Fig. 1. Muscles of the right forelimb of a male Bufo marinus are seen from a medial perspective (A) with hand pronated, and from lateral view (B) with hand supinated. Flexor carpi radialis (FCR) originates along the medial surface of the distal half of the humerus and inserts on the radiale. It is a ventromedial flexor of the wrist, and can also flex the elbow. The abductor indicus longus (AIL) originates laterally from the distal humerus and the radioulnar border and inserts by a narrow tendon onto metacarpal I. It can extend the wrist and abduct the first digit. These are both used in amplexus and are sexually dimorphic by size (see text). The extensor carpi ulnaris (ECU) is a non-dimorphic muscle that originates superficial to AIL on the lateral humeral condyle and inserts on the ulnare. It laterally extends the wrist and is not used in amplexus. (Modified from Peters and Aulner, 2000.)