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Lab Lecture 8

Lab Lecture 8


For this lab, we’re going to be transitioning
from basic description, and basic taxonomic concerns of primates, and moving towards looking
at comparative anatomy. So we want to identify the features that are so distinctive of primates.
And then at the end of this lecture, we will actually be transitioning into early primate
evolution. And this will begin our journey, through the
fossil record that leads us to modern homo sapiens. So to get us started, let’s talk
about our objectives for today. I’m going to show you how, to identify diet based on
dental patterns. And this is important for the fossil record, and considerations of fossils. When trying to decide, especially what the
diets were of these individuals. And if they are primates. And this is important for when
we first see, primates originating in the World. We’ll also compare and contrast, different
types of primate locomotion patterns based on the skeletal remains, and then identify
earliest major fossil primates, and describe their distinctive features. And for this lab we’re going to end up, with
the first apes. And in the next lab we’ll transition into the earliest hominid. Beginning
with teeth there are variety of different ways to describe dental patterns and the shape
of cast, one of them in homodont versus heterodont. So, homodont is having one type of tooth form. So if you look at the image of the shark.
You’ll notice that every single tooth in that shark’s dental arcade, is the exact same shape.
Each tooth has the same morphology. So, homo, meaning all the same, dont meaning teeth.
All of the teeth are just the same type. And this is distinctive from heterodont dentition.
And this is having more than, one type of tooth. So in most primates we see, we have
incisors, canines, premolars, and molars, more than one type of tooth. So the heterodont
condition, is indicative of primates. We can also talk about having generalized, versus
highly specialized teeth to infer diet. Generalized teeth, are those able to process
multiple types of food, and this is what we see for the order primates. Specialized teeth,
are those designed to process only one type of tooth. So the image on the bottom right
you’re seeing, is of a canid, and, the unique shape of the molars and premolars, is very
specialized. It’s designed for carnivory, those are called
carnacial teeth. So those are teeth designed to process, predominantly meat. Primates tend
to have generalized dentition, and were able to process many different types of food, and
this is shown in the fact that. A lot of different primates eat a lot of different things. We can also describe, and study different
molar patterns. So lophodont teeth are molars with transverse ridges, on the grinding surface.
And this is typical of herbivory, of only eating plants remains. So, looking at the
images on the screen, we can look at the chinchilla on the bottom left here. And you’ll these transverse ridges, on the
oclusal surface of the tooth, just on every single one. And that’s for grinding and processing
the plant material that these organisms are eating. In addition, herbivore can also be
identified on Selenodont teeth. And selenodont teeth, are mesiodistally elongated cusps,
to increase the cutting surfaces. So remember that teeth have a different directional
terminology. So mesiodistally basically means anterior posterior for those post-canine teeth.
So looking at this image, from here to here using my red pen. That is one individual tooth,
with two roots. And the cusps on the top, you’ll see they are elongated, mesiodistally,
anteriorly, posteriorly, to increase the cutting surfaces. And we see selenodont teeth, primarily in
large bodied grazers. So something like an antelope, would have selenodont teeth. Tribosphenic
teeth, are indicative of insectivores. So in animals that are eating mostly insects.
And these are molars, that have three triangle shaped cusps. It’s a primitive pattern of
mammals, and we see it in possums, for example. So looking at this, you can see the triangle
shape. And we also see tribosphenic teeth, in tarsiers. Tarsiers are predominately insectivorous,
and that is shown on their dental molar pattern. Within primates, specifically cercopithecoids,
we have bilophodont teeth. And again, these are teeth with two pairs of cusps, that are
linked by those transverse ridges. So remember we have the ridges on these bilophodont
teeth. And this is typical of omnivores, organisms that are eating a wide variety of different
foods. And finally, our own molar cusp pattern, the Y-5 molar cusp. Again, we have the five
individual cusps on the occlusal surface, separated by the Y-shaped groove. This is the hominoid pattern, the ape pattern.
And we are omnivores. Moving beyond general molar cusp pattern, we can also look at the
arrangement of teeth and the spacing between them as well. For something like, the sectorial
complex. Now the sectorial complex is defined by, three components. The first is a very
large upper canine. So on the top right picture, we can see that
very clearly. This individual has a massive upper canine. There is also a diastema, and
this is a new term, but a diastema is essentially just a gap in the lower. And it’s a gap in
the lower dentition, so that upper canine can come down and allude so the primate can
shut the mouth. So behind this large upper canine there is
a gap, and in this picture Pan troglodytes that the chimp, you can see the gap here between
the canine and the first pre-molar, so that would be the diastema. And the final component
is the Unicuspid lower. Premolar or P3 for abbreviation, and the unicuspid means, that
it just has one cusp. So that you can see that on both images there’s
just a single cusp, the unicuspid lower first premolar also has a shearing complex on it,
that helps keeps that canine sharp. So there’s a ridge along this portion of that premolar.
