(Isanosaurus attavipachi thigh bone). Isanosaurus was one of the first sauropod dinosaurs. It lived approximately 210 million years ago during the Upper Triassic (late Norian to Rhaetian stages) in Thailand. 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.