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Dinosaurs
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Dinosaurs
Tyrannosaurus Rex
Tyrannosaurus Klutz
T-Rex Dethroned?
A Very Large Dinosaur
Extinction
Dinosaurs
Dinosaurs lived on Earth for around 165 million years before
they became extinct.
Of all the animals that ever walked on land, those with the
largest skulls of all were the Torosaurus. These ceratopsians (horned dinosaurs) lived between 65 and 70 million years ago
during the late Cretaceous Period in what is now North America. Measuring up to nine feet (three meters) long, the skull of
a Torosaurus had a thin, bony frill with two holes. They were also decorated with two large horns over the eyes, a third horn
at the tip of the narrow snout, and a pointed beak. The entire animal was up to 24 feet (7.5 meters) long, and weighed up
to five tons.
Little is known about Torosaurus; only 21 specimens have
been identified, and there are no complete skeletons so far. From the shape of the skull and beak, it seems that they lived
in herds and ate plants, as did the better known herbivorous dinosaurs like Triceratops. It is believed that the beak was
adapted for tearing up very tough vegetation.
How can we tell what a dinosaur looked like
from a few bones?
We believe them -- some of us do, at least -- because their
reasoning is perfectly plausible. Bones are like machine parts -- their shape, size and structure tells us what part of a
body they come from, and the kind of work that part could have accomplished. We know this from studying the skeletons of creatures
for which we do have living examples. By analogy, the big bones that have been unearthed from creatures no longer with us
suggest the size, shape and strength of the critters from which they came.
When and where was the first nearly complete dinosaur skeleton found?
The first dinosaur skeleton that was complete enough to be reassembled was discovered
in 1858 by William Parker Foulke, in Haddonfield, New Jersey.
Foulke heard that gigantic bones had been found in a marl pit, and he investigated.
Many more bones were uncovered, and the shape of the animal began to emerge. It took twenty years from the initial discovery
of the bones in 1838 until the animal was reconstructed.
The skeleton showed the world that dinosaurs were more than short lumbering lizards.
The animal that is now called Hadrosaurus foulkii was a biped, able to stand on two legs and run. It was the beginning of
a revolution in paleontology.
From the Shores of a Bucolic Pond to World Fame: Haddonfield's Dinosaur
Birdwood, the historic Haddonfield, New Jersey, home of John E. Hopkins on the shore
of Hopkins Pond, played a central role in the discovery of the first dinosaur skeleton in 1858. Hopkins often invited vacationing
friends, such as William Parker Foulke, to his estate house for dinner. It was here that Foulke first heard the story of the
strange bones found 20 years earlier by Hopkins' diggers in a marl pit a short walk from the rear of the house. At that time
marl was used as fertilizer by farmers.
With Hopkins' permission, Foulke located and re-excavated the old pit, painstakingly documenting and
extracting ancient seashells, sharks' teeth and the nearly-complete skeleton of an enormous
reptilian creature
Dr. Joseph Leidy
Foulke also summoned Dr. Joseph Leidy to the site. A university professor of anatomy
and curator of the Academy of Natural Sciences in Philadelphia, Leidy determined the actual meaning of the find; made the
first sketches of the creature based on a careful study of the bones; and formally presented the startling data to the scientific
community. His Hadrosaurus foulkii studies would establish Leidy as the father of modern paleontology and make the
Academy North America's preeminent institution in that field throughout the rest of the nineteenth century.
Philadelphia Academy of Natural Sciences
Today, Hadrosaurus is still featured as the keynote specimen in the Academy’s extensive dinosaur
exhibit. The Academy still keeps some of the original Hardosaurus bones on display
in the same type of wooden boxes Leidy used to store them in the 1860s. Leidy officially named the animal Hadrosaurus foulkii
in honor of both the town of Haddonfield and the discoverer, William Foulke.
