Intermembral index

Last updated

The intermembral index is a ratio used to compare limb proportions, expressed as a percentage. [1] It is equal to the length of forelimbs (humerus plus radius) divided by the length of the hind limbs (femur plus tibia) multiplied by 100, [2] otherwise written mathematically as:

The intermembral index is used frequently in primatology, since it helps predict primate locomotor patterns. For scores lower than 100, the forelimbs are shorter than the hind limbs, which is common in leaping primates and bipedal hominids. Quadrupedal primates tend to have scores around 100, while brachiating primates have scores significantly higher than 100. This information can also be used to predict locomotion patterns for extinct primates in cases where forelimb and hind limb fossils have been found. [1]

Related Research Articles

Amblypoda was a taxonomic hypothesis uniting a group of extinct, herbivorous mammals. They were considered a suborder of the primitive ungulate mammals and have since been shown to represent a polyphyletic group.

<i>Rodhocetus</i> Genus of mammals

Rodhocetus is an extinct genus of protocetid early whale known from the Lutetian of Pakistan. The best-known protocetid, Rodhocetus is known from two partial skeletons that taken together give a complete image of an Eocene whale that had short limbs with long hands and feet that were probably webbed and a sacrum that was immobile with four partially fused sacral vertebrae. It is one of several extinct whale genera that possess land mammal characteristics, thus demonstrating the evolutionary transition from land to sea.

<i>Archaeoindris</i> Extinct giant lemur

Archaeoindris fontoynontii is an extinct giant lemur and the largest primate known to have evolved on Madagascar, comparable in size to a male gorilla. It belonged to a family of extinct lemurs known as "sloth lemurs" (Palaeopropithecidae) and, because of its extremely large size, it has been compared to the ground sloths that once roamed North and South America. It was most closely related to Palaeopropithecus, the second largest type of sloth lemur. Along with the other sloth lemurs, Archaeoindris was related to the living indri, sifakas, and woolly lemurs, as well as the recently extinct monkey lemurs (Archaeolemuridae). The genus, Archaeoindris, translates to "ancient indri-like lemur", even though it probably became extinct recently, around 350 BCE.

<i>Argyrosaurus</i> Genus of herbivorous titanosaurian sauropod dinosaur

Argyrosaurus is a genus of titanosaurian sauropod dinosaur that lived about 70 million years ago, during the Late Cretaceous Period of what is now Argentina.

<span class="mw-page-title-main">Dog anatomy</span> Studies of the visible part of a canine

Dog anatomy comprises the anatomical studies of the visible parts of the body of a domestic dog. Details of structures vary tremendously from breed to breed, more than in any other animal species, wild or domesticated, as dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head and body, and weighed only 113 grams (4.0 oz). The heaviest dog was an English Mastiff named Zorba which weighed 314 pounds (142 kg). The tallest known adult dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.

<span class="mw-page-title-main">Tristichopteridae</span> Extinct family of fishes

Tristichopterids (Tristichopteridae) were a diverse and successful group of tetrapodomorph fishes living throughout the Middle and Late Devonian. They first appeared in the Eifelian stage of the Middle Devonian. Within the group sizes ranged from a few tens of centimeters (Tristichopterus) to several meters.

Orthosuchus is an extinct genus of Notochampsidaean crocodyliform that lived during the Early Jurassic, about 196 million years ago. It was first discovered in 1963 in the Red Beds Formation in the Qacha's Nek Province of Lesotho, southern Africa. The characteristics showed on its postcranial skeleton and the skull indicated that it is a Crocodyliform. The finding is significant since some of the characteristics found on this specimen were believed to be absent until Jurassic.

A limb is a jointed, muscled appendage of a tetrapod vertebrate animal used for weight-bearing, terrestrial locomotion and physical interaction with other objects. The distalmost portion of a limb is known as its extremity. The limbs' bony endoskeleton, known as the appendicular skeleton, is homologous among all tetrapods, who use their limbs for walking, running and jumping, swimming, climbing, grasping, touching and striking.

<i>Archaeorhynchus</i> Extinct genus of birds

Archaeorhynchus is a genus of beaked avialan stem-birds from the early Cretaceous period. A fossil of its only known species, Archaeorhynchus spathula, was first reported in 2005 by Zhou & Zhang to have been found in Yixian Formation rocks at Yixian, Liaoning province, China, showing a well-preserved and essentially complete skeleton. Two more complete specimens were found in Lower Cretaceous deposits of Jianchang, Liaoning, northeastern China, preserving new anatomical information. These deposits are 120 million years old, whereas the original specimen was 125 million years old, meaning the age range for this species is 125-120Ma.

Suspensory behaviour is a form of arboreal locomotion or a feeding behavior that involves hanging or suspension of the body below or among tree branches. This behavior enables faster travel while reducing path lengths to cover more ground when travelling, searching for food and avoiding predators. Different types of suspensory behaviour include brachiation, climbing, and bridging. These mechanisms allow larger species to distribute their weight among smaller branches rather than balancing above these weak supports. Primates and sloths are most commonly seen using these behaviours, however, other animals such as bats may be seen hanging below surfaces to obtain food or when resting.

