For about 10 to 13 million years – relatively brief in the history of the Earth – megalodons ruled the oceans.
Professor Tim Flannery says megalodons (Carcharocles megalodon) were probably ‘hyper carnivores’ – a carnivore that eats other carnivores.
Flannery – a writer, explorer and one of Australia’s best known palaeontologists – says isotopic studies on the predatory shark’s teeth suggest the ocean giant probably ate other sharks, and perhaps snacked on small whales as well.
“When you think about the implications of that, it’s staggering,” Flannery says. “If you want to add an extra level to the height of the food pyramid, you’ve got to extend the base enormously.”
Feeding megalodons would have required “an unbelievably productive ocean”, which is almost unimaginable today, he says.
And although little is known about megalodon populations, Flannery says “I struggle to imagine a world that would support more than a few thousand”.
The colossal fish was a “weirdo in the history of life in the oceans”, says Dr Erich Fitzgerald, Senior Curator of Vertebrate Palaeontology at Museums Victoria. That’s because for most of the last 250 million years, most of the apex predators in the ocean were ancestors of animals that once lived on land.
Megalodon was a fish that grew to epic size: jaws larger than a tall human, teeth as big as an out-stretched palm, and a body the size of a city bus. If orcas are the largest ocean predator today – weighing 6 or 7 tonnes – megalodons might have weighed 60 tonnes.
And according to Fitzgerald, it wasn’t the only hyper carnivore roaming the ocean at the time.
An extinct species of giant-toothed gigantic killer whale known as livyatans (Livyatan melvillei) – named after the Biblical sea monster the leviathan – probably matched the meg in size, he says, and may have had an even more ferocious bite.
Flannery and Fitzgerald were speaking on a palaeological panel on ‘Megalodon and the Age of Ocean Giants’ with Professor Cheng-Hsiu Tsai from the department of life science at National Taiwan University at Melbourne Museum on 28 November.
Megalodon fossils suggest the animal lived from about 15 million years ago until 2.5 – 3 million years ago, Fitzgerald says. Megalodon teeth have cropped up all over the place, although are quite rare in Australia.
It was a megalodon tooth he found at age 16, which hooked Flannery into palaeontology, a story he recounts in his recent book Big Meg, co-authored with daughter and science writer Emma Flannery.
Professor Flannery muses: it’s possible that the species even coincided with the earliest human ancestors, Australopithecus. Maybe they spotted one from a clifftop?
“Or maybe stranded on a beach,” Fitzgerald jumps in. “A big, hulking megalodon carcus – rotting, putrid.”
Cheng-Hsiu says palaeontologists are interested in studying why some species survive while others become extinct. He says a recent paper in Science suggested megalodon survived a mass shark extinction about 20 million years ago.
Megalodon’s ultimate disappearance coincides with the cooling of the Earth and sea levels dropping. Fitzgerald says “megalodon kicks the geological bucket with a lot of other really big ocean giants at that time”.
Cryptozoologists believe some individuals may still exist, perhaps hiding in the depths of the Mariana Trench.
While there’s no evidence for those theories, Fizgerald says fossils from an “even stranger” cousin of megalodon called parotodus from the family Otodontidae – a shark with weird hook-like teeth – are securely dated into the Pleistoncene epoch.
“So, in a way, even if Megalodon didn’t make it into this Quaternary Period that we’re still in, at least some close relatives did.”
The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.