Abstract The unusual presence of long pennaceous feathers on the feet of basa l dromaeosaurid dinosaurs has recently been presented as strong evidence in support of the arboreal?gliding hypothesis for the origin of bird flight, but it could be a unique feature of dromaeosaurids and thus irrelevant to the theropod?bird transition. Here, we report a new eumaniraptoran theropod from China, with avian affinities, which also has long pennaceous feathers on its feet. This suggests that such morphology might represent a primitive adaptation close to the theropod?bird transition. The long metatarsus feathers are likely primitive for Eumaniraptora and might have played an important role in the origin of avian flight. Electronic Supplementary Material Supplementary material is available for this article at http://dx.doi.org/10.1007/s00114-004-0604-y
Rahonavis ostromi (Forster, Sampson, Chiappe and Krause, 1998) is an early bird found in late Cretaceous Madagascar that shows a mixture of bird-like and theropod-like features that strengthen the case for birds as descendents of theropod dinosaurs. The partial skeleton consists of dorsal and caudal vertebrae , ulna , radius , synsacrum (fused vertebrae over the pelvis), shoulder girdle, pelvic girdle, femur , tibia , f ibula , calcaneum , astragalus, t arsals , metatarsals and phalanges . The overall appearance is bird-like, and Rahonavis is only slightly larger than Archaeopteryx and smaller than the early bird Vorona, found in the same quarry. Of particular interest is the sickle-claw on the second toe - a feature characteristic of dromaeosaurids and troodontids . Because the wing was found nearby but not attached to the rest of the skeleton, it has been suggested that the wing actually belongs to Vorona. Forster et al acknowledge the possibility but consider it unlikely based on the scattered nature of the bird material from this quarry and the similar appearance of the wing bones and the remainder of the skeleton. Cladistic analyses both with and without including the wing give the same result, positioning Rahonavis close to Archaeopteryx.