The intermembral index is a ratio

Ratio

In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...

 used to compare limb proportions, expressed as a percentage

Percentage

In mathematics, a percentage is a way of expressing a number as a fraction of 100 . It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% is equal to 45/100, or 0.45.Percentages are used to express how large/small one quantity is, relative to another quantity...

. It is equal to the length of forelimb

Forelimb

A forelimb is an anterior limb on an animal's body. When referring to quadrupeds , the term foreleg is often instead used....

s (humerus

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

 plus radius

Radius (bone)

The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...

) divided by the length of the hind limb

Hind limb

A hind limb is a posterior limb on an animal. When referring to quadrupeds, the term hind leg is often instead used....

s (femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 plus tibia

Tibia

The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

) multiplied by 100, otherwise written mathematically as:



It is used frequently in primatology

Primatology

Primatology is the scientific study of primates. It is a diverse discipline and researchers can be found in academic departments of anatomy, anthropology, biology, medicine, psychology, veterinary sciences and zoology, as well as in animal sanctuaries, biomedical research facilities, museums and zoos...

 since it helps predict primate

Primate

A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

 locomotor patterns. For scores lower than 100, the forelimbs are shorter than the hind limbs, which is common in leaping

Jumping

Jumping or leaping is a form of locomotion or movement in which an organism or non-living mechanical system propels itself through the air along a ballistic trajectory...

 primates and bipedal hominids. Quadrupedal primates tend to have scores around 100, while brachiating

Brachiation

Brachiation is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms.- Brachiators :...

 primates have scores significantly higher than 100. This information can also be used to predict locomotor patterns for extinct primates in cases where forelimb and hind limb fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found.