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Teenage Life in Italy
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Some Arctic Dinos Lived in Herds
By Sid Perkins
Just as interesting, however, is how this was discovered. Scientists didn’t look at a single fossil bone.
Instead, they analyzed a large number of preserved footprints on a mountainside located toward the
southern end of central Alaska.
Anthony Fiorillo works at the Perot Museum of Nature and Science in Dallas, Texas. As a vertebrate
paleontologist, he studies the fossils of creatures with backbones. In 2007, he was part of a research
team exploring Denali National Park. “We rounded the corner and there they were,” he recalls.
Thousands of footprints had been preserved in stone. “It was amazing.”
Dinosaurs died out more than 65 million years ago (not
counting birds, their modern-day relatives). So, it’s a bit
surprising that scientists know so much about these
ancient creatures. Now, a new study reveals that a certain
type of duckbilled dinosaur lived in the Arctic year-round.
These animals also traveled in herds that included many
age groups, they find. The creatures even appear to have
gone through a “teenage growth spurt.”
Those tracks pepper a steep patch of exposed rock about twice as
long as a football field and up to 60 meters (roughly 200 feet) wide.
They sit at least 160 kilometers (100 miles) north of the Gulf of Alaska.
Between 69 million and 72 million years ago, that now-rocky material
was muddy sediment on a floodplain near a seacoast, Fiorillo explains.
The hadrosaurs walked across the squishy mud. Later, the footprints
they left turned to stone.
Previous studies suggested adult duckbills took care of their young,
says Fiorillo. The new evidence that these dinosaurs truly traveled in
herds with multiple age groups confirms that parents cared for their
young well beyond the time they left the nest, his team concludes. The
researchers published their findings June 30 in Geology.
© Science News for Students
Thousands of tracks cover this
rocky mountainside in Alaska’s
Denali National Park. They
provide a wealth of information
about the size, age and lifestyle
of certain dinosaurs.
COURTESY OF PEROT MUSEUM OF
NATURE AND SCIENCE
EVIDENCE FOR HERDS O F DINOSAURS
Small meat-eating dinosaurs called theropods had left behind a few of the tracks that Fiorillo’s team
found in Denali. Birds had left some others. But the vast majority came from creatures called
hadrosaurs. These large plant-eating duckbilled dinosaurs had been quite common during the
Cretaceous Period. That helps explain one of their nicknames: “cattle of the Cretaceous.”
For the new study, the researchers focused only on the hadrosaur tracks. More than half of the
footprints were preserved so well that they had clear impressions of the skin on the dinosaurs’ feet.
Most tracks had a similar level of preservation. That suggests all were probably left within a short
period. Other fossils in the nearby rocks, including insect burrows, suggest these hadrosaurs had left
their footprints during the summer. These are trace fossils — evidence of ancient life other than a
preserved carcass or bone.
At the time these dinosaurs lived, Fiorillio says, the average temperature in the warmest months was
between 10° and 12° Celsius (50° and 54° Fahrenheit). That’s about what conditions are like today
along the border between Canada and the lower 48 U.S. states, he notes.
The team measured a large sample of the duckbills’ footprints. They fell into four distinct size ranges.
The largest tracks, presumably made by adults, measured about 64 centimeters (25 inches) across. The
smallest tracks, 8 centimeters (3 inches) wide, were likely left by young duckbills. They would have
been no more than a year old. Tracks of two other size groups were probably made by juveniles and
near-adults.
These data suggest the community of hadrosaurs included four different age groups.
© Science News for Students
A hadrosaur footprint made
roughly 70 million years ago. For
scale, the long blue bar at right is
10 centimeters long; each small
blue or white bar measures 1
centimeter.
COURTESY OF PEROT MUSEUM OF NATURE
AND SCIENCE
© Science News for Students
THESE DINOSAURS DIDN’T MIGRATE
About 84 percent of the tracks sampled for the new study had been left by older hadrosaurs — adults or
near-adults. Roughly 13 percent came from the youngest members of the herd. And a mere 3 percent
came from herd members considered to be juveniles, says Fiorillo. The rarity of tracks by these tweens
suggests that the young of this species had a rapid growth spurt. If true, they would have spent relatively
little time at this vulnerable size — and therefore left very few tracks.
“What’s really neat is how many small tracks there are,” notes Anthony Martin. An ichnologist — or
expert in trace fossils — he works at Emory University in Atlanta, Ga.
Other scientists had analyzed fossil bones from duckbills. These studies had hinted that the equivalent of
adolescent hadrosaurs would have experienced growth spurts. But the new findings are “the best
evidence that I’ve seen,” says Eric Snively. He’s a vertebrate paleontologist at the University of Wisconsin-
La Crosse. “This is a great study,” he adds, “and further evidence that juvenile hadrosaurs grew up in an
eye-blink.”