And what the sectorial complex is relevant to isn’t necessarily diet. Instead it’s related more to social behavior.
In primates that we see a large. Sectorial complex, we know that there is, the males
are often typically much larger, and they compete in many cases for access to females
and for their own social hierarchy. So, this is related more to issues related to that
social complexity. And here we see the. The sectorial complex
on a living primate. So, again, we have the large upper canines on the maxlaw, the diastema,
that gap on the mandibular dentation, and then the unicuspid P3s as well. And what you’re
seeing here, this primate is. Is direct yawning, which is a move used in dominance related
interaction amongst males, in sexually dimorphic species that have this sectorial complex. They’re basically showing each other, the
very large canines, as some form of threat. Moving beyond the dentition, to the primate
locomotion patterns, we can also assess how primates are moving based on their bony skeleton.
Now all primates, have a very generalized anatomy that allows for multiple types of
locomotion. And for all of these, most are hind limbed
dominated. And there’s a tendency amongst all primates for an orthograde or upright
posture in the upper body. In terms of how we can classify, and categorize different
locomotion patterns, here are seven different types. So we have slow quadrupedal climbing,
like you might see in a loris. Vertical clinging and leaping is characteristic
of primates like tarsiers, for example. Quadrupedal walking, we see that in primates like baboons.
Brachiation is swinging through the trees, using the. The arms and we see that in Gibbons
especially. Knuckle-walking is a Quadrupedal terrestrial movement, where in the knuckles
are used instead of the flat of the palm for the fore limbs, so they walk on their knuckle. And you see this in something like a gorilla.
Slow quadramanual climbing, means that all four limbs, all four hands and feet are used
basically like hands. So quadra means four, manual meaning hands. The feet have the same
grasping ability as the hands. And we see that in orangutans. And finally there’s bipedalism, and that is
characteristic of hominins and of course humans. And for all of these seven categories there.
We can divide them down further, but they’re really just three main types of locomotion
patterns that we can detect on the bony skeleton. There’s bipeds, quadrupeds, and then suspensory
primates. So, how do we assess these three different
types? We can use the skeletal features of the scapula, the hands, the feet, the pelvis,
and the vertebrae. And there are a variety of different features on each that help you
distinguish between the three groups, that you’re going to be dealing with in lab today. Beginning with the scapula, the typical quadrupedal
scapula is oriented on the side of the body, it’s oriented laterally. The glenoid, which
is the articulation for the humerus just to review, is nearly in line with the arm. It
points inferiorally. It points downward. When you’re looking at, a quadrupedal skeleton
that’s in articulation, it looks like the scapulae are almost falling down. Off the sides of the body, and I’ll show you
that on the next slide. For bipeds, our scapulae are located on our back. We have a very shallow
glenoid, and this is related back to our suspensory adaptations in our lineage. And the shallow
glenoid allows for a very wide range of movement. So if you, sitting at your computer, rotate
your arm, like maybe you’re pitching a softball, you can move it all the way around. And that
is because we have that shallow glenoid. So we have greater flexibility in that joint,
but, it’s not as stable as in the quadruped. For the quadruped the glenoid is much deeper,
and in a lot of cases, there are more bony projections surrounding the glenoid for increased
stability, because quadrupeds are putting weight on that joint. Now finally, we can
also assess suspensory primates using scapuli. Again, the scapuli are located on the back. The glenoid is very shallow again for greater
flexibility when moving through the trees, and importantly the glenoid points more cranially
than humans. So it’s oriented more superiorly, than we see in bipeds. And to show you some
of these. Here we have a quadrapad on the left, and you can see here is the Scapula
the glenoid is facing downward, so it’s oriented almost perfectly in line with that arm. For humans, it is located on the back. The
glenoid is pointing fairly laterally. It is quite shallow. There’s not many bony projections
around it. And the main difference between the biped and the suspensory ape, is the positing
of that glenoid. Notice in the. Suspensory primates, it’s orange is more cranially, more
upward towards the cranium, rather than just straight to the side, which we see in bipeds. We can also assess the bony structures of
the hand. So for quadrupeds there hands are weight bearing, and they’re variable depending
on locomotory adaptation, and this will be also very similar to the hind limb and what
that means is the hands will look different depending on if they’re just a quadrupedal
walker. If they walk on their palms, or if they’re
a knuckle walker. And they’re putting all that weight on their knuckles. For bipeds
our hands are fairly distinctive. We don’t bear any weight on them. We have a very, very
broad palm. And our metacarpals, the bones of your palm are very straight and slender. We have straight, short, smooth phalanges,
and we have a very long and well muscled thumb. And it’s long, relative to the other digits.
