Isanosaurus

Isanosaurus ("North-eastern Thailand lizard") is an extinct genus of sauropod dinosaur from Thailand. It was originally dated to approximately 219-199  million years ago during the Late Triassic (late Norian to Rhaetian stages), which would make it one of the oldest known sauropods. Its age was later considered uncertain, and may be Early Jurassic or even as young as Late Jurassic. The only species is Isanosaurus attavipachi. Though important for the understanding of sauropod origin and early evolution, Isanosaurus is poorly known. Exact relationships to other early sauropods remain unresolved.

== Discovery and naming == The specimen was found in dark red sandstone of the Nam Phong Formation near the village of Ban Non Thaworn, in Chaiyaphum Province. When discovered in 1998, the skeleton had unfortunately been mostly eroded away. With regard to vertebrate fossils, the Nam Phong Formation is poorly explored: besides Isanosaurus, only two articulated ischia were found. Whether these ischia belong to Isanosaurus is unclear, because no pelvic bones are preserved in the holotype specimen.