For some of us “fossil geeks” that spend a great deal of time exploring Florida’s rivers, creeks, and phosphate mines, it’s shark week every week.
See, not too long ago (on geological time scales), much of the peninsula was engulfed under a shallow ocean. In fact, if I showed you a map of Florida approximately 2 million years ago, you probably wouldn’t recognize it. Florida’s land mass has undergone many changes. Over the last several epochs, Florida’s coastlines have expanded and retreated primarily due to changing climates.
It has been speculated that some parts of Florida which are now terrestrial landscapes may have once been prehistoric bays in the past. And that brings me back to the fossil hunters that spend their extra time exploring Florida in search of the biggest prize of them all — a megalodon shark tooth. Florida creeks and rivers provide a glimpse into the past. They almost serve as natural bulldozers eroding the layers of ground beneath. Fossil hunters from all over come to Florida annually during the dry season when water levels are at it’s lowest. This is the best time for “fossiling” (if there is such a word).
Without question, the Peace River gives you the best chances of finding those well sought out 2-10 million year old megs; which can be found in a variety of colors and (most importantly) sizes. The bigger the tooth, the better the prize. However, it is not uncommon to find the smaller varieties as well. Remember my reference to prehistoric bays in Florida? Well, some experts suggest (but has never been confirmed) that the Peace River formation may have been a nursery for adolescent megalodons. The fossils themselves tell the story; from the smaller megalodon shark teeth to the other fossils of extinct dugongs and crocodilians that lived alongside them (and as far we know, dugongs and crocodilians do not venture into deep ocean water). “The river was a prehistoric nursery where young megalodons hunted before growing giant and migrating up the Eastern Seaboard,” says author Mark Renz in an article for Tampa Bay Today.
Nature recently published a news article involving a study supporting the “Florida-Peace River” hypothesis, which has been floating around for a couple decades. The authors of the paper conducted their research in a different set of geographical locations (Northeastern Spain, to be exact). Nonetheless, the fossil record, geology, GIS elevation mapping, and possibly other sources, combined along with the methodology applied to the study below might one day confirm what many of us already know about the Peace River formation and it’s early Selachimorpha inhabitants.
Original article published in Nature
The prehistoric shark Otodus megalodon was an awe-inspiring beast, measuring up to three times the length of the modern great white shark. But even the mightiest of predators were babies once.
Carlos Martínez-Pérez at the University of Valencia in Spain, Humberto Ferrón at the University of Bristol, UK, and their colleagues compared megalodon teeth recently collected at two quarries in northeastern Spain with records of teeth found at eight other sites around the world. A disproportionate number of teeth gathered at five of the nine global locations were from young sharks, suggesting that those sites represent megalodon ‘nurseries’.
Nurseries are protected areas with shallow waters and abundant prey where young sharks can develop in relative safety. Big, slow-growing species of shark persist only when the survival rate of juveniles is high, and nurseries can make this possible. But the researchers note that there’s a downside, too: species can become dependent on the availability of suitable nursery sites, which can be disrupted by sea-level changes.
Peer-Reviewed Publication: Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes)