The Cenozoic - 65my to present.
One important part of the study of the fossil record is time, and that is difficult for most to understand. Until we get toward the very end of the course we will usually be dealing with time in units of millions of years. The abbreviation for millions of years is my, for billions of years (1,000 million years) the abbreviation is by, and ky = thousands of years.
All primates we know of lived during the last 65my of earth's history. This period of time is called the cenozoic era. It has been found during the history of studying the cenozoic fossil record that certain time spans within the cenozoic are characterized by fairly uniquely characteristic assemblages of fossils.
So, to make things easier to remember, the Cenozoic era is divided into 7 epochs. See your text, page 294. A graphic depiction of the Cenozoic and its 7 epochs is called the Cenozoic geologic column.
Epoch date of beginning
Holocene 10ky
Pleistocene 1.8My
Pliocene 5my
Miocene 22.5my
Oligocene 34my
Eocene 55my
Paleocene 65my
The Paleocene (65-55my). During the Paleocene we find the first primates and the first members of the living suborders of primates, Strepsirhini and Haplorhini. Some primate-like mammals that were not primates also existed, but were close relatives.
The first group of mammals that we think fits Matt Cartmill's definition of primate is the family Petrolemuridae, found in the early Paleocene of Asia.
They have grasping hands, nails, and at least a post-orbital bar that allowed them feed on fruits and/or insects on the small ends of the branches.
The Petrolemurids were probably primates and probably the ancestors of all later primates. They are assigned to the suborder Strepsirhini, the most primitive of the primates. In general, Strepsirhines (even living strepsirhines) have many primitive behaviors and traits. In particular, they tend to be more nocturnal (active at night) rather than diurnal (active during the day). Their eyes are still primitive in being adapted for seeing in conditions of little light, and the sense of smell is still important to them because smell works equally well in light or dark conditions.
The next major step in the evolution of the human lineage was when haplorhines evolved. The haplorhines branched off from the strepsirhines by becoming more diurnal and emphasizing vision over smell. If an animal is active during daylight hours it can develop its vision, particularly color vision to an extent impossible in a nocturnal animal. Whereas the strepsirhines used vision and smell about equally, haplorhines concentrated on their sense of vision at the expense of their sense of smell.
This emphasis on vision over smell is best seen in the eye and the nose. Haplorhines evolved a new type of retina that is adapted for seeing best in conditions where there is plenty of light. Also, the eyes of haplorhines are even more forwardly rotated than those of strepsirhines, and haplorhines usually have a fully developed enclosed eye socket rather than just a post-orbital bar. The haplorhines also lost the rhinarium, which is a nose that is moist and continuous with the upper lip - like a dog or a cat has. Haplorhines have a dry nose that is separated from the upper lip like ours is. We humans are haplorhines, and therefore part of this lineage that prefers daylight and emphasizes vision over smell.
By the Middle Paleocene we start picking up the first haplorhines, which were members of the family Omomyidae. The oldest omomyids were found in the middle Paleocene of Asia and Africa.
At the same time as primates were evolving in Asia and Africa during the Paleocene, nature was producing some interesting primate-like mammals in North America and Europe. These are referred to as the plesiadapiformes.
The plesiadapiforms seem to have eaten both fruit and insects, but instead of developing an adaptation for feeding at the ends of branches they developed a more rodent-like adaptation. Rodents have large ever-growing incisor teeth, which they use to gnaw through tough things (like nutshells) with. The plesiadapiforms also had large incisors and probably specialized in mouse-like and rat-like adaptations. The plesiadapiforms became extinct as true rodents began to evolve into their modern forms.
The plesiadapiforms used to be considered primates, and do have some similarities with primates in their molar teeth. However, they do not fit the definition of primates and are best thought of as closely related to primates.
The Eocene (55-35my). By the beginning of the Eocene most of the plesiadapiforms had gone extinct. The haplorhines had made it to North America and Europe. By the beginning of the Eocene the petrolemurids had become extinct and had been replaced by another group of strepsirhines - the family Adapidae.
