Temporal range: Early Oligocene (Rupelian)
Aegyptopithecus, which means "Egyptian Monkey", from Greek Αίγυπτος (Egypt) and πίθηκος (ape or monkey), is an early fossil catarrhine that predates the divergence between hominoids (apes and humans) and cercopithecids (Old World monkeys). It is known from a single species, Aegyptopithecus zeuxis, which lived around 30 million years ago in the early part of the Oligocene epoch. It likely resembled modern-day New World monkeys, and was about the same size as a modern howler monkey, which is about 56 to 92 cm (22 to 36 in) long. Aegyptopithecus fossils have been found in the Jebel Qatrani Formation of modern-day Egypt. Aegyptopithecus is believed to be a stem-catarrhine, a crucial link between Eocene and Miocene fossils.
Discovery, age and taxonomy
Aegyptopithecus was discovered by Elwyn Simons in 1965 in the Jebel Qatrani Formation, located in the Faiyum Governorate of central Egypt. Aegyptopithecus zeuxis fossils were originally thought to be between 35.4 and 33.3 million years old, based on initial analysis of the formation in which they were found. However, analysis by Erik Seiffert in 2006 concluded that the age of the Jebel Qatrani Formation should be revised. His assessment of more recent evidence indicates an age of between 30.2 and 29.5 million years ago.
If Aegyptopithecus is placed in its own genus, then there is one documented species named A. zeuxis. The type specimen for the species is CGM26901. Its scientific name means "linking Egyptian ape".
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.
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 shares characteristics with haplorrhines such as a fused mandibular and frontal symphyses, postorbital closure, and superior and inferior transverse tori.
In Egypt’s Fayum Depression a subadult female cranium, CGM 85785, was discovered by Rajeev Patnaik. This specimen’s cranial capacity was found to be 14.63 cm3 and reanalysis of a male endocast (CGM 40237) estimates a cranial capacity of 21.8 cm3. These estimates dispel earlier ones of approximately 30 cm3. These measurements, give an estimated male to female endocranial ratio of approximately 1.5, indicating A. zeuxis to be a dimorphic species.
In relation to other anthropoids, the frontal lobes of A. zeuxis are considered to be rather small but the olfactory bulbs are not considered to be small when taking into account the body size of A. zeuxis.
Overall, the brain to body weight ratio of A. zeuxis is considered to be strepsirrhine-like and perhaps even non-primate like.
Aegyptopitheccus zeuxis is thought to have been sexually dimorphic. Tooth size, craniofacial morphology, brain size, and body mass all indicate this. Due to A. zeuxis being sexually dimorphic, the social structure is thought to have been polygynous with intense competition for females.
Based on estimated femoral neck angle (120-130 degrees) of aforementioned remains, the femur is similar to that of a quadrupedal anthropoid. The greater trochanter’s morphology is inconsistent with that of leaping primates, serving as further evidence of the animal’s quadrupedalism.
Aegyptopithecus is thought to have been an arboreal quadruped due to the distal articular region of the femur, which is deeper than that of “later” catarrhines. Also, based on overall femoral morphology, A. zeuxis is thought to have been robust.
In addition, the ulna and distal articular surface of the humerus indicate that A. zeuxis was not only an arboreal quadruped, but also large and slow. This is consistent with evidence extrapolated from femoral morphology.
Studies in dental microwear and microsutures focusing on its molars, suggest that Aegyptopithecus was probably a frugivore. It is also possible that Aegyptopithecus ate hard objects on occasion.
Aegyptopithecus lived in the Fayum area of northern Egypt. Today, this area is semiarid and lacking in vegetation. At the time of Aegyptopithecus’ existence, the Oligocene, this area was heavily vegetated, subtropical, had many trees and had seasonal rainfall.
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- Ankel-Simons, Friderun; John G. Fleagle & Prithijit S. Chatrath (1998). "Femoral Anatomy of Aegyptopithecus zeuxis, An Early Oligocene Anthropoid". American Journal of Physical Anthropology. 106 (4): 413–424. doi:10.1002/(SICI)1096-8644(199808)106:4<413::AID-AJPA1>3.0.CO;2-K. PMID 9712474.
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- Harrison, Terry (2012). "Chapter 20 Catarrhine Origins". In Begun, David. A Companion To Paleoanthropology. Wiley Blackwell. ISBN 978-1-118-33237-5. Archived from the original on 2013.
- Simons, Elwyn L.; et al. (2007). "A remarkable female cranium of the early Oligocene anthropoid Aegyptopithecus zeuxis (Catarrhini, Propliopithecidae)". PNAS. 104 (21): 8731–8736. doi:10.1073/pnas.0703129104. PMC . PMID 17517628.
- Fleagle, John G. & Elwyn L. Simons (1982). "The Humerus of Aegyptopithecus zeuxis: A Primitive Anthropoid". American Journal of Physical Anthropology. 59 (2): 175–193. doi:10.1002/ajpa.1330590207. PMID 6816072.
- Teaford, Mark F.; Mary C. Maas & Elwyn L. Simons (1996). "Dental Microwear and Microstructure in Early Oligocene Primates From the Fayum, Egypt: Implications for Diet". American Journal of Physical Anthropology. 101 (4): 527–543. doi:10.1002/(SICI)1096-8644(199612)101:4<527::AID-AJPA7>3.0.CO;2-S. PMID 9016366.
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|Wikimedia Commons has media related to Aegyptopithecus.|
- Aegyptopithecus, Archaeology.info site
- Fleagle JG; Simons EL (October 1982). "The humerus of Aegyptopithecus zeuxis: a primitive anthropoid". Am. J. Phys. Anthropol. 59 (2): 175–93. doi:10.1002/ajpa.1330590207. PMID 6816072.
- Aegyptopithecus zeuxis, paragraph and picture on Duke University site.
- Aegyptopithecus zeuxis, article on members.tripod.com
- Rossie JB, Simons EL, Gauld SC, Rasmussen DT (June 2002). "Paranasal sinus anatomy of Aegyptopithecus: Implications for hominoid origins". Proc. Natl. Acad. Sci. U.S.A. 99 (12): 8454–6. doi:10.1073/pnas.092258699. PMC . PMID 12060786.