Proconsul africanus
Encyclopedia
Proconsul africanus is the first species of the oligocene
-era fossil
genus of primate
to be discovered and was named by Arthur Hopwood, an associate of Louis Leakey, in 1933.
in Lake Victoria
uncovered more species of Proconsul. Mary Leakey
made an especially complete find of Proconsul
there in 1948, which was for a number of decades labeled africanus, but was reclassified as heseloni in 1993 by Alan Walker. In 1951 Leakey and Le Gros Clark placed Hopwood's Xenopithecus koruensis ("strange ape from Koru, Kenya
") with africanus. In 1951 also T. Whitworth found more Proconsul on Rusinga, which he considered africanus, but they were lumped with 1992 finds by Walker to form heseloni.
The 18-million-year-old fossil species has been considered a possible ancestor of both great and lesser ape
s, and of human
s. The paleontologist Louis Leakey
, who was one of the foremost fossil-hunters of the 20th century and a champion of evolution
, said:
s of this species had thin enamel and there was a prominent molar cingula. This species also possessed a robust zygomatic bone
and a pronounced snout. This species had a broad interorbital region
and small frontoethmoidal sinuses
. The maxillary sinus
was restricted. This species had an auditory region which would be similar to that of extant ape
s and cercopithecoid monkeys
. The ectotympanic tube was well-developed. This species lacked a tail and the canines of this species were sexually dimorphic. The skull lacks supraorbital tori
and can be considered somewhat prognathous
. This species has a cranial capacity
of 167 cc and an encephalization quotient
of 1.5. Based on the cranium, this species had an external brain surface
much like that of gibbon
s and cercopithecoid monkeys. The wrist of this species has been described as monkey-like. This species has a talus in which the trochlear surface is highly curved and deeply grooved. The foot of this species possessed a transverse arch. Proconsul africanus had a brachial index of 96 which is comparable to the extant genus Pan
. Overall the skeleton of this species can be described as being robust. This species had an average body mass of around 18 kilograms.
, it is conjectured that Proconsul africanus was a frugivorous species. A study by Aiello in 1981 concluded it was a "below-branch feeder."
.
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
-era fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
genus of primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
to be discovered and was named by Arthur Hopwood, an associate of Louis Leakey, in 1933.
Discovery
The Leakey expedition of 1947-1948 to Rusinga IslandRusinga Island
Rusinga Island, with an elongated shape approx. 10 miles from end to end and 3 miles at its widest point, lies in the eastern part of Lake Victoria at the mouth of the Winam Gulf...
in Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
uncovered more species of Proconsul. Mary Leakey
Mary Leakey
Mary Leakey was a British archaeologist and anthropologist, who discovered the first skull of a fossil ape on Rusinga Island and also a noted robust Australopithecine called Zinjanthropus at Olduvai. For much of her career she worked together with her husband, Louis Leakey, in Olduvai Gorge,...
made an especially complete find of Proconsul
Proconsul (genus)
Proconsul is an extinct genus of primates that existed from 23 to 5 million years ago during the Early Miocene epoch. Fossil remains are present in Eastern Africa including Kenya and Uganda. Four species have been classified to date: P. africanus, P. heseloni, P. major and P. nyanzae. The four...
there in 1948, which was for a number of decades labeled africanus, but was reclassified as heseloni in 1993 by Alan Walker. In 1951 Leakey and Le Gros Clark placed Hopwood's Xenopithecus koruensis ("strange ape from Koru, Kenya
Koru, Kenya
Koru is a village in Nyando District, Nyanza Province, Kenya. It forms an electoral ward of Muhoroni Constituency and Muhoroni town council . Koru is also a location in the Muhoroni division of Nyando District . Elevation 1540m.- Transport :...
") with africanus. In 1951 also T. Whitworth found more Proconsul on Rusinga, which he considered africanus, but they were lumped with 1992 finds by Walker to form heseloni.
