Dino of the Week: Agilisaurus

Type Species: Agilisaurus louderbecki

Classification: Dinosauria – Ornithischia – Neornithischia 

Time Period: Middle Jurassic

Location: China 

Diet: Herbivore 

The small, bipedal ornithischian Agilisaurus is known from an almost complete specimen from China. Its classification in the ornithischian family tree is unknown, and most scientists categorize it as a basal ornithopod (though some have considered it a basal marginocephalian, which eventually led to the ceratopsians and pachycephalosaurs). Agilisaurus was only about four feet long head-to-tail, stood two feet in height, and weighed around eighty pounds. It had a short head with large eyes, and comparisons between its sclerotic rings and those of modern birds and reptiles suggest it was diurnal (active at dawn and dusk) rather than cathemeral like most larger herbivorous dinosaurs (active throughout the day at short intervals). Its teeth were leaf-shaped and larger and pointed at the front. The teeth had wavy enamel, a characteristic previously attributed only to the ‘duck-billed’ hadrosaurs (a type of ornithopod). Its hind limbs were much longer than the forelimbs, and the thigh bone was short compared to the leg bones; these features indicate it was a fast runner that used its long tail for balance while ‘on the foot.’