[3] The specimen was found in dark red sandstone of the Nam Phong Formation near the village of Ban Non Thaworn, in Chaiyaphum Province.

[3] With regard to vertebrate fossils, the Nam Phong Formation is poorly explored: besides Isanosaurus, only two articulated ischia were found.

[3] In prosauropods, but also in the very basal sauropod Antetonitrus, the thigh bone was slightly sigmoidal (S-curved).

[4] Also, like in other sauropods, bony processes of the femur were reduced in Isanosaurus; most notably, the lesser trochanter was lacking.

The following cladogram shows the position of Isanosaurus within Massopoda, according to Oliver W. M. Rauhut and colleagues, 2020:[1] Eucnemesaurus Riojasaurus Sarahsaurus Yunnanosaurus Jingshanosaurus Seitaad Coloradisaurus Glacialisaurus Lufengosaurus Massospondylus Adeopapposaurus Leyesaurus Xingxiulong Anchisaurus Leonerasaurus Mussaurus Aardonyx Sefapanosaurus Meroktenos Melanorosaurus Camelotia Lessemsaurus Antetonitrus Ingentia Blikanasaurus Pulanesaura Gongxianosaurus Schleitheimia Isanosaurus Tazoudasaurus Sauropoda