Scientists Discover How Some Dinosaurs Grew So Big
2020-12-04
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1Scientists studying the remains of ancient creatures say that large dinosaurs did not grow at the same rate.
2Some dinosaurs grew slowly and steadily.
3Others experienced a growth spurt as they neared adulthood.
4A "growth spurt" is when something or someone grows very quickly.
5For example, children usually have a growth spurt between the ages of 12 and 18.
6The same appears to be true for some dinosaurs!
7The research appeared recently in the Proceedings of the Royal Society B publication.
8To reach their findings, scientists cut through the fossilized bones of dinosaurs.
9They examined the yearly growth rings of the bones from 11 kinds of theropods.
10Theropods are a group of dinosaurs that mainly walked on two legs and include big meat-eating dinosaurs, like tyrannosaurus rex, commonly known as T. rex.
11Reuters news agency reports that this new study provides a look into the lives of some of the most fearsome hunters ever to walk the Earth.
12The research team looked at fossils from museums in the United States, Canada, China, and Argentina.
13They were able to cut into the fossilized bones of one of the world's most famous T. rexes, known as Sue.
14 Sue is housed at the Field Museum in Chicago.
15The researchers used machines to cut into Sue's largest leg bones.
16These bones showed that the T. rex and its relatives - known as tyrannosaurs - have a period of extreme growth during the years before adulthood.
17It also shows that they reached full adult size by around age 20.
18Sue is about 13 meters tall. She is believed to have lived to about 33 years.
19She lived in an area that is modern day South Dakota, a state in the north-central part of the United States.
20Other groups of large theropods had more steady rates of growth over a longer period of time.
21Examples of these include two kinds of North American dinosaurs -- Allosaurus and Acrocanthosaurus.
22Another dinosaur from Antarctica, Cryolophosaurus and a dinosaur recently discovered in Argentina also grew slowly.
23The Argentinian dinosaur has not yet been named, but it was as big as a T. rex.
24This dinosaur did not reach its full adult size until it reached about 40 years of age.
25It is believed to have lived to about age 50.
26Big theropods share the same basic body design.
27They walked on two legs and had large skulls and strong jaws.
28And of course, they had threatening teeth.
29The lead researcher on the study is Tom Cullen.
30He is a paleontologist with the North Carolina Museum of Natural Sciences and North Carolina State University.
31He said that before this study, "it was known that T. rex grew very quickly, but it was not clear if all theropod dinosaurs reached gigantic size in the same way," or if there were many ways they grew so big.
32I'm Anna Matteo.
1Scientists studying the remains of ancient creatures say that large dinosaurs did not grow at the same rate. 2Some dinosaurs grew slowly and steadily. Others experienced a growth spurt as they neared adulthood. A "growth spurt" is when something or someone grows very quickly. For example, children usually have a growth spurt between the ages of 12 and 18. 3The same appears to be true for some dinosaurs! 4The research appeared recently in the Proceedings of the Royal Society B publication. 5To reach their findings, scientists cut through the fossilized bones of dinosaurs. They examined the yearly growth rings of the bones from 11 kinds of theropods. Theropods are a group of dinosaurs that mainly walked on two legs and include big meat-eating dinosaurs, like tyrannosaurus rex, commonly known as T. rex. 6Reuters news agency reports that this new study provides a look into the lives of some of the most fearsome hunters ever to walk the Earth. 7The research team looked at fossils from museums in the United States, Canada, China, and Argentina. They were able to cut into the fossilized bones of one of the world's most famous T. rexes, known as Sue. Sue is housed at the Field Museum in Chicago. 8The researchers used machines to cut into Sue's largest leg bones. These bones showed that the T. rex and its relatives - known as tyrannosaurs - have a period of extreme growth during the years before adulthood. It also shows that they reached full adult size by around age 20. 9Sue is about 13 meters tall. She is believed to have lived to about 33 years. She lived in an area that is modern day South Dakota, a state in the north-central part of the United States. 10Other groups of large theropods had more steady rates of growth over a longer period of time. Examples of these include two kinds of North American dinosaurs -- Allosaurus and Acrocanthosaurus. 11Another dinosaur from Antarctica, Cryolophosaurus and a dinosaur recently discovered in Argentina also grew slowly. 12The Argentinian dinosaur has not yet been named, but it was as big as a T. rex. This dinosaur did not reach its full adult size until it reached about 40 years of age. It is believed to have lived to about age 50. 13Big theropods share the same basic body design. They walked on two legs and had large skulls and strong jaws. And of course, they had threatening teeth. 14The lead researcher on the study is Tom Cullen. He is a paleontologist with the North Carolina Museum of Natural Sciences and North Carolina State University. 15He said that before this study, "it was known that T. rex grew very quickly, but it was not clear if all theropod dinosaurs reached gigantic size in the same way," or if there were many ways they grew so big. 16I'm Anna Matteo. 17Will Dunham reported this story for Reuters news agency. Anna Matteo adapted it for VOA Learning English. Mario Ritter, Jr. was the editor. 18_______________________________________________________________ 19Words in This Story 20steadily -adv. not changing very much over time 21fossilized -adj. tissue that has changed into a mineral underground over time 22paleontologist -n. a scientist who studies fossils of animals that lived a very long time ago 23gigantic -adj. extremely large