Aorun

a pair of juvenile Aorun play together

Type Species: Aorun zhaoi

Classification: Dinosauria – Saurischia – Theropoda – Coelurosauria

Time Period: Late Jurassic

Location: China

Diet: Carnivore 

The predatory theropod Aorun is known from one specimen, and that one a juvenile that was probably around one year old (according to bone pathology). This toddler’s remains included parts of the skull, the lower jaws, a neck vertebra, a dorsal vertebra, three tail vertebrae, the left ulna and hand, the lower ends of both pubes, and both lower legs. In life it would’ve reached just over three feet long and would’ve weighed just four pounds. The length and weight of adults are unknown. Our single Aorun specimen has multiple infantile morphologies, such as enormous sclerotic rings around the eyes composed of overlapping ossicles, and teeth that either have no serrations or bear very fine serrations (such dental variability may be due to its young age). Aorun lived 160 million years ago during the Oxfordian age of the early Late Jurassic. Its remains were found in the Shishugou Formation of China, which during prehistoric times was covered by marshland and adjoined a small mountain range peppered with volcanoes. This formation has revealed that the environment was home to numerous dinosaurs, small crocodilians and amphibians, and pterosaurs. Dinosaur contemporaries of Aorun included ornithischians, sauropods, and other theropods. Aorun, at least in a juvenile state, likely hunted small lizards and mammals. 

Some scientists believe Aorun is the oldest known coelurosaur. The coelurosaurs are a subgroup of theropod dinosaurs that contains all theropods more closely related to birds than to carnosaurs (to which megalosaurs, spinosaurs, and allosaurs belong). Coelurosaurs include compsognathids, tyrannosaurs, ornithomimosaurs, and maniraptors. The maniraptors include birds, which is the only dinosaur group alive today. Because most of the feathered dinosaurs discovered so far have been coelurosaurs, some scientists – such as the preeminent Philip J. Currie – believe it probably that all coelurosaurs (such as Aorun) were feathered.