Dinosaurs bones, unlike those of humans, kept growing through adulthood.

At a conference of the Society of Vertebrate Paleontology in October, Jack Horner from the Museum of the Rockies in Montana presented new findings on the growth of dinosaur bones bones.

Fully-grown bones should produce a cross-section of tightly packed bone layers – indicative that the bone has ceased adding mass and length. This is the expected pattern in adult dinosaurs.

Close analysis of fossils belonging to young specimens show intricate blood vessel patterns – indicating that this bone was still growing. Horner found similar patterns where they weren’t expected: in adult dinosaurs.

In the past, some paleontologists have classified smaller Tyrannosaurus rex specimens as belonging to a different species than those that were more robust. But every one of Horner’s six T. rex fossils exhibited continued growth, meaning that this ancient beast was constantly getting bigger with age.

Allosaurus, a 150-million-year old meat-eater that weighed 3 tons and measured 40 feet long, revealed particularly surprising results. Allosaurus’ bones were in full growth mode when it met its untimely death.


Kaplan, M. (2013, November 01). T. rex grew beefier than museum fossils suggest. Nature News.

Published On: November 5, 2013

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