© 2006 Encyclopaedia Britannica, Inc.
ptarmigan ► public health I 1561
ptarmigan Ytar-mi-gsnV Any of three or four species of grouse (genus Lagopus ) of cold regions. Ptarmigan plumage changes from white in win¬ ter to gray or brown, with barring, in spring and summer. The toes are covered with stiff feathers above and below. The common ptarmigan (L. mutus ) occurs throughout the British Isles, Europe, and North America, where it is called rock ptarmigan. Ptarmigans survive winter in the Arc¬ tic and on mountaintops by browsing shrubs and scratching up lichens and leaves; they burrow in snow to sleep. Males begin group displays in early spring and then separate and display singly in adjoining territories.
Pteranodon Uo-'ra-no-.danX Genus of extinct flying reptiles, descen¬ dants of the pterodactyl. Fossils are known from Late Cretaceous (99-65 million years ago) deposits of Europe, Asia, and North America. Ptera¬ nodon had a wingspan of 23 ft (7 m) or more. The largest specimen had a wingspan of 50 ft (15.5 m). The body was about the size of a modem turkey. Pteranodon had a crest at the back of the skull and long, pelican¬ like, toothless jaws. They probably made nests and spent much time glid¬ ing over the ocean searching for fish. They probably depended on air currents for liftoff rather than on flapping their wings.
pterodactyl \,ter-3-'dak-t 3 l\ Any member of the pterosaur suborder Pterodactyloidea, known from Late Jurassic and Cretaceous fossils (159-65 million years ago) in eastern Africa and Europe. Members of the typical genus, Pterodactylus , ranged from the size of a sparrow to that of an albatross. Pterodactyls had slender, delicate teeth that were angled for¬ ward (possibly for use as straining devices), long metacarpal bones, and a short tail. They were probably able gliders but not efficient as active fliers, and they apparently lacked feathers. Unlike the archaeopteryx, the pterodactyl was not an ancestor of the birds.
pterosaur Vter-o-.sorX Any of several extinct flying reptiles (order Pte- rosauria) that flourished during the Jurassic and Cretaceous periods (206-65 million years ago). Pterosaurs hung by their long, slender hind limbs when at rest. They soared and glided on fragile, membranous wings that were attached to the long fourth finger of each forelimb and extended along the flank. The first three fingers were slender, clawed, clutching structures. Pterosaurs had a long, slender beak and a large brain. Ram- phorhynchus had strong, sharply pointed teeth, a long tail, and a wing- spread of about 3 ft (1 m). It probably obtained food by diving for fish. See also pterodactyl.
Ptolemais V.ta-b-'ma-osV Ancient coastal city, Cyrenaica. Located in modern Libya, it received its name in the 3rd century bc from Ptolemy
Ptah, holding the emblems of life and power, bronze statuette, Memphis, c. 600-100 bc; in the British Museum.
COURTESY OF THE TRUSTEES OF THE BRITISH MUSEUM
III, who united Cyrenaica with Egypt. Its economy was based on trade with the interior, and it flour¬ ished in Hellenistic times, in the early period of the Roman Empire, and again from the late 3rd century ad, when Diocletian made it the metropolis of the Roman province of Upper Libya.
Ptolemy \'ta-b-me\ Latin Clau¬ dius Ptolemaeus (b. c. ad
100—d. c. ad 170) Greek astronomer and mathematician. He worked prin¬ cipally in Alexandria. It is often dif¬ ficult to determine which findings in his great astronomical book, the Almagest, are Ptolemy’s and which are Hipparchus’s. The Sun, Moon, planets, and stars, he believed, were attached to crystalline spheres, cen¬ tred on Earth, which turned to create the cycles of day and night, the lunar month, and so on. In order to explain retrograde motion of the planets, he refined a complex geometric model of cycles within cycles that was highly successful at predicting the planets’ positions in the sky. The Earth-centred Ptolemaic system became dogmatically asserted in Western Christendom until the Sun- centred Copernican system replaced it.
