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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.
Figure 1:In mammals, the quadrate and articular bones are small and part of the middle ear; the lower jaw consists only of dentary bone.. While living mammal species can be identified by the presence of milk-producing mammary glands in the females, other features are required when classifying fossils, because mammary glands and other soft-tissue features are not visible in fossils.
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.
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.
The species is a tetrapod, its four legs adapting the fish-like body plan for walking on land. The specimen is 26 m (85 ft) long. The specimen is 26 m (85 ft) long. As embryos, vertebrates still have a notochord; as adults, all but the jawless fishes have a vertebral column, made of bone or cartilage , instead. [ 7 ]
These bones would otherwise connect the shoulder girdle with skull, making the shoulder girdle part of the skull. With the loss of the gill-covering bones, the shoulder girdle is separated from the skull, connected to the torso by muscle and other soft-tissue connections. The result is the appearance of the neck.
A new analysis of three-toed fossil footprints that date back more than 210 million years reveals that they were created by bipedal reptiles with feet like a bird’s.
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]