Mesomyzon
Extinct genus of lampreys
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Mesomyzon is an extinct lamprey genus from freshwater strata of the Early Cretaceous (Barremian–Aptian age) Yixian Formation of China. It contains a single species, M. mengae.[1]
| Mesomyzon Temporal range: Early Cretaceous | |
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| Fossil specimen | |
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| Speculative life restoration | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Infraphylum: | Agnatha |
| Superclass: | Cyclostomi |
| Class: | Petromyzontida |
| Order: | Petromyzontiformes |
| Genus: | †Mesomyzon Chang, Zhang & Miao 2006 |
| Species: | †M. mengae |
| Binomial name | |
| †Mesomyzon mengae Chang, Zhang & Miao 2006 | |
The animal's exquisitely preserved fossils show a creature very similar to modern-day lampreys, having a well-developed sucking oral disk, a branchial basket, at least seven pairs of gill pouches and corresponding gill arches, impressions of gill filaments, and at least 80 myomeres of its musculature.[1] It had the same three-phase life cycle found in modern lampreys.[2]
A phylogenetic analysis conducted in 2018 shows that Mesomyzon is the fossil lamprey most closely related to modern taxa, though it is not closely related to any modern group.[3] On the other hand, Brownstein & Near (2022) found it to be a member of the lamprey crown group, most closely related to Petromyzontidae.[4] However, a 2023 study found it again to be a derived stem lamprey, with the earlier Yanliaomyzon from the same region found to be more closely related to modern lampreys. This study also suggested Mesomyzon to be a blood feeder.[2]
