Yi qi and Scansoriopteryx (Fig. 1) and it is midway in size between the two. There is no controversy with that nesting.
We looked at the controversies
surrounding Ambopteryx earlier here. No one has reported a ‘stylifom’ bone in Scansoriopteryx nor any other scansoriopterygids (other than Yi qi, by mistake).
Figure 1. Ambopteryx nests midway and is phylogenetically midway between the larger Yi and the smaller Scansoriopteryx. None of these taxa have an extra long bone in the arm.
Ambopteryx longibrachium (Wang et al. 2019; Late Jurassic; IVPP V24192; 32 cm long) is a scansoriopterygid bird, a descendant of Archaeopteryx #12 (privately owned) . A dense layer of feathers is also preserved, not a bat wing, as originally described.
Wang M, O’Connor JK, Xu X and Zhou Z 2019. A new Jurassic scansoriopterygid and the loss of membraneous wings in theropod dinosaurs. Nature 569:256–259.