With their 18-centimeter (7-inch) toothy remnants, ancient sharks put the “mega” in Odontus megalodon, suggesting they were likely at least 15 meters (50 feet) long (but we still don’t know what they looked like). A new study published in Historical Biology proposes an explanation for why megatooth sharks became so huge, proposing that cooler waters may have been a factor. While icy ancient waters may appear to be a difficult environment in which to thrive, the link with larger body size is due to the fact that creatures require greater bulk to survive the frigid circumstances.
“Larger body size boosts an animal’s capacity to retain body heat more efficiently by decreasing heat loss,” Kenshu Shimada, a paleobiology professor at DePaul University in Chicago, told IFLScience. “As a result, such creatures will be able to remain metabolically active in cooler waters.” According to Shimada and colleagues, Megalodon’s gigantic body size may have been controlled by its topography, which follows an ecological pattern known as “Bergmann’s rule.” The hypothesis that enormous size is an adaptation to cooler climes in enhancing an animal’s capacity to remain warm was first proposed by German scientist Carl Bergmann in the mid-1800s.
If this is the case with O. megalodon, it suggests that lesser megatooths existed in warmer seas, but the supersized species were restricted to the ocean’s cooler regions. In a statement, Shimada noted, “The fundamental finding of our study is that not all geographically varied Megalodon individuals developed to giant sizes equally.” “The widely held belief that the species reached 18–20 m TL should be limited to groups that lived in milder climates.”
Megalodon nursery sites had previously been proposed as explanations for collections of smaller-than-average teeth, but the researchers discovered that these areas are linked to the equator’s warm waters. “It’s still plausible that O. megalodon used nursery regions to grow baby sharks,” said coauthor Harry Maisch, a New Jersey professor at Bergen Community College and Fairleigh Dickinson University.
“However, our research suggests that smaller Megalodon teeth may be the consequence of individual sharks achieving smaller total body sizes simply as a result of warmer water.” The discoveries might inform the future of modern-day (and comparably smaller) sharks, and how they might adapt to an ever-warming planet, in addition to creating the charming thought of mini-me megalodons.
Shimada intends to understand more about megalodon’s lives and times by studying their teeth in greater detail. “I am now examining the biology and lifestyle of O. megalodon and other ancient sharks, such as their nutrition and metabolism, based on chemical signatures retained in their petrified teeth, in partnership with a number of geochemists,” he added.
