A fresh analysis of fossil records suggests that dinosaurs defied an ecological rule known as Bergmann's rule.
The Nanuqsaurus depicted living in a cold environment. Image Source: Nobu Tamura via Wikimedia Commons
The rule was proposed by German biologist Carl Bergmann in 1847. Bergmann's rule suggests that the size of animals increases with latitude or altitude, meaning animals living in colder regions tend to be larger than those in warmer regions. This rule is most applicable to birds and mammals.
For example, the largest penguins inhabit Antarctica. Moving northward, penguins tend to be smaller on average, such as the Magellanic penguin. The Galápagos penguin, residing on the Galápagos Islands, is one of the smallest penguin species globally and also the northernmost penguin species, near the equator.
A similar pattern can even be observed in humans, with taller individuals often found in higher latitude regions like the Scandinavian Peninsula and Northern Europe.
A new paper published on April 5th in "Nature Communications" suggests that this rule isn't always applicable.
"Our research indicates that the evolution of different body sizes in dinosaurs and mammals cannot simply be attributed to latitude or temperature," said Lauren Wilson, lead author of the paper and a graduate student at the University of Alaska Fairbanks.
"We found that Bergmann's rule only applies to a small subset of endotherms and only when considering temperature, ignoring all other climate variables. This suggests that Bergmann's 'rule' is actually an exception rather than a rule."
The study encompassed hundreds of data points, including the northernmost dinosaur discovered, with fossils found in the Prince Creek Formation in northern Alaska. Analysis showed no significant size variation related to latitude.
Researchers then conducted similar analyses on modern mammals and birds, yielding comparable results.
Pat Druckenmiller, co-author of the paper and assistant professor in the Department of Geology at the University of Alaska Fairbanks, stated that ecological rules should apply to ancient organisms just as they do to modern ones. "You can't understand them if you ignore the evolutionary roots of modern ecosystems. You have to look back to understand how things got to be the way they are today."
"Fossil records provide a window into observing entirely different ecosystems and climate conditions, allowing us to evaluate the applicability of these ecological rules in an entirely new way," added Jacob Gardner, co-author of the paper and postdoctoral researcher at the University of Reading, UK.
For more information, refer to the related paper: https://doi.org/10.1038/s41467-024-46843-2