The 18-million-year-old fossil species has been considered a possible ancestor of both great and lesser ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s, and of human
Human
Humans are the only living species in the Homo genus...
s. The paleontologist Louis Leakey
Louis Leakey
Louis Seymour Bazett Leakey was a British archaeologist and naturalist whose work was important in establishing human evolutionary development in Africa. He also played a major role in creating organizations for future research in Africa and for protecting wildlife there...
, who was one of the foremost fossil-hunters of the 20th century and a champion of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
, said:
Morphology
Proconsul africanus had a dental formula of 2:1:2:3 on both the upper and lower jaws. The 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 of this species had thin enamel and there was a prominent molar cingula. This species also possessed a robust zygomatic bone
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...
and a pronounced snout. This species had a broad interorbital region
Interorbital region
The interorbital region of the skull is located between the eyes, anterior to the braincase. The form of the interorbital region may exhibit significant variation between taxonomic groups....
and small frontoethmoidal sinuses
Ethmoid sinus
The ethmoid sinus is each of the two paranasal sinuses within the ethmoid bone, comprising the ethmoidal air cells and filled with air. These are divided into anterior, middle and posterior group. The ethmoidal air cells consist of numerous thin-walled cavities situated in the ethmoidal labyrinth...
. The maxillary sinus
Maxillary sinus
The pyramid shaped maxillary sinus is the largest of the paranasal sinuses, and drains into the nose. It is present at birth as rudimentary air cells, and develops throughout childhood.-General characteristics:...
was restricted. This species had an auditory region which would be similar to that of extant ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s and cercopithecoid monkeys
Old World monkey
The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous...
. The ectotympanic tube was well-developed. This species lacked a tail and the canines of this species were sexually dimorphic. The skull lacks supraorbital tori
Supraorbital ridge
The supraorbital ridge, or brow ridge, refer to a bony ridge located above the eye sockets of all primates. In Homo sapiens sapiens the eyebrows are located on their lower margin.Other terms in use are:* supraorbital arch...
and can be considered somewhat prognathous
Prognathism
Prognathism is a term used to describe the positional relationship of the mandible and/or maxilla to the skeletal base where either of the jaws protrudes beyond a predetermined imaginary line in the coronal plane of the skull. In general dentistry, oral and maxillofacial surgery and orthodontics...
. This species has a cranial capacity
Cranial capacity
Cranial capacity is a measure of the volume of the interior of the cranium of those vertebrates who have both a cranium and a brain. The most commonly used unit of measure is the cubic centimetre or cc...
of 167 cc and an encephalization quotient
Encephalization quotient
Encephalization Quotient , or encephalization level is a measure of relative brain size defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which is hypothesized to be a rough estimate of the intelligence of the animal.This is a more refined...
of 1.5. Based on the cranium, this species had an external brain surface
Sulcus (neuroanatomy)
In neuroanatomy, a sulcus is a depression or fissure in the surface of the brain.It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals....
much like that of gibbon
Gibbon
Gibbons are apes in the family Hylobatidae . The family is divided into four genera based on their diploid chromosome number: Hylobates , Hoolock , Nomascus , and Symphalangus . The extinct Bunopithecus sericus is a gibbon or gibbon-like ape which, until recently, was thought to be closely related...
s and cercopithecoid monkeys. The wrist of this species has been described as monkey-like. This species has a talus in which the trochlear surface is highly curved and deeply grooved. The foot of this species possessed a transverse arch. Proconsul africanus had a brachial index of 96 which is comparable to the extant genus Pan
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
. Overall the skeleton of this species can be described as being robust. This species had an average body mass of around 18 kilograms.
Diet
Based upon the dental morphologyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, it is conjectured that Proconsul africanus was a frugivorous species. A study by Aiello in 1981 concluded it was a "below-branch feeder."
Range and Locomotion
Based on postcranial pieces, Proconsul africanus was likely an arboreal quadrupedQuadruped
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"...
.
See also
- Nakalipithecus
- List of fossil sites (with link directory)
- List of hominina (hominid) fossils (with images)
External links
- Proconsul africanus at members.tripod.com.
- Proconsulidae, Mikko's Phylogeny archives.