Genus: Hyphalosaurus GAO, TANG & WANG, 1999
Etymology: Greek, hyphalos, “submerged, underwater” and Greek, sauros, “lizard”; Underwater lizard.
= Sinohydrosaurus LI, ZHANG & LI, 1999
Etymology:

Species: lingyuanensis GAO, TANG & WANG, 1999
Etymology: In reference to Lingyuan, Liaoning Province, China.

Holotype: IVPP V11705

Locality: Fanzhangzi, Dawangzhangzi (Daxinfanzi) bed, Lingyuan, Liaoning Province, China.

Horizon: Horizon II, Yixian Formation, Jehol Group.

Biostratigraphy: Psittacosaurus fauna, Liaoxiornis Avifauna.

Age: Lower Hautervian Stage, Uppermost Neocomian Subepoch, Lower Early Cretaceous Epoch, Early Cretaceous.

Material: Complete specimen with 6 Lycoptera on the slab.

Referred material:

Note: Hundereds of specimens have been found in Liaoning ranging from babies to adults.

GAO & KSEPKA, 2008

PKUP V1052: Skull and skeleton.
Note: Has integument along the neck.

PKUP V1057, 1058, BMNHC V050: Fragmentary specimens.

GMC, unnumbered: Juvenile specimens.

 

BUFFETAUT, LI, TONG, & ZHANG, 2007

Locality: Wanfuotang, Yixian, Liaoning Province, China.

Horizon: Yixian Formation.

Biostratigraphy:

Age: Early Cretaceous.

Material:

SPM R10: Embryo.

Note: Mutation with two necks and heads.

SPM R13: Embryo.

 

= Sinohydrosaurus lingyuanensis LI, ZHANG & LI, 1999
Etymology: In reference to Lingyuan.

Holotype: BVC 398

Locality: Fanzhangzi, Dawangzhangzi, Lingyuan, Liaoning Province, China.

Horizon: Yixian Formation.

Biostratigraphy:

Age: Early Cretaceous.

Material: Complete specimen with 6 Lycoptera on the slab.
Note: Part and counterpart of the same specimen, Hyphalosaurus lingyanensis GAO, TANG & WANG, 1999 was published shortly after LI, ZHANG & LI, 1999

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Species: baitaigouensis JI, JI, CHENG, YOU, LÜ & YUAN, 2004
Etymology: In refererence to the Baitaigou village, northwest of the Yizhou town, Yixian County, Liaoning Province, China.

Holotype: CAGS-IG-03-7-02

Locality: Baitaigou village, northwest of the Yizhou town, Yixian County, Liaoning Province, China.

Horizon: Yixian Formation, Jehol Group.

Biostratigraphy: Psittacosaurus Fauna, Confuciusornis Avifauna.

Age: Valanginian Stage, Upper Neocomian Subepoch, Early Early Cretaceous Epoch, Early Cretaceous.

Material: Fragmentary adult with 12 leathery eggs and embryos.

Referred material:

AZUMA, 2005

IG-15, 16: Two skeletons.

HOU, LI, KSEPK, GAO, & NORELL, 2009

LPM-R168: Flex shelled egg and hatchling.

LPM-R169: Flex shelled egg.

JI, JI, LU, YOU & YUAN, 2006

CAGS-IG-03-7-08: 1 adult specimen and 1 juvenile.

GAO & KSEPKA, 2008

PKP V1056, LMPC R00052, R00065, R00066, BMNHC V050, V060, V014: Fragmentary skulls and skeletons.

JI, WU & CHENG, 2010

CAGS-IB-06131: Nearly complete specimen.

Note: Has 18 embryos in the body cavity.