For suspensory primates, typically the hands are hooked like, they’re permanently hooked.
So you see that curvature in the metacarpals a little bit, and definitely in the phalanges. And their thumb is proportionately smaller,
than we see in a biped. So looking at this, we have a quadruped, a biped, and a suspensory
primate. And the main comparison you’ll be doing in lab today is the difference, between
biped and suspensory. Because the quadrupeds have a tendency to be more variable. So, looking at the biped, we have very straight
phalanges and metacarpals. We have a proportionately long thumb. Looking at the suspensory primates,
notice how there’s this curvature. And it’s not just a curvature, because on the biped
the fingers are propped up a little bit. But, it’s actually the bones of these suspensory
primate are curving. For the ilia, we can look a little bit inferiorally,
and look at the pelvis to also assess. Modes of locomotion. For the ilia, the typical quadruped
pattern is a very long and narrow pelvis. It has a shallow, greater sciatic notch, that
forms a much more obtuse angle than in biped. The bipedal ilia is short and slayed with
a very deep greater sciatic notch. It’s much more pinched in. And the overall pelvis of
bipeds is having more bowl shape, and the ilia are actually oriented in an anterior-posterior
direction, rather than the medial-lateral positioning of the quadrupedal pelvis. For
suspensory primates, the pelvis can be intermediate. So we’re not going to emphasize that much
today. Looking at them individually, we have a quadruped, a biped, and suspensory primates.
And notice how, especially, the biped really sticks out from the other ones. And the ilia
are very broad and splayed, versus the narrow pattern we see. Especially in quadrupeds. And the greater sciatic notches of bipeds,
which I am outlining here with my red marker. Are much deeper, than the greater sciatic
notches, we see in quadrupeds. And finally, I talked about the orientation of the ilia,
and the iliac blade. So you see how the Iliac blade curves around laterally, and the blades
oriented almost in an anterior posterior direction, rather than in quadrupeds it’s oriented in
a medial lateral position. Moving imperially again, we can also talk
about primate locomotion by assessing the feet. So typical quadruped is similar to the
four limb. The feet are weight bearing but they vary depending on if the individual’s
a knuckle walker or. A standard quadrupedal walker that uses the palms. For bipeds, our
feet is, are very distinct to facilitate our unique mode of locomotion. We have incredibly robust tarsals, so looking
at our tarsals, those are the bones of. The heel and for part of the foot. They take up
almost half of the foot length. And they are very robust, especially that calcaneus, and
that is because we support all of our weight on those bones. Furthermore, our metatarsals are very long
and straight. We have straight, short phalanges. And importantly for the feet. We do not have
a grasping big toe. Our big toe has been reorganized, and is in line with the rest of our, the rays
of our foot. Compare that to the suspensory primates. They have curved phalanges very similar to
the hands, and the grasping ability is maintained. So, you see this curvature of each of the
raise, and suspensory primates do have that opposable big toe. And finally, if you look
at proportionally, relative to the rest of the foot, the tarsals of suspensory primates
are, much smaller overall. Now that we’ve covered some of the characteristics
that we can use to identify various primates and their modes of locomotion, in the fossil
record, let’s talk about the earliest primates that we see. In the fossil record. So starting
out at the Paleocene. We’re talking about 65 to 54 million years ago. Following the extinction of the dinosaurs,
there was an adaptive radiation of mammals. Primates went out and filled many niches,
that were previously occupied by dinosaurs. And the earliest primates were small, squirrel-like
creatures. They kind of looked like a shrew, and at the time of the Paleocene, we’re considering
Europe, Asia, and North America, as where we’re seeing primates, and at the time they
were connected as Laurasia. The primates that we see during the Paleocene
are called plesiadapiformes, and these are possible early primates. And I say possible,
because they have a suite of traits that suggest they might be protoprimates. But, they still
have some characteristics that are not usual for the order primates. So, in terms of what
we’re seeing for plesiadapiforms, for primates’ characteristics, they have molar that are
very similar to primates. The temporal region, looks a lot like a primate.
