Uncovering the Evolution of Different-Sized Dinosaurs: Researchers Examine Bones for Answers
For centuries, scientists have been perplexed by the evolution of different-sized dinosaurs, from the gigantic T. rex to the smaller Velociraptor. In a recent paper appearing in Science, Ohio University professor Patrick O'Connor and Ph.D. student Riley Sombathy, among other researchers, investigated the bones of non-avialan theropod dinosaurs and concluded that there is no correlation between growth rate and body size. The paper is titled “Developmental strategies underlying gigantism and miniaturization in non-avialan theropod dinosaurs.”
Michael D. D’Emic, a paleontologist at Adelphi University and lead author of the study, and his team of international researchers measured about 500 growth rings in about 80 different theropod bones, the two-legged, mostly meat-eating species of dinosaurs closely related to birds. It was discovered that 31% of theropod species had become larger than their predecessors due to more rapid growth, and 28% due to extended growth. Of the population, 21% experienced a decrease in size compared to their ancestors due to shortened growth spurts, and 19% experienced a decrease due to slowed growth.
“This has really important implications because changes in rate versus timing can correlate to many other things, like how many or how large your offspring are, how long you live, or how susceptible to predators you are,” said D’Emic. It is hoped that this research will motivate further research into other living and extinct species to identify the most significant developmental mechanisms in other animals.
Co-author Thomas Pascucci, whose graduate thesis contributed to the project, highlighted how awe-inspiring prehistoric animals like dinosaurs are due to how different they appear to be from our modern world. “Extinct animals like dinosaurs inspire awe because of how different they seem from those in our modern world, but they were animals that grew under constraints and environmental factors similar to those that exist today,” he said.
Riley Sombathy, Ph.D. student and co-author of the project, hopes to take up some of the investigations. “One of the things that interests me about the results of our project is the apparent decoupling between growth rate and body size,” he said. “My Ph.D. dissertation will investigate the impacts of growth rate and body size on bone shape and function.”
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