Are lampreys, the "underwater vampires", scary? Scientists discover that their carnivorous ancestors were even more "fierce"!

"Underwater vampire" - the ancestors of lampreys may not have sucked blood! On November 3, the reporter learned from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences that through the study of newly discovered large lamprey fossils in the Jurassic Yanliao Biota 160 million years ago, the institute's researchers found that the ancestors of modern lampreys may be carnivorous rather than blood-sucking, further revealing the evolutionary history of the lamprey's peculiar feeding method and its impact on the evolution of this species. The relevant research results were published online in the journal Nature Communications.

The carnivorous lamprey from the dinosaur era, the Yanliao eel, is about 160 million years old. Produced by Simulite Technology

In biological system classification, lampreys belong to primitive jawless species and have lived on Earth for at least 300 million years. Living lampreys are widely distributed in freshwater and offshore waters in cold and temperate zones. Many species feed on blood. Their image as "underwater vampires" is deeply rooted in people's minds and has become the artistic prototype of underwater killer monsters in some horror science fiction movies.

At the same time, lampreys are one of the few vertebrates that experience "metamorphosis" in their individual development history. Just like a tadpole turning into a frog, its life cycle begins with a long (up to 7 years or even longer) larval stage, and then undergoes a special metamorphosis process to enter adulthood. At this time, its anatomical characteristics and ecological habits are very different from those of the larvae.

Although lampreys have a long life history, their fossil species are very few, with only seven species known, one of which is questionable. Fossil data after the Carboniferous is particularly scarce, but it was during the nearly 200 million years from the Carboniferous to the Cretaceous that lampreys revolutionized their individual development: from the Paleozoic lack of modern lamprey larvae and metamorphosis, they evolved into a growth and development pattern that includes a metamorphosis stage.

"Due to the scarcity of fossil materials, how did the unique biological and ecological characteristics of lampreys evolve during the Late Paleozoic, an important period in the evolutionary history of lampreys? When, where and why did modern lampreys originate? These questions have always puzzled paleontologists," said Wu Feixiang, the corresponding author of the paper and a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.

Fortunately, researchers have successfully collected large lamprey fossils in the Jurassic fossil treasure house, the Yanliao Biota. The newly collected fossils are materials from two types of lampreys, the killer Yanliao and the big-toothed Yanliao. Among them, the killer Yanliao is more than 64 centimeters long, the largest size of the known fossil lampreys.

The carnivorous lamprey in the Yanliao biota 160 million years ago - Yanliao eel (ae, killer Yanliao eel; fh, big-toothed Yanliao eel; e, h, produced by Simulite Technology; b, d, drawn by the author of the paper)

"Most Paleozoic lampreys were a few centimeters long, and the largest was only about ten centimeters, even smaller than the size of modern lamprey larvae approaching metamorphosis. The reported Cretaceous Jehol Biota lampreys were larger, but no published fossils have been found that are longer than the killer Yanliao eel," said Wu Feixiang.

After in-depth analysis, researchers found that the tooth structure of the Yanliao eel is significantly different from that of the common vampire lampreys (such as sea lampreys) in the Northern Hemisphere, but it has many similarities with the sac lampreys that live in southern Australia, New Zealand and southern Chile in the Southern Hemisphere today. "This shows that these Jurassic lampreys, like sac lampreys, are typical carnivorous lampreys, and the bone fragments in the digestive tract of the Yanliao eel fossils also confirm this," said Wu Feixiang.

Further analysis showed that the Yanliao eel is the most recent fossil ancestor of the modern lamprey. Wu Feixiang explained that people generally believe that the ancestor of modern lampreys is a blood-sucking type similar to sea lampreys, but the research and analysis of the Yanliao eel and the reconstruction of its ancestral state show that the ancestor of modern lampreys is more likely to be a carnivorous lamprey.