Paleontologists have unearthed fossils of two types of lampreys dating back 160 million years, and discovered that the once-tiny fish evolved into monster dippers that grew ten times taller than the earliest lampreys. The oldest fossilized remains of lampreys date back 360 million years, earning them the nickname “living fossils” because they have a long history with little evolutionary change.

Today, they can grow up to a meter in length, although the oldest lampreys in the Paleozoic were only a few centimeters tall. The largest of the recently discovered species, Yanliaomyzon oxisor, measured just over 64 centimeters (25 in) from tip to tail. A surprisingly giant ancient species has been discovered in the Yanliao terrestrial biota in northern China. Thanks to these exceptionally well-preserved fossils found in Lagerstätte, we can learn more about the evolutionary history of lampreys and where they came from.

“By combining recorded fossil remains and extant lampreys, these fossils offer the opportunity to reconstruct the evolutionary process and ancestral status of the nutritional biology of modern lampreys,” wrote a group of researchers led by Feixiang Wu of the Chinese Academy of Sciences.

Wu and fellow paleontologists Chi Zhang of the Chinese Academy of Sciences and Philippe Janvier of France’s National Museum of Natural History conducted a comprehensive analysis of the two species using X-ray microcomputed tomography scans to visualize the fossils in 3D.

Together with myxins, lampreys constitute the living group of jawless vertebrates. Although these sea creatures resemble eels with their long and scaleless bodies, eels are actually a much newer species with updated body technologies such as jaws and bones.

Lampreys are among the oldest vertebrates, and instead of using jaws like most “normal” fish, their huge round mouths with sharp teeth suck the blood of other fish.

“Lamblammers have a great importance in studies of vertebrate evolution,” Wu, Jeanvier and Zhang write in their published article.

“They are characterized by specialized feeding behaviors, such as feeding on blood or cut tissue from hosts or prey to which they are tightly attached by serrated mouth suckers.”

However, it is still difficult to determine the evolutionary history of lampreys, as few fossils have been found. It is not known when lampreys developed compound teeth for feeding; The feeding structures of the first lampreys in the Paleozoic appeared to be too weak for hunting. And they didn’t have the first larval stage of the modern lamprey’s life cycle, in which their eggs hatch as blind worm-like creatures that burrow in mud.

The physiological implications of their size, along with other fossil evidence, suggest that the newly discovered species had already developed a three-stage life cycle, like modern lampreys.

According to the authors, before the Jurassic period, lampreys had better feeding methods, larger bodies, and were predators. These newly discovered Jurassic lampreys have the strongest bite structure of any known fossil lamprey, indicating a carnivorous lifestyle.

“As far as we know, Yanliaomyzon oxisor“The largest lamprey fossil known to date is among the largest of any modern species,” Wu and colleagues write.

The size of adult lampreys is directly related to some of their most important biological characteristics. Larger species can migrate farther and range over larger areas, lay more eggs, and cope better with salt water. It’s easier to learn how Jurassic lampreys lived (and ate) if you know how large their bodies were.

The guts of both fossil species were most preserved in skeletal remains, including teeth, jawbones, and even the skulls of unidentified bony fish.

“The bones and skeletal remains indicate a carnivorous habit of these fossil lampreys,” the team wrote, “making them the earliest record of their group having a well-defined feeding regime.”

Researchers believe the sea lamprey’s smaller, older mouthparts may have been used to scrape algal mats from other aquatic animals rather than predation. This could have helped them find a food niche in a world full of jawless fish, such as similarly shaped conodonts.

According to the authors, the diet and habits of lampreys have changed dramatically since the Devonian period, and these fossils fill some evolutionary gaps as well as changing the idea of ​​where living lampreys came from.

“Unlike previous efforts,” they write, “our study points to the Southern Hemisphere as the biogeographic source of modern lampreys.” Source