Tyrannosaurus rex’s tiny arms have launched a thousand sarcastic memes: I really like you this a lot; are you able to cross the salt?; row, row, row your … oh.
But again off, snarky jokesters. A newfound species of big-headed carnivorous dinosaur with tiny forelimbs suggests these arms weren’t simply an evolutionary punchline. Arm discount — alongside big heads — advanced independently in several dinosaur lineages, researchers report July 7 in Current Biology.
Meraxes gigas, named for a dragon in George R. R. Martin’s “A Song of Ice and Fire” e book collection, lived between 100 million and 90 million years in the past in what’s now Argentina, says Juan Canale, a paleontologist with the nation’s CONICET analysis community who relies in Buenos Aires. Despite the resemblance to T. rex, M. gigas wasn’t a tyrannosaur; it was a carcharodontosaur — a member of a distantly associated, lesser-known group of predatory theropod dinosaurs. M. gigas went extinct almost 20 million years earlier than T. rex walked on Earth.
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The M. gigas particular person described by Canale and colleagues was about 45 years previous and weighed greater than 4 metric tons when it died, they estimate. The fossilized specimen is about 11 meters lengthy, and its cranium is closely ornamented with crests and bumps and tiny hornlets, ornamentations that most likely helped entice mates.
Why these dinosaurs had such tiny arms is an everlasting thriller. They weren’t for looking: Both T. rex and M. gigas used their huge heads to hunt prey (SN: 10/22/18). The arms could have shrunk in order that they had been out of the way in which through the frenzy of group feeding on carcasses.
But, Canale says, M. gigas’ arms had been surprisingly muscular, suggesting they had been extra than simply an inconvenient limb. One risk is that the arms helped raise the animal from a reclining to a standing place. Another is that they aided in mating — maybe displaying a mate some love.