Fig. 3. Underdeveloped thumb flexor. A in Anatomical Study of the Right Forearm and Hand of One Western Gorilla (Gorilla gorilla) for Comparison with Humans with Respect to Motions of the Thumb and Fingers

Fig. 3. Underdeveloped thumb flexor. A. The tendon of the thumb flexor is much thinner than that of FDS or FDP; B. Its muscle belly (uFPL) bifurcates from the distal portion of FDP muscle of the index finger; C. Pulling FDP index finger at its myotendinous junction with a retractor revealed that the thumb and the index finger were flexed simultaneously.