2023-11-06 07:00:02
In the far reaches of northeastern China, scientists have unearthed two exceptionally well-preserved lamprey fossils, dating back 160 million years, with well-stocked teeth.
A Jurassic Yanliaomyzon lamprey with a feeding apparatus that surprisingly resembles that of pocket lampreys (Geotria australis).
Crédit: Heming Zhang
Lampreys, belonging to one of two groups of jawless vertebrates still alive (Life is the name given:), appear for the first time in the fossil record (A fossil (derived from the Latin verb noun fodere: fossil , literally…) regarding 360 million years ago, during the Devonian. These fish (Pisces is a constellation of the zodiac crossed by the Sun from March 12 to 18…) ancient, now comprising 31 species, are characterized by their mouth (The mouth (also called oral cavity or oral cavity) is the opening through…) shaped suction cup with teeth, allowing them to anchor themselves on their prey (A prey is an organism captured alive, killed then consumed by another,…) to suck blood (Blood is a liquid connective tissue made up of free cell populations, including…) and other bodily fluids.
The newly discovered fossils date back to the Jurassic and bridge a gap between early fossil discoveries and existing lineages. The researchers extracted these specimens from a fossil bed and named them Yanliaomyzon occisor and Y. ingensdentes, meaning “killer” in Latin and “big teeth” in Greek, respectively.
Y. occisor measures 64.2 centimeters long and is the largest lamprey fossil ever found. Current lamprey species can reach much larger sizes; for example, sea lampreys (Petromyzon marinus) grow up to 120 centimeters long, and Pacific lampreys (Entosphenus tridentatus) up to 85 centimeters.
These Jurassic lampreys exhibit the most developed “bite” structures among known fossil lampreys, suggesting an ancestral predatory feeding habit among present-day lampreys.
Crédit: Heming Zhang
Early lampreys were significantly smaller, with just tiny teeth and probably without anticoagulant-producing glands, unlike their descendants who use the substance to keep their prey’s blood flowing. The researchers add that the oral morphology of ancient lampreys indicates that they were neither predatory nor parasitic, but probably fed on algae. The newly described fossils show “broadly toothed” mouths, suggesting that lampreys were already feeding on other animals at least 160 million years ago. The resemblance of the oral structures of Y. occisor and Y. ingensdentes with those of current pouch lampreys (Geotria australis) underlines an ancient carnivorous diet. in modern lampreys, according to the study authors. This predatory lifestyle would probably have led to an increase in the size of lampreys in the Jurassic.
The large size of Y. occisor is particularly reminiscent of later species that developed a three-phase life cycle—larval, metamorphic, and adult—indicating that it may also have had a triphasic cycle and moved uprivers.
This discovery fills a gap in the evolutionary history of lampreys, revealing both changes in the feeding habits of these fish and the modernization of their life cycle during the Jurassic, the authors conclude in the study.
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