The Meaning of the Hadrosaurus Find: Proof That Dinosaurs Were Real
Colonial Americans understood neither the concept of geological time nor the actual
process by which fossils were created. Their society was one that still looked largely to scripture for explanations of much
of the surrounding natural world. For instance, the fossil fish and seashells found at quarries and construction excavations
in the 1700s were widely believed to be residue from the great flood survived by Noah.
Paleontology -- the scientific study of fossils -- emerged in the years after the American revolution
as all the sciences began evolving into more objective investigative disciplines that pursued their research independently
of religious dogma.
The First Hints
Throughout the early 1800s, various individuals in Europe and North America documented
finds of peculiar fossilized bones unlike those of any living animal. These finds were small -- a metatarsal fragment scooped
up here; a vertebra pried from the rock there; a few odd teeth sieved from loose gravel further on; and so forth. Nevertheless,
anatomists of the era noted striking similarities between the mysterious bones and those of living species of lizards such
as iguanas. One major difference between the two was size. Some of the fossil bones and teeth were more than a hundred times
larger than those of living animals.
In 1841, Dr. Richard Owen, a leading British authority on anatomy, completed a review
of all that was known about such strange bones. He published a report concluding that the individual bones were from animals
that had all been members of a group of large reptiles that had completely died out in some past age. Because of their apparent
size, as well as their fangs and claws, Owen called them by a combination of the Greek words for "terrible lizards" -- dinosaurs.
But neither Owen nor anyone else could say what such animals would have actually looked like because no one had found enough
bones from a single animal to reconstruct its anatomy.
Biblical Implications
The very idea -- that previously unknown species of monstrously large reptiles could
have existed outside of the events documented in the Bible -- was a highly controversial one. It also exerted a deliciously
exotic pull on the imaginations of nineteenth-century scientists and laymen alike.
It became fashionable among the members of the new fossil hunting set to mix tantalizing
handfuls of fossil bone bits with equal amounts of speculation and populist whimsy to conjure up visions of how such beasts
might have looked. Above (left) is an illustration from the 1851 Iconographic Encyclopedia of Science, one of the most
renowned reference books of the era. It shows the latest "knowledge" available about the structure of dinosaurs ten years
after Dr. Owen coined the term. Note the figure is essentially a formless, serpentine string of vertebrae topped with a crocodile-like
skull. There is no clear anatomical structure. Meanwhile, many scientific and ecclesiastic authorities rejected all such theories
about so-called dinosaurs as wild fantasy.
The First Real Proof of Dinosaur Existence
Eight years after this reference book was published the first full skeletal form of
a real dinosaur -- Hadrosaurus foulkii -- was unearthed in Haddonfield, New Jersey. Taller than a house, it had the
pelvic structure of a bird, the tail of a lizard and, incredibly, it walked upright on two legs, foraging with arm-like forelimbs.
That nearly-complete skeleton was like a lightning bolt in the scientific community,
cutting through decades of murky speculation, skepticism and debate to dramatically confirm a historical reality so new and
vast and meaningful, it took the breath away.
First Dinosaur Skeleton Mounted for Display
Haddonfield's Hadrosaurus soon became the world's first dinosaur skeleton to be mounted
and put on exhibit. That display, at the Philadelphia Academy of Natural Sciences (above, right), opened in 1868 and allowed
members of the public to walk up close to a prehistoric creature for the first time. In the first year, daily attendance at
the Academy more than doubled. The second year it nearly doubled again--and the general public's interest in dinosaurs has
continued to expand ever since.
Until the erection of other dinosaur finds in 1883, Hadrosaurus foulkii was
the only dinosaur on public display anywhere in the world. The Academy's Hadrosaurus mount was so popular that duplicates
were cast for display at Princeton University, The Smithsonian Institution in Washington and the 1876 Centennial Exhibition
in Philadelphia. Another duplicate was erected at the Royal Scottish Museum in Edinburgh in 1879 -- the first dinosaur skeleton
to be exhibited anywhere in Europe.
