It was a medium-sized, ground-dwelling, bipedal herbivore that represents the third therizinosaur taxon from the Bayan Shireh Formation, although it is known from the lower part.

The genus is monotypic, including only the type species E. mongoliensis, known from a well preserved pelvis and other tentative body remains.

[1] In 1980, it was mentioned again, this time in the new infraorder created by the Mongolian paleontologists Rinchen Barsbold and Altangerel Perle: Segnosauria.

These specific traits may indicate the advanced age of the individual, if true, the fusion of the obturator process and pubic body could be discarded as an authentic autapomorphy for the species.

[5] Enigmosaurus was by the describers assigned to a separate Enigmosauridae (now obsolete) due to its aberrant pelvis, but later considered a member of the Segnosauridae which are today called the Therizinosauridae.

[5] Below are the results of the recently performed phylogenetic analysis of the Therizinosauria by Hartman et al. 2019, in which Enigmosaurus is recovered as a derived therizinosauroid.

[12] Falcarius Jianchangosaurus Beipiaosaurus "Chilantaisaurus" zheziangensis Enigmosaurus Alxasaurus Therizinosauridae The remains of Enigmosaurus were found in sediments that were deposited during the Late Cretaceous period on the Bayan Shireh Formation, Khara Khutul locality, about 95.9 ± 6.0 million to 89.6 ± 4.0 million years ago, Cenomanian-Santonian ages.

[10] At the locality, diverse paleoflora has been discovered, such as Cornaceae reported with Bothrocaryum gobience and Nyssoidea mongolica as fine representatives.

[21] Numerous fossil fruit findings at the locality reflect the large presence of angiosperm plants on the formation.