Study Provides New Details about Teenage T. Rex
2020-01-06
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1Scientists say they have discovered new details about young Tyrannosaurus rex dinosaurs.
2Researchers examined fossilized skeleton samples from two small Tyrannosaurus rex - also known as T. rex.
3The skeletons were discovered in the western American state of Montana in the early 2000s.
4Researchers named the two dinosaurs Jane and Petey.
5Each T. rex was estimated to have stood a little taller than a horse and was about twice as long.
6The researchers say the fossilized bone samples have helped them better understand the history and development of this famous dinosaur.
7The findings are described in a study recently published in Science Advances.
8The examination team was led by Oklahoma State University's Center for Health Sciences.
9Holly Woodward was a lead writer of the study.
10She said in a statement that it was unusual to study such small fossils from the T. rex family.
11This is because researchers usually seek to collect the largest fossil samples they can find to study and to show in public.
12"The problem is that those smaller fossils may be from younger animals," Woodward said.
13"So, for a long while we've had large gaps in our understanding of how dinosaurs grew up, and T. rex is no exception."
14The team removed thin pieces from the leg bones of Jane and Petey and examined the samples under a microscope.
15Woodward said the study of the bones' "microstructure" can provide valuable information about the animals' growth rate, age and metabolism.
16Researchers said they were able to use this method to count rings within the fossil bone to estimate age.
17They said Jane lived to be age 13, while Petey was 15.
18The size of the blood vessel openings showed the two dinosaurs were still experiencing growth at a fast rate at the time of death.
19It takes a T. rex about 20 years to reach adulthood. Fossil evidence shows that when fully grown, the T. rex was about 12 meters long and about 5 meters tall.
20The researchers say the samples have already provided important details about young T. rex's growth and development.
21The fossil examinations suggest the small T. rex grew as fast as modern-day warm-blooded animals such as mammals and birds, the team reported.
22The researchers said the findings suggest that the teenage T. rex animals were very quick on their feet and had knife-like teeth for cutting.
23By comparison, the adult T. rex had teeth meant to crush large bones.
24The researchers said they found a clear link between T. rex growth rates and the availability of food.
25This was discovered in spacing between the yearly growth rings of the fossil bones.
26"The spacing between the rings within Jane, Petey, and even older individuals is inconsistent," Woodward said.
27"Some years the spacing is close together, and other years it's spread apart."
28This finding suggests the T. rex grew less during years in which food supplies were limited.
29If a large supply of food was available, the T. rex experienced far more growth.
30Some scientists have questioned whether the two small skeletons really came from a T. rex.
31Those scientists said they believed the two represented evidence of a newfound kind of dinosaur species called Nanotyrannus.
32The researchers said they believed Nanotyrannus was similar to T. rex, but was smaller and showed different skull and bone development.
33But Woodward and her team said the latest evidence from the two examined skeletons suggests they belonged to teenage T rex dinosaurs - not a new species with a smaller body size.
34I'm Bryan Lynn.
1Scientists say they have discovered new details about young Tyrannosaurus rex dinosaurs. 2Researchers examined fossilized skeleton samples from two small Tyrannosaurus rex - also known as T. rex. The skeletons were discovered in the western American state of Montana in the early 2000s. 3Researchers named the two dinosaurs Jane and Petey. Each T. rex was estimated to have stood a little taller than a horse and was about twice as long. 4The researchers say the fossilized bone samples have helped them better understand the history and development of this famous dinosaur. The findings are described in a study recently published in Science Advances. 5The examination team was led by Oklahoma State University's Center for Health Sciences. 6Holly Woodward was a lead writer of the study. She said in a statement that it was unusual to study such small fossils from the T. rex family. This is because researchers usually seek to collect the largest fossil samples they can find to study and to show in public. 7"The problem is that those smaller fossils may be from younger animals," Woodward said. "So, for a long while we've had large gaps in our understanding of how dinosaurs grew up, and T. rex is no exception." 8The team removed thin pieces from the leg bones of Jane and Petey and examined the samples under a microscope. Woodward said the study of the bones' "microstructure" can provide valuable information about the animals' growth rate, age and metabolism. 9Researchers said they were able to use this method to count rings within the fossil bone to estimate age. They said Jane lived to be age 13, while Petey was 15. The size of the blood vessel openings showed the two dinosaurs were still experiencing growth at a fast rate at the time of death. 10It takes a T. rex about 20 years to reach adulthood. Fossil evidence shows that when fully grown, the T. rex was about 12 meters long and about 5 meters tall. 11The researchers say the samples have already provided important details about young T. rex's growth and development. The fossil examinations suggest the small T. rex grew as fast as modern-day warm-blooded animals such as mammals and birds, the team reported. 12The researchers said the findings suggest that the teenage T. rex animals were very quick on their feet and had knife-like teeth for cutting. By comparison, the adult T. rex had teeth meant to crush large bones. 13The researchers said they found a clear link between T. rex growth rates and the availability of food. This was discovered in spacing between the yearly growth rings of the fossil bones. 14"The spacing between the rings within Jane, Petey, and even older individuals is inconsistent," Woodward said. "Some years the spacing is close together, and other years it's spread apart." This finding suggests the T. rex grew less during years in which food supplies were limited. If a large supply of food was available, the T. rex experienced far more growth. 15Some scientists have questioned whether the two small skeletons really came from a T. rex. Those scientists said they believed the two represented evidence of a newfound kind of dinosaur species called Nanotyrannus. The researchers said they believed Nanotyrannus was similar to T. rex, but was smaller and showed different skull and bone development. 16But Woodward and her team said the latest evidence from the two examined skeletons suggests they belonged to teenage T rex dinosaurs - not a new species with a smaller body size. 17I'm Bryan Lynn. 18Bryan Lynn wrote this story for VOA Learning English, based on reports from Agence France-Presse, Oklahoma State University and Science Advances. Ashley Thompson was the editor. 19We want to hear from you. Write to us in the Comments section, and visit our Facebook page. 20________________________________________________________________ 21Words in This Story 22gap - n. an empty period between things happening 23metabolism - n. the chemical processes by which a plant or an animal uses food and water to grow and heal and to make energy 24mammal - n. a kind of animal that feeds milk to its young and that usually has hair or fur covering most of its skin 25inconsistent - adj. not staying the same in quality or behavior 26skull - n. the bones of the head that surround the brain