The Biggest Animals that have Ever Lived on Earth

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The Biggest Animals that have Ever Lived on Earth
The Biggest Animals that have Ever Lived on Earth

Dinosaurs – ranging in size from a small chicken to half the length of a football field – lived on this earth for 140 million years. Researchers are learning that these diverse and mysterious creatures cared for their young, ran like elephants, and sniffed out their prey like the cleverest fox.

And a few of ten actually survived. On any good day you can see then, if you look into the sky or search the branches of trees. Birds are now thought to be the modern descendants of carnivorous dinosaurs that lived millions of years ago, and scientists are discovering that dinosaurs had many of the same features that birds have, including feathers, which are modified scales. The oldest bird in the fossil record, Archaeopteryx, was a one-foot-long carnivorous amalgam of dinosaur and bird that lived 145 million years ago in what is now Europe. For years some palaeontologists argued that instead of being a bird, this creature was just a dinosaur with feathers, but scientists now accept that the archaeopteryx was the first bird.

At a recent conference in Germany, most of the attending palaeontologists agreed that the birds are clearly derived from dinosaurs. Scientists had been arguing over the comparison since the 1920s when a researcher first suggested the relationship, based on the observed similarities. Pterosaurs, however with their beaks and feathery wings weren’t birds but airborne reptiles. During 1970s and 1980s, renewed interest in the bird-dinosaur problem led to discoveries with the help of modern technology, as well as good old fashioned digging.

Birds were thought to have evolved from a specific branch of small, sleek dinosaurs, far removed from the giant meat eaters. But the CAT scans (a kind of X-ray that provides three-dimensional images of body interiors), have revealed interestingly birdlike structures inside the skulls of even the biggest meat-eating dinosaurs, such as the fearsome Tyrannosaurus Rex, five tons of bad news that certainly couldn’t fly.

T-Rex and its relatives appear to have had birdlike air chambers and nerve pathways inside their heads too.

The recent discovery of hundreds of dinosaur nests, eggs, and nestlings-so rare that scientists didn’t expect to find enough of them to draw any conclusions- has strengthened the connection. More than five hundred eggs and a herd of thousands of dinosaurs were uncovered in the Badlands of Montana, providing evidence that duckbill dinosaurs nested together and cared for their young until they were big enough to fend for themselves and avoid being trampled by their parents big feet.

The nests, similar to those of trumpeter swans and sandhill cranes, were big mounds of mud with scooped-out hollows to hold the eggs. They were built a dinosaur length away from each other, suggesting that these animals might have lived as part of a community and a family. These findings contradict the image of the coldblooded lizard that lays its eggs and walks away.

Image has been a problem for the dinosaur, whose name derives from the Greek words meaning “terrible lizard”. The most important new development in the study of dinosaurs may be the emerging change in attitude towards these misunderstood creatures. Recent finds, as well as a new look at museum specimens, are changing the image of the dinosaur from a plodding evolutionary failure to a complex, dynamic, and socially active creature.

CAT scans reveal that carnivorous dinosaurs may have had acute sense of smell and hearing, making them clever hunters. Their skulls were engineered to be lightweight and efficient killing machines. And, like birds, they may have woodwinds or horns. Computer analyses of the size and shape of vocal cavities in dinosaur skulls have led them to compare dinosaur herds to brass bands.

Researchers have taken a fresh look at the way dinosaurs were put together, and how they stood, walked, and ran. They’ve examined the tracks that were left in the mud and preserved by sediments for millions of years. This new information is eroding the image of the lumbering, clumsy, lizard reduced to spending its life buoyed by water.

All these evidence points to even the biggest dinosaurs as being capable of chugging along like angry elephants, some with their tails held high.      

That’s the latest thinking about Diplodocus, a graceful, giant herbivore that lived at the beginning of the Cretaceous Period, about 144 million years ago. The first nearly perfect specimen was uncovered in the late 1800s and reassembled for display in the Pittsburgh. But it wasn’t until recently, at the science Museum of Minnesota, that the animal was mounted with its tail held aloft, an arrangement that palaeontologists now agree is the right one, based on the shapes of the bones.

It’s not surprising that in the study of dinosaurs-animals that have been dead for at last 65 million years-old ideas are only occasionally overthrown. There’s very little evidence left on which to build a hypothesis. It takes a lot of conjecture and creative thinking to piece together the bare bones of creatures we hardly know.

Most of the diverse population of dinosaurs were not preserved for scientists to examine. Like most of the other living things that have occupied the earth, dinosaurs’ bodies decomposed or were eaten by other creatures. Only thin slices of time were trapped in sediments that turned to rock. Scientists have catalogued as many as 1500 species so far, as small as chickens and as large as the 140-foot-long Seismosaurus or “earth shaker,” discovered recently in New Mexico. Even so, that may be less than half of the number that really existed.

