The fourth trochanter is pendant and located in a rather high position.

The fourth trochanter is a shared characteristic common to archosaurs.

The fourth trochanter provides a large site for the attachment of muscles on the femur.

The thighbone is short, robust and straight with a low fourth trochanter positioned below the midpoint of the shaft.

The shaft of the femur is straighter and the fourth trochanter is more distally placed.

Moreover, there is a prominent fourth trochanter on the femur for the attachment of muscles that would have aided in upright walking.

The fourth trochanter first appeared in the Erythrosuchidae, large basal archosaurian predators of the early Triassic period.

The triradiate pelvis and fourth trochanter are both features which indicate that erythrosuchids had an erect stance similar to later archosaurs.

They rejected the placement within Ornithomimidae, partly because of the much higher position of the fourth trochanter on the back of the femur.

The femur of Aristosuchus has a wing-like anterior trochanter and a markedly reduced fourth trochanter.

An accessory or posterior trochanter is lacking; likewise a fourth trochanter on the back shaft is absent.

The fourth trochanter, a ridge of bone on the femur for muscle attachment seen in nearly all archosaurs, is absent in Group Y.

Although it is small, the fourth trochanter, a ridge on the femur that serves as a muscle attachment in archosaurs, first appears in erythrosuchids.

The thigh bone had a lesser trochanter that was clearly lower than the greater trochanter; the fourth trochanter was well-developed.

The French femur is similar in general appearance to the Elopteryx type but it differs in diagnostic traits, e.g. lacking a fourth trochanter.

The archosaurian fourth trochanter on the femur may have made it easier for ornithodires to become bipeds, because it provided more leverage for the thigh muscles.

Taquet concluded that Ouranosaurus was not a good runner because the fourth trochanter, the attachment point for the large retractor muscles connected to the tail base, was weakly developed.

The femur of Antlerpeton is much more robust than that of Ichthyostega, and has prominent ridges like the fourth trochanter that are attachment points for well-developed leg muscles.

At it rear side, the femur mid-shaft featured a well-developed drooping fourth trochanter, a process for the attachment of the retractor tail muscle, the Musculus caudofemoralis longus.

Nesbitt assigned Dongusuchus to Archosauriformes on the basis of the following traits: its femur has a low fourth trochanter, and the distal condyles do not expand markedly beyond the shaft.

The femur assigned to Vytshegdosuchus is consistent with proterosuchids, Euparkeria and archosaurs since, according to Gower and Sennikov (2000), it has no intertrochanteric fossa and a low fourth trochanter.

However, it also includes several features found in more derived eumaniraptoran dinosaurs, such as a frontlimb/hindlimb ratio of 60%, a lack of expansion of the distal scapula and the lack of a fourth trochanter on the thighbone.

The presence of certain archosaurian features such as the triradiate pelvic girdle, the fourth trochanter, and the third metatarsal longer than the fourth, indicate that erythrosuchids are closer to the true archosaurs than the Proterosuchidae, which lack these features.

In all aetosaurs, the limbs are very robust, with large muscle attachments such as the deltopectoral crest of the humerus, the fourth trochanter of the femur, the intracondylar ridge of the tibia, and the iliofibularis trochanter of the fibula.

The simplest and most widely agreed synapomorphies of archosaurs include teeth set in sockets, antorbital and mandibular fenestrae (openings in front of the eyes and in the jaw, respectively), and a fourth trochanter (a prominent ridge on the femur).