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In the latest sequence of a long - standing debate over the identity of a set of dinosaur fossils , a controversial unexampled study has found that the dino pearl belong not to a youngTyrannosaurus rexbut to a separate specie : Nanotyrannus lancensis .
In the decades since the first skull was discovered in Montana in 1942,paleontologists have blend in back and forthon whether the skull andlater fossil discoveriesbelong to a distinct species or to juvenileT. Rex .
An adultNanotyrannus lancensisattacking a youngTyrannosaurus rex.
The authors of the young subject , published Wednesday ( Jan. 3 ) in the journalFossil Studies , claim to have snuffed out the babyT. rexhypothesis once and for all — although other expert are n’t convinced .
" I was very skeptical aboutNanotyrannusmyself until about six years ago when I took a close expression at the fossils and was surprised to realize we ’d get it faulty all these years , " conduce authorNicholas Longrich , a paleontologist and senior lecturer at the University of Bath in the U.K. , said in astatement . " When I see these results I was pretty blown away . "
Longrich and co - authorEvan Saitta , a paleontologist at the University of Chicago and research comrade at Chicago ’s Field Museum of Natural History , value increase rings on the dodo and found they were closely packed towards the outside of the ivory . This pattern is inconsistent with the rapid growing of a young dinosaur and intimate outgrowth was slowing and the dinosaur was strive its full size when it died .
The skull of an adultTyrannosaurus rexcompared to a skull thought by some paleontologists to belong to a distinct species,Nanotyrannus lancensis.
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" If they were youngT. rexthey should be growing like unhinged , putting on hundreds of kilogram a yr , " Longrich said . When the researchers modeled the increment of the fossils , they regain that the dinosaur would have reached just 15 % the size of a matureT. rex , weighing around 2,000 to 3,300 pounds ( 900 to 1,500 kilograms ) and measuring 16 substructure ( 5 meters ) long . In comparison , an adultT. rexwas about 17,600 pounds ( 8,000 kg ) and stretched 30 feet ( 9 m ) in length .
The research worker also reconstructed the dinosaur ’s anatomy and institute it share no distinctive features with an adultT. male monarch — which it probably would have done if it was a youngT. rex , " in the same way that kitten bet like cat-o'-nine-tails and puppies await like click , " Longrich said . " It could be growing in a way that ’s completely unlike any other tyrannosaurus , or any dinosaur — but it ’s more potential it ’s just not aT. king . "
Young juvenileT. rexfrontal skull bone from the Hell Creek of Montana.
The reconstruction also did n’t match other fossils of a youngT. rexthat did share features with adultT. king , the researchers say . UnlikeT. rex , the dinosaur had a light build , long limbs and large arm that would have been " pretty formidable weapons , " Longrich said . " It ’s really just a completely dissimilar animal , " he bestow .
But other experts are n’t support the idea that the fossils belong toNanotyrannus . " The article does n’t settle the question at all,“Thomas Carr , a vertebrate paleontologist and an associate professor of biology at Carthage College in Wisconsin , told Live Science in an email . " The authors do n’t seem to have a firm hold on growth variance in tyrannosaurs . "
In 2020 , Carr foundmore than 1,800 differencesbetween juvenile and adultT. Rex — considerably more than the over 150 differences emphasize in the new study , he said . " We should await that magnitude of differences between juveniles and adults , " he added .
Opponents to theNanotyrannustheory say the skulls of these dinosaur have alone features only seen inT. rex — including a wide frontal bone and narrow snout , Carrpreviously order Live Science .
Thomas Holtz , a main lecturer in vertebrate paleontology at the University of Maryland , is also disbelieving . " Ultimately , the key fossils require to finalise this — fully adultNanotyrannusthat are notTyrannosaurus , or 11 [ to ] 13 twelvemonth oldTyrannosaurusthat are definitely notNanotyrannus — have n’t been fall upon , " he told Live Science in an e-mail .
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And so the saga continues , saidDavid Hone , a paleontologist and reader in zoological science at Queen Mary University of London . " There ’s a cluster of old estimate resurface [ in the new survey ] that are n’t any more convincing than they were before , and there ’s some new ideas which mostly are n’t very convincing either , " Hone told Live Science in an electronic mail .
Currently , onlyT. rexis recognized in theTyrannosaurusgenus , but Hone suggestedNanotyrannusor another set of fossils could essay to be a 2nd , closely related species in the genus . He and other paleontologists are " happy with the mind that there might be more than one metal money , " Hone said . " It is rum in some ways thatTyrannosaurusis apparently a uniquely big predator in its ecosystem , " he enounce .
The find of a 2nd species in the genus " might fill some break and explain away some mutual exclusiveness , " he added . " But that was always proceed to have to be with some really convincing disputation that overturn a lot of ideas and data that citizenry have been progress for year , even ten . "
