The Dueling Dinosaurs Thriller May Have Been Solved — The Child T. rex Was Instead a Nanotyrannus

In the badlands of Montana, time doesn’t go a lot as settle. Beneath layers of sandstone and historic river mud, two dinosaurs — a horned Triceratops and a smaller, sharp-toothed predator — entombed collectively for the reason that ultimate days of the Cretaceous. To paleontologists, the fossilized pair, often known as the “Dueling Dinosaurs,” was each a spectacle and a riddle: Was the smaller skeleton a younger Tyrannosaurus rex, or one thing else totally?

Now that thriller has been answered. New analysis revealed in Nature reveals that the smaller predator wasn’t a juvenile T. rex in any respect, however a completely grown Nanotyrannus lancensis — a species that rewrites the tyrant’s household story.

“This fossil doesn’t just settle the debate. It flips decades of T. rex research on its head,” mentioned Lindsay Zanno, co-author of the research, in a press release.

Read More: The Tyrannosaurus Rex Origin Story May Not Have Started in North America

Juvenile T. rex, or Nanotyrannus lancensis?

For over a century, T. rex has been the celeb of paleontology — a mannequin organism for learning dinosaur biology, from feeding and locomotion to progress and life historical past. But that fame, consultants say, might have blinded science to a vital fact hiding in plain sight.

“For Nanotyrannus to be a juvenile T. rex, it would need to defy everything we know about vertebrate growth,” mentioned James Napoli, co-author of the research. “It’s not just unlikely — it’s impossible.”

The discovering forces a re-examination of a long time of T. rex analysis. Many research on progress, feeding, and biomechanics might have unknowingly mixed two separate animals — species that truly lived facet by facet within the final million years earlier than the asteroid influence.

Paleontology’s Fiercest Feud

To guarantee their outcomes may stand up to shut scrutiny, Zanno and Napoli carried out an exceptionally detailed research of the fossil’s bone tissue — among the many most complete histological investigations ever utilized to a tyrannosaur. Thin-section evaluation revealed progress rings marking about 20 years of life, displaying the animal had already reached maturity by the point it died.

The anatomy instructed a fair clearer story. The dinosaur’s mouth held noticeably extra tooth than a typical T. rex, and its forelimbs — significantly the arms — have been proportionally and completely longer than these of even the most important tyrant lizards, in accordance with Nature. For such options to remodel into these of T. rex, its limbs must shorten, and tooth would want to vanish throughout progress — a sample just about unprecedented in vertebrate evolution. Together, these particulars, together with different refined skeletal distinctions, made the argument decisive.

While evaluating greater than 200 tyrannosaur specimens, the researchers additionally revisited the well-known “Jane” skeleton, figuring out that it was nonetheless rising but destined to stay far smaller than an grownup T. rex. On the premise of these findings, they named a brand new species, Nanotyrannus lethaeus — a tribute to the mythic River Lethe, for a way this predator’s identification was forgotten for generations.

Their phylogenetic evaluation locations Nanotyrannus simply past the core Tyrannosauridae lineage, hinting at a extra intricate evolutionary tree of apex hunters flourishing within the final days earlier than the dinosaurs vanished.

Rival Predators within the Shadow of Extinction

The findings recommend that, even within the planet’s ultimate million years earlier than the asteroid strike, tyrannosaurs have been radiating into new types slightly than fading away.

“This discovery paints a richer, more competitive picture of the last days of the dinosaurs,” Zanno mentioned within the press launch. “With enormous size, a powerful bite force, and stereoscopic vision, T. rex was a formidable predator — but it did not reign uncontested. Darting alongside was Nanotyrannus — a leaner, swifter, more agile hunter.”

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