{"source_url": "https://www.newscientist.com", "url": "https://www.newscientist.com/article/2228746-tiny-t-rex-fossils-arent-a-new-species-they-are-just-teenagers/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home", "title": "Tiny T. rex fossils aren't a new species - they are just teenagers", "top_image": "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg", "meta_img": "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg", "images": ["https://images.newscientist.com/wp-content/uploads/2015/08/ns-logo-for-featured-image.jpg?width=800", "https://www.newscientist.com/wp-content/themes/new-scientist/assets/img/logo.svg", "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg"], "movies": [], "text": "The dinosaur formerly known as Nanotyrannus Friedrich Saurer/Alamy\n\nSometimes the simplest explanation is the right one. Two controversial dinosaur skeletons have been held up as evidence that Tyrannosaurus rex shared its environment with a second, tiny species of tyrannosaur. Now, a detailed study of the fossilised leg bones suggests the diminutive dinos are really just teenage T. rexes.\n\nThe two skeletons, one nearly complete, were discovered in the early 2000s in rocks known as the Hell Creek Formation, which spans Montana, Wyoming and North and South Dakota. The formation also yielded some of the first T. rex bones, early in the 20th century.\n\nThe more complete specimen is nicknamed Jane, and the other is nicknamed Petey. Along with one other small skull found in 1942, they have been used to argue for a new type of dinosaur called Nanotyrannus, which was like a T. rex but smaller.\n\nAdvertisement\n\nAs researchers performed more detailed analysis of the specimens, it seemed more and more likely that the small predators were simply young T. rexes, but there was still some disagreement. The newest analysis by Holly Woodward at Oklahoma State University and her colleagues may be the final nail in the coffin of Nanotyrannus.\n\nRead more: T. rex evolved into a monster predator by dumbing down its brain\n\nAll modern vertebrates have a period every year where bone growth briefly pauses. We don\u2019t know exactly why this happens, but it leaves a circle in every bone that shows when the growth stopped, Woodward says. \u201cWe can just count the rings like with a tree to find the dinosaur\u2019s age.\u201d\n\nWoodward and her team counted the rings in Jane and Petey\u2019s femurs and tibias. They found that Jane was probably around 13 years old and Petey about 15 when they died. Other fossils such as Sue, one of the largest and most complete T. rex skeletons we\u2019ve found, have shown that T. rexes lived to around 30, so that makes Jane and Petey adolescents. Because they are so young, there is no need to invoke a whole new species to explain their small size.\n\n\u201cWe know the T. rex as this giant king of dinosaurs,\u201d says Woodward. \u201cBut it didn\u2019t start that way, and we didn\u2019t know much about how it got from baby T. rex-sized\u2026 to Sue-sized.\u201d\n\nAt a little more than half Sue\u2019s 12.3-metre body length, these young dinos are starting to fill in that gap.\n\nJournal reference: Science Advances, DOI: 10.1126/sciadv.aax6250", "keywords": [], "meta_keywords": ["tyrannosaurus rex", "t. Rex", "dinosaurs", "nanotyrannus", "fossils", "Sue", "bones"], "tags": [], "authors": ["Leah Crane"], "publish_date": null, "summary": "", "article_html": "", "meta_description": "A handful of unusually small tyrannosaur fossils are not evidence of a new species \u2013 they simply show us what adolescent T. rexes looked like", "meta_lang": "en", "meta_favicon": "/wp-content/themes/new-scientist/img/layup/new-sci-favicon.ico", "meta_data": {"viewport": "width=device-width, initial-scale=1.0, maximum-scale=1.5", "thumbnail": "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg", "p": {"domain_verify": "c64e8f4ac4f50bca3404abba4882a79d"}, "og": {"locale": "en_US", "type": "article", "title": "Tiny T. rex fossils aren't a new species - they are just teenagers", "url": "https://www.newscientist.com/article/2228746-tiny-t-rex-fossils-arent-a-new-species-they-are-just-teenagers/", "site_name": "New Scientist", "description": "A handful of unusually small tyrannosaur fossils are not evidence of a new species \u2013 they simply show us what adolescent T. rexes looked like", "image": "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg"}, "twitter": {"card": "summary", "creator": "@newscientist", "site": "@newscientist", "image": "https://images.newscientist.com/wp-content/uploads/2020/01/31114325/e67pt5.jpg", "description": "A handful of unusually small tyrannosaur fossils are not evidence of a new species \u2013 they simply show us what adolescent T. rexes looked like", "title": "Tiny T. rex fossils aren't a new species - they are just teenagers | New Scientist"}, "news_keywords": "tyrannosaurus rex,t. rex,dinosaurs,nanotyrannus,fossils,sue,bones", "author": "Leah Crane", "description": "A handful of unusually small tyrannosaur fossils are not evidence of a new species \u2013 they simply show us what adolescent T. rexes looked like", "keywords": "tyrannosaurus rex, t. 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