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In humans and elephants, a vertical-column orientation of the bones in the limbs and feet is also evident for associated skeletal muscle-tendon units. [6] The horse's foot contains an external nail (hoof) oriented about the perimeter in the shape of a semicircle. The underlying bones are arranged in a semi-vertical orientation.
A mammal (from Latin mamma 'breast') [1] is a vertebrate animal of the class Mammalia (/ m ə ˈ m eɪ l i. ə /).Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones.
The following is a list of selected animals in order of increasing number of legs, from 0 legs to 653 pairs of legs, the maximum recorded in the animal kingdom. [1] Each entry provides the relevant taxa up to the rank of phylum. Each entry also provides the common name of the animal.
Both sets of bones connect the shoulder girdle to the skull. With the loss of these bones, tetrapods acquired a neck, allowing the head to rotate somewhat independently of the torso. This, in turn, required stronger soft-tissue connections between head and torso, including muscles and ligaments connecting the skull with the spine and shoulder ...
The hoof surrounds the distal end of the second phalanx, the distal phalanx, and the navicular bone. [5] The hoof consists of the hoof wall, the bars of the hoof, the sole and frog and soft tissue shock absorption structures. [5] The weight of the animal is normally borne by both the sole and the edge of the hoof wall.
A skeleton is the structural frame that supports the body of most animals.There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.
Most birds are classified as digitigrade animals, meaning they walk on their toes rather than the entire foot. [3] [4] 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. [5] [6] The upper bones of the foot , in turn, are fused with ...
The implication that the ancestors of snakes had hind legs is confirmed by fossil evidence: the Cretaceous snake Pachyrhachis problematicus had hind legs complete with hip bones (ilium, pubis, ischium), thigh bone , leg bones (tibia, fibula) and foot bones (calcaneum, astragalus) as in tetrapods with legs today. [38]