Vampire squids have been dormant in the dark corners of the ocean for 30 million years, a new analysis of a long-lost fossil find.
Contemporary vampire squid hell Vampyroteuthis) can thrive in deep, oxygen-poor ocean waters, unlike many other squid species that require shallower habitat along the continental shelf. However, there are few fossil ancestors of today’s vampire squid, so scientists aren’t sure when these elusive cephalopods developed the ability to live on low oxygen levels.
The new fossil analysis helps close a 120 million year gap in vampire squid evolution, revealing that the ancestors of today’s vampire squid lived in the deep oceans during the Oligocene, 23 million to 34 million years ago. This squid likely adapted to oxygen-deficient waters during the Jurassic, said study co-author Martin Košťák, a paleontologist at Charles University in Prague.
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“Living in stable low oxygen levels brings evolutionary benefits: low predation pressure and less competition,” Košťák wrote to Live Science in an email.
A rediscovered fossil
Košťák and his colleagues found the long-lost fossil in the collections of the Hungarian Natural History Museum in 2019 while looking for fossils of squid ancestors. The fossil was originally discovered in 1942 by Hungarian paleontologist Miklós Kretzoi, who identified it as a squid about 30 million years old and named it Necroteuthis hungaricaHowever, later researchers argued that it was an ancestor of a squid. In 1956, during the Hungarian Revolution, the museum was burned and the fossil was thought to have been destroyed. The rediscovery was a happy surprise.
“It was a great moment,” said Košťák of the rediscovery, “to see something that was previously suggested to be lost forever.”
Košťák and his colleagues studied the fossil with scanning electron microscopy and performed a geochemical analysis. They first discovered that the original identification of Kretzoi was correct: the fossil belongs to a squid, not an ancestor of a squid. The animal’s internal shell, or gladius, which forms the spine of its body, was about six inches long, suggesting that the squid grew to about 13 inches long with arms. That’s just slightly larger than the modern vampire squid, which reaches a total body length of about 11 inches.
The sediments around the fossil showed no trace of microfossils commonly found on the sea floor, suggesting that the squid did not live in shallow water. The researchers also analyzed levels of variations in carbon in the sediment and found that the sediment probably came from an anoxic or oxygen-poor environment.
Those conditions are characteristic of the deep ocean floor. By looking at rock layers above where the fossil was deposited outside of present-day Budapest, the researchers were also able to show that the squid probably could not have survived in the shallower seas of the time. The shallow sea deposits showed very high levels of a particular plankton that thrives in low-salt, high-nutrient environments – conditions that the modern vampire squid cannot tolerate.
(Researchers at the Monterey Bay Research Institute found that while lurking in the deep sea, these squids do not behave like the nightmare predators their name suggests; they wait in their dark habitat for crumbs of organic matter that whirling down, catching those pieces with slime-covered suction cups, MBARI discovered.)
Adjust to the depth
The new research, published Thursday (Feb. 18) in the journal Communication biology, shows how the ancestors of vampire squid learned to live where other squid could not. If we look deeper into the fossil record, the oldest fossils of this group of squid are found in the Jurassic periodbetween 201 million and 174 million years ago, Košťák said, and they are mostly found in anoxic sediments.
“The main differences are that these low-oxygen conditions were found on the shelf, [a] shallow water, “he said.” This means that the ancestors were inhabitants of shallow-water environments, but they were already adapted to low-oxygen conditions. ”
There is a hole in the Lower Cretaceous fossil record that began about 145 million years ago. The squid may have already shifted to the deeper ocean by this point, Košťák said, primed by their experiences with anoxic conditions in the Jurassic. This deepwater lifestyle could explain why the squid survived the crisis that killed non-avian dinosaurs at the end of the Cretaceous Period, he added.
The deep-floating squid from 30 million years ago helps connect recent history with the deep past, Košťák said. He and his colleagues are now trying to make similar connections for squids, a group of cute, color-changing cephalopods whose origins are also obscure.
Originally published on Live Science