An Epochal Scientific Event
This Haddonfield skeleton proved dinosaurs were for real. It was the find that changed
paleontology from a quaint Victorian gentleman's hobby to a mainstream scientific activity commanding world attention. The
wild popularity of the original Hadrosaurus exhibits also proved the dizzying commercial possibilities inherent in dinosaur
discovery, setting off a mad race by competing diggers who subsequently supplied the menagerie of other bony prehistoric beasts
that continue to be the most popular attractions in today's natural history museums.
Hadrosaurus: A Duckbill that Roamed the Coast of what is Now Pennsylvania
In life, Hadrosaurus foulkii would dwarf a six-foot man. Nearly as tall as a
two-story building, the animal weighed up to four tons and was a member of the dinosaur family that later became known as
"duckbills" because of the bird-like nature of their jaws and skull structure. Hadrosaurus foulkii was up to 30 feet
long from the tip of its nose to the tip of its tail but despite its bulk, the animal was not particularly ferocious. Much
the same as a large, placid cow, it was a plant eater that browsed leaves and branches along the marshes and shrub lands of
the Atlantic coast. It was also a good swimmer and could have regularly lolled about in the water a substantial distance from
shore.
Duckbills lived and traveled in herds, not unlike ponderous flocks of birds. They laid
eggs in nests. Some paleontologists believe they protected the eggs until hatched and then continued to nurture the brood
for a substantial period of time, just as birds do.
Teeming Rookeries of Duckbill Dinosaurs
It is not all that difficult to imagine how the edges of conifer forests along the
Cretaceous coast of what is now Pennsylvania were once alive with teeming rookeries of such duckbill dinosaurs. One of those
creatures ultimately got into trouble near fast moving water and died. Its body floated out to sea, where it sank and was
quickly covered in mud and sediment. After the flesh decayed, the bones absorbed minerals, surviving intact as a skeleton
until about 70 million years later when a Haddonfield workman wrenched one from sticky marl, hefted it aloft into harsh sunlight
and wondered aloud what it could possibly be.
The Changing Shape of Hadrosaurus foulkii
The original reconstruction of Hadrosaurus foulkii featured a creature in a
kangaroo stance -- an animal that used its tail as a third leg. At the same time, while the excavated fossil was nearly complete,
it lacked a skull. Because parts of its skeleton resembled those of an iguana, the skull of a modern iguana was used as a
model for the skull created for the original display in 1868. That sculpted skull is
currently on display at the Academy of Natural Sciences in Philadelphia as a historical curiosity.
It was later believed that Hadrosaurus did not use its tail as a third leg but rather
as something of a low-slung counterweight that allowed it to walk upright on two legs.
The most accurate life-size representation of Hadrosaurus foulkii on exhibit
today is to be found at the Academy of Natural Sciences in Philadelphia. The latest evidence indicates that the huge creature
held its entire rear body aloft as a counterweight while projecting its upper body forward to move in a manner amazingly similar
to that of a modern bird. The front limbs were used for foraging. The skull shape is based on the latest information from
studies of Hadrosaurus and its near relatives.
DINOSAUR NOSTRILS PINPOINTED
A study in this week's edition of the journal Science pinpoints the position of a dinosaur's nostrils. The
finding is important because it could shed light on how the creatures found food, detected predators, reproduced and regulated
brain and body temperature. Whereas nostrils have usually been drawn on the top of dinosaurs' heads, the new results suggest
they appear just above the mouth. "Scientists have been interested because dinosaurs really seem to stretch the bounds of
physiological form," said Lawrence Witmer, an associate professor of biomedical sciences at Ohio University. The misconception
dates to the earliest recovered dinosaur fossils, many of which were of the long-necked, giant sauropods. Early paleontologists
assumed they must have been aquatic because of their massive size, and so placed the nostrils near the top of the head to
allow breathing while partially submerged. "Despite the fact that many years later we realized sauropods weren't primarily
aquatic, we never addressed the nostril position again," Witmer said. "And somehow, we translated that nostril position to
other dinosaurs." To arrive at his conclusions, Witmer studied the soft tissues of 62 animals from 45 species of crocodiles,
birds and lizards. He compared the etch markings on bones left by muscles, veins and arteries, and then examined dinosaur
bones to infer the location of these and other soft tissues.
