Paleontologists have conducted the largest analysis of the fossil bone structure of a Tyrannosaurus rex and discovered evidence that these ancient predators continued to grow for about 40 years after birth, calling into question previous theories about the reptile's rapid and short-term development.
The scientists' findings were published in an article in the scientific journal PeerJ.
Professor Jack Horner of Chapman University (USA) said: “Four decades of continuous growth allowed young tyrannosaurs to occupy a large number of ecological niches and fulfill many roles in the environments in which they grew up. This likely explains how they achieved their position as dominant predators in the late Cretaceous period.”
In recent years, paleontologists have actively debated what newborn tyrannosaur babies looked like and how quickly they grew. Some scientists believe, based on the structure of the “growth rings” in the bones of tyrannosaurs, that these ancient predators could increase in size very quickly during their first years of life, but then their growth rate slowed down. Others suggest that tyrannosaurs developed slowly over decades of their lives.
Scientists discovered evidence supporting the second hypothesis in a comprehensive study of the bones of 17 tyrannosaurid species, including both very young individuals and full-grown adult predators. Previously, as scientists note, researchers have estimated tyrannosaur growth rates based only on the bones of reptiles of only one age range, which could have skewed the measurements.
American paleontologists have overcome this deficiency and studied “growth rings” in the bones of young and adult royal tyrannosaurs using four different techniques. Scientists then analyzed the results of these measurements using a new statistical method that takes into account age-related differences in dinosaur bone structure and constructed a mathematical graph that reflects the growth rates of these ancient predators.
These calculations show that tyrannosaurs grew much more slowly than scientists had previously assumed: they reached their eight-ton mass and typical adult size not 25 years after birth but at the end of their fourth decade of life. This, the scientists concluded, significantly changes scientists' understanding of the role that young, medium-sized tyrannosaurids played in ecosystem functioning during the late Mesozoic period.
About the tyrannosaur
The royal tyrant dinosaur (Tyrannosaurus rex) was the largest predator at the end of the Cretaceous period living in future North America and many other regions of the world. Over the past two decades, their supposed appearance has changed radically as scientists discovered that these lizards were warm-blooded creatures and that many close relatives of the Tyrannosaurus rex also had feathers.
