Fig. 3. CT scans of the internal anatomy of the raptorial appendage and the degree of mineralization of the merus exoskeleton (gray is mineralized; transparent regions represent relatively unmineralized exoskeleton). (A) Medial view of the raptorial appendage (proximal to right of page; ventral toward the bottom of the page) showing the large lateral extensor apodeme (e). Ventrally, the lateral flexor apodeme (f) attaches to sclerite 2 (orange). Medial to sclerite 2 is the small, rod-shaped sclerite 1 (green). (B) An internal perspective of the merus viewed from the distal end (lateral to left). Sclerite 2 (s2) is in its resting, unlocked position such that it hangs externally between the merus and carpus. The surface of the distal meral-V (v) articulation, which loosely articulates with the carpus, contrasts with the large internal joint, which forms the medial carpus joint articulation (j). (C) Same view as in B with sclerite 2 and sclerite 1 (s1) in closed and braced positions. Note that sclerite 1 does not appear to directly articulate with sclerite 2 when in the closed position and instead folds medially relative to the edge of sclerite 2. (D) Sclerites in resting position (medial view; distal to left). (E) Locked positions of the sclerites with the carpus rotated counter-clockwise in preparation to strike (medial view). m, merus; c, carpus; s, saddle; p, propodus; b, ventral infolding of merus. Scale bars, 4 mm.