The adapids were strepsirhines and were probably the ancestors of the living strepsirhines - lemurs and lorises. Most of them looked a lot like the living strepsirhines. The only major difference between the adapids and the living strepsirhines is that all but one of the living strepsirhines have what is called a dental comb. The tooth comb is a dental structure that looks like a comb. It is formed from the incisor and canine teeth of the lower jaw. This is a shared derived trait of the living strepsirhines.
The living strepsirhines include the superfamilies Lemuroidea and Lorisoidea. The lemuroids all live on the island of Madagascar.
The lorisoids all live on the mainland of Africa or in Asia except for one family, the Cheirogaleidae, that lives on Madagascar. The Cheirogaleidae are intermediate in some respects between the lemuroids and the lorisoids, and are the most primitive lorisoids.
The second haplorhine lineage is the anthropoids. The anthropoids are the monkeys (both South American and African), the apes, and humans. The anthropoids are a group of primates that have adapted by becoming smarter. All mammals have in general increased their brain size. The brains of the strepsirhines and the tarsier have not kept up with this general increase in brain size among the mammals, so that they now have brains that are about the size of an average mammal. The anthropoids, on the other hand, did expand their brains along with the rest of the mammals, so modern monkeys and apes have brains that are about twice as large as those of an average mammal. The anthropoids kept the advantage in brain size.
Another trait of anthropoids, which is not really relevant in terms of their way of life, but which allows us to distinguish them in the fossil record is that anthropoids have 5 or fewer cusps on their lower molar teeth. The cusps are the points that stick up from the surface of the tooth. The primitive number of cusps on the lower molars of mammals is 6. Anthropoids have lost at least 1 cusp on their lower molars and some have lost two.
The question of what is the oldest anthropoid fossil is really hot now. The oldest possible anthropoid discovered so far is Eosimias, from the Eocene of China. We don't know much about Eosimias yet, because it was only recently discovered and isn't well known. The oldest definite anthropoid is Catopithecus, from the late Eocene of Egypt.
The family Propliopithecidae.
Everyone agrees that the family Propliopithecidae is ancestral to the catarrhines - Old World monkeys, apes, and humans. One trait that they share with the catarrhines is a distinctive dental formula, 2123, as compared to the more typical primate dental formula of 2133. This dental formula means that the propliopithecids and later catarrhines had 2 incisors, 1 canine, 2 premolars, and 3 molars. Most other primates have 3 premolars instead of 2.
Phylogeny for Paleocene, Eocene, and Oligocene primates
...............................................................
: Primates (Cartmill's definition) :
: .................................. :
: : Haplorhini : :
Miocene : ....................... : ........................ : :
To : : Strepsirhini : : : Anthropoidea : : :
recent : : living living : :living :living living : : :
: :Lemuroidea Lorisoidea: :tarsier:Platyrrhini Catarrhini: : :
25my- - -:-:- - | - - - - -|- - -:- - - | - - - | - - - - -|- - - -:-:-:
: : | | : : | : | | : : :
Oligocene: : | | : : | : | Propliopithecidae: : :
: : +----+-----+ : : | :Parapithecidae| : : :
35my- - -:-:- - - - -|- - - - - -:- - - | - - - | - - - - -|- - - -:-:-:
: : | : : | : | Eosimias : : :
Eocene : : | : : | : +----+-----+ : : :
: : | : : | :........|.............: : :
: : Adapidae : : +-------+----+ : :
55my- - -:-:- - - - -|- - - - - -:- - - - - - - | - - - - - - - - - -:-:
: : | : : | : :
: : | : : Omomyidae : :
: : | : :...........|....................: :
Paleocene: : Petrolemuridae-------------------+ :
: :.........|...........: :
:...........|.................................................:
| Plesiadapiformes To Living Colugos
65my- - - - - - - - -|- - - - - - - - - -|- - - - - - - - - |- - -- - -
To Living | | |
Fruit Bats | +--------+---------+
| | |
+----------Purgatorius---------------------+
|
The oldest platyrrhine fossil is Branisella dated to about 25my. By the Middle Miocene (16-10my) fossils are found that are very similar to living platyrrhine species.
