Vampire squid have lurked in the dark corners of the ocean for 30 million years, a new analysis of a long-lost fossil.
Modern vampire squid (Vampyroteuthis infernalis) can thrive in deep, oxygen-poor ocean waters, unlike many other squid species that require shallower habitat along continental shelves. However, few fossil ancestors of today’s vampire squid survive, so scientists aren’t sure when these elusive cephalopods developed the ability to live with little oxygen.
New fossil analysis helps fill a 120-million-year gap in vampire squid evolution, revealing that the ancestors of today’s vampire squid already lived in deep oceans during the Oligocene, 23 million to 34 million ago. of years. These squids likely developed adaptations to low-oxygen water during the Jurassic, said study co-author Martin Košťák, a paleontologist at Charles University in Prague.
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“Life in stable low oxygen levels brings evolutionary advantages: low predation pressure and less competition,” Košťák wrote in an email to Live Science.
A rediscovered fossil
Košťák and his colleagues found the long-lost fossil in the collections of the Hungarian Natural History Museum in 2019 while searching for fossils of cuttlefish ancestors. The fossil was originally discovered in 1942 by Hungarian paleontologist Miklós Kretzoi, who identified it as a squid dating back some 30 million years and named it Necroteuthis hungarica. However, later researchers argued that it was an ancestor of the cuttlefish. In 1956, during the Hungarian Revolution, the museum was burned down and the fossil was thought to have been destroyed. The rediscovery was a happy surprise.
“It was a great moment,” Košťák said of the rediscovery, “seeing something that was previously suggested was definitely lost.”
Košťák and his colleagues studied the fossil with scanning electron microscopy and performed a geochemical analysis. They first found that the initial identification of Kretzoi was correct: the fossil is from a squid, not a cuttlefish ancestor. The animal’s inner shell, or gladius, which forms the spine of its body, was about 6 inches (15 centimeters) long, suggesting that the squid grew to about 13.7 inches (35 cm) long with the arms included. That’s only slightly larger than the modern vampire squid, reaching about 11 inches (28 cm) in total body length.
The sediments surrounding the fossil did not show traces of microfossils often found on the seafloor, suggesting that the squid did not live in shallow water. The researchers also analyzed the levels of variations in Coal in the sediment and found that the sediment likely came from an anoxic or low-oxygen environment.
These conditions are characteristic of the deep ocean floor. By looking at layers of rock above where the fossil was deposited outside of what is now 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 water deposits showed very high levels of a particular plankton that flourishes in low-salt, nutrient-rich environments, conditions that today’s 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 nightmarish predators their name suggests; rather, they wait in their dark habitats for crumbs of matter to fall. organic – they capture those chunks with mucus-covered suction cups, MBARI found).
Adapt to the deep
The new research, published Thursday (February 18) in the journal Communications biology, hints at how the ancestors of the vampire squid learned to live where other squid could not. Looking deeper into the fossil record, the oldest fossils of this group of squid are found in the Jurassic Period, between 201 million and 174 million years ago, Košťák said, and are typically found in anoxic sediments.
“The main difference is that these oxygen starvation conditions were established on the platform, [a] shallow water environment, “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 gap in the fossil record in the Lower Cretaceous, which began about 145 million years ago. The squid may have already drifted into the deeper ocean at this point, Košťák said, prepared for his experiences with anoxic conditions in the Jurassic. This deep-sea lifestyle could explain why squid survived the crisis that killed non-avian dinosaurs at the end of the Cretaceous period, he added.
The deep-living squid from 30 million years ago helps link recent history to the deep past, Košťák said. He and his colleagues are now trying to make similar connections for the cuttlefish, a group of cute, color-changing cephalopods whose origins are just as murky.
Originally posted on Live Science.