In paragraph 13, what did the author mean by the metaphor, "crocodilians are a living bridge to the age of dinosaurs?

crocodiles and alligators both existed at the same time as dinosaurs

crocodiles, alligators, and dinosaurs can live to age 100 or more

crocodiles and alligators lay eggs just like dinosaurs

crocodiles, alligators, and dinosaurs are all reptiles

In paragraph 1, what is the definition of the word crocodilians?

group of reptiles that includes crocodiles and alligators

a group of reptiles whose noses are shaped like a "U"

any group of reptiles whose teeth stick out

any group of cold-blooded animals that has a backbone and is covered in scales

Which sentence tells why Modern Dinosaurs is a good title for the passage?

crocodilians were on earth at the same time as dinosaurs

these water-lovers make up a group of animals called crocodilians

the alligator and the crocodile are very much alike

alligators and crocodiles haven't changed much over the years

What three characteristics do crocodiles and alligators have in common?

powerful tails, scaly skin, and webbed feet

cold-blooded, lay eggs, and V shaped noses

cold-blooded, lays eggs, and greyish black skin

powerful tails, scaly skin, and "U" shaped noses

Modern Dinosaurs Part 3

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.”

Modern Dinosaurs Part 1

Jack-o-Lanterns What Is a Jack-o'-Lantern? Carved pumpkins are called jack-o'- lanterns. Jack-o'-lanterns are used to decorate for Halloween. People started carving jack-o'-lanterns more than a hundred years ago. At first, people didn't carve pumpkins. They used other vegetables instead. An old fable from Ireland may tell how people began carving jack-o'-lanterns. The fable is about a man named Stingy Jack, who liked to play tricks on everyone. When he died, he was cursed to walk in darkness forever. He carved a turnip and put a light inside. His ghost was known as "Jack of the Lantern," and then "Jack-o'-lantern." Modern Jack-o'-Lanterns The Stingy Jack fable later became part of a night called All Hallows' Eve. In Europe, people lit fires and dressed up to keep away ghosts. In Ireland and England, people carved scary faces on vegetables and placed a light inside. All Hallows' Eve later became known as Halloween. When jack-o'-lantern carving was brought to the United States, people started using pumpkins. About 1.5 billion pounds (more than 680 million kg) of pumpkins are grown in the United States each year. Carving Jack-o'-Lanterns Carving pumpkins is fun for people of all ages. Smooth pumpkins work well for jack-o'-lanterns. Some people buy carving kits, while others carve without any help. First, with help from a parent, cut a hole in the top of the pumpkin to make a lid. Next, scoop out the inside flesh and seeds. Draw a design on the pumpkin, and then carve it carefully. After the pumpkin is carved, place a candle or other light inside. Finally, put the pumpkin lid back on toр. Jack-o'-Lantern Events Many cities have events to show off their carved pumpkins. In Hudson Valley, New York, jack-o'-lanterns make up a big display with spooky sounds and music. Pumpkins are used to make snakes, dinosaurs, and a dome carved with twinkling stars. A huge display in Los Angeles, California, has pumpkin cars and dinosaurs, and pumpkin carvings of famous people. The artists carve their pumpkins at the event while people watch. A town in New Hampshire broke a world record for the most lit jacko'-lanterns. The town had thirty thousand jack-o'-lanterns lit at once! The Tradition Continues. Carving pumpkins into jack-o'- lanterns is a fun holiday activity. However they are carved, jack-о'- lanterns are a sure sign that Halloween is around the corner.

Modern Dinosaur Part 2

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