A new study provides new insights into how sauropods, the largest animals ever to have existed, achieved their massive sizes. Through measuring hundreds of weight-bearing bones and mapping reconstructed body masses of nearly 200 sauropod species, the study concluded that these super-giants evolved their unrivaled sizes multiple times, defying the popular 19th-century “Cope’s Rule” and suggesting sizes were dictated by ecological context and available niches.
The evolutionary process behind the remarkable size of super-giant Sauropods.
Sauropods, which encompass renowned dinosaurs with elongated necks such as Brachiosaurus and Apatosaurus, were the most massive animals to have ever roamed the earth. No other dinosaur or land mammal even comes close. A recent study from Adelphi University now offers insight into the gradual process through which these colossal titans attained their record-breaking sizes over time.
“It was previously thought that sauropods evolved their exceptional sizes independently a few times in their evolutionary history, but through a new analysis, we now know that this number is much higher, with around three dozen instances over the course of 100 million years around the globe,” said paleontologist Michael D’Emic, assistant professor of biology at Adelphi University in New York and author of the study which was recently published in the journal
To investigate sauropod body size evolution, D’Emic compiled measurements of the circumferences of hundreds of weight-bearing bones, correlated with the weight of the animal they belonged to. He then used a technique called ancestral state reconstruction to map the reconstructed body masses of nearly 200 sauropod The results show that sauropods reached their exceptional sizes early in their evolution and that with each new sauropod family to evolve, one or more lineages independently reached superlative status.
The evolutionary tree of sauropod dinosaurs showing their body masses projected onto geologic time. Each branch represents a species. Species that evolved body masses greater than any other animal that lived on land are highlighted in red. Silhouettes are positioned at the body masses of the largest sauropod, mammoth-like mammal, rhinoceros-like mammal, duck-billed dinosaur, and carnivorous dinosaur. Credit: Silhouettes by Scott Hartman, Nobu Tamura (vectorized by T. Michael Keesey), Steven Traver.
“Before going extinct with the other dinosaurs (besides birds) at the end of the
Untangling why certain lineages evolved their super-giant sizes while other ones didn’t will be the next step in the research.
Reference: “The evolution of maximum terrestrial body mass in sauropod dinosaurs” by Michael Daniel D’Emic, 8 May 2023, Current Biology.
DOI: 10.1016/j.cub.2023.02.067