Also previously, researchers had proposed that Arctic dinosaurs migrated farther south for the winter.
That’s because even if the region was much warmer than it is today, nights in the high Arctic would have
been 24 hours long. So, with no sunshine for several months, Alaska would have had long periods of very
bleak, chilly weather.
But finding juveniles in the herd
strongly suggests that these
dinosaurs remained in the Arctic all
year. That’s because adolescents and
preadolescents wouldn’t have had
the strength or stamina to make
those long treks, Fiorillo maintains.
Field work is often harsh. Paleontologists studying the dinosaur
footprints here on an Alaskan mountainside sometimes worked
in cold and fog.
COURTESY OF PEROT MUSEUM OF NATURE AND SCIENCE
© Science News for Students
The presence of very young dinosaurs might have been expected, he notes: If this were a nesting region,
the babies would have hatched sometime just before summer. And remember, that’s when these tracks
were left. But that wouldn’t explain the juveniles, he says.
The team’s findings “suggest that these dinosaurs were overwintering in Alaska somehow,” says Snively.
At the time, the average temperature in the region remained above freezing even during the winter, he
notes. But, he adds, “this study raises interesting issues about how the dinosaurs could live in the region
when it was pretty dark for several months at a time.”1. What does the name Mlungisi mean? A. The Helper B. The Fixer C. The Brave One D. The Giver → B 2. What kind of person is Mlungisi? A. Rebellious and lazy B. Always fixing problems and helping others C. A mysterious, quiet boy D. A selfish older cousin → B 3. What does the name Velile mean? A. One Who Builds B. The Beloved One C. He Who Popped Out of Nowhere D. He Who Carries Others → C 4. How does Velile behave according to Trevor? A. He is very responsible and hardworking B. He often vanishes and suddenly reappears C. He is a caring father figure D. He is always around to help the family → B 5. Patricia’s name means: A. She Who Gives Back B. She Who Demands More C. The Fighter D. The Lost One → A 6. What did Patricia do as a child in Soweto? A. She went to school and stayed away from others B. She took care of abandoned children and fed them C. She ran away from home frequently D. She helped her father manage a shop → B 7. Where did Patricia find the money to buy food for the children? A. From her allowance B. From selling her toys C. From collecting bottles from shebeens D. From stealing it → C 8. What is a shebeen in this context? A. A school for orphans B. A place for young kids to play C. An informal bar where men would drink D. A shelter for street children → C 9. How old was Patricia when she started helping other children? A. 4 or 5 B. 6 or 7 C. 10 or 11 D. Teenager → B 10. Why did Trevor’s mother choose the name “Trevor”? A. It was the name of her favorite Bible character B. It was her father’s name C. It had no meaning, and she wanted him to be free D. It was a popular name in her family → C 11. What does it mean that Trevor's name had “no precedent” in South Africa? A. It was illegal to use B. It had no cultural or family history C. It came from ancient African myths D. It was a translation of a Zulu name → B 12. What is the deeper reason behind Patricia giving Trevor a name with no meaning? A. She didn’t like traditional names B. She didn’t know what the name meant C. She wanted him to escape fate and create his own identity D. She thought names were unimportant → C 13. According to Trevor, what kind of effect do traditional Xhosa names usually have? A. They are just for decoration B. They are often meaningless C. They tend to become self-fulfilling D. They reflect colonial history → C 14. What literary device is mainly used in the idea of names becoming destiny? A. Hyperbole B. Irony C. Symbolism D. Pun → C 15. Trevor’s mother wanted him to be: A. Bound to cultural tradition B. Free to be anyone he wanted C. A preacher D. Another fixer like Mlungisi → B ★ True or False Questions (判断题)（共10题） 16. Trevor’s cousin Mlungisi was known for always creating trouble. → False 17. Velile’s name and personality are both connected to sudden appearances and disappearances. → True 18. Patricia started caring for others when she was already an adult. → False 19. Shebeens were places where children gathered to play and eat. → False 20. Patricia used money she earned at a job to feed other children. → False （她用换瓶子的钱） 21. Trevor’s name has no Biblical or cultural background. → True 22. Patricia believed that names could shape a person’s life. → True 23. Trevor’s mother gave him a name with no meaning because she didn’t care about names. → False 24. Xhosa names often carry strong cultural or symbolic meanings. → True 25. Trevor’s mother gave him a name with no meaning so that he could be free from expectations. → TrueTeenage Lifeteenage life and school vocabularyTeenage Life Across the Globe: Italy, the UK, and the USACreate a quiz about teen life by using these words, 6th grade, 5 questionsoften once opera pool pop music prefer rap music rarely realistic relative respectful rhythm ridiculous sometimes surf the Internet take a bath techno music teen life teenager tradition train trendy twice types of music typical unbearable usually wonderfulThe life of a Roman teenagerHuman life cycle , the stages are: baby, child, teenager and adult