mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

including

humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

, the medial surface of the

greater trochanter The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system. It is directed lateral and medially and slightly posterior. In the adult it is about 2–4 cm lower than the femoral head.Stan ...

has at its base a deep depression bounded posteriorly by the

intertrochanteric crest The intertrochanteric crest is a prominent bony ridge upon the posterior surface of the femur at the junction of the neck and the shaft of the femur. It extends between the greater trochanter superiorly, and the lesser trochanter inferiorly. Ana ...

, called the trochanteric fossa. This fossa is the point of insertion of four muscles. Moving from the inferior-most to the superior-most, they are: the tendon of the

obturator externus The external obturator muscle, obturator externus muscle (; OE) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis. It is sometimes considered part of the medial compartment of thigh, and sometimes ...

muscle, the

obturator internus The internal obturator muscle or obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis. It exits the pelvic cavity through the lesser sciatic foramen. The i ...

, the superior gemellus and inferior gemellus. The width and depth of the trochanteric fossa varies taxonomically.Gray's AnatomyNetter 2003Romer 1956 In

reptiliomorphs Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...

such as

Seymouria ''Seymouria'' is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. Although they were amphibians (in a biological sense), ''Seymouria'' were well-adapted to life on land, with many reptilian features—so ...

Diadectes ''Diadectes'' (meaning ''crosswise-biter'') is an extinct genus of large reptiliomorphs or synapsids that lived during the early Permian period ( Artinskian- Kungurian stages of the Cisuralian epoch, between 290 and 272 million years ago). ''Diad ...

and basal reptiles such as

Pareiasaurus ''Pareiasaurus'' is an extinct genus of pareiasauromorph reptile from the Permian period. It was a typical member of its family, the pareiasaurids, which take their name from this genus. Fossils have been found in the Beaufort Group. Descript ...

, the trochanteric fossa (also known as the intertrochanteric fossa) is a very large depression on the ventral/posterior side of the femur. It is bounded medially by the internal trochanter (also known as the lesser trochanter), laterally by the posterior branch of the ventral ridge, and inferiorly by the convergence of the anterior and posterior branches of the ventral ridge and the adductor ridge. In these taxa, the trochanteric fossa is the insertion point for the puboischiofemoralis externus muscle. In

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s, the intertrochanteric fossa is bounded anteriorly by the trochanter minor (sometimes called the lesser trochanter) and posteriorly by the trochanter major (sometimes called the greater trochanter; neither of these structures is likely homologous to the greater or lesser trochanter in mammals). Often, the intertrochanteric fossa is small and shallow due to the expansion of the two trochanters. In

lepidosaurs The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 species ...

, the intertrochanteric fossa is shallow but broad. It is bounded medially by the internal/lesser trochanter and anterior branch of the ventral femoral ridge, and often less distinctly bounded laterally as the greater trochanter and posterior branch of the ventral ridge are highly reduced or absent. In

archosaurs Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avi ...

and especially in

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s, the intertrochanteric fossa is highly developed as both the internal/lesser trochanter and the greater trochanter are better developed. In dinosaurs, this area serves as the insertion point of the iliofemoralis muscles (analogous to the gluteus muscles in mammals).

Notes

References

* * {{Authority control Bones of the lower limb Femur