FEATHERY DINOSAUR FOSSIL FOUND
A feathery 130-million-year-old fossil of a dinosaur closely related to the cunning predators
portrayed in the movie "Jurassic Park" was recently found in China. A team of Chinese and American scientists identified the
dinosaur as a dromaeosaur, a small, fast-running dinosaur that was kin to sickle-clawed Velociraptors and a distant relative
of the sharp-toothed Tyrannosaurus rex. All these two-legged carnivorous dinosaurs are collectively known as advanced theropods.
"This fossil radically modifies our vision of these extinct animals," says researcher Mark Norell, Chairman of the Division
of Paleontology at the American Museum of Natural History. "It shows us that advanced theropod dinosaurs may have looked more
like weird birds than giant lizards." The fossil is the first one found with the entire body covering intact. The detail on
the dinosaur allows scientists to see how its primitive feathers attached to the dinosaur's body. In small, flightless dinosaurs
like this one, its layer of downy fluff may have evolved to help the predator stay warm, the researchers report in the April
25 issue of the journal Nature.
GIANT CROC RELATIVE MAY HAVE EATEN SMALL
DINOSAURS
A 110-million-year-old crocodile-like creature known as Sarcosuchus was as long as a school bus and may have
made an occasional meal of small dinosaurs, researchers report in this week's online edition of the journal Science. Led by
Paul C. Sereno of the University of Chicago, the team described the newly discovered fossil skulls and partial skeletons that
were found in Niger. The giant crocodilian was covered from head to mid tail in an overlapping armor of bony plates embedded
in the skin, each sporting annual growth rings that the researchers used to estimate the age of a given animal. They believe
that the animals took 50 to 60 years just to reach their adult size. It was a good time for crocodilian reptiles, as the researchers
have found six different species at the Niger site, most of them smaller than Sarcosuchus and one that Sereno said was an
"Oreo cookie" in comparison. "That's the fascinating thing about crocodile evolution. It seems like modern crocodiles have
been trimmed at each end of their size range, with the little ones and the big ones disappearing," said Sereno.
SECOND LARGEST DINOSAUR FOUND IN EGYPT
In an oasis in an Egyptian desert, paleontologists have uncovered the remains of what may
be the second largest dinosaur that ever existed, according to a report in this week's edition of the journal Science. The
dinosaur, named Paralititan stromeri, may have been 80 to 100 feet long and weighed as much as 70 tons, and apparently lived
along the coast. It was a species of titanosaurid, a group of long-necked, long-tailed, plant-eating dinosaurs. If the estimates
are correct, Paralititan would be second in size only to a South American titanosaurid, Argentinosaurus, which is regarded
as the most massive terrestrial animal known. The site where the remains were found could be a boon to fossil hunters. "Nobody
knows much about the paleoecology of this region or all of North Africa in the late Cretaceous," Joshua Smith, a graduate
student at the University of Pennsylvania who led the expedition, told the New York Times. "Many of the dinosaurs and other
vertebrates were giants. The amount of biomass in this area had to be enormous to support all that.... We may have stumbled
on dinosaur heaven at Bahariya."
