Finds made by two paleontologists in eastern Montana in 1964 suggest that some very early primates may have existed as far back as the Late Cretaceous period some 70 million years ago. Molars from two species (one from the Cretaceous period, the other from the Paleocene) of the genus Purgatories show some primate characteristics.
The earlier of these species is very old indeed. It was contemporaneous with at least six species of dinosaurs. In fact, this specimen was recovered from the same site that contained the selection of a triceratops a large horned dinosaur of the late Cretaceous now mounted in the American Museum of Natural History in New York City. Both of these earliest primate finds illustrate how much of the paleontologists’ work depends on inference.
Purgatories may have been a primate, but it is impossible to tell for sure. The Cretaceous specimen consists of only one tooth found with fauna dating from that period. Because the tooth has some characteristics like those found in the teeth of some later Paleocene primates, some paleontologists think it represents a very early primate form.
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Fossil finds from later primates (that lived in the middle Paleocene epoch, about 60 million years ago) are much more abundant; several genera have been identified. The earliest Purgatories remain consist only of teeth, but we have some skeletal parts of the later primates.
Fossil Distribution:
Paleocene and early Eocene archaic primates have been found in both Europe and North America. Several different particular species have been found in both areas. At one time, about 180 million years ago, the continents were not separated as they are today.
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Instead, they formed a single supercontinent; the rest of the earth was covered by sea. Continental drift has since broken up that I super continent. But even after the primates emerged, until about 60 million years ago, North America and Europe were connected in the vicinity of Greenland.
Only in relatively recent times (geologically speaking) have the continents moved far enough apart so that the intervening seas could block gene flow between related population.
1. Oligocene Primates
Not many fossil remains have been discovered from Oligocene epoch. None has been collected from Europe. Specimens from America are also rare. Most of the remains are from Africa. All the
African remains have been discovered in Egypt. The Egyptian varieties include Parapithecus, Propliopithecus, Mocropithcus, Oligopitheciis, Aeolopithecus, Aegyptopithecus, etc. of which two, namely I Aegyptopitheciis and Propliopithecus, will be briefly described here.
2. Aegyptopithecus
Aegyptopitheciis, the best known propliopithecid, probably moved around quadrupedally in the trees, weighed about thirteen pounds, and ate mostly fruit.
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Although its teethes and jaws are ape like, the rest of Aegyptopithecus skeleton is similar to that of the modern South American howler monkey. Because the propliophithecides lack the specialized characteristics of living old world monkeys and apes (catarrhines), but share the dental formula of the catarrhines, it is thought that the propliopithecides were primitive catarrhines, ancestral to both the old world monkeys and the hominoids (apes and humans).
3. Propliopithecus
From the lower Oligocene deposits at Faye in Egypt, another incomplete lower jaw with its teeth but without the ascending ramie was discovered. This is Propliopithecus which is considered to be a primitive anthropoid ape and to be very closely related to the gibbon.
The jaw was somewhat deeper, shorter and more pointed than the jaw of modern gibbon. The canines were not so big. The jaw was about the size of that of a small gibbon.
Though Propliopithecus is considered to be the ancestral form of the gibbons, Aeolopithecus, another African variety of the Oligocene primates, show much more close resemblances to the modern gibbon.
Therefore, some authorities are of opinion that while Aeolopithecus may be the ancestor of the gibbons, Propliopithecus is the ancestor of the other Hominoid. Again, it is stated by others that Parapithecus possibly gave rise to Propliopithecus, the nearest representative of the common ancestor which led, on the one hand to the existing anthropoid apes, and on the other to man.
Whatever that might be, it can be said that some of the Oligocene primates are definitely closely related to the ancestors of the various living Hominoid; while the other may be the direct ancestors of the same. The Oligocene primates are put under Anthropoid.
4. Meocene-Pliocene Primates
Since there seems to be continuity of certain lineages of Anthropoid during the Miocene and Pliocene epochs, the fossil primates of these epochs can be considered together. From this period fossil remains of several Hominoid forms, besides that of Carbide, Cercopithecidae and Lorisidae have been found from different parts of Asia, Europe and Africa.
As now we are more concerned with the fossil primates of the Ape grade, here we shall be dealing with certain important members of the Hominoid group only. Some of these hominoids are closely related to the apes to be the ancestral forms of the latter while others are most likely ancestral to the Pleistocene hominids, and therefore, some of them are included as members of the family Homicide. It has already been stated earlier that the living monkeys represent a stage of evolution between prosimians and hominoids.
