The teeth of the Jurassic lampreys Yanliaomyzon (a-d, Yanliaomyzon ingensdentes, specific name significance large teeth; e, f, Yanliaomyzon occisor, specific name significance killer) and those of the living pouched lamprey Geotria australis (g) now inhabits in Southern Hemisphere. Credit: NICE Vistudio and IVPP
Both fossils superbly preserve the lampreys keratinous teeth. After thoroughly taking a look at the fossils, the scientists reinterpreted lamprey advancement, especially their feeding device, life cycle, and historical biogeography.
Modifying Evolutionary Understanding
The Jurassic fossils feeding apparatus noticeably looks like that of the living pouched lamprey Geotria australis, a flesh-feeding species. “Our study solved these Jurassic lampreys as the closest fossil family members to extant lampreys,” said WU Feixiang, lead author of the study.
” Contrary to standard wisdom that modern-day lampreys ancestors fed upon blood, our study revealed that these 2 Jurassic lampreys should be flesh eaters, which foreshadows the flesh-eating practice of the most recent typical forefather of modern-day lampreys,” included WU.
Evolutionary Milestones and Methodology
The study also recognized the Jurassic as a watershed in lamprey evolutionary history.
Most other simultaneous ancient fishes were greatly armored– with tough scales and body covers that avoided these tiny lampreys from biting through. As the plentiful emergence of the advanced teleost fishes with thinned scales since the Early Jurassic– modifications that increased food schedule– lampreys also altered.
a-e, Yanliaomyzon occisor; f-h, Yanliaomyzon ingensdentes. Credit: NICE Vistudio and IVPP
” The abundant introduction of innovative teleost fishes with thinned scales by the Early Jurassic may have provided an essential evolutionary opportunity for lampreys,” stated WU. “With the improved feeding structures, Jurassic lampreys onward had the ability to grow sufficiently big to fulfill the energy requirement of the development of a prolonged life process interposed by the metamorphosis stage and associated with significant ecological shifts.”
A time-calibrated ancestral tree is the basis of an evolutionary history story. Inference of the time tree for lamprey development was performed in a Bayesian total-evidence dating framework. “Compared with the parsimony approach, Bayesian reasoning has the ability to integrate different sources of info in a probabilistic setting while representing the unpredictabilities of the parameters, hence avoiding ad-hoc decisions and partial use of the information,” said ZHANG Chi, another corresponding author of the study.
Biogeographical Implications
The history of the anti-tropical distribution pattern of lampreys has baffled biogeographers due to the incredibly thin fossil record of the group. With the calibrations of the Jurassic lampreys, the lineage of the pouched lamprey in the Southern Hemisphere was resolved as the earliest diverged family tree among living lampreys.
” This discovery clearly indicates that the extant southern lampreys maintain a feeding morphology that already occurred in the Jurassic, which modern lamprey phylogeny is now constant with a Southern Hemisphere origin, integrated with an adaptation to a carnivorous diet plan,” stated Prof. Philippe JANVIER of Frances National Museum of Natural History, a co-author of the research study.
Although big spaces in the long evolutionary history of lampreys still exist, the discovery of Jurassic lamprey fossils is expected to promote more research in the future.
Reference: “The increase of predation in Jurassic lampreys” by Feixiang Wu, Philippe Janvier and Chi Zhang, 31 October 2023, Nature Communications.DOI: 10.1038/ s41467-023-42251-0.
Restoration of the Jurassic (ca. 160 million years ago) lampreys Yanliaomyzon from the Yanliao Biota, northern China. Credit: NICE Vistudio
Scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, alongside their partners, have revealed two exceptionally uncommon fossil lampreys from the Jurassic period in northern China, modifying our understanding of lamprey evolution.
The findings were just recently released in the journal Nature Communications.
Discovery of the Fossils
The precious specimens were found in the famed Lagerstätte Yanliao Biota from rocks going back 158– 163 million years. Among them, Yanliaomyzon occisor or “Yanliao sucker killer,” is 642 mm long (about 25 inches) and is the biggest fossil lamprey ever found.
As the abundant development of the innovative teleost fishes with thinned scales because the Early Jurassic– changes that increased food schedule– lampreys likewise altered.
The history of the anti-tropical circulation pattern of lampreys has actually baffled biogeographers due to the exceptionally thin fossil record of the group. With the calibrations of the Jurassic lampreys, the lineage of the pouched lamprey in the Southern Hemisphere was fixed as the earliest diverged lineage among living lampreys. Hence, the study approximates that modern-day lampreys originated in the Southern Hemisphere throughout the Late Cretaceous. This opposes the traditional wisdom that lampreys originated in the Northern Hemisphere, where most extant lamprey types live.