And they have post-cranial arboreal adaptations. So they have a very long tail, and agile limbs.
And these are all the characteristics, that suggest and link them to later primates. Non-primate
characteristics include a very small brain. They don’t have that post-orbital bar, or
closure protecting the orbits. And the orbits themselves are oriented more
laterally, rather than anteriorly. They have rodent-like jaws and teeth, like you would
see in a modern rodent, so they have a very large diastema, between the post-canine indentition
and the incisors. And they’re very prognathic, they have a very long snout, indicating that
they were far more reliant on olfaction than modern primates. Some of what they look like include, we have
two artist reconstructions. So purgatorius, is a possible proto-primate. And these are
some plesiadapiform skulls and artist renditions. And so you see, not post orbital bar, small
brain size, it’s very small. And they have this diastema, and the dental formation looks
a lot more like a rodent than it does a primate. And finally, a characteristic. That we see
post cranial is the, post cranially, pardon me, is that they have claws rather than nails.
Moving to the Eocene. We’re jumping ahead in time from 55, or 54 to 35 million years
ago. There’s pockets of isolation for mammals resulting in diversification. And we see an adaptive radiation of primates
in North America, Europe, Asia and Africa, and this was a much more tropical climate
than the Paleocene. During the Eocene, we see two superfamilies developing, we have
Adapoidea. Which are lemur-like and omomyoidia, which are tarsier-like. Some general trends
we’re seeing in the primate lineage, during this time for both superfamilies, include
an enlarged brain-to-body ratio. So greater encephalization, more forward facing
orbits. We see the development of a post orbital bar, protecting that orbit. Nails, instead
of claws, appear. And that opposable hallux, that opposable big toe. And what all this
suggests is a nocturnal arboreal insectivorious snitch for both Adapoids and Omomyoids. Looking
at them individually, Adapoids are found in North America, Europe, Asia, and Africa. And these guys are the possible fossil ancestors
of Strepsirhines, they look more like lemurs. They don’t have any dental comb, comb or grooming
cloth, but there’s a lot of similarities specially in the wrist and ankle morphology. They have
a longer snouts than omomyoids as well, and an example of that you will be hearing about
enlarge today would be Haplorhines and that’s an example of an Adapoid that is very -like. Omomyoids are found in Asia, Europe, and North
Africa, and we’re still in the Eocene here. Here. And these are fossil ancestors of Haplorhines.
They look a lot like Tarsiers, actually, and you can see that in this reconstruction on
the page. Some characteristics, they have a very elongated calcaneus, they have a shorter
snout than adapoids, larger orbits. So these were probably nocturnal primates,
and they do look a lot like tarsiers and we know that tarsiers have been separated from
the rest of the primate lineage, are the Haplorhines especially for a very long time. But the process
and the actual split event is unclear but it probably post dates the Omomyoids. It’s for cene in the Eocene. Moving to the
Oligocene, we have an adaptive radiation of anthropoids specifically, and our evidence
for this adaptive radiation is primarily coming from Africa at a site called El Fayum, Egypt.
And we find over 1,000 specimens in this area, representing over 60 genera. During this time period; there’s a climatic
change. We have a much cooler climate. And we also see, the New World Monkey, and Old
World Monkey. Split and it’s been suggested that, New World Monkeys goes to the new World
by erupting event. Duo by the Oligocene straps have their own separate leniege as our tarsiers. They have three main families of primate during
the Oligocene. The Parapithecidae, Propliopithecidae and Oligopithecidae. Some general trends that
we see. Post-orbital closure develops. We have a fused frontal, and fused mandible.
The primates we’re seeing are much larger in body size. They’re still small, but they
are larger than anything we’ve seen up to this point. And there’s a shift from nocturnal adaptations,
to diurnal adaptations. Furthermore, we see less clinging and leaping, a shift towards
greater herbivory rather than insectivory, and then grasping hands are appearing very
clearly in the. The fossil record. What the first family we’ll talk about is the Parapithecidaes
and these are fossils ancestors of Platyrrhines they’re very much like Platyrrhines, and the
reason we say that is because they have the 2:1:3:3 dental formula, they have those pre-molars
characteristics of new world monkeys today. Parapithecids were likely arboreal quadrupeds,
and likely subsisted on fruit and seeds. Again, that is quite similar, to a lot of our modern
Platyrrhines as well. Propliopithecids are Catarrhine like fossils. Some characteristics
that link them with catarrhine’s include a 2:1 2:3 dental formula, and that’s quite important.
