page_title: Jianianhualong
section_title: Limbs
hierarchical_section_title: Jianianhualong / Description / Limbs
caption_attribution_description: English: Figure 5: Plumage of Jianianhualong tengi holotype DLXH 1218. (a) Feathers over dorsals, (b) feathers attached to anterior caudals, (c) asymmetrical tail feather, (d) line drawing of asymmetrical tail feather, (e) tail frond and (f) negative LSF image of tail frond. All scale bars, 2 cm.
context_page_description: Jianianhualong is a genus of troodontid theropod dinosaur from the Early Cretaceous of China. It contains a single species, Jianianhualong tengi, named in 2017 by Xu Xing and colleagues based on an articulated skeleton preserving feathers. The feathers at the middle of the tail of Jianianhualong are asymmetric, being the first record of asymmetrical feathers among the troodontids. Despite aerodynamic differences from the flight feathers of modern birds, the feathers in the tail vane of Jianianhualong could have functioned in drag reduction whilst the animal was moving. The discovery of Jianianhualong supports the notion that asymmetrical feathers appeared early in the evolutionary history of the Paraves.
  Jianianhualong possesses a combination of traits seen in basal as well as traits seen in derived troodontids. This is consistent with its phylogenetically intermediate position among the troodontids. This mixture of traits shows a distinct spatial organization, with basal traits being present in the forelimbs and pelvis, and derived traits being present in the skull and hindlimbs.
context_section_description: The bottom of the large, four-sided coracoid extends backwards with a hook-like projection, the postglenoid process, which is similar in length to that of Sinornithoides but longer than that of Sinovenator. Unlike Sinornithoides but like Mei, the furcula in Jianianhualong is robust, flattened, and U-shaped like that of Mei. Like derived troodontids, the slender humerus is shorter than the femur. The ulna exhibits a slight backward bow; Mei has a much stronger bow, while the bow is absent in most other troodontids altogether. Contrary to most other theropods, the top portion of the radius bears a backwards bow similar to that of the ulna.
  The hand bears three digits, typical of the Maniraptora, which respectively bear 2, 3, and 4 phalanges. The overall length of the hand is 112 mm (4.4 in). Several distinguishing characteristics of Jianianhualong are found among the phalanges. The first phalanx of the first digit is unusually long; it bears a "heel" at its top end, as well as a large groove on the interior surface that extends for more than half the bone's length. Additionally, the second phalanx of the second digit is also very long, being longer than the metacarpal of the corresponding digit. The claws are highly robust, with their bases being at least half as wide as their overall length; the claw of the first digit is the largest.
  The pelvis of Jianianhualong is overall similar to that of Sinovenator. Like Archaeopteryx and basal dromaeosaurids, the ilium is small. A distinguishing trait is that the top margin of the ilium is slightly concave. Below the ilium, the left and right pubes are conjoined into the unusually broad "pubic apron" that is characteristic of troodontids, with a ridge on the rear surface as in Sinovenator. Behind the pubes, the forward-projecting obturator process of the ischium is located near the bottom of the bone. There is a small recess, or lamina, on the margin of the process, another distinguishing trait of Jianianhualong.
  Among the four metatarsal bones, the second is the shortest and most slender after the first (corresponding to the hallux). The third metatarsal is shorter relative to the femur than that of Sinovenator. Unlike other troodontids, the bottom end of the second metatarsal lacks a hinge joint, and a flange on the bottom of metatarsal IV is also missing. The latter is a distinguishing characteristic. Further below, like derived troodontids and dromaeosaurids, the "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.
caption: Feathers of J. tengi as preserved on the back (a) and base of the tail (b); photograph (c) and diagram (d) of an asymmetrical feather; photographs (e,f) of the tail frond
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