[ti:Study Provides New Details about Teenage T. Rex] [by:www.51星和彩票.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]Scientists say they have discovered new details about young Tyrannosaurus rex dinosaurs. [00:10.16]Researchers examined fossilized skeleton samples [00:14.84]from two small Tyrannosaurus rex – also known as T. rex. [00:22.52]The skeletons were discovered in the western American state of Montana in the early 2000s. [00:31.52]Researchers named the two dinosaurs Jane and Petey. [00:36.92]Each T. rex was estimated to have stood a little taller than a horse and was about twice as long. [00:47.04]The researchers say the fossilized bone samples [00:51.04]have helped them better understand the history and development of this famous dinosaur. [00:58.00]The findings are described in a study recently published in Science Advances. [01:06.56]The examination team was led by Oklahoma State University's Center for Health Sciences. [01:15.64]Holly Woodward was a lead writer of the study. [01:19.60]She said in a statement that it was unusual to study such small fossils from the T. rex family. [01:28.64]This is because researchers usually seek to collect the largest [01:34.48]fossil samples they can find to study and to show in public. [01:41.00]"The problem is that those smaller fossils may be from younger animals," Woodward said. [01:48.76]"So, for a long while we've had large gaps in our understanding [01:54.12]of how dinosaurs grew up, and T. rex is no exception." [02:01.12]The team removed thin pieces from the leg bones of Jane and Petey [02:06.76]and examined the samples under a microscope. [02:11.48]Woodward said the study of the bones' "microstructure" can provide valuable information [02:18.92]about the animals' growth rate, age and metabolism. [02:25.08]Researchers said they were able to use this method to count rings [02:30.20]within the fossil bone to estimate age. [02:34.28]They said Jane lived to be age 13, while Petey was 15. [02:40.20]The size of the blood vessel openings showed the two dinosaurs [02:45.84]were still experiencing growth at a fast rate at the time of death. [02:52.40]It takes a T. rex about 20 years to reach adulthood. [02:57.84]Fossil evidence shows that when fully grown, [03:01.04]the T. rex was about 12 meters long and about 5 meters tall. [03:06.92]The researchers say the samples have already provided [03:12.04]important details about young T. rex's growth and development. [03:18.80]The fossil examinations suggest the small T. rex grew as fast [03:24.56]as modern-day warm-blooded animals such as mammals and birds, the team reported. [03:32.76]The researchers said the findings suggest that the teenage T. rex animals [03:39.04]were very quick on their feet and had knife-like teeth for cutting. [03:45.72]By comparison, the adult T. rex had teeth meant to crush large bones. [03:53.04]The researchers said they found a clear link between T. rex growth rates and the availability of food. [04:01.44]This was discovered in spacing between the yearly growth rings of the fossil bones. [04:10.16]"The spacing between the rings within Jane, Petey, [04:14.80]and even older individuals is inconsistent," Woodward said. [04:20.96]"Some years the spacing is close together, and other years it's spread apart." [04:28.00]This finding suggests the T. rex grew less during years in which food supplies were limited. [04:36.24]If a large supply of food was available, the T. rex experienced far more growth. [04:44.56]Some scientists have questioned whether the two small skeletons really came from a T. rex. [04:52.08]Those scientists said they believed the two represented evidence [04:58.04]of a newfound kind of dinosaur species called Nanotyrannus. [05:04.12]The researchers said they believed Nanotyrannus was similar to T. rex, [05:11.12]but was smaller and showed different skull and bone development. [05:17.92]But Woodward and her team said the latest evidence from the two examined skeletons [05:24.60]suggests they belonged to teenage T rex dinosaurs – not a new species with a smaller body size. [05:34.84]I'm Bryan Lynn. 更多听力请访问51VOA.COM