They also have an enlarged brain. We see some sexual dimorphism, especially
in the presence of the canines and partial sectorial complexes. We have evidence of fru,
frugivory, insectivary, and folivory. For propliopithecidae and in terms of size I said
that during the Oligocene we have larger primates. We’re talking around ten to 12 pounds, and
one of the examples you will be experiencing in the lab activity is Aegyptopithecus, which
is shown in this image right here. And Aegyptopithecus is considered, to be the
ancestor of the all modern Catarrhines. The, there are about several hundred specimens
of Aegyptopithecus at this point. And the estimates are that these individuals were
12 to 13 pounds. They did have the 2:1:2:3 dental formula. And, ape-like dentition, enclosed
forward facing eyes, and sagittal crest as well characterizes Aegyptopithecus. Moving to the last time period we’ll be covering
in this lab lecture let’s talk about the Miocene. It occurred from 22 to around 5 million years
ago. And here we see an adaptive radiation of hominoids in Europe, Asia, and Africa.
And hominoids, again, are our apes. There were significant changes to the climate, and
there were some slight changes to the positioning of land mass. Is relative that are related to that climate.
By 23 million years ago, the major continental locations approximated those of today. Though
North and South America were still separated. And during this adaptive radiation of hominoids.
There were a lot of apes existing on the World, and since that time period there’s been a
drastic decrease, and today we have very few living ape species. When talking about the Micoene apes, we’ll
do so geographically. So from Africa we have evidence of Proconsul, and this is the best
known genus from the time. As well as Kenyapithecus. Eurasian forms, dates from 16 to about 5 million
years ago. Most forms are quite arrived, but they are varied and pull the understood in
many cases. The two are emphasizing in lab include Sivapithecus
and Gigantopithecus, in addition Dryopithecus, was also and has also been the focus of much.
I should study. General trends for this time period, include the dental apes, and by dental
apes we mean that we are identifying them as hominoids, because they have that Y-5 molar. Post cranially they are still very monkey
like. They have monkey like, proportions. No curved digits for suspensory locomotion.
Origin. And importantly they have no tails. We have no evidence, these genera have tails.
Beginning in Africa, some characteristics that we see of both Proconsul and KenyaPithecus,
include post-cranial remains that are quite similar to monkey. Like I said, this especially clear in the
proportions of the limbs. They also have sectorial complexes. So that tells us a little bit about
their social dynamic possiblly, and their social behavior. And the two characteristics
that make them apes. No evidence of any tail and the Y-5 molar. particular, in particular, proconsul is important
because it’s the best known genus of this time. It has the ape like dentition as well,
and it predates the old world monkey and ape split. So it’s a close ancestor, or possible
stem ancestor of both groups. And by the end of the early Miocene, from 16 to 18 million
years ago, apes migrated out of Africa and into Eurasia. Moving to Asia, Sivapithecus is a fossil that
has a lot of similarities to modern orangutans, and is possibly ancestral. Although sivapithecus
doesn’t have the same suspensory adaptations as orangutans, there are a lot of similarities
especially in the facial skeleton, and the skull shape. There, in terms of other characteristics
of Sivapithecus, there is sexual dimorphism in this species, which we also see in modern
orangs. And they have very thick enamel as well. Gigantopiticus,
is the largest primate to have ever lived. And that’s represented in the name, gigantic
basically. It was estimated to have been around six to nine feet at height, at full growth.
It’s contemporary with Homo. This so it was existing in Asia for a very long time and
based on the dental remains and the occlusal surface, it’s possible that Gigantopithecus
ate bamboo and because we say that because the teeth are quite similar. To a Giant Panda. Now Gigantopithecus, is
used in a lot of pop culture as being quote evidence for Bigfoot. But unfortunately that
just isn’t the case obviously. To sum up the Miocene, and really our trek through early
primate evolution thus far. Apes thrive in the early part of the Miocene. And then there’s a population crash around
8 to 5 million years ago associated with significant environmental change. And the end result of
that is very few species, are living today of ape. And monkeys take over as the dominant
primate, after that population crash. And unfortunately, during this time period when
we’re saying apes and hominides split, they’re huge gaps in the fossil record, between the
last common ancestor of the apes and hominins and the earliest hominins. And to sum up our primate evolution discussion
for today, this is a chart that might help you, moving forward, trying to figure out,
which. Primate groups are for which time eras, and what was important going on at that time
period. Now as you go through the lap state, feel free to review this lecture, and as always
if you have any questions or concerns, don’t hesitate to contact your Anthropology 225
lab TAs

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