A new species of lamprey from Cretaceous semisaline environment in China

ABSTRACT

A new fossil species of lamprey, Caeruleum gracilis sp. nov. is described from the Early Cretaceous Jiufotang Formation in China Hebei province, North China. Caeruleum gracilis sp. nov. is characterised by a slender body shape and a dorsal fin originating above the second branchial pouch. Given the intricate life history of lampreys, their presence in saltwater and freshwater, and their convoluted and ambiguous evolutionary trajectory, it is imperative to investigate whether the living environment of fossil lamprey species encompassed varying levels of salinity. This inquiry will facilitate our understanding and tracing of the earliest adaptations of lampreys to freshwater and saltwater environments. Based on salinity analysis, the environment of the Jiufotang Formation may be attributed to brackish conditions. Therefore, the lampreys Caeruleum gracilis sp. nov. and Caeruleum miraculum from the Jiufotang Formation may represent the one of earliest lampreys records that acquired adaptations to freshwater environments.

KEYWORDS:

• Caeruleum gracilis sp. nov
• brackish conditions
• Jiufotang Fomation
• Early Cretaceous
• Mayomyzon
• lamprey

Nomenclatural acts

lsid:zoobank.org:pub:9F9F3D46-50BA-4DD5-B67A-7817786E2A57

Acknowledgments

The inspiration for the restoration image comes fromMr. Zhou Jia Jun of the Zhejiang Forest ResourceMonitoring Center. Thank you to Professor Emmanuel Fara for providing numerous comments on the initial draft.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 41972120; 42172129] and Popular science research of multi-dimensional digitization of paleontological fossils and its ecology-taphonomy, a case study of Triassic Marine reptiles in Geological Museum of Guizhou. No. Qian Sci-Tech Support Plan[2022] General 257. The ICP experiment was conducted free of charge by China Tianneng Group Prospective Energy Research Institute (laboratory technician:Xinjin Yan).