A PREHISTORIC Megalodon shark has been declared the world’s ‘ultimate predator of predators’ 由科学家.
In a new 学习, researchers from Princeton University ranked predators from the past and revealed that Megalodon sharks reigned supreme.
Megalodons are an extinct species of mackerel shark that lived approximately 23 到 3.6 million years ago.
The creatures, which evolved after the extinction of dinosaurs, could measure up to 65 feet – about the size of three long SUVs.
“We’re used to thinking of the largest species — blue whales, whale sharks, even elephants, and diplodocuses — as filter feeders or herbivores, not predators,” study author Emma Kast, 一种 2019 Ph.D. graduate in geosciences, 说.
“But Megalodon and the other megatooth sharks were genuinely enormous carnivores that ate other predators, and Meg went extinct only a few million years ago.”
This type of predatory activity places Megalodon at “the highest trophic level” scientists know of.
A trophic level describes the place a specific organism occupies in a food chain.
And because Megalodons didn’t have any known predators, they are the only apex predators at the highest level ever measured.
实际上, Megalodon’s trophic signature was so high that they must have devoured predators and even predators of predators, the study claims.
“Ocean food webs do tend to be longer than the grass-deer-wolf food chain of land animals because you start with such small organisms,” said Kast.
“To reach the trophic levels we’re measuring in these megatooth sharks, we don’t just need to add one trophic level — one apex predator on top of the marine food chain — we need to add several onto the top of the modern marine food web.”
确实, the Megalodon’s presence in the ocean was so domineering, that it would have even impacted today’s humans.
“If Megalodon existed in the modern ocean, it would thoroughly change humans’ interaction with the marine environment,” Danny Sigman, a professor of geological and geophysical sciences at Princeton, 说.
How do the researchers know this?
The team of scientists was able to come to their conclusions by measuring the nitrogen isotopes in the sharks’ teeth.
Researchers know that levels of nitrogen-15 isotopes increase at higher trophic levels as nitrogen is metabolized.
具体来说, nitrogen-15 isotopes increase by 3 到 4 parts per thousand (ppt) per trophic level, 根据一个 2001 学习.
“We have a series of shark teeth from different time periods, and we were able to trace their trophic level versus their size,” said Zixuan (Crystal) Rao, a graduate student, and study co-author.
Teeth are designed to be chemically and physically resistant so they can survive in chemically reactive environments, Sigman explained.
And sharks have hundreds of teeth – Megalodon, specifically, 有 276 teeth that were constantly falling and growing.
“When you look in the geologic record, one of the most abundant fossil types are shark teeth,” said Sigman.
“And within the teeth, there is a tiny amount of organic matter that was used to build the enamel of the teeth — and is now trapped within that enamel.”
This novel method, the team of researchers hopes, will help to demystify the pasts of other marine animals.
“Our tool has the potential to decode ancient food webs; what we need now is samples,” said Kast.