Caeruleum (lamprey)

Caeruleum; Temporal range: Early Cretaceous, 122.1 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Class:	Hyperoartia
Order:	Petromyzontiformes
Genus:	† Caeruleum ; Huang, 2023
Type species
	†Caeruleum miraculum; Huang, 2023
Other species
	†C. gracilisHuang et al., 2024 ;

Last updated October 17, 2024

Caeruleum is an extinct genus of lamprey from the Lower Cretaceous Jiufotang Formation of China. The genus contains two species, C. miraculum and C. gracilis, known from various specimens including complete and partial bodies.

Discovery and naming

C. miraculum

C. gracilis

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Approximate location of the Caeruleum species type localities near Weichang County, China

The first described Caeruleum fossil material was discovered in sediments of the Jiufotang Formation near Naizi (or Naitou) Mountain in Weichang County of Chengde City, Hebei Province, China. Various lamprey specimens were found in this formation.^[1]

In 2023, Weijia Huang described Caeruleum miraculum as a new genus and species of lamprey based on several fossil remains. The holotype specimen, BMM 3770, consists of a complete animal preserved on a slab and counterslab. Several additional specimens of various levels of completion were also assigned to Caeruleum as paratypes. These include BMM 3771 (an incomplete specimen with a complete tail), BMM 3772 (the posterior end of an animal with a mutilated tail), BMM 3776 (the anterior end with a complete head), and BMM 3775, 3777, and 778 (nearly complete specimens missing the posterior ends).^[1]

The generic name, "Caeruleum", implements the blue color caeruleum. The specific name, "miraculum", is derived from the Latin "mirabilis", meaning "wonderful", in reference to the nature of the fossil specimens. The full binomial name references the Blue Miracle Museum Science Research Studio in Guangzhou (Guangdong Province), China, where the specimens are housed.^[1]

In 2024, Huang and colleagues named a second species of the genus Caeruleum, Caeruleum gracilis, also from Naizi Mountain outcrops. C. gracilis is only known the holotype specimen, BMM 3990, a partial individual missing the end of the tail. The specific name, "gracilis", is derived from a Latin word meaning "slender", in reference to the body shape of the species in comparison to C. miraculum.^[2]

Caeruleum is the sixth named genus of fossil lamprey, after Mayomyzon , Pipiscius , Hardistiella , Mesomyzon , and Priscomyzon . After Mesomyzon , Caeruleum is also the second Cretaceous fossil lamprey genus named from China.^[1] A short time after the initial description of Caeruleum, Xu, Janvier & Zhang (2023) named the new genus Yanliaomyzon , containing the two species Y. occisor and Y. ingensdentes, from the Middle–Late Jurassic Tiaojishan Formation of China.^[3]

Description

The Caeruleum specimens exhibit significant variation in size; C. miraculum specimens range from 24–46.2 centimetres (9.4–18.2 in) in length. This is significantly larger than most other fossil lampreys and is comparable to some extant species. Contrastingly, the C. gracilis holotype is even smaller, with a preserved length of 6 centimetres (2.4 in) and an estimated total length of 9.6 centimetres (3.8 in) or longer. Like modern lampreys, Caeruleum had seven gill pouches. In C. miraculum, the anterior dorsal fin originates after the last gill pouch, while in C. gracilis, the dorsal fin is smaller, beginning after the second gill pouch and extending only 7 millimetres (0.28 in) past the last. In comparison, the Cretaceous Mesomyzon from the Yixian Formation ranged from 15–21.7 centimetres (5.9–8.5 in) long, with the dorsal fin beginning after the fourth gill pouch.^[1]^[2]^[4]

Paleoenvironment

The fossil material of both Caeruleum species was discovered in layers of the Jiufotang Formation, which dates to the Aptian age (122.1±0.3 Ma) of the Early Cretaceous period. Huang et al. (2024) suggested that Caeruleum inhabited a brackish freshwater environment.^[2] Well-preserved fossils of many other animals, including non-avian dinosaurs, early birds, pterosaurs, mammals, turtles, lizards, and fish, have also been found in the Jiufotang Formation.^[1]^[5]

Related Research Articles

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Liaoningosaurus is an unusual genus of basal ankylosaurid dinosaur from the Liaoning Province, China that lived during the Early Cretaceous in what is now the Yixian and Jiufotang Formation. The type and only species, Liaoningosaurus paradoxus, is known from more than 20 specimens, with some representing juveniles. It was named in 2001 by Xu, Wang and You.

Graciliraptor is a genus of theropod dinosaur from the early Cretaceous Period. It is a microraptorine dromaeosaurid.

Nurhachius is a genus of istiodactylid pterodactyloid pterosaur from the Barremian to Aptian-age Lower Cretaceous Jiufotang Formation of Chaoyang, Liaoning, China. Its fossil remains date back about 120 million years ago.

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Largirostrornis is a genus of enantiornithean bird. One species has been named, Largirostornis sexdentoris. It lived during the Early Cretaceous and is known from fossils found in the Jiufotang Formation in Liaoning province, People's Republic of China. Some researchers believe this species to be a junior synonym of the similar Cathayornis yandica.