The living platyrrhines can be divided into two families and many subfamilies. Several subfamilies have developed a prehensile tail that they use as a fifth limb to hold onto branches with. Two subfamilies have developed modified finger and toe nails that look like claws. For a long time this fooled people into thinking about them as the most primitive platyrrhines. However, we now know that they are probably the most specialized of the platyrrhines.
Living platyrrhines are characterized as a group by several shared derived traits. Let me talk about 2 of them. The first is a reduction in the size of the upper central incisors, which they shared with the family Parapithicidae from the Oligocene. The second is that the nostrils open to the sides of the nose, rather than in front of the nose like those of other primates.
The Miocene (25-5my)
The Miocene lasted from 25my to 5my ago. The Miocene was a very complex period of time, and because of this it is divided into 3 parts: lower or early, middle, and upper or late.
Early Miocene = 25-16my. The Early Miocene was fairly warm and wet. During this subepoch great forests covered most of east Africa, where we find a lot of fossil sites
.
Middle Miocene = 16-10my. During the Middle Miocene the climate got a lot cooler. When it gets cooler in Africa it also gets dryer. Because of this cooling down and drying out the east African forests began to break up into patches.
Late Miocene = 10-5my. During the Middle Miocene the climate got even cooler and dryer and the forest patches shrank.
By the end of the Late Miocene, East Africa had become mostly open grassland like it is today.
The infraorder Catarrhini
This infraorder includes the Old World monkeys, apes, and humans. Within this infraorder are 2 living superfamilies (Cercopithecoidea - the Old World monkeys, and Hominoidea - the apes), and 1 extinct superfamily (Pliopithecoidea - the non-apes).
The pliopithecoids were the most primitive of the catarrhines and are all extinct now, although we think that their descendants are the living catarrhines.
The pliopithecoids lived during the Oligocene and Miocene. During the Oligocene and early Miocene the pliopithecoids were the most abundant and successful anthropoids. By the Middle Miocene, most pliopithecoids were extinct and had been replaced by the cercopithecoids and hominoids.
The family Proconsulidae The most important family of Pliopithecoids was Proconsulidae. This family was found during Early Miocene of Africa. Proconsulidae is an important family because it probably contained the last common ancestor shared by the Old World monkeys and the apes.
The cercopithecoid monkeys
From the Late Miocene on to the present, the cercopithecoid monkeys have been the most abundant type of catarrhine in the Old World (excluding humans). They were apparently able to out-compete apes in the evolutionary war for survival, probably because of their ability to incorporate more leaves into their diets. Leaves are generally easier to come by than fruits, which are typical ape foods, and when the forests began to vanish altogether in the Late Miocene, the monkeys were able to survive and the apes became restricted to the remaining tropical rain forests of the world, like West Africa and Southeast Asia.
What helped the cercopithecoid monkeys become more able to eat leaves was the changes in their teeth. In addition to losing a cusp on their lower molars, the cusps of their molars developed what are called lophs. Lophs are ridges of enamel running from side to side between the cusps of the teeth. The cercopithecoids have two lophs, so their molars are called bilophodont.
The lophs on cercopithecoid teeth act as very efficient shearing mechanisms. They slice past each other like the blades of a pair of scissors. This is the best way to process a leaf.
There are many different kinds of cercopithecoids. There is only one living family of cercopithecoids, Cercopithecidae, which ought to be easy to remember.
The Apes (Hominoids)
The hominoids (apes) were most the most abundant catarrhines during the Middle Miocene. More than 30 genera have been discovered. An ape is defined by the ability to move through the trees swinging arm over arm in a form of locomotion called brachiation. The apes began to decline in abundance during the late Miocene and are actually quite rare today (except for humans).
Ape adaptations
Apes belong to the superfamily Hominoidea. The apes are those anthropoids which have specialized by evolving a new way of moving around in the trees - brachiation. Brachiation is arm-over-arm swinging from one branch to another.