TRACKS SHOW PREDATORY DINOSAURS WERE SPEEDY
A recently-discovered collection
of fossilized dinosaur tracks show that Jurassic-era predators were fleeter of foot than previously supposed, according to
a report in The Telegraph. Made by a one-ton theropod carnivore known as a megalosaurus apparently in pursuit of giant plant-eating
sauropods, the tracks show that this distant ancestor of Tyrannosaurus Rex was breaking into a run. It started off sauntering
at about 4 miles per hour, then abruptly began to run, reaching a speed of 20 miles per hour. "We knew that small theropods
could run fast, but it wasn't clear if the same was true for large theropods," said Julia Day, from Cambridge University,
who led the research published today in this week's edition of the journal Nature. "The evidence here shows that these animals
weren't lumbering beasts. They were much more agile than some people have imagined. Although we don't know if they could sustain
a run, they could clearly run for short bursts."
DINOSAUR HAD FULLY MODERN FEATHERS
A newly discovered fossil represents a dinosaur with fully formed feathers, suggesting
that feathers evolved before birds, according to a report in this week's edition of the journal Nature. Chinese paleontologists
discovered the fossil in the famous Jiufotang rock formations at Shangheshou, near the town of Chaoyang. The animal was the
size of a pheasant and had "unequivocally modern feathers, with a single rachis down the middle and barbs coming off the sides,"
paleontologist Mark Norell of the American Museum of Natural History in New York told New Scientist. Previous finds had unearthed
filaments or fluffy feathers on dinosaurs, but this find represents the first fully modern feathers seen on a non-bird. The
animal was related to predatory dinosaurs that included velociraptor, and this group is in turn closely related to the ancient
bird archaeopteryx. "I hope this ends the argument about birds being related to dinosaurs," said Norell.
Dinosaurs slashed the
flesh of their victim with their teeth when they dined. Allosaurus fragilis,
a creature whose ferocity belied its name, had a thick skull that it used like an ax, slamming into its prey with its head
and ripping away the flesh when it withdrew. Source: THE NEW YORK TIMES
Used
without permission, but with the best of intentions.
Tyrannosaurus Rex
Tyrannosaurus ('tyrant lizard') is the most famous dinosaur genus and
a fixture in popular culture. Known colloquially as T. rex, the species Tyrannosaurus rex hails from what is now western North
America. Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Although others rivaled
or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring
over 40 feet in length and weighing as much as an elephant.
Fossils of T. rex have been found in North American rock formations dating
to the very end of the Cretaceous Period; it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction
event. More than 30 specimens of T. rex have now been identified, some nearly complete, which has allowed significant research
into many aspects of its biology, including its life history and biomechanics. The feeding habits and potential speed of T.
rex remain controversial.
Since it was first described in 1905, Tyrannosaurus has become the most
widely-recognised dinosaur in popular culture. It's the only dinosaur commonly referred to by its specific name, Tyrannosaurus
rex, among the general public, and the scientific abbreviation T. rex (often mistakenly spelled "T-Rex") has also come into
wide usage.
Museum exhibits featuring T. rex are very popular and the dinosaur has
appeared numerous times on television and in movies. A number of books and comic strips, have also featured Tyrannosaurus,
which is typically portrayed as the biggest and most terrifying carnivore of all. At least one musical group, the band T.
Rex, is named after the species. Tyrannosaurus-related toys, video games, and other merchandise remain popular.
Tyrannosaurus has been at the centre of the warm-blooded versus cold-blooded
debate ever since its beginnings with the paleontologist Robert T. Bakker. Like many other theropods, Tyrannosaurus is thought
to have been warm-blooded due to its heightened levels of activity - for example, to have been able to capture prey actively
the creature would have needed to have been warm-blooded. T. rex also has anatomical features distinctly similar to birds,
which are warm-blooded. However, since the birth of the theory that Tyrannosaurus was in fact a scavenger, the theory has
been cast into doubt and paleontologists are still divided on the issue.
Copyright © 2006 ArcaMax Publishing, Inc. and its licensors.
Tyrannosaurus Klutz
For years, textbooks and Steven Spielberg have taught us
that Tyrannosaurus rex ("king of the tyrant lizards") was the biggest killer in the prehistoric park. Turns out, they may
have been dead wrong.
