Plantigrade

In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. The other options are digitigrade, walking on the toes with the heel and wrist permanently raised, and unguligrade, walking on the nail or nails of the toes (the hoof) with the heel/wrist and the digits permanently raised. The leg of a plantigrade mammal includes the bones of the upper leg (femur/humerus) and lower leg (tibia and fibula/radius and ulna). The leg of a digitigrade mammal also includes the metatarsals/metacarpals, the bones that in a human compose the arch of the foot and the palm of the hand. The leg of an unguligrade mammal also includes the phalanges, the finger and toe bones.

Among extinct animals, most early mammals such as pantodonts were plantigrade. A plantigrade foot is the primitive condition for mammals; digitigrade and unguligrade locomotion evolved later. Among archosaurs, the pterosaurs were partially plantigrade, walking on the whole of the hind foot and the fingers of the hand-wing.

Plantigrade mammal species include (but are not limited to):

The primary advantages of a plantigrade foot are stability and weight-bearing ability; plantigrade feet have the largest surface area. The primary disadvantage of a plantigrade foot is speed. With more bones and joints in the foot, the leg is both shorter and heavier at the far end, which makes it difficult to move rapidly.

In humans and other great apes, another possible advantage of a plantigrade foot is that it may enhance fighting performance.[1]

Plantigrade foot occurs normally in humans in static postures of standing and sitting. It should also occur normally in gait (walking). Hypertonicity, spasticity, clonus, limited range of motion, abnormal flexion neural pattern, and a plantarflexor (calf) muscle contracture, as well as some forms of footwear such as high heeled shoes, may contribute to an individual only standing and/or walking on his or her toes. This would be evident by the observable heel rise.

Plantigrade
Human skeleton, showing plantigrade habit

References

  1. ^ Carrier, David R; Cunningham, Christopher (15 February 2017). "The effect of foot posture on capacity to apply free moments to the ground: implications for fighting performance in great apes". Biology Open. 6 (2): 269–277. doi:10.1242/bio.022640. PMC 5312108. PMID 28202470.
Archaeocyon

Archaeocyon ("beginning dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived during the Oligocene epoch 32-24 Ma., existing for approximately 8 million years. Species of Archaeocyon are among the earliest known borophagines, although a species of Otarocyon has a slightly earlier first appearance. Fossils have been found across the northern Great Plains and along the west coast of North America.Archaeocyon was a comparatively small and unspecialized dog. Its dentition (teeth) suggests a slightly more hypocarnivorous (omnivorous) diet than the otherwise similar Hesperocyon. The skeleton is also generalized, lacking specializations for running and retaining a plantigrade foot posture.

A few derived features of the dentition support a relationship to Borophaginae and Caninae (the subfamily that includes living canids), rather than to the basal canid subfamily Hesperocyoninae. The temporal position of Archaeocyon suggests an affinity to borophagines because the first members of Caninae appear substantially earlier.

Arctocyon

Arctocyon ('bear dog') is an extinct genus of ungulate mammals. Arctocyon was a "ground dwelling omnivore", that lived from 61.3-56.8 Ma. Synonyms of Arctocyon include Claenodon, and Neoclaenodon. Arctocyon was likely plantigrade, that is, walked like a bear.

Bird feet and legs

The anatomy of bird legs and feet is diverse, encompassing many accommodations to perform a wide variety of functions.Most birds are classified as digitigrade animals, meaning they walk on their toes, rather than the entire foot. Some of the lower bones of the foot (the distals and most of the metatarsal) are fused to form the tarsometatarsus – a third segment of the leg, specific to birds. The upper bones of the foot (proximals), in turn, are fused with the tibia to form the tibiotarsus, as over time the centralia disappeared. The fibula also reduced.The legs are attached to a strong assembly consisting of the pelvic girdle extensively fused with the uniform spinal bone (also specific to birds) called the synsacrum, built from some of the fused bones.

Caniformia

Caniformia, or Canoidea (literally "dog-like"), is a suborder within the order Carnivora. They typically possess a long snout and nonretractile claws (in contrast to the cat-like carnivorans, the Feliformia). The Pinnipedia (seals, walruses and sea lions) are also assigned to this group. The center of diversification for Caniformia is North America and northern Eurasia. This contrasts with the feliforms, the center of diversification of which was in Africa and southern Asia.

Chebyshev's Lambda Mechanism

The Chebyshev's Lambda Mechanism is a four-bar mechanism that converts rotational motion to approximate straight-line motion with approximate constant velocity. The precise design trades off straightness, lack of acceleration, and the proportion of the driving rotation that is spent in the linear portion of the full curve.The example to the right spends over half of the cycle in the near straight portion.

The Chebyshev's Lambda Mechanism is a cognate linkage of the Chebyshev linkage.

The linkage was first shown in Paris on the Exposition Universelle (1878) as "The Plantigrade Machine".The Chebyshev's Lambda Mechanism looks like the Greek letter lambda, therefore the linkage is also known as Lambda Mechanism.

Chriacus

Chriacus is an extinct genus of prehistoric mammal which lived in North America around 63 million years ago. There are 9 valid species currently recognized.

