The vampire squid lurks in the dark corners of the ocean for 30 million years, a new analysis of long-lost fossil discoveries.
Modern vampire squid (iad Vampyroteuthis) can thrive in deep, oxygen-poor ocean water, unlike many other squid species that require more shallow habitat along the continental shelves.
Few fossil ancestors of today’s vampire squid survive, so scientists are unsure when these elusive cephalopods have developed the ability to live on low oxygen.
The new fossil analysis helps fill a 120-million-year gap in the evolution of the vampire squid, revealing that the ancestors of today’s vampire squid already lived in the deep oceans during the Oligocene, 23 to 34 million years ago.
These squid probably evolved to adapt to low-oxygen water during the Jurassic, said study co-author Martin Košťák, a paleontologist at Charles University in Prague.
“Living in stable low oxygen levels brings evolutionary benefits – low prey pressure and lower competition,” Košťák wrote in an email to Live Science.
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A rediscovered fossil
Košťák and his colleagues found the long-lost fossil in the collections of the Hungarian Museum of Natural History in 2019, while searching for fossils of cuttlefish ancestors. The fossil was first discovered in 1942 by Hungarian paleontologist Miklós Kretzoi, who identified it as a squid about 30 million years old and named it Necroteuthis hungarica. Subsequent researchers, however, claimed that he was an ancestor of cuttlefish.
In 1956, during the Hungarian Revolution, the museum was burned and the fossil was considered destroyed. The rediscovery was a happy surprise.
“It was a great moment,” Košťák said of the rediscovery, “to see something that previously suggested it was lost forever.”
Fossil. (Košťák et al., Communications Biology, 2021)
Košťák and colleagues studied the fossil with scanning electron microscopy and performed a geochemical analysis. They first discovered that Kretzoi’s initial identification was correct: the fossil came from a squid, not a cuttlefish ancestor.
The inner shell of the animal, or gladius, which forms the spine of its body, was about 15 cm long, suggesting that the squid grew up to 35 cm long, with its arms included. It is only slightly larger than the modern vampire squid, which reaches about 28 cm in total body length.
The sediments around the fossil showed no traces of microfossils often found on the seabed, suggesting that the squid did not live in shallow water. The researchers also looked at the levels of carbon variations in the sediment and found that the sediment probably came from an anoxic or low-oxygen environment.
These conditions are characteristic of the deep ocean floor. Looking at the layers of rock above where the fossil was deposited outside of what is now Budapest, researchers have also been able to show that the squid probably could not have survived in the shallower seas of the time.
The shallow deposits showed very high levels of a special plankton that blooms in environments with low salt content, high nutrient content – conditions that today’s vampire squid cannot tolerate.
(Researchers at the Monterey Bay Research Institute have found that while hiding in the deep sea, these squid do not behave as nightmare predators suggest their names; rather, they wait in their dark habitats for crumbs of organic matter to they catch those bits with mucus-covered suckers, MBARI found.)
Adapting to the deep
The new research, published in the journal on Thursday (February 18th) Biology of communications, suggests how vampire squid ancestors learned to live where other squid could not.
Looking deeper into the fossil record, the oldest fossils in this group of squid are found in the Jurassic period, between 201 million and 174 million years ago, Košťák said, and are usually found in anoxic sediments.
‘The major differences are that these depleted oxygen conditions have been established on the shelf, [a] “This means that the ancestors lived in shallow water, but were already adapted to low-oxygen conditions,” he said.
There is a gap in fossil records from the Lower Cretaceous, about 145 million years ago. Perhaps the squid has already moved into the deeper ocean by now, said Košťák, initiated by their experiences with anoxic Jurassic conditions. This deep-seated lifestyle could explain why the squid survived the crisis that killed the Nonavian dinosaurs in the late Cretaceous, he added.
The deep-life squid 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 cuttlefish, a group of cute, color-changing cephalopods whose origins are just as murky.
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This article was originally published by Live Science. Read the original article here.