Saadanius

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Saadanius
Temporal range: 29–28 
Ma
↓
"Saadanius hijazensis"
Saadanius hijazensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Parvorder: Catarrhini
Superfamily: †Saadanioidea
Zalmout et al., 2010
Family: †Saadaniidae
Zalmout et al., 2010
Genus: †Saadanius
Zalmout et al., 2010
Species:
†S. hijazensis
Binomial name
†Saadanius hijazensis
Zalmout et al., 2010

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. It is represented by a single species, Saadanius hijazensis, which is known only from a single partial skull tentatively dated between 29 and 28 million years ago. It was discovered in 2009 in western Saudi Arabia near Mecca and was first described in 2010 after comparison with both living and fossil catarrhines.

Saadanius had a longer face than living catarrhines and lacked the advanced frontal sinus found in living catarrhines. However, it had a bony ectotympanic and teeth comparable to those of living catarrhines. Its discovery provided new information about the early evolution of catarrhines.

Taxonomy

The specimen was found with the palate and teeth facing upward.

Saadanius is known from a single specimen, the holotype, named "SGS-UM 2009-002", stored in Jeddah, Saudi Arabia, at the Paleontology Unit of the Saudi Geological Survey (SGS).[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. While looking for dinosaur fossils in an area that, according to the maps he was working from, contained rock layers that dated to the Cretaceous, Zalmout found the jawbone of an anthracotheriid, which dated to the Eocene or Oligocene. This indicated that the rock layers were much younger than what was dated on the maps. The following day, he noticed fossil teeth, which he immediately recognized as those of a primate. Zalmout emailed a photo of the teeth to paleontologist Philip D. Gingerich, with whom he was working as a postdoctoral fellow. Gingerich, an expert on ancient primates and whales, confirmed that it was indeed a primate. Due to a tight schedule, Zalmout had to leave the exposed fossil embedded in the rock for the next few days because collecting it would require days of work.[3] The fossil was soon recovered by a joint expedition involving the SGS and the University of Michigan.[1]

The fossil was formally described in 2010 when its discovery was announced in the journal

Arabic: سَعدان), which is the collective term for apes and monkeys. The species name, hijazensis, is a reference to the al Hijaz region, in which it was discovered.[1]

Description

Front and side view of Saadanius hijazensis.

The only known fossil of Saadanius is a partial skull, preserving much of the face and palate and many of the teeth. Two bite marks, one of which may have been fatal, are visible on the skull.

diastema between its canine teeth and second incisors, and its sagittal crest suggest that the specimen was a male.[1] These features are shared among male Old World monkeys.[2]

Saadanius had a longer face than living catarrhines,

stem group of catarrhines, which date back 35 to 30 mya, lacked a fully developed ectotympanic.[1][4]

The upper molars were relatively wide, with prominent well-separated cusps. The third upper molar (M3) was larger than the second (M2). The canines were relatively smaller than in some later taxa like Proconsul, with an approximately oval cross-section. The nasal aperture is relatively large, though unlike in Dendropithecus it does not extend between the roots of the first incisors. The nasals are long and narrow and do not touch the premaxillae.[1]

Phylogeny

Saadanius placement within the catarrhine clade[1]
 Catarrhini 

 Propliopithecoidea (Aegyptopithecus) 

 Pliopithecoidea (Pliopithecus) 

 Saadanius 

crown catarrhines
(living and fossil)

hominoids, placing it among crown catarrhines.[6][7]

Animated 3D view of the skull

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. Another reconstruction, based on the morphology of early Miocene apes and the basal cercopithecoid Victoriapithecus, predicts that the last common ancestor had a projecting snout and tall face, like that of living baboons and the oldest fossil apes and Old World monkeys. 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.[4]

According to Zalmout et al., Saadanius may also help resolve the age of the hominoid–cercopithecoid split.

fossil record does not indicate that crown groups have evolved, and stem taxa may survive for millions of years after the crown taxa appear. 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. Furthermore, Pozzi et al. pointed out that the supplementary material published by Zalmout et al. demonstrated that Pliopithecoidea were more closely related to living catarrhines than Saadanius.[8] In 2013, two other Oligocene catarrhines were announced, the proposed Old World monkey Nsungwepithecus and the hominoid Rukwapithecus.[9]

The fossil find has also been seen by the SGS as an important find for Saudi Arabia, because it enriches the fossil record for the region. As a result of the find, both the SGS and the University of Michigan are considering more collaborative field explorations in the country.[3]

Paleoecology

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. Other fossils recovered from the same horizon include a few teeth and jaws of the following mammals:[1]

The presence of a gomphothere and mammutid suggests that the deposits are younger than the

Fayum in Egypt, while the other taxa indicate an older age than the Chilga Formation of Ethiopia. This led Zalmout's team to assign an age of 28 or 29 million years to the Shumaysi Formation fauna.[1][4] However, the date has yet to be confirmed by other dating techniques.[4] A 2020 review assigned the Harrat Al Ujayfa locality to the Turkwelian African land mammal age, which started 28.2 million years ago.[10]

Like other catarrhine primates, Saadanius was probably a tree-dweller.[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.[2]

The specimen had serious puncture wounds on the front of the skull, indicating that it had been preyed upon by a large

frontal trigone.[1]

References

  1. ^
    S2CID 205220837
    .
  2. ^ a b c d e f Sample, I. (14 July 2010). "Ape ancestors brought to life by fossil skull of 'Saadanius' primate". The Guardian.
  3. ^ a b c Ross-Flanigan, N. (14 July 2010). "Fossil find puts a face on early primates". University of Michigan News Service.
  4. ^
    doi:10.1038/news.2010.354
    .
  5. ^ a b c d Ghosh, P. (14 July 2010). "Fossil links humans and monkeys". BBC News. Archived from the original on 15 July 2010.
  6. PMID 32900315
    .
  7. S2CID 4397839
    .
  8. ^
    PMID 21497373
    .
  9. S2CID 4395931
    .
  10. S2CID 229372221
    .

External links

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