This week, U.S. researchers published a new study that
basically calls T-rex a klutz. And evidence has long been mounting that the reputed super-predator was really more of a scavenger,
feasting on what had already bitten the dust.
In the new study, researchers used sophisticated computer
models to reconstruct T-rex's biomechanics. (Basically, they took what we know about T-rex biology and applied the laws of
physics to see how the massive monster might have moved.) Their key finding: the 7-ton prehistoric predator would have taken
about two seconds to make a quarter turn.
At that rate, nimble prey could have easily run circles
around T-rex. Surprised? Don't be. The study gibes with other recent biomechanical research. Though Jurassic Park showed a
T-rex chasing a car at 45 mph (72 km/h), scientific studies say the beast topped out at 10-25 mph (16-40 km/h). That's a jog
or a moderate run, not a sprint after high-speed prey.
Ironically, Steven Spielberg's Jurassic Park advisor--famed
paleontologist Jack Horner--has long maintained that T-rex scavenged meals rather than chasing them down. Just last year,
Horner reported evidence that T-rex had a rigid ligament running down its back. That would have restricted the 40-foot (12-meter)
animal's range of movement and made it difficult for T-rex to turn without tipping over.
But don't consider the tyrant toppled just yet. Many experts
say T-rex was both a scavenger and a killer. They point out that large carnivores often scavenge what they can and hunt what
they must. (Why turn down a free meal, especially when you weigh 7 tons?) They also note that T-rex only needed enough speed
and agility to run down Cretaceous giants, not Serengeti gazelles--or Jurassic Park jeeps.
--Steve Sampson
KnowledgeNews is brought to you by Every Learner, Inc., an independent
small business dedicated to supporting lifelong learners. Copyright © 2007, Every Learner, Inc. All rights reserved.
T-Rex Dethroned?
By Steve Sampson
Tyrannosaurus rex, the "king of the
tyrant lizards," could grow to 42 feet (13 meters) in length and weigh 14,000 pounds (6,350 kg). You'd think that would be
enough to make T-rex the largest land carnivore ever to walk the Earth.
You'd think wrong. Scientists have discovered a colossal
Cretaceous carnivore that was at least as big as T-rex. Working in Argentina's Patagonian wilderness, the team found seven
sets of bones from the new species buried together in a prehistoric riverbed. The largest set of fossils belonged to a creature
41 feet (12.5 m) long.
The new species is called Mapusaurus roseae--from
"mapu," a Patagonian Indian word meaning "of the earth," and "Rose," the name of an expedition donor. Mapusaurus's finders
think the massive meat-eaters might have worked together to bring down what may be the largest land animal that ever lived:
the 125-foot, 200,000-pound (38-meter, 91,000-kg) Argentinosaurus, which lunched on leaves in the same neighborhood
100 million years ago.
Mapusaur finder Philip Currie says that "Mapusaurs had
long, thin skulls with knifelike teeth and jaws that can close very fast," while "T-rex had a short skull with powerful, banana-shaped
teeth better for biting through bone"--making the one a flesh slicer and the other a bone crusher. Like wolves hunting a buffalo,
Mapusaurs attacking a much larger prey could have quickly bit off flesh and backed away.
So, if scientists find even bigger Mapusaur bones, should
we call Mapusaurus the biggest, baddest dino-carnivore of all? Not necessarily. It's just the latest claimant to the throne.
Check out these two other would-be tyrant kings:
Giganotosaurus ("giant southern
lizard") ? Closely related to Mapusaurus, Giganotosaurus, too, hailed from the rough and tumble jungles of ancient Argentina.
It likely grew as long as 45 feet (13.5 meters) and weighed as much as 16,000 pounds (7,250 kg). Giganotosaurus's skull was
6 feet (2 meters) long, but its braincase was smaller than T-rex's. The two looked a lot alike, but Giganotosaurus (and Mapusaurus)
lived 30 million years earlier.