His Geography contained an estimate of the size of Earth, a description of its surface, and a list of places located by latitude and longitude. Ptolemy also dabbled in mechanics, optics, and music theory.
Ptolemy I Soter \ , ta-b-me... , so-t3r\ (b. 367/366, Macedonia—d. 283/ 282 bc, Egypt) Ruler of Egypt (323-285) and founder of the Ptolemaic dynasty. A Macedonian general of Alexander the Great, he and the other generals divided the empire after Alexander’s death, Ptolemy becoming satrap of Egypt. Alexander’s successors were soon at war. Ptolemy was defeated in 306 by Antigonus I Monophthalmus, though he and the others rebuffed Antigonus’s attack on Egypt. He earned the name Soter (“Sav¬ iour”) after defeating Antigonus on Rhodes (304), but Antigonus was not finally crushed until 301 at the Battle of Ipsus. Ptolemy secured and expanded his empire through alliances and marriages. He and his fellow kings won a final war (288-286) against Demetrius of Macedonia, freeing Athens from Macedonian occupation. He obtained control of the League of Islanders (including most of the Aegean islands), which formed the basis of Egypt’s maritime supremacy. As king he respected Egyptian cul¬ ture, blended Greek and Egyptian peoples and religions, and founded the Library and Museum of Alexandria. After his death the Egyptians raised him to the level of a god. He was succeeded by his son, Ptolemy II Phila- DELPHUS.
Ptolemy II Philadelphus (b. 308, Cos—d. 246 bc) King of Egypt (285-246 bc), second king of the Ptolemaic dynasty. He reigned as coruler (285-282) with his father, Ptolemy I Soter, then purged his family of rivals, including his first wife, and married his sister, Arsinoe II. Wars with the rulers of the Seleucid and Antigonid dynasties weakened his influence in the Aegean and brought near-disaster to his allies Athens and Sparta. He concluded these wars by diplomacy and marriage alliances and managed to regain his influence in the Aegean. He devised a buffer zone of pos¬ sessions to protect Egypt from attack, and he dealt with reverses through diplomacy. A prudent and enlightened ruler, he promoted economic devel¬ opment and made Alexandria into a centre for poets and scholars.
Ptolemy lll-XV (r. 246-30 bc) Macedonian kings of the Ptolemaic dynasty in Egypt. Ptolemy III Euergetes (“Benefactor”) (fl. 246-221) defeated the ruler of the Seleucid dynasty in the Third Syrian War (245- 241). Ptolemy IV Philopator (“Father-loving”) (r. 221-205) allowed Egypt to decline under his debauched rule. Ptolemy IX Soter II ruled with his mother (116-110, 109-107), until she expelled him and installed his brother Ptolemy X Alexander (r. 107-88). Alexander’s unpopularity resulted in his expulsion, and he died at sea in 88. Soter II assumed sole rule (88-81), installing his brother’s widow, his own daughter, with him. Ptolemy XI Alexander II (r. 80) was the last fully legitimate Ptolemaic king of Egypt. On the orders of Sulla, whose hostage he had been, he took Ptolemy IX Soter II’s widow as wife and attempted to rule with her. This being unacceptable to the queen, Ptolemy murdered her and took sole power, for which the people of Alexandria killed him; his rule lasted 19 days. Of the remaining Ptolemies, Ptolemy XIV Theos Philopator II shared power (47-44) with his sister Cleopatra; it was probably she who had him assassinated, to make way for her son by Julius Caesar. Ptolemy XV Caesar, or Caesarion, shared power with his mother from 44; he was killed by Octavian (later Augustus) after Cleopatra’s suicide in 30. His death marked the Roman conquest of Egypt and the dynasty’s end.
puberty In human physiology, the period of first becoming capable of reproducing sexually. Occurring at about age 12 in girls and age 14 in boys, puberty is characterized by the maturing of the genital organs, devel¬ opment of secondary sex characteristics, and, in girls, onset of menstrua¬ tion. Both sexes experience a swift increase in body size and changes in body shape and composition. Puberty marks the beginning of adolescence.