phalanx(redirected from ungual phalanx)
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in anatomy, one of the small tubular bones of the fingers and toes in vertebrates. The structure of the digits in an animal is closely related to the animal’s way of life.
A convenient way of expressing the number of phalanges in the digits is provided by what is called the phalangeal formula, which gives the number of phalanges in each digit, beginning with the first. For the tailed amphibians and for the ancient terrestrial vertebrates known as the Stegocephalia, the number of phalanges in the first through fourth digits of the forelimbs is expressed by the formula 126.96.36.199; for the forelimbs of most tailless amphibians, the formula is 188.8.131.52. The hind limbs of the Stegocephalia and tailless amphibians are characterized by the formula 184.108.40.206.3, and the hind limbs of the tailed amphibians by the formula 2(1).220.127.116.11.
Reptiles have a greater number of phalanges, ordinarily 18.104.22.168.3(4), in both the anterior and posterior extremities; among turtles the number may drop to 1 or 2 per digit. The extinct ichthyosaurs had as many as several dozen phalanges; this hyperphalangia increased the flexibility of the extremity that had been transformed into a fin. In birds the forelimb was transformed into a wing and retained only three digits—the second through fourth. The third digit has two or three phalanges; the second and fourth usually have one rudimentary phalanx each.
Among mammals five digits are most frequently found on both anterior and posterior extremities, and the phalangeal formula is 22.214.171.124.3. The flippers of aquatic mammals (Cetacea) exhibit hyperphalangia. Among flying mammals (Chiroptera) the second through fifth digits are elongated and webbed for flying. The phalanges of the digits of climbing mammals are broadened and are convex on the back side of the extremity and concave on the palm side.
In man each finger and toe, except the thumb and big toe, consists of three phalanges: the proximal, middle, and terminal, or ungual. The thumb and big toe have two phalanges. The proximal phalanges are connected with the heads of the metacarpal bones (in the hand) and the metatarsal bones (in the foot) by means of ball-and-socket joints. The phalanges are connected to each other by hinge joints, which allow the digits to bend and unbend.
N. S. LEBEDKINA
a close line formation of the Greek infantry (hoplites) in battle. A phalanx was deployed along the front in eight to 16 ranks, sometimes as many as 25. When a rank comprised 1,000 men, the phalanx could extend for 500 m. It was used as early as the Trojan War but assumed its final form in the sixth century B.C. The formation was refined by Philip II of Mace-don, who added peltasts (seePELTASTS) and cavalry. The large Macedonian phalanx contained 16,384 hoplites, 8,192 peltasts, and 4,096 cavalry.
The main subdivisions of the phalanx were the lochus, consisting of one rank of 16 hoplites, the syntagma, comprising 16 lochi, and the small phalanx, comprising 16 syntagmas. A given maneuver could be executed using combinations of the various subdivisions. The battle formation could also assume various forms, including a square, an echelon unit, or pincers. The phalanx was best suited to frontal attack by hoplites armed with the sarissa, a long pike. The tactical phalanx operated as a single unit and struck with considerable force in a frontal assault. It was relatively immobile, however, and in motion its ranks quickly became disorganized. The formation was used in ancient Rome until the introduction of the maniple in the late fourth century B.C., as well as in later Rome in wars against the barbarians.