The next step in the evolution of humans was becoming a brachiator. Brachiation probably evolved as a way to get at fruits that were at the very tips of branches. This is a very early primate behavior - feeding on the end branches. However, apes are better at it than other primates because as the hand under a branch and move out along it, the end of the branch bends in their direction. This allows apes to get at fruits that a monkey couldn't reach.
Anatomical adaptations for brachiation are shown in the postcrania - the body from the neck down.
Early Miocene apes: most people are convinced that some Pliopithecoid, probably a member of family Proconsulidae was ancestral to the apes. Many people also think that Proconsul was also the ancestor of the cercopithecoid monkeys. Proconsul had all the traits that are shared by both apes and monkeys in common, and none of the derived traits of either. So, apes have primitive teeth and derived brachiating bodies; cercopithecoids have derived bilophodont teeth and primitive quadrupedal bodies; Proconsul had both primitive teeth and a primitive body.
There are no true brachiating apes in the Early Miocene that can be demonstrated at the present time.
Middle and Late Miocene apes: there are two families of apes in the middle and Late Miocene - Dryopithecidae and Ramapithecidae. By the Middle Miocene brachiation had evolved.
Family Dryopithecidae: Dryopithecids are found in the Middle and Late Miocene of Europe. The most famous dryopithecid is Dryopithecus.
The dryopithecids are a good model for the common ancestor of the gibbon lineage and the great ape lineage. The gibbons (family hylobatidae) retains a few primitive traits with the dryopithecids that became derived in all other apes.
The living family Hylobatidae is often referred to as the lesser apes. It includes the gibbon and the siamang which live in the tropical forests of Southeast Asia. The hylobatids are super brachiators. In fact they are the only apes that really do much brachiating anymore, because the great apes have all gotten too large to brachiate effectively. Interestingly, when a gibbon or siamang comes down to the ground, it walks bipedally.
Family Ramapithecidae: this family is found in the Middle and Late Miocene of Europe, Asia, and Africa. There are at least 3 genera and maybe more - Sivapithecus, Ouranopithecus, and Gigantopithecus.
Sivapithecus is found in Asia during the Middle and Late Miocene. There seem to be two different kinds of Sivapithecus, and early form and a late form. The early form of Sivapithecus lived during the Middle Miocene and was probably the common ancestor of the orangutan and the African great ape lineage which includes the chimp, gorilla, and human.
The late variety of Sivapithecus lived in the Late Miocene of Asia and is definitely the ancestor of the orangutan. The orangutan has a peculiarly shaped area between the bottom of the nose hole and the upper teeth, this area is called the premaxilla. This very same shape of premaxilla is found in the late variety of Sivapithecus.
The living orangutan is now found only on the islands of borneo and sumatra off the coast of southeast asia. From fossils, however, we know that it once inhabited the mainland of Southeast Asia as well.
The locomotion of the orangutan has been described as cautious climbing. It hates to let go with more than one of its hands or feet at the same time. Often, they will use their weight to make a tree or branch sway in the direction they want to go. Orangs do a little brachiating, but they are really too large to do much of it.
When orangs come to the ground they use a form of locomotion called fist walking, where they walk on their fists.
Ouranopithecus is found in Europe during the middle and Late Miocene. It seems pretty clearly linked to the African branch of the apes - chimps, gorillas, and humans. One derived trait that Ouranopithecus shares with the African apes is the presence of frontal sinuses.
The African pongids - the chimpanzees and gorilla. These two genera are very closely related. You probably have to include humans in this group too. . Many people don't realize it, but there are 2 kinds of chimpanzees. The one that most of us are familiar with is the common chimp. However, there is another kind of chimp, the bonobo.
There is a debate currently about whether chimp and gorilla are most closely related to each other or whether they are equally related to humans. In other words was there a 3-way split between chimp, gorilla, and human, or way it a split into a chimp/gorilla lineage and a human lineage with the chimp and gorilla diverging later.
