Scientists have identified more than a dozen species of prehistoric sharks and rays that once lived in a single marine ecosystem, providing a fascinating glimpse into this ancient world.
The sharks and rays were "mainly predators" that roamed the ocean around 58 million to 56 million years ago in an area that is now located in Chile. That's according to Diego Rodríguez, an author of a study published in the journal Andean Geology that describes the findings.
All of the species, which come in a variety of forms, are now extinct, Rodríguez told Newsweek. But some of their close relatives still live in present times.
For the study, Rodríguez and his colleagues examined several fossils originally uncovered from a rocky outcrop in the Talcahuano area of south-central coastal Chile.
The fossils, which were being kept at a local museum, form part of a single collection—what researchers refer to as an "assemblage."
The researchers said the sharks and rays once lived in the same ecosystem. While the fossils were found on land, this area was once under the ocean.
Because the sediments in which the fossils were found are of similar age, it is likely these sharks and rays existed around the same time—toward the end of the Paleocene. This is the geological epoch that lasted from around 66 million to 56 million years ago.
The fossils the scientists looked at were primarily teeth, but they also examined some vertebrae and even a ray's stinging spine. In rays, this spine or barb—located at the end of the tail—is capable of delivering venom and is used for defensive purposes.
While the collection of fossils has been studied before, the latest study represents the first time that the various species have been correctly identified. In total, the researchers identified 17 species of sharks and rays, which both belong to the group of fish known as the elasmobranchs.
"The sharks of this assemblage had different habits, some preferring deeper waters, others being more comfortable in shallower waters," Rodríguez said. "Also, the rays were more likely to feed in the bottom of this past sea, and also at least some of them were able to eat hard-shelled marine creatures."
He continued: "It's safe to say that even though the remains found comprise mostly sharks and rays, other kinds of smaller fishes would [have also been part of this] community, as prey of these sharks and rays. Also, it is likely that these species shared an ecosystem with [sediment-living] crustaceans."
The scientists did not identify any completely new species among the fossil teeth, but some have never been seen before in South America. Others were documented for the first time in the Southern Hemisphere.
"These findings are very significant because they comprise the first extensive descriptions of these kinds of fishes during the Paleocene of South America," Rodríguez said.
"The implications of this are that now there is a better understanding of the global distribution for many of these species and that they are practically identical with ones found in northwestern Europe during similar geological times," he said.
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