Afropithecus
Encyclopedia
Afropithecus turkanensis, a new Miocene
hominoid, was excavated from a small site near Lake Turkana
called Kalodirr in northern Kenya
in 1986 and was named by Richard Leakey
and Meave Leakey
. The estimated age of Afropithecus is between 16 and 18 million years old, which was determined with radiometric dating
techniques and the geological studies conducted by Broschetto and Brown from the University of Utah
. In total there are 46 recovered specimens from Kalodirr relating to Afropithecus consisting of cranial, mandible
, dentition
and post-cranial remains. The type specimen of Afropithecus turkanensis is KNM-WK 16999.
s that indicated a general distinction from known large early catarrhines, and later concluded that A. turkenensis was a primitive, arboreal quadruped
similar to P. nyanzae, and that A. turkanensis had primitive facial morphology and derived dental characteristics that would suggest a diet of hard fruits.
, the facial skeleton, frontal
, much of the coronal structure, most of the sphenoid
, and relatively unworn adult dentition; the right orbit (virtually complete), the right zygomatic
, the pterygoid
, most of the sphenoid and lesser wings, the maxilla
and premaxilla
, and adult dentition with procumbent incisor
s. The surface on the right side maxilla and premaxilla along with the enamel
on the right molars has been lost over time and has been replaced with calcite crystals, which only provide the general shape and not the details.
From dentition its known that the palate, which is almost completely calcified, of A. turkanensis is shallow, long and narrow with tooth rows that converge posteriorly, and it is probable the tooth rows were originally nearly parallel. A. turkanensis had a 6.5mm diastema
between its very procumbent second incisor (KNM-WT 16999 had large, broad incisors) and the canine
.
The thickness of the enamel on the molars is often reported when fossils are being recorded and used to make comparisons across taxa. The thickness is referred to either as "thin" or "thick" and is commonly assessed as a linear measurement of the enamel on worn or naturally fractured teeth. From enamel testing it has been suggested that A. turkanensis is the oldest known thick-enamelled hominoid, which is what would distinguish it from Kenyapithecus.
Other post-cranial remains include: KNM-WK 17016P a large right ulna
, and foot or hand bones: KNM-WK 17008, KNM-WK 18395.
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
hominoid, was excavated from a small site near Lake Turkana
Lake Turkana
Lake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...
called Kalodirr in northern Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
in 1986 and was named by Richard Leakey
Richard Leakey
Richard Erskine Frere Leakey is a politician, paleoanthropologist and conservationist. He is second of the three sons of the archaeologists Louis Leakey and Mary Leakey, and is the younger brother of Colin Leakey...
and Meave Leakey
Meave Leakey
Meave G. Leakey is together with her husband Richard Leakey one of the most renowned contemporary paleontologists. She studies the origin of mankind in Africa.-Flat-Faced Man of Kenya:...
. The estimated age of Afropithecus is between 16 and 18 million years old, which was determined with radiometric dating
Radiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
techniques and the geological studies conducted by Broschetto and Brown from the University of Utah
University of Utah
The University of Utah, also known as the U or the U of U, is a public, coeducational research university in Salt Lake City, Utah, United States. The university was established in 1850 as the University of Deseret by the General Assembly of the provisional State of Deseret, making it Utah's oldest...
. In total there are 46 recovered specimens from Kalodirr relating to Afropithecus consisting of cranial, mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
, dentition
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
and post-cranial remains. The type specimen of Afropithecus turkanensis is KNM-WK 16999.
Morphology
Leakey and Leakey first described Afropithecus turkanensis to be a large hominoid which appeared to have relatively thick enamel. Leakey suggested that A. turkanensis shared postcranial features with the species Prosconsul nyanzae, which is the best known genus Miocene with literally hundreds of fossils having been found representing almost all skeletal elements, and sharing cranial features with Aegyptopithecus zeuxis and dental features with Heliopithecus leakeyi which had two weathered molarMolar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
s that indicated a general distinction from known large early catarrhines, and later concluded that A. turkenensis was a primitive, arboreal quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
similar to P. nyanzae, and that A. turkanensis had primitive facial morphology and derived dental characteristics that would suggest a diet of hard fruits.
Cranial Morphology
The type specimen, KNM-WT 16999 is composed of a long distinct snoutSnout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
, the facial skeleton, frontal
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
, much of the coronal structure, most of the sphenoid
Sphenoid bone
The sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...
, and relatively unworn adult dentition; the right orbit (virtually complete), the right zygomatic
Zygomatic bone
The zygomatic bone is a paired bone of the human skull. It articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. The zygomatic is homologous to the jugal bone of other tetrapods...
, the pterygoid
Pterygoid processes of the sphenoid
The pterygoid processes of the sphenoid, one on either side, descend perpendicularly from the regions where the body and great wings unite.Each process consists of a medial pterygoid plate and a lateral pterygoid plate, the upper parts of which are fused anteriorly; a vertical sulcus, the...
, most of the sphenoid and lesser wings, the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
and premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
, and adult dentition with procumbent incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s. The surface on the right side maxilla and premaxilla along with the enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
on the right molars has been lost over time and has been replaced with calcite crystals, which only provide the general shape and not the details.
From dentition its known that the palate, which is almost completely calcified, of A. turkanensis is shallow, long and narrow with tooth rows that converge posteriorly, and it is probable the tooth rows were originally nearly parallel. A. turkanensis had a 6.5mm diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
between its very procumbent second incisor (KNM-WT 16999 had large, broad incisors) and the canine
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
.
The thickness of the enamel on the molars is often reported when fossils are being recorded and used to make comparisons across taxa. The thickness is referred to either as "thin" or "thick" and is commonly assessed as a linear measurement of the enamel on worn or naturally fractured teeth. From enamel testing it has been suggested that A. turkanensis is the oldest known thick-enamelled hominoid, which is what would distinguish it from Kenyapithecus.
Post-Cranial Morphology
Post cranial remains such as KNM-WK 16901, includes an associated right fibula (lacking the proximal portion, and is approximately the same size as Pan troglodytes; 184 mm), a right proximal third metatarsal, a right fourth metatarsal lacking the head, and an incomplete first metatarsal head.Other post-cranial remains include: KNM-WK 17016P a large right ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
, and foot or hand bones: KNM-WK 17008, KNM-WK 18395.
See also
- List of fossil sites (with link directory)
- List of hominina (hominid) fossils (with images)
- HeliopithecusHeliopithecusHeliopithecus is an extinct genus of primates that existed 16 million years ago during the Miocene epoch. Fragmentary fossil remains of a jaw and isolated teeth were found in Saudi Arabia which have been described as belonging to H. leakeyi...
External links
- http://www.primates.com/history/
- http://www.mc.maricopa.edu/~reffland/anthropology/anthro2003/origins/primates/primate_evol/miocene.html
- Mikko's Phylogeny archives