Scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, along with their partners, have unveiled the discovery of two exceedingly rare fossil lampreys originating from the Jurassic era in northern China.
This groundbreaking find has significantly reshaped our comprehension of lamprey evolution.
Published in Nature Communications on October 31, the study presents these precious specimens extracted from the renowned Lagerstätte Yanliao Biota, dating between 158 to 163 million years old. Among these fossils is the Yanliaomyzon occisor, dubbed the “Yanliao sucker killer,” measuring an impressive 642 mm in length (around 25 inches) and holding the title as the largest fossil lamprey ever unearthed.
These well-preserved fossils offer remarkable insights into the lampreys’ keratinous teeth. Through meticulous examination, the scientists have reimagined the evolutionary journey of lampreys, particularly regarding their feeding apparatus, life cycle, and historical distribution.
The feeding structure observed in these Jurassic fossils strikingly resembles that of the living pouched lamprey Geotria australis, a species known for its flesh-eating tendencies. “Our study positions these Jurassic lampreys as the closest fossil relatives to modern lampreys,” stated WU Feixiang, the lead author of the study.
“Contrary to the commonly held belief that ancestors of modern lampreys fed on blood, our research demonstrates that these two Jurassic lampreys were flesh eaters, foreshadowing the flesh-eating habits of the most recent common ancestor of present-day lampreys,” added WU.
The study also identifies the Jurassic period as a turning point in the evolutionary trajectory of lampreys. In the earlier Paleozoic era, lampreys likely weren’t predatory, given their diminutive body size and rudimentary, feeble teeth. Additionally, contemporaneous ancient fishes were heavily armored, making it difficult for these small lampreys to penetrate their scales. However, with the proliferation of ‘advanced’ teleost fishes boasting thinner scales since the Early Jurassic, providing increased food resources, the lampreys adapted.
“The surge of advanced teleost fishes with thinned scales from the Early Jurassic possibly offered a significant evolutionary window for lampreys,” explained WU. “With enhanced feeding structures, lampreys from the Jurassic era onward could grow larger, meeting the energy demands of an evolutionary life cycle marked by metamorphosis and involving substantial environmental changes.”
A time-calibrated family tree forms the foundation of the evolutionary narrative. Employing a Bayesian total-evidence dating framework enabled the inference of a time tree for lamprey evolution. “Bayesian inference, unlike the parsimony method, integrates diverse data sources probabilistically while considering parameter uncertainties, avoiding arbitrary determinations and partial data use,” noted ZHANG Chi, another corresponding author of the study.
This methodology facilitated the inference of ancestral geographical regions for lampreys. The puzzling history of the anti-tropical distribution pattern of lampreys, owing to the scarcity of fossils, was clarified by calibrating the Jurassic lampreys. It was revealed that the lineage of the pouched lamprey in the Southern Hemisphere signifies the earliest divergence among living lampreys. Consequently, the study posits that modern lampreys originated in the Southern Hemisphere during the Late Cretaceous, opposing the traditional notion of a Northern Hemisphere origin, where most extant lamprey species reside.
“This discovery unequivocally shows that the existing southern lampreys maintain a feeding morphology established in the Jurassic. Additionally, it aligns modern lamprey phylogeny with a Southern Hemisphere origin, coupled with an adaptation to a carnivorous diet,” stated Prof. Philippe JANVIER from France’s National Museum of Natural History, a co-author of the study.
Despite substantial gaps in the extensive evolutionary history of lampreys, the unearthing of Jurassic lamprey fossils is anticipated to catalyze further exploration in the field.
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