Dino of the Week: Epidexipteryx

Type Species: Epidexipteryx hui

Classification: Dinosauria – Saurischia – Theropoda – Coelurosauria – Maniraptora – Paraves – Scansoriopterygidae

Time Period: Late Jurassic

Location: China

Diet: Carnivore 

The paravian theropod Epidexipteryx grew only ten inches long and weighed just over a third of a pound. It had a distinctive short snout and large eye sockets. Its teeth were restricted to the front of the jaws, and they were unusually angled forward, a feature seen again only in the Late Cretaceous theropod Masiakasaurus. Skull similarities between Epidexipteryx and later oviraptosaurs has led some researchers to speculate that Epidexipteryx may be the sort of dinosaur that was ancestral to the oviraptosaurs. A key similarity between the two is how the lower jaw curves down and away from the upper jaw, especially towards the end; thus the lower front teeth always pointed forward instead of up into the upper jaw. Researchers speculate that this strange design in Epidexipteryx was to catch specific prey. Its diet was probably small insects, worms, and larvae, especially those found in trees. That it was arboreal (a tree-dweller) is evidenced in its incredibly long fingers. Its second finger was much longer than the first, and the third finger was much longer than the second, growing half as long as Epidexipteryx’s body. This has been interpreted as an adaption for an arboreal lifestyle. Its long fingers enabled it to climb trees while gripping firmly to the trunk. The long fingers could also snatch worms and larvae burrowed into tree holes. As a tree-dweller, it may have made nests for its young. The short forelimbs and long fingers would’ve made walking about the ground a difficult task, and thus prone to predation, so it may have rarely gone down to the forest floor. 

Epidexipteryx was covered in simple body feathers composed of parallel barbs; these body feathers were unique in that some appear to arise from a ‘membranous structure’ at the base of each feather, a facet that some scientists believe is a critical stage in the evolution of modern flight feathers. Epidexipteryx’s most fascinating feathers are found on the tail. Its tail bore unusual vertebrae toward the tip which resembles the feather-anchoring pygostyle of modern birds (and some oviraptosaurs, strengthening the possible oviraptosaur connection); and spreading from this base of its tail were four unusually long feathers. Each was composed of a central rachis and vanes; unlike modern tail feathers, the vanes weren’t branched into individual filaments but made up of a single ribbon-like sheet. These feathers are thought to have been similar to those of a peacock; as strict display feathers, they may have been present only in male Epidexipteryx in order to attract females. If these were indeed strict tail display feathers, they are the first in the fossil record and the precedent of hundreds of different bird species today.