'Bone scars' reveal the varied growth of dinosaur cousins

Focusing on fossils from a dog-sized cousin of the dinosaurs, paleontologists have learned more about the variable growth patterns between individuals of an ancient species.

The researchers focused their analysis on 27 femur bones from a reptilian species called Asilisaurus kongwe, which lived about 240 million years ago and predated dinosaurs by about 10 million years. What they learned sheds new light about the variable ways that these creatures grew into adults.

The scientists studied bone scars, which result from where muscle connected to bone, to learn more about how the species grew. The bones scars increase in number and size as an animal ages.

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Christopher Griffin, a master’s student at Virginia Tech and the lead author of the paper announcing the results in the Journal of Vertebrate Paleontology, said that what they learned was that these animals varied in their growth orders and size— for example, a larger individual might not have necessarily been older, or two animals that were about the same size might not have been the same age. The creatures also can’t be cleanly divided by body type and gender into two different groups.

“It was arranged along a spectrum, where the very smallest individuals were immature, and the very largest were mature, but there’s this big grey area in the middle, where there’s lots and lots of variation based on the different ways these things grow,” Griffin told FoxNews.com.

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In fact, Griffin said, individual Asilisaurus kongwe— which probably didn’t weigh any more than 65 pounds— may have even been more varied in their growth than modern-day relatives like birds.

The study has implications for scientists’ understanding of the growth of dinosaurs, and provided important data because of the large number of bones the scientists could study.

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“We have this amazing sample size of a close dinosaur relative,” Griffin added. “And because of that, if we see similar things in early dinosaurs, we can use this Asilisaurus, with a much better sample size, a much wider range of differently-sized individuals, as kind of a lens to interpret similar variation in its close relatives.”