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The order of Acipenseriformes (Sturgeon-like fishes) both includes sturgeons (Acipenseridae) and paddlefish (Polyodontidae). At least three Sturgeon-like fishes (Acipenseriformes) can be found in the Jiufotang Formation (Jehol Group) and in the Yixian Formation in western Liaoning and northern Hebei Province China: Peipiaosteus pani Liu and Zhou, 1965, Protopsephurus liui Lu, 1994 and Yanosteus longidorsalis Jin, Tian, Yang & Deng, 1995. The Jiufotang Formation - where Peipiaosteus comes from - is dated to about 120.3+/-0.7 million years ago, which was during the Aptian age of the Cretaceous; the Yixian Formation - where Protopsephurus liui and this Y. longidorsalis can be found - is dated slightly older, around 125-121 million years ago (Barremian-early Aptian). Diagnosis from Hilton et al 2021, p. 2: "A †peipiaosteid (sensu Grande and Bemis, 1996) that differs from all other members of the family by possessing an extremely elongate dorsal fin. Other characters that, in combination, differentially diagnose †Yanosteus from other Acipenseriformes include short, stout pectoral fin spine, supraorbital sensory canal anterior to frontal surrounded by a series of small bony tubes, and the absence of epaxial caudal-fin rays." Line drawing from Jin et al. 1995: Identified by oilshale using Jin et al. 1995. References: Jin Fan, Tian Yanping, Yang Youshi, Deng Shaoying (1995) An early fossil sturgeon (Acipenseriformes, Peipiaosteidae) from Fengning of Hebei, China. Vertebrata PalAsiatica, Vol 33, Issue 1, pp. 1-16. Hilton, E., Grande, L., & Jin, F. (2021) Redescription of †Yanosteus longidorsalis Jin et al., (Chondrostei, Acipenseriformes, †Peipiaosteidae) from the Early Cretaceous of China. Journal of Paleontology, 95(1), 170-183. doi:10.1017/jpa.2020.80

Synonym: Manchurochelys liaoxiensis. Taxonomy from Fossilworks.org. Modified diagnosis for the genus from Brinkman and Peng, 1993a by Tong et al. 2004, p. 2: "A cryptodire with a low domed shell and plastron loosely connected to the carapace as in macrobaenids, differing from all other macrobaenids in having a shell that is nearly as wide as long, in the presence of a preneural and in the presence of a medial fontanelle between the hypoplastron and xiphiplastron; differering from Macrobaena Tatarinov, 1959, Anatolemys Khozatskii and Nesov, 1979, Hangaiemys Sukhanov and Narmandakh, 1974, and Kirgizemys Nesov and Khozatskii, 1973 in that the vertebral scutes are wider than they are long; differering from Sinemys Wiman, 1930 and Manchurochelys Endo and Shikama, 1942 in having the posterior lobe of the plastron wider at the basis. Skull similar to Macrobaena and differing from Hangaiemys and Dracochelys Gaffney and Ye, 1992 in having a wider triturating surface; canalis caroticus internus unfloored or with a thin floor, the foramina anterior canalis caroticus interni located close together at the base of the sella turcica, with sella turcica reduced in size, not reaching the dorsum sellae. Diagnosis for the species from Tong et al., p. 3 (modified from Ji, 1995, Li and Liu, 1999): "A species of Ordosemys, differing from O. leios in having a slight ornamentation on the shell surface, a large semicircular lateral fontanelle on the bridge, and in having the first peripheral not contacting or barely contacting the first costal plate." Line drawing of the shell (dorsal view) from Tong et al. 2004, p. 13: Identified by oilshale. References: Tong, H.; Ji, S. U. A.; Ji, Q. (2004) Ordosemys (Testudines: Cryptodira) from the Yixian Formation of Liaoning Province, Northeastern China: new specimens and systematic revision. American Museum Novitates 438: 1. Zhou, C.-F. and Rabi, M. (20159 A sinemydid turtle from the Jehol Biota provides insights into the basal divergence of crown turtles. Scientific Reports 5:16299:1-12.