The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with estimates ranging from the Late Jurassic to the Early Cretaceous. New uranium-lead dates reveal the formation is deposited in the Aptian stage of the Early Cretaceous. Fossils of Microraptor and Jeholornis are from the Jiufotang.

Paraprotopteryx is a genus of enantiornithean birds from the Mesozoic of China.

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Longicrusavis is an extinct genus of basal ornithuromorph bird found only at Dawangzhangzi village in Liaoning Province, China. Longicrusavis was a ground dwelling carnivore, a wader, and part of biological family Hongshanornithidae, considered to have been a dominant species in the Jehol Biota, the prehistoric Chinese ecosystem which supported them. The name Hongshanornithidae represents one of China's oldest recorded cultures in the region, the Hongshan culture.

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<i>Jeholochelys</i> Extinct genus of turtles

Jeholochelys is an extinct genus of sinemydid turtle that lived during the Early Cretaceous of what is now China. The holotype specimen was discovered in the Jiufotang Formation of Sihedang in Lingyuan, western Liaoning. In 2018, the Chinese palaeontologist Shuai Shao and colleagues named the new genus and species Jeholochelys lingyuanensis based on the specimen. The generic name consists of "Jehol", which refers to the Jehol biota, and "chelys", which is Greek for turtle. The specific name refers to the type locality. Seven skeletons were described in the study, five nearly complete, and two consisting of shells, and hundreds of turtle fossils have been found in the area. The described specimens are kept in the Paleontological Museum of Liaoning.

Lingyuanosaurus is a genus of therizinosaurian dinosaur from the Early Cretaceous of China. It contains a single species, L. sihedangensis. It was found within a layer of the Jehol Group.

Wulong is a genus of microraptorine dromaeosaurid dinosaurs from the Early Cretaceous (Aptian) Jiufotang Formation of China. The genus includes a single species, Wulong bohaiensis. The skeletal remains, which include preserved feathers, represent a juvenile.

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Cratonavis is an extinct genus of pygostylian avialian from the Early Cretaceous Jiufotang Formation of Liaoning Province, China. The genus contains a single species, C. zhui, known from a complete skeleton.

<i>Yanliaomyzon</i> Extinct genus of predatory lampreys

Yanliaomyzon is an extinct genus of predatory lampreys that lived approximately 163 million years ago during the Middle Jurassic. It is found in the Yanliao Biota, including both the Daohugou Beds and the Tiaojishan Formation in Liaoning province, northern China. The genus has two species: Yanliaomyzon occisor and Yanliaomyzon ingensdentes. These species are significant for being the earliest lampreys to closely resemble modern species.

Meilifeilong is an extinct genus of chaoyangopterid pterosaurs from the Early Cretaceous Jiufotang Formation of China. The genus contains two species: M. youhao, known from an almost complete skeleton and a partial skull, and M. sanyainus, originally described as a species of Shenzhoupterus. The Meilifeilong youhao holotype represents the best-preserved and most complete chaoyangopterid discovered so far.

References

1 2 3 4 5 6 Huang, Weijia (2023-09-01). "A new species of fossil lamprey (Petromyzontida: Petromyzontiformes) from Hebei, China". Historical Biology : 1–13. doi:10.1080/08912963.2023.2252443. ISSN 0891-2963.
1 2 3 Huang, Weijia; Ma, Zhiheng; Fu, Lihong; Guo, Shilong (2024-01-14). "A new species of lamprey from Cretaceous semisaline environment in China". Historical Biology : 1–7. doi:10.1080/08912963.2024.2303350. ISSN 0891-2963.
↑ 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 .
↑ 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.
↑ Yu, Zhiqiang; Wang, Min; Li, Youjuan; Deng, Chenglong; He, Huaiyu (2021-12-01). "New geochronological constraints for the Lower Cretaceous Jiufotang Formation in Jianchang Basin, NE China, and their implications for the late Jehol Biota". Palaeogeography, Palaeoclimatology, Palaeoecology. 583: 110657. doi: 10.1016/j.palaeo.2021.110657 .

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[Caeruleum-1] 1 2 3 4 5 6 Huang, Weijia (2023-09-01). "A new species of fossil lamprey (Petromyzontida: Petromyzontiformes) from Hebei, China". Historical Biology : 1–13. doi:10.1080/08912963.2023.2252443. ISSN 0891-2963.

[C.gracilis-2] 1 2 3 Huang, Weijia; Ma, Zhiheng; Fu, Lihong; Guo, Shilong (2024-01-14). "A new species of lamprey from Cretaceous semisaline environment in China". Historical Biology : 1–7. doi:10.1080/08912963.2024.2303350. ISSN 0891-2963.

[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 .

[Mesomyzon2021-4] 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.

[JiufotangFm-5] Yu, Zhiqiang; Wang, Min; Li, Youjuan; Deng, Chenglong; He, Huaiyu (2021-12-01). "New geochronological constraints for the Lower Cretaceous Jiufotang Formation in Jianchang Basin, NE China, and their implications for the late Jehol Biota". Palaeogeography, Palaeoclimatology, Palaeoecology. 583: 110657. doi: 10.1016/j.palaeo.2021.110657 .

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