Spinosaurus ("spiny lizard")
? In the movie Jurassic Park III, Spinosaurus kicks T-rex's tail. Prehistorically speaking, that never happened--Spinosaurus
lived closer to Giganotosaurus's time. Yet the movie may have had a point. Recent research suggests Spinosaurus grew as long
as 60 feet (18 meters) and weighed up to 18,000 pounds (8,150 kg)--putting it in a different weight class from any seven-ton
T-rex. A native of ancient Africa, Spinosaurus had a long, crocodile-like snout filled with sharp teeth, and a spiny sail
down its back. The long snout may have helped Spinosaurus feast on prehistoric fish, or even snag low-flying pterosaurs.
Steve Sampson
April 20, 2006
Copyright © 2006 ArcaMax Publishing, Inc. and its licensors.
A Very Large Dinosaur
Scientists in Brazil discovered the skeleton of a gigantic
dinosaur that was probably one of the largest creatures ever to walk the earth.
Called Futalognkosaurus dukei (say "foo-ta-long-koh-saurus"),
the plant-eating behemoth lived around 88 million years ago and grew to 105 feet (32 meters) in length. Its neck alone likely
stretched more than 55 feet, and its excavated spinal column tips the scales at around 9 tons.
How big is that, really? Think of it this way: the Futalognkosaurus
stood as tall as a four-story building and was twice as long as a Greyhound bus. Its fossilized spinal column alone weighs
more than a male African bush elephant, the modern world's largest land animal.
Not only is the skeleton huge, its finders say it's also
"one of the most complete of these giants" ever found. They began to unearth it seven years ago, in Argentina's Patagonia
region. They've now recovered more than two-thirds of the giant dino's bones.
Just as important, they found all those bones among plant,
fish, and reptile fossils--not to mention among remnants of a prehistoric predator called "Megaraptor," who had a foot-long
(30 cm) sickle-shaped claw. Finding so many fossils together means they can reconstruct more than Futalognkosaurus
itself; they can also reconstruct its environment.
So, at 105 feet, was big "Futa" the largest dinosaur that
ever lived? Probably not. There are actually plenty of contenders for that title--from India's Bruhathkaysosaurus to
America's Supersaurus. One of the big favorites these days is Argentinosaurus, which lunched on leaves in what's
now Patagonia around 100 million years ago and may have reached 125 feet (38 meters) in length.
"What about Brontosaurus?" you ask. The dino-giant
you may have loved in grade school has now been reduced to a middleweight. Officially called Apatosaurus, not Brontosaurus,
it grew only to around 75 feet (23 meters). That's still plenty big enough to feed the Flintstones, but too small to warrant
a heavyweight title shot these days.
Steve Sampson
Copyright © 2007, Every Learner, Inc. All rights reserved.
Extinction
A new computer model suggests that North American hunters may
have been responsible for the extinction of the woolly mammoth and its large mammalian kin 12,000 to 13,000 years ago, according
to a report in this week's edition of the journal Science. A second report in the issue implicates humans in a similar extinction
of large mammals in Australia. At the end of the Pleistocene era in North America, approximately 30 large, plant-eating mammals
disappeared. Whether that was due to climate or human activity has long been a subject of debate. John Alroy of the University
of California's National Center for Ecological Analysis and Synthesis simulated the extinction process with a computer model,
which correctly predicted the extinction or survival of 32 of 41 prey species as the result of a "total overkill" by hunters.
In the second study, Richard G. Roberts of the University of Melbourne and his colleagues investigated the extinction of all
Australian land mammals, reptiles and birds over 45 kilograms some time over the past 1.8 million years. They studied fossils
at 28 sites and inferred that the extinction occurred within about 10,000 years after human beings arrived on the continent,
which suggests that human activity could be responsible.
