DINOSAURS: CELEBRITIES OFEXTINCTION
Dinosaurs dominated life on Earth for some 180 million years, from their beginnings in the Triassic period 200 million years ago until their abrupt exit during the Cretaceous period, more than 65 million years ago. They flourished during the Jurassic period when there were only two basic continents, but by the beginning of the Cretaceous period, 145 million years ago. they inhabited a seven-continent planet albeit a warmer and wetter one where many species, both plant and animal, were gigantic ehis ever . the was a filling Based on the evidence studied by paleontologists, dinosaurs fall into two basic physiological categories: those with bird hips and those with lizard hips, determined by the angle at which the pelvis tilted. Most had long tails; most laid eggs Dinosaurs could be either carnivorous or herbivorous. Little is known about their temperature-regulating mechanisms.
A catastrophic event occurred at the end of the Cretaceous period, believed to be a giant asteroid that hit the Yucatán Peninsula and formed the Chicxulub crater, still recognizable today. Such an event would have caused huge environmental changes leading to mass extinctions. Yet dinosaurs seem to have been on the decline for 20 million years before that In any case, by the beginning of the Cenozoic era, about 65.5 million years ago, dinosaurs were history.
Can species ever come back?
Occasionally a species considered extinct reappears. Recently a rare giant turtle believed to be extinct in the wild was found in northern Vietnam. The Swinhoe’s soft_shelled turtle, which can weigh up to 300 pounds and live for more than 100 years, was discovered and photographed by zoologists. A second sighting in southern China has been confirmed, so the species likely has survived a brush with extinction. Bird enthusiasts live in hope of the same outcome for the ivory-billed woodpecker. last photographed in northeastern Louisiana in 1938 and last reliably sighted in 1944 It lived in the southeastern forests of the United States and the upland pine forests of Cuba. It is presumed extinct by many ornithologists, but sightings in 2004 and 2005 have given bird lovers cause for optimism.
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