Coccygeal muscle

Origin: Ischiatic spine, cranial to the internal obturator muscle.

Insertion: Transverse processes of the second to fifth caudal vertebrae.

Action: Bilateral to press the tail against the anus and genital parts and, in conjunction with the depressors, to draw the tail between the rear legs. Unilateral, lateral flexion.

Nerve: Ventral branches of the third sacral nerve.

Variation:

In cats, Martin et al. 1974 described two parts to the coccygeus muscle. The cranial three quarters inserted on the transverse processes of the caudal vertebrae 1 to 3. The caudal quarter of the muscle, which is separated from the cranial part by adipose tissue, inserts onto the deep caudal fascia covering the sacrocaudalis ventralis lateralis muscle at the level of caudal vertebrae 4 and 5.

In equids, the coccygeal muscle is thin, flat, and weak. It originates from a short aponeurosis on the ischial spine and on the inner surface of the sacrotuberous ligament. The muscle inserts on the transverse processes of the last sacral vertebra and the first two coccygeal vertebrae, passing between the dorsal and ventral intertransverse muscles.