5. Dryopithecine
During Miocene and Pliocene epochs the Dryopithecine primate of different varieties flourished in Europe, Africa and Asia. Fossil remains of Dryopithecine have been discovered from Europe, East Africa, Middle East, China and India.
As in most of the cases lower jaw and teeth of this extinct type have been discovered, their phylogenetic relationships are determined on the basis of dental anatomy mostly. Gregory and Hellman fully studied their dental characters and they believed that Dryopithecine were the common ancestor of the living anthropoid apes and man.
The numerous Dryopithecine animals assigned to different geological ages show considerable variation in their dental anatomy and other morphological traits suggesting various evolutionary trends towards the apes of today.
Some would seem to approach the gore some to the chimpanzee and some to the orange. Again, others show such dental characters which would require a slight modification to produce human characteristics of dentition. Gregory, Hellman and others are of opinion that Dryopithecine primates were on a distinctly infrahuman grade of evolution.
The Dryopithecine primates may be grouped under two major headings. One is the Dryopithecinae, a sub-family of the Pontiac, which again includes two groups Dryopithecus and Gigantopithecus.
Dryopithecus again comprises of several varieties of genera. The other major group is formed by Ramapithecus, which has been assigned to the family Hominidae. Ramapithecus also includes several types like Brahmapithecus, Kenyapithecus. 6.
6. Dryopithecus
Dryopithecus fossil primate was first known from some teeth and jaw bone from Miocene and Pliocene deposits of Europe and the Siwalik Hills of India. Now the remains have been discovered from different parts of Europe, Africa and Asia (India and China). Most of the remains are jaws and teeth.
It is difficult if distinguish between mandibles of Dryopithecus and Hominoid on the basis of definite features. The teeth, however, show certain variations. The incisors are smaller and more vertical in Dryopithecus than those in Paginate.
The canines are larger than those of Homicide. The molars increase in size from the first to the third. There is a definite pattern, known as Dryopithecus pattern, in the arrangement of the cusps of the lower molar teeth.
Out of five cusps, three are arranged along the cheek side and two along the tongue side. The five cusps are so separated that it forms a ‘Y’. Such pattern, or in modified form, is found in the gibbons, other and man.
Dryopithecus primates were probably quite ape like. In size, perhaps they were larger than Ilk modern gorilla, the smallest being larger than the modern gibbon. The limbs were very generalize giving indication neither of brachiating nor bipedal locomotion. The authorities are of opining that Dryopithecus are most likely ancestors of the modern Paginate, i.e., gorilla and chimpanzee >
7. Proconsul
The remains of Proconsul were discovered from the early Miocene of Kenya, East Africa. Certain specimens came from Uganda also.
(i) Characters:
Most of the remains of Proconsul were discovered by Leakey. The remains exitConsiderable variation in size and features. Accordingly, three species have been identified. These are Proconsul Africans, Proconsul Major and Proconsul Nana. It appears from the structure of that limb bones that Proconsul was not adapted to an arboreal brachiating mode of life.
(ii) Proconsul Africans:
Proconsul Africans is represented by several individuals, but the best preserve one is a fairly complete skull of an adult. In size it is intermediate between that of a gibbon and chimpanzee. The skull has no supraorbital torus, the incisive region of the upper jaw is narrow, to nasal bones are relatively broad and the nasal aperture is constricted at the lower extremity the lower jaw is marked by the absence of simian shelf and the reduction in the size of talk premolars. The mandible condoyle is of hominid form. The skull is, however, cercopithecoidit appearance.
(iii) Proconsul Major:
Proconsul Major is represented by right side of a mandible with the second* premolar and all the molar teeth in it. The mandible is massive, which suggests that the animal resembled the gorilla in size.
Rising Island an almost complete mandible of an adult was discovered. Proconsul Nyanzae was approximately of the size of Chimpanzee.
(v) Resemblance with Dryopithecus:
Proconsul may be regarded as African varieties of Dryopitheciis, because of the close resemblances between the two. Simons and Pilbara prefer to call them by the names Dryopithecus Africans, Dryopithecus major and Dryopithecus nyanzae respectively.
Dryopithecus Africans is thought to be ancestral to the chimpanzee, and Dryopithecus major may be the ancestor of the gorilla. Again, judging from the characteristics of the three species of Proconsul, by some they are regarded as ancestral to both the Pagoda and Hominoid.