Aegyptopithecus

Aegyptopithecus Fossil range: Oligocene (35-33 MYA)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Suborder: Haplorrhini (unranked) Catarrhini Superfamily: †Propliopithecoidea Family: †Propliopithecidae Genus: †Aegyptopithecus Species: †A. zeuxis
Binomial name
Aegyptopithecus zeuxis

Aegyptopithecus, also called the Dawn Ape, is an early fossil catarrhine that predates the divergence between hominoids (apes) and Old World monkeys. It is known from a single species Aegyptopithecus zeuxis and lived some 35-33 million years ago in the early part of the Oligocene epoch. It likely resembled modern-day New World monkeys (it is about the same size as a modern howler monkey). Aegyptopithecus fossils have been found primarily in modern-day Egypt. Aegyptopithecus is a crucial link between Eocene fossil and Miocene hominoids.

Morphology

Aegyptopithecus zeuxis was a species that had a dental formula of 2:1:2:3 on both the upper and lower jaws, with the lower molars increasing in size posteriorly. The molars showed an adaptation called compartmentalizing shear, which is where the cutting edges involved in the buccal phase serve to surround basins in such a way that food is cut into fragments that are trapped and then ground during the lingual phase.

The canines of this species were sexually dimorphic. The ascending mandibular ramus of this species is relatively broad. The orbits are dorsally oriented and relatively small which suggested that this was a diurnal species. This species showed some postorbital constriction. The interorbital distance of Aegyptopithecus zeuxis is large much like that found in colobines.

A sagittal crest developed in older individuals and extends over the brow ridges. This species had an auditory region which is similar to that found in platyrrhines, having no bony tube and the tympanic fused to the lateral surface of the bulla. This species had a relatively small brain compared to other haplorrhines; the cranial capacity was about 30 cc. But the brain is advanced when compared to strepsirhines in that this species had an expanded visual cortex, comparatively small olfactory bulbs, and a central sulcus.

The humerus has a head which faces posteriorly and is narrower than primates that practice suspensory behavior. The humerus also shares some features with extinct hominoids: a large medial epicondyle and a comparatively wide trochlea. This species had an ulna that compares to the extinct members of the genus Alouatta.

On the foot bones, this species had a grasping hallux. Aegyptopithecus zeuxis had an average body mass of around 6.7 kilograms. Aegyptopithecus zeuxis shares characteristics with haplorrhines such as a fused mandibular and frontal symphyses, postorbital closure, and superior and inferior transverse tori.

In May 2007 it was announced that a skull that is about half the size of the male skull has been found and identified as belonging to a female of this species. The size difference between the Aegyptopithecus genders is comparable to that of gorillas, which genetically are humans' second-closest relatives.^[1]

Brain Size

Aegyptopithicus had an unusually small brain for a primate. Because it is considered a common ancestor of old and new-world monkeys, or at least a close relative of one, it is considered by some to be evidence that large-brained primates evolved separately in the Old and New World primates.^[2]

Locomotion and Range

Aegyptopithecus zeuxis was most likely an arboreal quadruped, based upon postcranial remains. The first metatarsal and the morphology of the talus suggest this.

Diet

Due to the dental morphology, it's believed that this was a frugivorous species in which leaves also played an important part of its diet.

See also

• List of fossil sites (with link directory)
• List of hominina (hominid) fossils (with images)

References

1. ^ http://www.sciencedaily.com/releases/2007/05/070514174240.htm
2. ^ http://www.newscientist.com/article.ns?id=dn11841&feedId=online-news_rss20

External links

• Aegyptopithecus, Archaeology.info site
• Aegyptopithecus zeuxis Skull, skullsunlimited.com site
• The humerus of Aegyptopithecus zeuxis: a primitive anthropoid, abstract of article by Fleagle JG, Simons EL, in Am J Phys Anthropol. 1982 Oct;59(2):175-93, shown on pubmed.gov
• Aegyptopithecus zeuxis, paragraph and picture on Duke University site.
• Aegyptopithecus zeuxis, article on members.tripod.com
• Paranasal sinus anatomy of Aegyptopithecus: Implications for hominoid origins, article by James B. Rossie et al. in PNAS 2002;99. Entire text, pictures, bibliography.

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