Mesomyzon

Mesomyzon; Temporal range: Early Cretaceous
	Fossil specimen
	Speculative life restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Class:	Petromyzontida
Order:	Petromyzontiformes
Genus:	†Mesomyzon; Chang, Zhang & Miao 2006
Species:	†M. mengae
Binomial name
	†Mesomyzon mengae; Chang, Zhang & Miao 2006

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'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 Its anterior (first) dorsal fin was very long, running down 44%-48% of its body, and it had a ribbon-like preanal skin fold not known in any other lamprey.² It had the same three-phase life cycle found in modern lampreys.³

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.⁴ On the other hand, Brownstein & Near (2022) found it to be a member of the lamprey crown group, most closely related to Petromyzontidae.⁵ 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.³

References

Chang, M. M.; Zhang, J.; Miao, D. (2006). "A lamprey from the Cretaceous Jehol biota of China". Nature. 441 (7096): 972–974. Bibcode:2006Natur.441..972C. doi:10.1038/nature04730. PMID 16791193. S2CID 4427676.
Wu, Feixiang; Chang, Mee-Mann; Janvier, Philippe (2021-11-25). "A new look at the Cretaceous Lamprey Mesomyzon Chang, Zhang & Miao, 2006 from the Jehol Biota". Geodiversitas. 43 (23): 1293–1307. doi:10.5252/geodiversitas2021v43a23. ISSN 1280-9659.
Wu, Feixiang; Janvier, Philippe; Zhang, Chi (2023-10-31). "The rise of predation in Jurassic lampreys". Nature Communications. 14 (1): 6652. doi:10.1038/s41467-023-42251-0. ISSN 2041-1723. PMC 10618186.
Miyashita, Tetsuto; Coates, Michael I.; Farrar, Robert; Larson, Peter; Manning, Phillip L.; Wogelius, Roy A.; Edwards, Nicholas P.; Anné, Jennifer; Bergmann, Uwe; Palmer, A. Richard; Currie, Philip J. (2019-02-05). "Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny". Proceedings of the National Academy of Sciences. 116 (6): 2146–2151. Bibcode:2019PNAS..116.2146M. doi:10.1073/pnas.1814794116. ISSN 0027-8424. PMC 6369785. PMID 30670644.
Brownstein, C. D.; Near, T. J. (2022). "Phylogenetics and the Cenozoic radiation of lampreys". Current Biology. 33 (2): 397–404.e3. doi:10.1016/j.cub.2022.12.018. PMID 36586410. S2CID 255278945.

[chang-1] Chang, M. M.; Zhang, J.; Miao, D. (2006). "A lamprey from the Cretaceous Jehol biota of China". Nature. 441 (7096): 972–974. Bibcode:2006Natur.441..972C. doi:10.1038/nature04730. PMID 16791193. S2CID 4427676.

[2] Wu, Feixiang; Chang, Mee-Mann; Janvier, Philippe (2021-11-25). "A new look at the Cretaceous Lamprey Mesomyzon Chang, Zhang & Miao, 2006 from the Jehol Biota". Geodiversitas. 43 (23): 1293–1307. doi:10.5252/geodiversitas2021v43a23. ISSN 1280-9659.

[Yanliaomyzon-3] Wu, Feixiang; Janvier, Philippe; Zhang, Chi (2023-10-31). "The rise of predation in Jurassic lampreys". Nature Communications. 14 (1): 6652. doi:10.1038/s41467-023-42251-0. ISSN 2041-1723. PMC 10618186.

[4] Miyashita, Tetsuto; Coates, Michael I.; Farrar, Robert; Larson, Peter; Manning, Phillip L.; Wogelius, Roy A.; Edwards, Nicholas P.; Anné, Jennifer; Bergmann, Uwe; Palmer, A. Richard; Currie, Philip J. (2019-02-05). "Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny". Proceedings of the National Academy of Sciences. 116 (6): 2146–2151. Bibcode:2019PNAS..116.2146M. doi:10.1073/pnas.1814794116. ISSN 0027-8424. PMC 6369785. PMID 30670644.

[5] Brownstein, C. D.; Near, T. J. (2022). "Phylogenetics and the Cenozoic radiation of lampreys". Current Biology. 33 (2): 397–404.e3. doi:10.1016/j.cub.2022.12.018. PMID 36586410. S2CID 255278945.

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