Jakarta, domclub Indonesia
—
Long before the era of the pope,
shark
modern white, or
megalodon
the size of a bus, the ancient seas of northern Australia were once dominated by monster sharks said to be the ancestors of today’s great white sharks.
Researchers discovered this giant shark fossil lived 15 million years earlier than any large shark that had been discovered before.
In the age of dinosaurs, during the Cretaceous period (
Cretaceous
), this monster shark roamed the waters of what is now known as northern Australia.Researchers studying a giant vertebra found on a beach near the city of Darwin say the creature is the earliest known mega-predator of the modern shark lineage.
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The six-meter-long ancestor of the modern white shark is estimated to have reached a length of about eight meters, say the authors of the study published in the journal
Communications Biology
.
“Cardabiodontids were very, very common ancient mega-predatory sharks from the late Cretaceous period, after 100 million years ago,” said Benjamin Kear, senior curator of paleobiology at
Swedish Museum of Natural History
and one of the study authors, as reported
Irish News
.
“But this discovery has pushed back the timeline for when we will find truly enormous cardabiodontids,” he added.
Although shark history stretches back 400 million years, lamniforms, the ancestors of today’s great white sharks, only appeared in the fossil record about 135 million years ago.At that time, they were small, perhaps only one meter in size.
The discovery that lamniforms had become giants 115 million years ago was unexpected for researchers.
The shark’s spine was found on the coastline near Darwin, Northern Australia.This area was once mud from the floor of an ancient ocean that stretched from Gondwana (now Australia) to Laurasia (now Europe).
The region is rich in fossil evidence of prehistoric marine life, with long-necked plesiosaurs and ichthyosaurs among the creatures discovered so far.
The five vertebrae used to estimate the size of the mega-predator shark are not a new discovery, but rather an old find that was overlooked, Kear said.The 12-centimetre fossils, which were unearthed in the late 1980s and 1990s, have been kept in the museum for many years.
When studying ancient sharks, vertebrae are a treasure trove for paleontologists.Shark skeletons are made of cartilage, not bone, and their fossil record consists mostly of teeth that are shed throughout the shark’s life.
“The importance of vertebrae is that they give us clues about size,” Kear said.”If you try to measure it from the teeth, it’s difficult. Are the teeth big but the body small? Or are the big teeth accompanied by a big body?,” he continued.
Scientists have used mathematical formulas to estimate the size of extinct sharks such as the megalodon, according to Kear, a massive predator that appeared later and may have reached a length of 17 meters.However, the rarity of vertebrae makes questions about the size of ancient sharks difficult to answer.
An international team of researchers spent years testing different ways to estimate the size of Darwin’s cardabiodontids, using fisheries data, CT scans and mathematical models.Eventually, they arrived at an estimate of the predator’s size and shape.
“This creature would have looked like a giant modern shark, because that’s the beauty of it,” Kear said.”This is a body model that has worked for 115 million years, like an evolutionary success story,” he added.
This study of Darwin’s sharks shows that modern sharks rose early in their adaptive evolution to the top of the prehistoric food chain.Kear added that studying ancient ecosystems like this can help researchers understand how species today might respond to environmental changes.
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