Saadanius is a genus of fossil primates dating to the Oligocene that is closely related to the common ancestor of the Old World monkeys and apes, collectively known as catarrhines.

[1] The specimen was discovered in southwestern Saudi Arabia in February 2009[2] by paleontologist Iyad Zalmout, who had traveled to the region to search for ancient whale and dinosaur fossils.

[2] Saadanius had a longer face than living catarrhines,[4] more closely resembling New World monkeys in appearance,[5] although it was larger, similar in size to the siamang.

Propliopithecoids, the oldest stem group of catarrhines, which date back 35 to 30 mya, lacked a fully developed ectotympanic.

[6][7] The discovery of Saadanius provides new evidence for competing hypotheses about the facial appearance of the ancestral crown catarrhines, or common ancestor.

One reconstruction is based on living catarrhine traits and predicts a short face and a rounded braincase, similar to that of a gibbon.

The conservative features of Saadanius, similar to those of the older stem catarrhines, support the latter hypothesis, according to Zalmout et al.[1][4][3] However, one palaeontologist, Eric Delson, has cautioned that geological pressure may have distorted the shape of the skull.

[1][5] However, Pozzi et al. later argued that although Saadanius is a significant discovery, because it is a stem catarrhine, it could not be used to date the divergence of the crown group.

For this reason, the fossil record can only suggest a hard minimum boundary for divergence dates, which corresponds to the first appearance of a crown taxon.

[3] Saadanius was found on top of an oolitic ironstone fossil bed of the middle Shumaysi Formation located in the southwest corner of Harrat Al Ujayfa, in western Saudi Arabia, close to Mecca.

[4] A 2020 review assigned the Harrat Al Ujayfa locality to the Turkwelian African land mammal age, which started 28.2 million years ago.

[5] During the time it would have lived, the Red Sea had not yet formed, and new plant and animal species would have been arriving from nearby Eurasia as it converged with the Afro-Arabian landmass.