In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones (wrist bones), which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.
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Metacarpals in the context of Pterosaur
Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger.
Traditionally, pterosaurs were divided into two major types. Basal pterosaurs (also called non-pterodactyloid pterosaurs or 'rhamphorhynchoids') were smaller animals, up to two meter wingspan, with fully toothed jaws and, typically, long tails. Their wide wing membranes probably included and connected the hindlimbs. On the ground, they would have had an awkward sprawling posture due to short metacarpals, but the anatomy of their joints and strong claws would have made them effective climbers, and some may have lived in trees. Basal pterosaurs were insectivores, piscivores or predators of small land vertebrates. Later pterosaurs (pterodactyloids) evolved many sizes, shapes, and lifestyles. Pterodactyloids had narrower wings with free hindlimbs, highly reduced tails, and long necks with large heads. On the ground, they walked well on all four limbs due to long metacarpals with an upright posture, standing plantigrade on the hind feet and folding the wing finger upward to walk on the metacarpals with the three smaller fingers of the hand pointing to the rear. They could take off from the ground, and fossil trackways show that at least some species were able to run, wade, and/or swim. Their jaws had horny beaks, and some groups lacked teeth. Some groups developed elaborate head crests with sexual dimorphism. Since 2010 it is understood that many species, the basal Monofenestrata, were intermediate in build, combining an advanced long skull with long tails.
Metacarpals in the context of Long bone
The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities and they are crucial for skeletal mobility. They grow primarily by elongation of the diaphysis, with an epiphysis at each end of the growing bone. The ends of epiphyses are covered with hyaline cartilage ("articular cartilage"). The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate. Bone growth in length is stimulated by the production of growth hormone (GH), a secretion of the anterior lobe of the pituitary gland.
The long bone category includes the femora, tibiae, and fibulae of the legs; the humeri, radii, and ulnae of the arms; metacarpals and metatarsals of the hands and feet, the phalanges of the fingers and toes, and the clavicles or collar bones. The long bones of the human leg make up nearly half of adult height. The other primary skeletal component of height are the vertebrae and skull.