Also from Cretaceous China, Zhenyuanlong suni is unique in that its fossil provided the first evidence of pennaceous (veined) feathers in large, non-flying dromaeosaurs. Zhenyuanlong was over 122.6 centimetres (4.02 ft) long… but half of its tail is broken off. When compared to its close relative Tianyuraptor, it can be estimated to have been around 165 centimetres (5.41 ft) long in life, and with the addition of tail feathers could have been up to 2 metres (6.6 ft) long! There is only one fossil of Zhenyuanlong, and it is a subadult, so the animal could have been even larger in adulthood. This puts it at about the midway point between Velociraptor and Deinonychus, about the size of a modern condor.
Zhenyuanlong had very short arms, but (comparatively) very large, broad wings, as well as long, wide feathers on its tail. However, due to its body size, it’s unlikely the animal could have flown or even glided. This raises the question of what such a large dromaeosaur was doing with such complex wings. They could have been remnants of a flying ancestor, and retained for sexual display. They could have also been used for aerodynamics, as Zhenyuanlong had very long legs and was likely a pursuit predator, the wings would have assisted in balance. Zhenyuanlong also lacked the veined leg-feathers of its Microraptorian relatives, freeing its legs up for quicker speeds.