Genus: Hydrorion GROßMANN, 2007
Etymology: Greek, hydro, "water" and Orion, the hunter of Greek mythology.
Species: brachypterygius (HUENE, 1923) GROßMANN, 2007
Etymology: Greek, brachys, "short" and Greek, pterygium, "wing-like."
= Plesiosaurus brachypterygius HUENE,
1923
= Microcleidus brachypterygius (HUENE,
1923), BAKKER, 1993
Holotype: GPIT/477/1/1
Locality: Quarry (Steinbuch) 29, Ohmden near Holzmaden, Baden-Wurttemberg State, Southern Germany.
Horizon: Posidonienschiefer.
Biostratigraphy: Lias epsilon II, 4 (unterer Schiefer), Harpoceras falcifer zone.
Age: Lower Toarcian Stage, Upper Lias Epoch, Late Early Jurassic.
Material: Skull and skeleton.
Referred material:
SMNS 51143: A nearly complete specimen in lateral view, only the anterior part of the skull is preserved.
SMNS 51141: A nearly complete juvenile specimen.
MH Nr 8: A nearly complete specimen.
Note: LIas E, uppemost ii, diretly below II2)