Study: Dinosaurs evolved gigantism over and over again

study
Dinosaurs evolved gigantism over and over again

Dinosaur gigantism has evolved independently much more frequently than previously thought. According to a new study, such giant animals arose in 36 lineages with different characteristics and ecological niches over a period of 100 million years. For his study, Michael D’Emic from Adelphi University in Garden City (US state New York) used measurement data from fossil leg bones, from which he calculated the evolution of the body mass of almost 200 dinosaurs. He presents the results in the journal “Current Biology”.

All of the dinosaurs studied belong to the group of sauropods, which gave rise to such well-known genera as Brontosaurus, Brachiosaurus and Diplodocus. Characteristic of sauropods are a massive body on thick legs, a very long tail and neck with a relatively small head. “It was previously thought that sauropods evolved their extraordinary size independently a number of times in their evolutionary history, but with the new analysis we now know that number is much higher,” D’Emic said in a statement from his university.

As the limit for gigantism, the researcher chose the body mass of the largest mammal that has ever lived on land: the mammoth. “These largest of the largest sauropods were ecologically diverse, had differently shaped teeth and heads, and differently proportioned bodies, indicating they occupied the ‘large body’ niche somewhat differently,” D’Emic said.

There are also no traits that only characterize those sauropods that exceed the size of land mammals, the study author writes. Climate probably plays a minor role in evolution, since there is no relationship between global mean temperature and body mass in sauropods. Hence the new research question of why some lineages developed gigantism while others did not.

dpa