Yuanmouraptor

Yuanmouraptor lived about 174 to 168 million years ago, during the Aalenian and Bajocian ages of the Middle Jurassic.2

The only known fossil of Yuanmouraptor includes a nearly complete skull, lower jaws, ten neck vertebrae, and the first back vertebra.1

Its skull was about 60 centimetres (24 inches) long when fully reconstructed, which is smaller than the skull of its relative Yangchuanosaurus.1

Yuanmouraptor had special air sacs in its neck bones, shown by deep holes called pneumatic foramina on the third neck vertebra.1

The bones of the holotype show that the neural arches were fused to the vertebrae, meaning this dinosaur was nearly full-grown when it died.1

Yuanmouraptor is one of the oldest and most primitive members of the family Metriacanthosauridae, a group of allosauroid theropods.31