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DEEP HIP MUSCLES

LATERAL ROTATORS

     Tetrapods possess a puboischiofemoralis externus (which develops into obturator externus and quadratus femoris in mammals) and an ischiotrochantericus (which develops into obturator internus and gemellus in mammals) (Kardong, p. 387; Romer, p. 297).  In humans, chimps, and gorillas, the insertions of the adductor magnus and quadratus femoris meet (Gibbs, 2002)

 

OPOSSUM

LATERAL ROTATORS

LATERAL ROTATORS

GOAT

LATERAL ROTATORS

 

SHEEP

LATERAL ROTATORS

COW

LATERAL ROTATORS

 

 

HUMAN MODEL

MONKEY

LATERAL ROTATORS

DEEP HIP MUSCLES

    Early tetrapods possess a puboischiofemoralis internus which divides to becomes psoas, iliacus, and pectineus muscles in mammals) (Kardong 387; Romer, p. 297)

The Iliopsoas group

FROG

ILIOPSOAS GROUP

The puboischiofemoralis in turtles is homologous to the iliacus and psoas muscles in mammals.

OPOSSUM

ILIOPSOAS GROUP

 

CAT

ILIOPSOAS GRUOP

GOAT

ILIOPSOAS GRUOP

PIG

PIG

 

MONKEY

ILIOPSOAS GRUOP

ILIOPSOAS GRUOP

 

The psoas minor may be absent in African apes but seems constant in other mammals (Hartman, 1933, p. 149). 

As apes became larger in size and began to swing/walk vertically, they needed additional support for their pelvic organs. The loss of the external tail allowed for the modification of tail muscles to form a pelvic sling for internal organs. In apes, vestiges of the muscles which are used in tailed primates to flex the tail usually exist (such as the sacrococcygeus anterior in humans).  In apes the ancestral pubo-iliocaudalis is attached to the visceral organs and becomes the levator ani.  Humans have lost the caudorectalis while the retractor recti persists as the rectococcygeus (Hartman, 1933).  Humans may retain vestiges of the sacrococcygeus posterior and dorsal abductors of the tail (Hartman, 1933, p. 127)