Chriacus was a raccoon-like mammal of the Paleocene epoch, with a length of about 1 metre (3.3 ft) including its long, robust tail, which may or may not have been prehensile. It had a light build, weighing approximately 7 kg (15 lb), and was an agile tree-climber. Chriacus was plantigrade, that is, it walked on the soles of its five-toed feet, which had long claws. Its legs were powerfully built, with flexible joints. The front legs could be used for digging, while the hind legs were best suited for climbing. It was probably an omnivore, like its relative, Arctocyon, eating fruit, eggs, insects and small mammals.

Digitigrade

A digitigrade (), is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds (what many assume to be bird knees are actually ankles), cats, dogs, and many other mammals, but not plantigrades or unguligrades. Digitigrades generally move more quickly and quietly than other animals.

There are anatomical differences between the limbs of plantigrades, like humans, and both unguligrade and digitigrade limbs. Digitigrade and unguligrade animals have relatively long carpals and tarsals, and the bones which would correspond to the human ankle are thus set much higher in the limb than in a human. In a digitigrade animal, this effectively lengthens the foot, so much so that what are often thought of as a digitigrade animal's "hands" and "feet" correspond only to what would be the bones of the human finger or toe.

Humans usually walk with the soles of their feet on the ground, in plantigrade locomotion. In contrast, digitigrade animals walk on their distal and intermediate phalanges. Digitigrade locomotion is responsible for the distinctive hooked shape of dog legs.

Unguligrade animals, such as horses and cattle, walk only on the distal-most tips of their digits, while in digitigrade animals, more than one segment of the digit makes contact with the ground, either directly (as in birds) or via paw-pads (as in dogs).

Humanoid

A humanoid (; from English human and -oid "resembling") is something that has an appearance resembling a human without actually being one. The earliest recorded use of the term, in 1870, referred to indigenous peoples in areas colonized by Europeans. By the 20th century, the term came to describe fossils which were morphologically similar, but not identical, to those of the human skeleton.Although this usage was common in the sciences for much of the 20th century, it is now considered rare. More generally, the term can refer to anything with distinctly human characteristics or adaptations, such as possessing opposable anterior forelimb-appendages (i.e. thumbs), visible spectrum-binocular vision (i.e. having two eyes), or biomechanic plantigrade-bipedalism (i.e. the ability to walk on heels and metatarsals in an upright position). Science fiction media frequently present sentient extraterrestrial lifeforms as humanoid as a byproduct of convergent evolution theory.

Leg mechanism

A leg mechanism (walking mechanism) is an assembly of links and joints (a linkage) intended to simulate the walking motion of humans or animals. Mechanical legs can have one or more actuators, and can perform simple planar or complex motion.

Compared to a wheel, a leg mechanism is potentially better fitted to uneven terrain, as it can step over obstacles.

Mesonychid

Mesonychia ("middle claws") is an extinct taxon of small- to large-sized carnivorous ungulates related to the cetartiodactyls. Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, Mongolestes, became extinct in the early Oligocene. They resembled wolves, albeit superficially. Early mesonychids probably walked on the flats of their feet (plantigrade), while later ones walked on their toes (digitigrade). These later mesonychids had hooves, one on each toe, with four toes on each foot.Mesonychids probably originated in China, where the most primitive mesonychid, Yangtanglestes, is known from the early Paleocene. They were also most diverse in Asia, where they occur in all major Paleocene faunas. Since other carnivores, such as the creodonts and condylarths, were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of Eastern Asia.

One genus, Dissacus, had successfully spread to Europe and North America by the early Paleocene. Dissacus was a jackal-sized carnivore that has been found all over the Northern Hemisphere, but its daughter genus, Ankalagon, from the early to middle Paleocene of New Mexico, was far larger, growing to the size of a bear. Species of the later genus, Pachyaena, entered North America by the earliest Eocene, where they evolved into huge species surpassing even Ankalagon in size. Mesonychids in North America were by far the largest predatory mammals during the early Paleocene to middle Eocene.

Numidotherium

Numidotherium ("Numidia beast") is an extinct genus of early proboscideans, discovered in 1984, that lived during the middle Eocene of North Africa some 46 million years ago. It was about 90-100 cm tall at the shoulder and weighed about 250-300 kg.The type species, N. koholense, is known from an almost complete skeleton from the site of El Kohol, southern Algeria, dating from the early/middle Eocene period. The animal had the size and the appearance of a modern tapir. In appearance, it was more slender and more plantigrade than an elephant, its closest modern relative.Numidotherium savagei, named by Court (1995) for material from late Eocene deposits at Dor el Talha, Libya, has been reassigned to its own genus, Arcanotherium.

Oxyaena

Oxyaena ("sharp" or "drawn-out" + hyena) is an extinct genus of oxyaenid mammal from the latest Paleocene to early Eocene of North America (most specimens being found in Colorado). The species were superficially cat or wolverine-like, with a flexible body 1 metre (3.3 ft) long, and short limbs. Some species like Oxyaena forcipata were bigger with a body mass estimated to be 20 kg.

