"sickle claw" of the second digit is strongly curved and bears a prominent flexor tubercle (the portion which articulates with the phalanx). It is also much larger than the other phalanges in the digit; it is longer than the first phalanx, whereas they have the same length in Sinovenator. Feathering Feathers are preserved alongside the entire vertebral column of Jianianhualong. On the bottom of the neck, feathers are preserved with a length of at least . Those along the back and over the hip are longer, with a length of about . Behind the tibia, there are also some feathers measuring in length. Additionally, some poorly preserved feathers are associated with the humerus and ulna, having an unknown length. Like Jinfengopteryx, Anchiornis, and Archaeopteryx, the tail of Jianianhualong supports a frond-like fan of pennaceous feathers along its entire length. Unlike Archaeopteryx and potentially Jinfengopteryx, the feathers are curved. Feathers from the middle of the tail are long. At least some of the long pennaceous feathers lining the tail are asymmetric; one feather has a trailing (hind) vane that is about twice as wide as the leading (front) vane, with the barbs being respectively at angles of 10° and 15° for the two vanes. Classification A number of characteristics allow Jianianhualong to be identified as a member of the Troodontidae. These include the long forward-projecting branch and flange of the lacrimal bone; the foramina on the nasal bone; the smooth transition between the eye socket and the backward-projecting branch of the frontal bone; the ridge on the forward-projecting branch of the jugal bone; the triangular dentary bearing a widening groove; the robust forward-projecting branch of the surangular bone; the relatively large number of unevenly-distributed teeth; the flattened chevrons with blunt forward projections and bifurcated backward projections; and the broad and flat "pubic apron" formed by the pubic bones. Within the troodontids, Jianianhualong displays a unique combination of characteristics from both basal ("unspecialized") and derived ("specialized") troodontids, organized in distinct regions of its body. The forelimbs and pelvis largely resemble basal troodontids such as Sinovenator: the short deltopectoral crest on the humerus; the long hand, metacarpal II, and phalanx III-2 on the hand; the small ilium; the ridge on the pubic apron; and the short ischium with two projections and an obturator process near the bottom of the bone. At the same time, the skull and hindlimbs resemble derived troodontids: the deep