Chimp and gorilla share at least one derived trait. This is the knuckle-walking form of locomotion. They walk on all fours, but instead of walking with their palms down flat like a monkey, they walk on the backs of their knuckles.
The last family of African hominoids is the hominidae - the humans.
Gigantopithecus
Gigantopithecus is possibly the largest primate which ever lived. The smallest Gigantopithecus were about the size of a gorilla and some of them got even larger.
Gigantopithecus is found only in asia, but persisted from the Middle Miocene clear until 500,000 years ago. They co-existed with members of our own genus, Homo erectus. Some people think that Gigantopithecus is not extinct yet, and that we know it today as the yeti and bigfoot. If there is such a thing as a bigfoot, which is unlikely, then it is as likely to be Gigantopithecus as anything.
PHYLOGENY FOR THE CATARRHINES, CERCOPITHECOIDS, AND HOMINOIDS
.............................................
: CATARRHINI :
: ............................ ............ :
.................. : : CERCOPITHECOIDEA : :HOMINOIDEA: :
: PLATYRRHINI : : : CERCOPITHECIDAE : : : :
: : : : : : : :
:Living Living : : : Living Living : : Living : :
RECENT :Cebidae Atelidae: : :Colobinae Cercopithecinae: : Apes : :
: | | : : : | | : : | : :
5MY - -:- - | - -|- - - - - - - -|- - - - - - -|- - - -:- - - | - - - :
LATE : | | : : : | | : : | : :
MIOCENE: | | : : : | | : : | : :
10MY- -:- - | - -|- - - - - - - -|- - - - - - -|- - - -:- - - | - - - :
MIDDLE : | | : : : | | : : | : :
MIOCENE: | | : : : +-----+-------+ : : | : :
: | | : : : | : : | : :
16MY- -:- - | - -|- - - - - - - - - - -|- - - - - - - -:-:- - | - - - :
: | | : : :..........|...............: :....|.....: :
: | | : : ..|......................|..... :
EARLY : +----+ : : : +-----------+----------+ : :
MIOCENE: | : : : |PLIOPITHECOIDEA: :
: | : : : | : :
: | : : : Proconsul(idae) : :
:Branisella : : : | : :
:....|...........: : : Pliopithecidae : :
25MY- - - - | - - - - - - - - - - - - - - - - - - -|- - - - - - - -:- :
OLIGOCENE | : : Propliopithecidae : :
Parapithecidae : : Catopithecus : :
35MY- - - - | - - - - - - : - - - - -:- - - - - - -|- - - - - - - -:- :
| : :.............|...............: :
EOCENE | :........................|..................:
+-----------------+--------------------+
Eosimias
|
PHYLOGENY FOR THE APES
..........................................................
: APES :
: ........................................... :
: : GREAT APES : :
: : ............................ : :
: : : PONGIDAE : : :
: : : : : :
: : : : : :
: : : Chimp/ : : :
RECENT :Hylobatidae : :Orang-utan Gorilla Bonobo : Hominidae : :
: | : : | | | : | : :
: | : : | | +----+----+ : :
: | : :....|.........|...........:| : :
5MY - - - - - - | - - -:- - - -|- - - - -|- - - - - - | - - - - -:-:
: | : | +------+-----+ : :
LATE : | :.......|................|........... : :
MIOCENE : | :: | RAMAPITHECIDAE| : : :
: | :: Late | : : :
10.5MY- - - - - | - - -:-Sivapithecus - - -Ouranopithecus:-:- - -:-:
: | :: | | : : :
: | :: +---------+------+ : : :
: | :: | : : :
MIDDLE : | :: Early : : :
MIOCENE : | :: Sivapithecus : : :
: | ::................|.................: : :
: | :.................|.......................: :
: | | :
: +-----------------Dryopithecidae :
16MY- - - - - - - - - - - - - - - - - - -|- - - - - - - - - - - - -:
: ?Afropithecus Group? :
: | :
: Morotopithecus :
:..............................|.........................:
|
EARLY Proconsulidae
MIOCENE |