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October 30, 2025<\/p>\n
3 min read<\/p>\n
\u2018Dueling Dinosaurs\u2019 Fossil Solves the Mystery of a \u2018Mini T. rex\u2019<\/p>\n
An analysis suggests Nanotyrannus is a separate, smaller dinosaur that lived alongside T. rex, settling a 30-year debate<\/p>\n
By Anirban Mukhopadhyay edited by Sarah Lewin Frasier<\/span><\/p>\n Nanotyrannus appears to be a separate, smaller relative of Tyrannosaurus rex that shared its habitat. This illustration visualizes a Nanotyrannus pack attacking a juvenile T. rex.<\/p>\n For more than three decades, paleontologists have argued over whether a lithe predatory dinosaur called Nanotyrannus ever really prowled Cretaceous North America\u2014or whether the bones that some researchers attributed to the creature instead belonged to teenage examples of Tyrannosaurus rex that were still growing into their monstrous frame. A new study in Nature may have finally settled the score in favor of Nanotyrannus based on an analysis of Montana\u2019s striking \u201cDueling Dinosaurs\u201d fossil, discovered in 2006. The fossil shows a triceratops entwined with a small tyrannosaurlike dinosaur, both with significant injuries.<\/p>\n \u201cSimply put, the Dueling Dinosaur Nanotyrannus is fully grown at half the length and one tenth the body mass of a mature T. rex,\u201d says study co-author Lindsay Zanno, a paleontologist at North Carolina State University. \u201cThere is no scenario in which this animal morphs into a T. rex.\u201d She explains that Nanotyrannus must have been a smaller, sleeker predator that hunted alongside Tyrannosaurus.<\/p>\n Skull of Nanotyrannus lancensis.<\/p>\n North Carolina Museum of Natural Sciences (CC BY-NC-ND)<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n The most definitive evidence comes from a microscopic feature called an external fundamental system\u2014a series of tightly packed growth rings in bone\u2014that suggests the fossilized animal had finished growing, explains study co-author James G. Napoli, a paleontologist at Stony Brook University. Zanno and Napoli argue this confirms Nanotyrannus as a distinct genus alongside T. rex in the ecosystem of the fossil-rich Hell Creek Formation site in Montana, which spanned the last million years of the Cretaceous.<\/p>\n Using high-resolution scans, the team also found the Nanotyrannus skull contained more tooth sockets than a T. rex of any age and different routes for cranial nerves and sinuses than T. rex exhibits. These features would have been established early in embryonic development and remain fixed for life.<\/p>\n The researchers conducted a computer-based evolutionary analysis, which positioned Nanotyrannus in a new clade just outside the T. rex line. This clade, called Nanotyrannidae, may have originated in eastern North America.<\/p>\n The N. lancensis specimen from the Dueling Dinosaurs fossil included the first complete tail of the Nanotyrannus genus to be found.<\/p>\n North Carolina Museum of Natural Sciences (CC BY-NC-ND)<\/p>\n Additionally, the team compared the Dueling Dinosaurs specimen with two earlier finds that were also made in Montana\u2019s Hell Creek Formation\u2014a skull unearthed by a team from the Cleveland Museum of Natural History (CMNH) that first defined Nanotyrannus and a fossil called \u201cJane\u201d that was discovered by a team from the Burpee Museum of Natural History. In doing so, Zanno and Napoli formalized the names of these specimens: They confirmed the Dueling Dinosaurs fossil represented the same species as the CMNH skull, which was named Nanotyrannus lancensis in 1988. And they described Jane as a new species, Nanotyrannus lethaeus.<\/p>\n That picture builds on hints noted decades ago by paleontologist Philip J. Currie, who co-authored the 1988 paper that first named Nanotyrannus. Currie says he still points to Nanotyrannus\u2019s higher tooth counts as a definitive difference from T. rex. Thomas R. Holtz, Jr., a paleontologist at the University of Maryland, who was not part of the new paper, observes that such pairing isn\u2019t unprecedented\u2014Asia\u2019s tyrannosaur Tarbosaurus lived beside the smaller tyrannosaur Alioramus, with the two splitting the menu between giant and fleet-footed prey.<\/p>\n A comparison of the arms of Nanotyrannus and T. rex.<\/p>\n North Carolina Museum of Natural Sciences (CC BY-NC-ND)<\/p>\n Long-time advocates of the juvenile T. rex hypothesis, though acknowledging the strong evidence in the new paper, aren\u2019t yet ready to rewrite the family tree of T. Rex and its kin. Stephen Brusatte, an evolutionary biologist at the University of Edinburgh, who was not involved in the study, asks, \u201cIf every small skeleton is Nanotyrannus, where are the juvenile T. rexes?\u201d Paleontologist Thomas Carr of Carthage College, who was also not part of the research, argues that skeletal maturity alone doesn\u2019t define a species. Without more small T. rex fossils, he says, distinguishing growth from evolution remains difficult.<\/p>\n Nevertheless, Nanotyrannus adds a fresh dimension to the final days of the dinosaurs. Rather than a one-species monopoly under T. rex, the Hell Creek landscape may have hosted a tiered guild of hunters. Zanno calls the next challenge \u201ca completely new question\u201d for research on tyrannosaurs and their relatives: understanding how Nanotyrannus and Tyrannosaurus coexisted, avoided competition and shaped the evolution of their prey. Napoli says the findings challenge decades of interpreting these littler dinosaurs as juvenile T. rexes. \u201cNow that we\u2019ve corrected the record on Nanotyrannus, we think it\u2019s possible that other smaller tyrannosaur fossils are misidentified and that there may be many more species awaiting recognition.\u201d<\/p>\n If you enjoyed this article, I\u2019d like to ask for your support. 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I hope you\u2019ll support us in that mission.<\/p>\n","protected":false},"excerpt":{"rendered":" October 30, 2025 3 min read \u2018Dueling Dinosaurs\u2019 Fossil Solves the Mystery of a \u2018Mini T. rex\u2019 An analysis suggests Nanotyrannus is a separate, smaller dinosaur that lived alongside T. rex, settling a 30-year debate By Anirban Mukhopadhyay edited by Sarah Lewin Frasier Nanotyrannus appears to be a separate, smaller relative of Tyrannosaurus rex that<\/p>\n","protected":false},"author":1,"featured_media":31685,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[10389,257,18413,18412,1392,18414],"class_list":{"0":"post-31684","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-dinosaur","9":"tag-isnt","10":"tag-juvenile","11":"tag-nanotyrannus","12":"tag-separate","13":"tag-trexits"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/31684","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=31684"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/31684\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/31685"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=31684"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=31684"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=31684"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}On supporting science journalism<\/h2>\n
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