Terrestrial locomotion in the context of "Bipeds"

Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped /ˈbaɪpɛd/, meaning 'two feet' (from Latin bis 'double' and pes 'foot'). Types of bipedal movement include walking or running (a bipedal gait) and hopping.

Several groups of modern species are habitual bipeds whose normal method of locomotion is two-legged. In the Triassic period some groups of archosaurs, a group that includes crocodiles and dinosaurs, developed bipedalism; among the dinosaurs, all the early forms and many later groups were habitual or exclusive bipeds; the birds are members of a clade of exclusively bipedal dinosaurs, the theropods. Within mammals, habitual bipedalism has evolved multiple times, with the macropods, kangaroo rats and mice, springhare, hopping mice, pangolins and hominin apes such as australopithecines, including humans, as well as many other extinct groups evolving the trait independently.

Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, chickens, ants, most spiders), as compared with aquatic animals (e.g., fish, whales, octopuses, lobsters, etc.), who live predominantly or entirely in bodies of water; and semiaquatic animals (e.g., crocodilians, seals, platypus and most amphibians), who inhabit coastal, riparian or wetland areas and rely on both aquatic and terrestrial habitats. While most insects (who constitute over half of all known species in the animal kingdom) are terrestrial, some groups, such as mosquitoes and dragonflies, spend their egg and larval stages in water but emerge as fully terrestrial adults (imagos) after completing metamorphosis.

Terrestrial animals conduct respiratory gas exchange directly with the atmosphere, typically via specialized respiratory organs known as lungs, or via cutaneous respiration across the skin. They have also evolved homeostatic features such as impermeable cuticles that can restrict fluid loss, temperature fluctuations and infection, and an excretory system that can filter out nitrogenous waste in the form of urea or uric acid, in contrast to the ammonia-based excretion of aquatic animals. Without the buoyancy of an aqueous environment to support their weight, they have evolved robust skeletons that can hold up their body shape, as well as powerful appendages known as legs or limbs to facilitate terrestrial locomotion, although some perform limbless locomotion using body surface projections such as scales and setae. Some terrestrial animals even have wings or membranes that act as airfoils to generate lift, allowing them to fly and/or glide as airborne animals.

A limb (from Old English lim, meaning "body part") 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.

All tetrapods have four limbs that are organized into two bilaterally symmetrical pairs, with one pair at each end of the torso, which phylogenetically correspond to the four paired fins (pectoral and pelvic fins) of their fish (sarcopterygian) ancestors. The cranial pair (i.e. closer to the head) of limbs are known as the forelimbs or front legs, and the caudal pair (i.e. closer to the tail or coccyx) are the hindlimbs or back legs. In animals with a more erect bipedal posture (mainly hominid primates, particularly humans), the forelimbs and hindlimbs are often called upper and lower limbs, respectively. The fore-/upper limbs are connected to the thoracic cage via the pectoral/shoulder girdles, and the hind-/lower limbs are connected to the pelvis via the hip joints. Many animals, especially the arboreal species, have prehensile forelimbs adapted for grasping and climbing, while some (mostly primates) can also use hindlimbs for grasping. Some animals (birds and bats) have expanded forelimbs (and sometimes hindlimbs as well) with specialized feathers or membranes to achieve lift and fly. Aquatic and semiaquatic tetrapods usually have limb features (such as webbings) adapted to better provide propulsion in water, while marine mammals and sea turtles have convergently evolved flattened, paddle-like limbs known as flippers.

Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined as an "inverted pendulum" gait in which the body vaults over the stiff limb or limbs with each step. This applies regardless of the usable number of limbs—even arthropods, with six, eight, or more limbs, walk. In humans, walking has health benefits including improved mental health and reduced risk of cardiovascular disease and death.

Running is a method of terrestrial locomotion by which humans and other animals move quickly on foot. Running is a gait with an aerial phase in which all feet are above the ground (though there are exceptions). This is in contrast to walking, a slower form of movement where at least one foot is always in contact with the ground, the legs are kept mostly straight, and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion. A feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride co-occur, with energy storage accomplished by springy tendons and passive muscle elasticity. The term "running" can refer to a variety of speeds ranging from jogging to sprinting.

