Fantastic Fossil Finds.
For an animal or plant to fossilize it must die and be quickly buried--before scavengers can eat it or bacteria decomposes the remains. Though only one in a organisms ends up a fossil, remains are scientists' best guide to Earth's past. For m, dirt on fossil finds, read on!
How Fossils Form
Here's a scenario in which a rare specimen becomes a fossil: 1. More than 65 million years ago, a Triceratops (three-horned dinosaur) meanders to a drinking hole. 2. A flash flood suddenly drowns the Triceratops. 3. Sediments (eroded rock particles) bury the dino skull. 4. Fifteen million years later, minerals have begun to replace the bone tissue in a process called petrification. The minerals retain the shape of the organisms' bones. 5. Fifty million years later (or 20,000 years ago) Earth's moving land plates create mountains, gradually pushing the fossil closer to the surface. 6. Today, rain, sun, and wind erode the mountainside, revealing part of the fossil. A lucky fossil hunter unearths the prize!
Frigid winds and temperatures are no big deal to Jarkov, a 9-year-old reindeer hunter who roams northern Siberia's tundra, a sub-arctic treeless region with frozen soil. What did seem peculiar one day in 1997 was the object he found in recently melted ice: a weird furry rock protruding from the ground.
Jarkov's discovery turned out to be no rock, but part of the head of a giant wooly mammoth, a species that has been extinct for 10,000 years. Ice had perfectly preserved the specimen. Suddenly scientists from around the world converged on Siberia. For two years they scraped away frozen soil to unearth a 47-year old male wooly mammoth. Its tissue was so intact that scientists had to fight the acrid smell of elephant feces. Now they've stored their prize in a cave. In April 2000, when Siberia's -40 [degrees] C temperatures warm, scientists will probe every inch of their prize. "It's the first time a complete mammoth has been recovered," says Larry Agenbroad, a University of Northern Arizona paleontologist.
"Jarkov" the mammoth (named after its discoverer) fossilized through quick freezing. Fossilization by ice requires a sudden plunge in temperature almost immediately after an animal or plant's death. While some bacteria thrive in such extreme environments (see SW 2/7/00, p. 15), most bacteria that are decomposers can't survive frigid cold. To be fossilized by ice, a dead organism must not be exposed to any sunlight that can heat it--otherwise bacteria return.
Scientists speculate that if Jarkov's DNA (hereditary material in cells) has not deteriorated, or if ice preserved the animal's sperm, they could insert the preserved DNA into an elephant egg (female reproductive cell), and then implant the embryo into the womb of elephant. The result: an elephant-mammoth hybrid, or crossbred organism. Shades of Jurassic Park 3?
Imagine an animal as tall as a six-story building, weighing in at 60 tons--as much as a tractor-trailer! If you'd been around 110 million years ago in southeastern Oklahoma, you just might have run into one. Sauroposeidon (sore-uh-po-SIGH-don) means "earthquake god lizard." "It could have been the biggest creature ever to walk Earth," says paleontologist Richard Cifelli at the University of Oklahoma.
Scientists first uncovered the neck bones of Sauroposeidon, a member of the sauropod (long-necked plant-eating dino) family, in 1994. Over the past five years, scientists discovered several other bones and began to assemble the gigantic reptile to see how it measured up. By last November, they realized what they'd found. "It had the longest neck of anything that ever lived," says Cifelli. The dino was also the last sauropod believed to have lived in North America, he explains.
How do paleontologists know that? They discovered the fossil in sediments, eroded rock particles in layers of earth strata, that belong to the Cretaceous Period (140-65 million years ago). The deeper the sediment, the older the fossil. Since most sauropods have been found in layers of the Jurassic Period (210-140 million years ago), they're older than Sauroposeidon. During the Cretaceous Period, Earth was warmer than today. Ice caps melted, and the waters of the Gulf of Mexico reached much farther inland. "Imagine Oklahoma on the Gulf coast," says Cifelli. "It was a different world!"
LAYERS & SEDIMENTS
125 ml each of 3 different colors of gravel * 3 bowls * spoon * 375 ml of soil * 2-liter rectangular glass dish * tap water * timer
1. Pour one color of gravel into each of three bowls,
2. Add 125 ml of soil to each bowl,
3. Mix ingredients thoroughly with a spoon.
4. Fill a baking dish halfway with water.
5. Slowly sprinkle ingredients from one bowl into the water. Wait 10 minutes.
6. Repeat step 5 with the other mixture, then the final mixture.
7. Observe what happens and take notes.
Waiting 10 minutes between sprinkling the different mixtures allows the gravel to set. Flow do the layers in the dish compare to Earth's layers and sediments?
The only thing better than fun in the sun may be relaxing by a shady tree. But until the appearance of Archaeopteris (or "ancient fern) 370 million years ago, scientists think Earth had no shade at all. Discovered by paleobotanists (scientists who study fossilized plants) last spring in Morocco, Archaeopteris grew to heights of more than 27 meters (90 feet) and had a 1-meter-wide trunk. Like animal fossils, Archaeopteris died and became buried in sediment with little oxygen, which can harbor bacterial decomposers. Many plants leave only impressions, or fossilized imprints, on sediment. The impressions look like two-dimensional photocopies of leaves, stems, or bark.
Scientists speculate that a group of Archaeopteris may have formed the planet's first forests, creating a new environment for emerging land animals. "When Archaeopteris appeared, it quickly became the dominant vegetation all over Earth," says Stephen Sheckler, a geologist at Virginia Polytechnic Institute in Blacksburg. Although the planet's earliest plants were algae, which appeared only in oceans more than 1 billion years ago, by 500 million years ago some plants had adapted to survival outside water. Archaeopteris paved the way for trees as you know them today.
Fantastic Fossil Fake
Not all fossils are the real thing. Paleontologists thought a recent find in China clearly established an evolutionary link between birds and dinosaurs (see SW 11/2/98). Now scientists have egg on their face! It seems the 120-million-year-old fossil imprint of an Archaeoraptor (ancient bird of prey) is nothing more than a fake. A Chinese digger may have glued tailbones on the fossilized remains of Archaeoraptor. The actual creature featured an avian (bird-like) feathered body and rigid tail common to predatory dinos (like Velociraptors in Jurassic Park).
Scientists first sent the fossil to Chinese museums early last year, then to the U.S., where some paleontologists quickly proclaimed it the "missing link" between dinos and birds. However, skeptical ornithologists (bird experts), who argue that dinos and birds evolved separately, declared the fossil a phony. The skeptics used X-rays to photograph it, which clearly showed that two rocks--one with an imprint of an Archaeoraptor tail fossil and one with a body fossil--had been glued together. Later, a CAT-scan (computerized 3-dimensional photograph) showed that the rocks had different densities (space between rock particles), explains Martin' "That was the kicker!"
By the time scientists warned the media not to promote the find, it was too late. Last November, National Geographic published an article that pronounced the fossil "a true missing link." Now the magazine and embarrassed scientists have to apologize for one gigantic mistake.
The digger who first found the bird-like fossil glued on a fossilized dino tail because "the long tail helps sell the fossil" claims Larry Martin, bird fossil expert at the University of Kansas. But Martin doesn't blame scientists for their mistakes: "We're all gullible to some degree!"
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|Date:||Mar 6, 2000|
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