Strange new discoveries are being made every day, though, especially in Australia, South America, and China. Some seem to have had weird anatomies, such as the pug-faced and oddly built carnosaurs found in South America, and Mongolia’s toothless, parrotlike creatures with unusually long forelimbs and short tails.

US palaeontologists have pitched a previously unknown dinosaur equipped with body armour, a dragon-like snout and horns into the league of extinct reptiles with an Indian name.

The scientists from the North American Museum of Ancient Life in Lehi, Utah, have pronounced a fossil skull from the Gobi desert as a new species of plant-eating dinosaurs and named it Minotaurasaurus ramachandrani. Palaeontologist Clifford Miles, who examined the skull in detail, named it in honour of the renowned Indian-born neuroscientist Vilayanur S. Ramachandran (Incidentally it was Ramachandran who had purchased it from a Japanese fossil collector several years ago). Ramachandran, who is now the Head of the Brain and perception Laboratory at the University of California, San Diego, is himself studying the skull to understand the evolution of the brain in ancient creatures. Clifford Miles and co-author Clark J. Miles have proposed that the 30cm-long skull represents a new dinosaur that grew to about four metres in length from a family of extinct reptiles called ankylosaurs whose fossils have been reported from Mongolia and China.

“It is the most complete and preserved ankylosaur skull known,” Ramachandran said. The skull’s features suggest it comes from a period geologists call the late Cretaceous — about 70 million years ago. The examination of the skull suggests that this dinosaur had more ornamental features on its face than any known member of its family.

Some questions about dinosaurs may never be answered scientifically. Certain physiological characteristics-colour markings, and plate arrangements-are probably lost forever. But the positioning of things like tails and feet can be inferred from the shapes of the bones. A new look at the bone structure of the Diplodocus, for example, has convinced many palaeontologists that this creature had been misunderstood. Now they believe that this long-necked herbivore stood on its toes like an elephant an used its tail, fully half its body length, not only as a powerful whip but also as an instrument for shedding surplus heat, just as humans swear and dogs pant to cool down. The energy it would take to carry such a tail aloft and brandish its 15-foot whiplash might have required a high pressure metabolism, suggesting that the dinosaur was a warm-blooded animal, another recent controversial idea that may never be settled.

But something happened 66 million years ago that the big dinosaurs couldn’t survive. The most dramatic explanation is a six-mile-wide meteor hitting Earth. Scientists have found evidence of two impacts, one in the Gulf of Mexico and the other in Manson, Iowa. The Gulf impact came first, in mid-June, scientists think, setting off immense tidal waves an blowing material sky high, blocking out the sun and causing freezing temperatures. Two to four weeks later, a second impact left a 30-mile-wide crater un Iowa and scattered quartz sand grains all over North America. The impact may have come from huge object that split apart and made two hits and scientists from several disciplines have studied the blobs of melted glass, fossils of strangely damaged plants, dust layers, sea sediments and craters that are clues to this one-or two-stage cataclysmic event.

Nevertheless, the impact theory itself remains controversial, since a giant meteor wasn’t the only blow to fell dinosaurs. Many of them were already gone by the time the meteor hit, done in by changes in climate and sea levels, food shortages, and disappearance of small mammals that are their food. After the meteor hit, the oxygen content of the air was reduced by 10 percent, a serious problem for big animals.

The mass extinction that wiped out the dinosaurs (and more than 60 percent of the other species on the planet) has acquired fresh importance lately. The prospect of another chunk of space junk hitting Earth has stimulated some scientists to suggest unusual defence plans. For example, rockets carrying nuclear bombs could race out to meet a threatening asteroid, explode nearby, and deflect it from Earth’s path.

In addition to this renewed interest in the way dinosaurs died, there is also an active interest in how they lived and what sorts of plants and animals shared Earth with them. The increasing importance of the dinosaurs’ environment also influences the way in which fossils are exhibited in museums. Exhibitors are interested in presenting these creatures as biological organisms that were products of the same evolutionary stream that produced us and every other form of life on Earth.

By the evolutionary scorecard, dinosaurs were a great success, dominating the planet for 140 million years, much longer than humans have existed. Indeed, most species average about a million years. It was the demise of the big dinosaurs that made more room for mammals like us to evolve. Together we are part of a vast stream of life that stretches across millions of years into today. After all, dinosaurs still roam the earth, represented by almost nine thousand species of birds. The humble birds we see today are the direct descendents of the fearsome Dinosaurs that lived millions of years ago.

So then, Dinosaurs first appeared during the Triassic period, between 243 and 233.23 million years ago. Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years. These are time intervals, which the human mind cannot even imagine.

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