Lateral dorsal sacrocaudal muscle

Origin: Continuation of the longissimus, fleshy from the aponeurosis of the longissimus and a tendinous origin from the mamillary processes of the first to sixth lumbar vertebra, the articular processes of the sacrum, and the mamillary processes of at least the first eight caudal vertebrae.

Insertion: Mamillary processes of the fifth to last caudal vertebrae.

Action: Extension or lifting of the tail, possibly also to move it to the side.

Nerve: Branches of the plexus caudalis dorsalis.

Variation:

In equids, the lateral dorsal sacrocaudal muscle is well developed and originates (at a more cranial level than the medial dorsal sacrocaudal muscle) from the last lumbar mammillary process via an aponeurotic lamina, from the middle portion of the spinous processes of the first three sacral vertebrae, and from the base of the mammillary processes of the last two sacral vertebrae. The first bundle is long and inserts on the mammillary process of the ninth coccygeal vertebrae. Each bundle terminates in a long tendon, shared with the tendons of the medial dorsal sacrocaudal muscle, extending to the last vertebrae.