Wednesday, July 16, 2008

Not living anymore

This month scientists reported that the Caribbean monk seal has joined a long and growing list of species that carry the "extinct" label.
The seals were first sighted during Christopher Columbus' second voyage in 1494 and once numbered in excess of 250,000. But the docile creatures proved easy prey and were killed primarily for their blubber.
The last confirmed sighting was in 1952.
After several decades of searching, the National Oceanic and Atmospheric Administration finally confirmed the extinction. The seal joins millions of species that have come and gone over Earth’s 4.5 billion-year history – including the dinosaurs, which vanished about 65 million years ago.
The dodo is perhaps the best-known example of a species driven to extinction by human activity.
Their numbers dwindled quickly after the arrival of Portuguese and Dutch sailors to the Indian Ocean island of Mauritius in the 1500s.
Some of the flightless birds were hunted by humans, though competition with dogs, pigs and other animals introduced by settlers may have been the true cause of extinction.
The last recorded sighting of a live bird was in 1663.
Despite the bird's immortalization in the phrase "to go the way of the dodo," however, scientists have an imperfect image of its physique. A cache of dodo bones, reported found in 2005, should help scientists paint a better picture.
The saber-toothed cat was a fearsome predator of Ice Age giants on the grasslands of North and South America until about 10,000 years ago.
To eat, the cat used its powerful body to wrestle large prey such as bison and mammoths to the ground. Only then did the iconic sabers come into play with a relatively wimpy chomp at the throat, according to research reported in October 2007. The hunting strategy likely proved less effective once the large prey disappeared and meals were limited to the quicker gazelles and antelopes. When the lumbering mega-fauna vanished, so did the cat.
About 8 million years ago, the 1,545-pound rodent roamed the swampy grasslands of Venezuela, scientists reported in September 2003.
The buffalo-sized creature, named Phoberomys pattersoni, had continuously growing teeth suited for gnawing on abrasive grasses in the brackish water. Its rear legs were much larger and more powerful than its smaller forelimbs – much like its modern-day relative, the guinea pig. Unlike small rodents, however, experts say this giant was probably too big to burrow and escape predators such as crocodiles, which may have contributed to its demise.
Modern elephants are giant landlubbers, well-known for tromping across African savannahs and through Asian forests.
But scientists now know they are related to aquatic creatures such as manatees and dugongs. Where's the link?
Research focusing on the teeth enamel of an ancient elephant ancestor called a moeritherium, suggests that the creatures ate a diet of plants found in rivers and swamps about 37 million years ago.
Scientists speculate the 500- to 700-pound creature had a lifestyle similar to a hippo.
Not all mammals were afraid of the dinosaurs.
In 2005, Chinese scientists reported the discovery a 130 million-year-old, opossum-sized mammal with the remains of a young dinosaur in its belly.
Nearby, the scientists found a 3-foot long mammal that probably weighed more than 30 pounds, putting it in a class of its own as a formidable dinosaur predator. Why these early mammals went extinct remains a mystery.
There are big bugs, and then there are giant bugs.
The sea scorpion known as Jaekelopterus rhenaniae in this image was clearly the latter.
Based on the discovery of an 18-inch-long claw reported in 2007, scientists estimate the scorpion was 8 feet long. Good thing it lived some 360 million years ago.
The elevated levels of oxygen then may have allowed the extinct ancestor of modern scorpions – and perhaps all arachnids – to reach such mammoth size.
Experts believe these sea scorpions were eventually wiped out by big, toothy fish.

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