ASTEROID IMPACT TIED TO LARGEST EARTH EXTINCTION
New evidence lends support to the idea
that the largest known mass extinction on Earth-which occurred during the Permian Period some 251 million years ago-was caused
by an asteroid impact, according to a report in the September issue of Geology. Most scientists think gradual sea fall, climate
change, oceanic anoxia, and volcanism were the causes, but Kunio Kaiho from Tohoku University reports the team's findings
of mineral and isotopic deposits that are consistent with an impact similar to the one that killed the dinosaurs 65 million
years ago. The discoveries suggest that it hit the ocean triggering a massive release of sulfur from the Earth's mantle, which
led to acid rain and possibly worldwide volcanism. "Understanding the cause of this event is important because it represents
the largest mass extinction," Kaiho said, "and it led to the subsequent origination of recent biota on Earth."
COSMIC IMPACT LED TO LARGEST EXTINCTION
New findings of extraterrestrial origin suggest that the largest
mass extinction in Earth's history -- bigger than even the extinction of the dinosaurs -- was triggered 250 million years
ago by a collision with a comet or asteroid. Scientists say the cosmic killer, which they estimate to be about 6 to 12 kilometers
(4 to 7 miles) wide, triggered a catastrophic chain of events that led to the rapid extinction of 90 percent of all marine
species and 70 percent of all land vertebrates in as few as 8,000 to 100,000
years -- virtually a microsecond in the nearly 4-billion-year history of life on Earth. The scientists do not know where the
impact took place, but they say it left behind a calling card -- globular cages of carbon called buckyballs that have trapped
within them nuclear isotopes of helium and argon normally found in outer space. Researchers suggest that perhaps the only
way these gases could be forced inside carbon cages is inside the extreme temperatures and gas pressures found in stars nearing
the end of their lives.
MASS EXTINCTION OCCURRED TWICE
A mass extinction of life on Earth may have occurred 10
million years before the largest known extinction took place around 250 million years ago, according to Japanese scientist,
Yukio Isozaki, The Japan Times reports. The professor of life extinction history at the University of Tokyo, who will report
his findings at a conference on Earth science next Monday in Tokyo, says he studied the fossils of fusulinidae, a unicellular
organism, in a 40-meter-thick layer of limestone. The limestone bears traces of coral reefs that piled up near the surface
of the sea during a period of some 10 million years prior to Earth's largest mass extinction. In the largest extinction, 96
percent of all invertebrate life in seas -- such as trilobites -- disappeared between the Paleozoic and Mesozoic eras some
250 million years ago. The study finds that larger fusulinidae, measuring up to 1 cm in length, became extinct about 260 million
years ago, he says. Isozaki also found that smaller fusulinidae, measuring less than 1 mm, survived at that time. However,
the smaller fusulinidae became extinct about 250 million years ago, underscoring the two-stage theory of extinction. Scientists
say they believe extinction occurred at those times due to a lack of oxygen caused by unusual volcanic activity. Isozaki says
he suspects such volcanic activity occurred twice and that larger fusulinidae were unable to cope with environmental changes
brought on by the first wave.
ASTEROIDS, NOT COMETS, WERE SOURCE OF ANCIENT BOMBARDMENT
Asteroids, not comets, according to a report in the Journal of
Geophysical Research -- Planets, caused a cataclysm that occurred 3.9 billion years ago. The finding suggests that the bombardment
was so severe that it destroyed older rocks on Earth, which is why the oldest rocks ever found are less than 3.9 billion years
old, according to David Kring of the University of Arizona Lunar and Planetary Laboratory. The collisions may also have caused
the formation of hydrothermal systems that would have been good incubators for pre-biotic chemistry and the early evolution
of life. The same bombardment of asteroids affected other bodies of the inner solar system, including Mercury, Venus, the
Moon and Mars. The event produced at least 22,000 impact craters on Earth, some with diameters of 3,000 miles, and one that
is bigger than Australia.
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