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| Four-winged dinosaurs from China |
| Microraptor gui can be unequivocally referred to Dromaeosauridae based on the following derived characters20: extremely elongate prezygapophyses and chevrons; manual phalanges III-1 significantly longer than III-2; specialized pedal digit II; and long metatarsal V. Furthermore it can be referred to Microraptor on the basis of the following features20: metacarpal III subequal to metacarpal II in length; extremely short manual phalanx III-2 that is less than one-quarter of manual III-1 length; manual III-3 extremely slender and shorter than III-1 in length, and small distal articulation of manual III-3 skewed ventrally. However, a few features distinguish it from M. zhaoianus. A prominent biceps tuberocity is present close to the proximal end of the radius and this feature has not |
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| credits Nature Page 2 article given by markm photos researched and contributed for the story by Ackers |
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| been reported in most other non-avian theropods except a recently described therizinosauroid22. As in most birds, M. gui has a proportionately very short manual digit I (metacarpal I + phalanx I-1/metacarpal II length ratio is 0.80–0.84). For comparison, this ratio is 0.97 in M. zhaoianus and more than 1.0 in most other non-avian theropods and the basal birds Archaeopteryx and Confuciusornis. The pubis of M. gui is strongly curved (120°), whereas the pubis is relatively straight in most other non-avian theropods, including M. zhaoianus. The other distinctive feature of M. gui is the bowed tibia whereas in most other theropods, it is straight. These features suggest that M. gui is a new species. |
| Recent discoveries suggest that pennaceous feathers are present on Dromaeosauridae17, a non-avian theropod group, and our observations on the newly collected specimens provide new information that is important for understanding the transition towards birds. The most unusual feature is the attachment of pennaceous feathers to the whole length of the metatarsus (Figs 1a,c, 2g and 3a). They are long and some have asymmetrical vanes like flight feathers (Fig. 3a–d). We exclude the possibility that these are preservation artefacts because we observed this feature in all six specimens in the present study, most of which are represented by well-articulated skeletons. Pennaceous feathers are also associated with the tibia and femur19 and they display symmetrical vanes. In general, the leg feathers are arranged in a pattern similar to wing feathers in modern birds, suggesting the presence of a hindlimb wing. Although there is no modern analogue, our observations are concordant with some early hypotheses25, 26 that there is a tetrapteryx stage in bird evolution. |
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