estimates run from 3.5 to 4 m). Mass about 120 kg. Hip height about 1.2 m. That is 2.2 human-lengths, or 0.34 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

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