rhachides

However, the rhachides in the proximal portion of the tail of Zhenyuanlong appear to be longer than those of Microraptor 5 6 and Changyuraptor 10, which had relatively small and simple feathers proximally on the tail but much larger and more complex feathers distally, which expanded outwards into a large fan.

2015 July 16, Junchang Lü, Stephen L. Brusatte, “A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution”, in Scientific Reports, volume 5, →DOI