Girls T.Rex with Flowers T-Shirt

How do scientists tell the age of a dinosaur they've found? Sometimes animal bones, like the trunks of trees, accumulate yearly growth rings. The number of rings tells scientists the age of a specimen; the width reveals whether the animal was still growing. But only certain bones preserve a complete set of growth rings; unfortunately, the large limb bones that survive best as fossils are not among them.

T. rex bones are rare, so scientists knew little about the growth rates and ages of individual animals in this group...until now. Fossil finds over the past 10 years have tripled the number of fairly complete T. rex specimens. From them, scientists have identified bones with readable ring series. Now they can begin to reconstruct T. rex's life history.