Oxyaena had a broad, low skull (20 cm. long) with a long facial part and a massive lower jaw, while its body and tail were long and its five-toed limbs were short.

Often compared to martens or cats, the Oxyaenids tended to have long bodies and tails with short legs. They most likely relied on their sight and hearing for hunting.

Unlike true cats, Oxyaena was plantigrade, treading on the whole surface of its soles.

It is presumed that Oxyaena was a leopard-like predator that could climb trees in search of prey.

Paenungulata

Paenungulata is a clade that groups three extant mammal orders: Proboscidea (including elephants), Sirenia (sea cows, including dugongs and manatees), and Hyracoidea (hyraxes). At least two more orders are known only as fossils, namely Embrithopoda and Desmostylia (desmostylians, however, have been placed in Perissodactyla by a 2014 cladistic analysis, and the taxonomic placement of embrithopods has also been questioned though recently supported). Each of these extinct orders was as unique in its members' ways as the surviving orders. Embrithopods were rhinoceros-like herbivorous mammals with plantigrade feet, and desmostylians were hippopotamus-like amphibious animals. Their walking posture and diet have been the subject of speculation, but tooth wear indicates that desmostylians browsed on terrestrial plants and had a posture similar to other large hoofed mammals.Of the five orders, hyraxes are the most basal, followed by embrithopods; the remaining orders (sirenians, desmostylians and elephants) are more closely interrelated. These latter three are grouped as the Tethytheria, because it is believed that their common ancestors lived on the shores of the prehistoric Tethys Sea; however, recent myoglobin studies indicate that even Hyracoidea had an aquatic ancestor. Although morphological evidence continues to support the position of paenungulates with the ungulates, the molecular evidence suggests that Paenungulata (or at least its extant members) is part of the cohort Afrotheria, an ancient assemblage of mainly African mammals of great diversity. The other members of this cohort are the orders Afrosoricida (tenrecs and golden moles), Macroscelidea (elephant shrews) and Tubulidentata (aardvarks).

Pampatheriidae

Pampatheriidae ("Pampas beasts") is an extinct family of large plantigrade armored xenarthrans related to armadillos. However, pampatheriids have existed as a separate lineage since at least the middle Eocene Mustersan age, 45 to 48 million years ago. Pampatheres evolved in South America during its long period of Cenozoic isolation. Although widespread, they were less diverse and abundant than the armadillos. Holmesina spread to North America after the formation of the Isthmus of Panama as part of the Great American Interchange. They finally disappeared on both continents in the end-Pleistocene extinctions, about 12,000 years ago.

Paroodectes

Paroodectes is a miacid animal that lived during the early Eocene (ca. 50 million years ago) in the rain forests and swamps of the present-day Germany. It was a prehistoric predator that had the size and the appearance of a cat and was well adapted to climbing, as is apparent from its limbs, joints and shoulder bones. Its long tail gave balance for tree climbing and jumping from branch to branch. Paroodectes probably hunted in the tree tops on insects, rodents and small monkeys.

Only one species of Paroodectes (P. feisti) has been found, and this was at the Messel Pit located southeast of Frankfurt, Germany. The pit was formed during the Geiseltalian Period (or Middle Eocene) about 50 million years ago. The fossil was found by private collector Otto Feist in 1974. It was described in 1980 by Rainer Springhorn who said the following about the species: "The odontological features of the Messel-Miacid are nearest to the new world genus Oodectes from the Bridger Basin (Bridgerian). No direct relationship exists to European species. The structure of the postcranial skeleton shows great conformity with North American Miacinae. Differences result from proportions skull-length/stature and length of vertebral column/length of limbs. A well-developed clavicle is extant. Scaphoid, lunar and central are distinct. Metatarsals are elongated. Hand and foot are adapted to plantigrade locomotion. An arboricole [living in trees] habit is assumed. Some morphologic features are reminiscent of the Viverridae and some Procyonidae."

Quercylurus

Quercylurus major is an extinct nimravid carnivoran, or "false sabre-tooth," from the early Oligocene of France. Its fossils are found from Early Oligocene strata in Quercy. Q. major. was possibly the largest nimravid ever known, as its fossils suggest it was similar in size to the modern-day brown bear and was scansorial. It was very muscular, walked on plantigrade (flat-footed). So far, there is only one described species within this genus - Q. major.

Saja-Besaya Natural Park

Saja-Besaya Natural Park is a natural park in Cantabria, Spain.

In the northern slope of the Cantabrian mountains, beech and oak groves of the Saja-Besaya Natural Park spread out; an important nature reserve abundant with deers, roe deers and golden eagles. The presence of Iberian wolves is not very rare, and brown bears have been sighted, thus considering this zone as an important nexus of communication between isolated populations of this plantigrade. There are also important colonies of griffon vultures. Other interesting species of animals that populate the area are: eagle owls, martens, badgers, stoats and desmans.

Sansanosmilus

Sansanosmilus is an extinct genus of carnivorous mammal of the family Barbourofelidae (false saber-tooth cats) endemic to Europe and Asia, which lived during the Miocene, 13.6—11.1 mya, existing for approximately 2.5 million years.

Toe

Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of their toes.

Gait class
Anatomy
Specific

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