Running in humans is associated with improved health and life expectancy.

Horses can use various gaits (patterns of leg movement) during locomotion across solid ground, either naturally or as a result of specialized training by humans.

Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the southern United States as an invasive species. About 80 species are recognized.

Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. The adult length of extant species ranges from 20 cm (7.9 in) in some species such as Varanus sparnus, to over 3 m (10 ft) in the case of the Komodo dragon, though the extinct megalania (Varanus priscus) may have reached lengths of more than 7 m (23 ft). Most monitor species are terrestrial, but many are also arboreal or semiaquatic. While most monitor lizards are carnivorous, eating smaller reptiles, fish, birds, insects, small mammals, and eggs, a few species also eat fruit and vegetation.

African ground pangolin (Smutsia - "Smuts's animal") is a genus of pangolins from subfamily Smutsiinae within family Manidae. It was formerly considered a subgenus of genus Manis. Its members are the more terrestrial of the African pangolins. In the past, this genus was also present in Europe.

The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the diving petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes (or tubenoses), which also includes the albatrosses and the storm petrels.

The procellariids are the most numerous family of tubenoses, and the most diverse. They range in size from the giant petrels with a wingspan of around 2.0 m (6 ft 7 in), that are almost as large as the albatrosses, to the diving petrels with a wingspan of around 34 cm (13 in) that are similar in size to the little auks or dovekies in the family Alcidae. Male and female birds are identical in appearance. The plumage colour is generally dull, with blacks, whites, browns and greys. The birds feed on fish, squid and crustacea, with many also taking fisheries discards and carrion. Whilst agile swimmers and excellent in water, petrels have weak legs and can only shuffle on land, with the giant petrels of the genus Macronectes being the only two species that are capable of proper terrestrial locomotion. All species are accomplished long-distance foragers, and many undertake long trans-equatorial migrations. They are colonial breeders, exhibiting long-term mate fidelity and site philopatry. In all species, a single white egg is laid each breeding season. The parents take it in turns to incubate the egg and to forage for food. The feeding area can be at a great distance from the nest site. The incubation times and chick-rearing periods are exceptionally long compared to other birds.

The New Zealand rock wren (Xenicus gilviventris) is a small New Zealand wren (family Acanthisittidae) endemic to the South Island of New Zealand. Its Māori names include pīwauwau ("little complaining bird"), mātuitui, and tuke ("twitch", after its bobbing motion). Outside New Zealand it is sometimes known as the rockwren to distinguish it from the unrelated rock wren of North America.

The rock wren is currently restricted to alpine and subalpine areas of the South Island. It is a poor flier and highly terrestrial, feeding in low scrub, open scree, and rockfalls. The rock wren and rifleman are the only two surviving New Zealand wrens; the rock wren's closest relatives were the extinct stout-legged wrens, followed by the extinct bushwren. Its numbers are declining due to predation by introduced mammals.

Mudskippers are any of the 25 extant species of amphibious fish from the subfamily Oxudercinae of the goby family Oxudercidae. They are known for their unusual body shapes, preferences for semiaquatic habitats, limited terrestrial locomotion and jumping, and the ability to survive prolonged periods of time both in and out of water.

Mudskippers can grow up to 30 cm (12 in) long, and most are a brownish green colour that ranges anywhere from dark to light. During mating seasons, the males will also develop brightly coloured spots in order to attract females, which can be red, green or blue. Unlike other fish, the mudskipper's eyes protrude from the top of its flat head. Another notable feature is that their side pectoral fins are located more forward and underneath their elongated bodies. These fins are jointed and function similarly to limbs, which allow the mudskipper to crawl from place to place. Although they have the typical body form of any other gobiid fish, pectoral fins allow the mudskipper to actively "skip" across muddy surfaces (hence the common name) and even climb low-hanging tree branches and scrub. Mudskippers can leap distances of up to 61 centimetres (24 in) by laterally flexing and pushing with their tails.