dominance to front-limb dominance and that all modern birds may have evolved from four-winged ancestors, or at least ancestors with unusually long leg feathers relative to the modern configuration. Feeding In 2010 researchers announced that further preparation of the type fossil of M. zhaoianus revealed preserved probable gut contents, and a full study on them was later published in 2022 by David Hone and colleagues. These consisted of the remains of a mammal, primarily a complete and articulated right foot (including all tarsals, metatarsals, and most of the phalanges) as well as the shafts of additional long bones and potentially other fragments. The foot skeleton is similar to those of Eomaia and Sinodelphys. It corresponds to an animal with an estimated snout to vent length of and a mass of . The unguals of the foot are less curved than in Eomaia or Sinodelphys, indicating that the mammal could climb but less effectively than in the two latter genera and so was likely not arboreal but potentially scansorial. It is ambiguous whether the mammal had been predated upon or scavenged by the Microraptor, although the lack of other definitive body parts consumed may suggest the low-muscle mass foot may have been eaten during a late stage of carcass consumption, possibly through scavenging. The find is a rare example of a theropod definitively consuming a Mesozoic mammal, the only other being a specimen of the compsognathid Sinosauropteryx. In the December 6, 2011 issue of Proceedings of the National Academy of Sciences, Jingmai O'Connor and coauthors described a specimen of Microraptor gui containing bones of an arboreal enantiornithean bird in its abdomen, specifically a partial wing and feet. Their position implies the bird was swallowed whole and head-first, which the authors interpreted as implying that the Microraptor had caught and consumed the bird in the trees, rather than scavenging it. In 2013 researchers announced that they had found fish scales in the abdominal cavity of another M. gui specimen. The authors contradicted the prior suggestion that M. gui hunted only in an arboreal environment, proposing that it was also an adept hunter of fish as well. They further argued that the specimen showed a probable adaptation to a fish-eating diet, pointing to the first three teeth of the mandible being inclined anterodorsally, a characteristic often associated with piscivory. They concluded that Microraptor was an opportunistic feeder, hunting the most common prey in