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

Species: baitaigouensis JI, JI, CHENG, YOU, LÜ & YUAN, 2004
Etymology:

Holotype:

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.

Referred material:

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-03-7-02: Fragmentary adult with 12 leathery eggs and embryos.