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In effect, "tetrapod" is a name reserved solely for animals which lie among living tetrapods, so-called crown tetrapods. This is a node-based clade , a group with a common ancestry descended from a single "node" (the node being the nearest common ancestor of living species).
A tetrapod is a form of wave-dissipating concrete block used to prevent erosion caused by weather and longshore drift, primarily to enforce coastal structures such as seawalls and breakwaters. Tetrapods are made of concrete , and use a tetrahedral shape to dissipate the force of incoming waves by allowing water to flow around rather than ...
Pentadactyly (from Greek πέντε pénte "five") is the condition of having five digits on each limb. It is traditionally believed that all living tetrapods are descended from an ancestor with a pentadactyl limb, although many species have now lost or transformed some or all of their digits by the process of evolution.
A nail is a protective plate characteristically found at the tip of the digits (fingers and toes) of all primates, corresponding to the claws in other tetrapod animals. . Fingernails and toenails are made of a tough rigid protein called alpha-keratin, a polymer also found in the claws, hooves, and horns of ver
The proximal phalanx bone of each toe articulates with the metatarsal bone of the foot at the metatarsophalangeal joint. Each toe is surrounded by skin, and present on all five toes is a toenail. The toes are, from medial to lateral: the first toe, also known as the hallux ("big toe", "great toe", "thumb toe"), the innermost toe;
Limbs are attached to the torso via girdles, either the pectoral girdle for the forelimbs, or the pelvic girdle for the hindlimbs.In terrestrial tetrapods, the pectoral girdles are more mobile, floating over the rib cage connected only via the clavicles (to the sternum) and numerous muscles; while the pelvic girdles are typically fused together anteriorly via a fibrocartilaginous joint and ...
In the tetrapod and higher clades from the lower-middle Famennian there are several defining changes on the basis of anatomy of Ichthyostega, Tulerpeton, and Acanthostega. In the cranium, there is a stapes derived from the hyomandibular of fishes; a single bilateral pair of nasal bones, and a fenestra ovalis in the otic capsule of the braincase ...
It is unclear whether polydactylous tetrapods survived to the Carboniferous. Crassigyrinus, from the fossil-poor Romer's gap in the early Carboniferous, is usually thought to have had five digits to each foot. The anthracosaurs, which may be stem-tetrapods [7] [8] or reptiliomorphs, [9] retained the five-toe pattern still found in amniotes.