<i>Diamantinasaurus</i> Extinct genus of reptiles

Diamantinasaurus is a genus of titanosaurian sauropod from Australia that lived during the early Late Cretaceous, about 94 million years ago. The type species of the genus is D. matildae, first described and named in 2009 by Scott Hocknull and colleagues based on fossil finds in the Winton Formation. Meaning "Diamantina lizard", the name is derived from the location of the nearby Diamantina River and the Greek word sauros, "lizard". The specific epithet is from the Australian song Waltzing Matilda, also the locality of the holotype and paratype. The known skeleton includes most of the forelimb, shoulder girdle, pelvis, hindlimb and ribs of the holotype, and one shoulder bone, a radius and some vertebrae of the paratype.

<i>Toretocnemus</i> Extinct genus of reptiles

Toretocnemus is an extinct genus of ichthyosaur. Its remains have been found in California, United States, in Triassic layers of the Carnian Hosselkus Limestone.

<i>Aardonyx</i> Extinct genus of dinosaur of the Jurassic from South Africa

Aardonyx is a genus of basal sauropodomorph dinosaur. It is known from the type species Aardonyx celestae found from the Early Jurassic Elliot Formation of South Africa. A. celestae was named after Celeste Yates, who prepared much of the first known fossil material of the species. It has arm features that are intermediate between prosauropods and sauropods.

<i>Mesopropithecus</i> Extinct genus of small to medium-sized lemur from Madagascar

Mesopropithecus is an extinct genus of small to medium-sized lemur, or strepsirrhine primate, from Madagascar that includes three species, M. dolichobrachion, M. globiceps, and M. pithecoides. Together with Palaeopropithecus, Archaeoindris, and Babakotia, it is part of the sloth lemur family (Palaeopropithecidae). Once thought to be an indriid because its skull is similar to that of living sifakas, a recently discovered postcranial skeleton shows Mesopropithecus had longer forelimbs than hindlimbs—a distinctive trait shared by sloth lemurs but not by indriids. However, as it had the shortest forelimbs of all sloth lemurs, it is thought that Mesopropithecus was more quadrupedal and did not use suspension as much as the other sloth lemurs.

Vertical clinging and leaping (VCL) is a type of arboreal locomotion seen most commonly among the strepsirrhine primates and haplorrhine tarsiers. The animal begins at rest with its torso upright and elbows fixed, with both hands clinging to a vertical support, such as the side of a tree or bamboo stalk. To move from one support to another, it pushes off from one vertical support with its hindlimbs, landing on another vertical support after an extended period of free flight. Vertical clinging and leaping primates have evolved a specialized anatomy to compensate for the physical implications of this form of locomotion. These key morphological specializations have been identified in prosimian fossils from as early as the Eocene.

Tonganosaurus is a genus of mamenchisaurid sauropod dinosaur, similar to Omeisaurus. It is known from one specimen consisting of twenty vertebrae, a front limb and pectoral girdle, and a complete hind limb with partial hip. It was discovered in the Yimen Formation, China. The horizon of the specimen and the age of the Yimen Formation is controversial. The formation has been divided into three levels, and Tonganosaurus appears to be of late Early Jurassic (Pliensbachian) age. Tonganosaurus is the oldest known member of the mamenchisaurids, being almost 15 million years older than the next-oldest members of the group. It was first named by Li Kui, Yang Chun-Yan, Liu Jian and Wang Zheng-Xin in 2010 and the type species is Tonganosaurus hei.

<i>Xiaotingia</i> Genus of dinosaur

Xiaotingia is a genus of anchiornithid theropod dinosaur from Middle Jurassic or early Late Jurassic deposits of western Liaoning, China, containing a single species, Xiaotingia zhengi.


Innovations conventionally associated with terrestrially first appeared in aquatic elpistostegalians such as Panderichthys rhombolepis, Elpistostege watsoni, and Tiktaalik roseae. Phylogenetic analyses distribute the features that developed along the tetrapod stem and display a stepwise process of character acquisition, rather than abrupt. The complete transition occurred over a period of 30 million years beginning with the tetrapodomorph diversification in the Middle Devonian.

<i>Chucarosaurus</i> Genus of titanosaurian dinosaurs

Chucarosaurus is an extinct genus of titanosaurian dinosaur from the Late Cretaceous Huincul Formation of Argentina. The genus contains a single species, C. diripienda, known from various limb and pelvic bones.

References

  1. 1 2 Ankel-Simons, F. (2007). Primate Anatomy (3rd ed.). Academic Press. pp. 49–53. ISBN   0-12-372576-3.
  2. Conroy, G.C. (1990). Primate Evolution (1st ed.). New York: W.W. Norton and Co. ISBN   978-0-393-95649-8.