Fig. 1. Plan-view of the ventral surface of the wing of a Pteropus poliocephalus held in a horizontal plane, a position similar to that at the middle of the downstroke. The wing is subdivided into 14 chordwise strips; there are seven segments between the shoulder and the carpus (the plagiopatagium or armwing), three between the carpus and the metacarpophalangeal (MCP III) joint of the third digit (the proximal handwing) and four between the MCP III joint and the wingtip (the distal handwing). The locations of the centers of mass of these strips relative to a reference line connecting the two shoulders (broken line) are indicated by the filled circles. The large circles labeled shoulder (glenohumeral joint), carpus, MCP III and wingtip were used as digitizing markers for collecting kinematic data. For the third wing segment (subscript p), the length of the wing chord, c_p, the leading edge position, e_p, and the distance from the segmental center of mass to the reference line, d_p, are also indicated. The variation in these parameters within the wingbeat cycle is represented in the model by a second subscript, q, that ranges from 1 to 40 with the 40 equal time increments within the complete wingbeat cycle.