Kevin Callahan's Lab Notebook Fall 1997

Anthropology 1101 Human Origins Lab 4: The Primates
Primate characteristics and phylogenetics
Kevin L. Callahan
Purpose of the Lab
You can tell primates apart because they each have distinctive characteristics.
You will learn many of these so that you can quicklly tell them apart.
These unique characteristics evolved over time as adaptations related to diet, 
environment, and locomotion.
Evolutionary relationships are illustrated by noting differences in comparative 
anatomy.
Terms to know
Taxonomy - sorting out species by similarities and differences.
Linnaeus’ Binomial nomenclature - gives us family andd species names, etc. and 
was developed by Carolus Linnaeus.
Cladistics - uses derived traits (novel or new traits) to sort out species.
Ancestral or primitive traits - traits inherited from a common ancestor.
Terms to Know
Convergent evolution - traits that evolve separately that are similar and 
useful like bird wings and bat (mammal) wings.
Homoplasies (analogies) with the same shape.
Homologies - similar traits coming from the same origin.
Arboreal- living in the trees
Terrestrial - living on the ground
Terms to know
Stereoscopic vision - two eyes facing forward that overlap giving depth 
perception.
Snout - a protruding area where the nose is.
Prognathism - the lower face juts forward.
Prehensile tail - a tail that grasps a branch like hands do.
Opposable thumbs - the thumb can touch the fingers to grasp things.
Terms to Know
Nocturnal - awake at night
Diurnal - awake during the day
Unfused mandibular symphysis - the suture that connects the two halves of 
the mandible (lower jaw) never fully closses and fuses e.g. in prosimians 
like lemurs.
Hominoids - apes
Hominids - habitually bipedal
Positional repertoire - postures and locomotion
Terms
Pentadactyly - 5 fingers
Auditory meatus - ear hole
Bilophodont molars - two cusps with a distinctively appearing sharp ridge 
between them found in Old World Monkeys.
4 Forms of Primate Locomotion
Quadrupedalism - walking on 4 feet like a Baboon with equally long forearms 
and hind limbs.
Brachiation - moving with an overhead arm swing like a Gibbon (longer arms 
than legs)
Knucklewalking like a Gorilla
Bipedalism - habitual upright walking like a human (longer legs than arms)
Steroscopic Vision
Does the primate have partial or full stereoscopic vision (or no stereoscopic 
vision).
Many non-primates like rabbits and horses have eyes on ths SIDES of their head 
and can see almost 180 degrees. What is the advantage of that?
Stereoscopic vision
Some primates have partial stereoscopic vision like the prosimians (e.g.lemurs 
in Madagascar).
You have fully stereoscopic vision which gives you good depth perception 
allowing you to judge distances accurately.
Post orbital wall or "partition"
Your eyes are fully enclosed in the back behind the eyeball except for a 
small hole to connect the eye to the brain called the optic nerve. You have 
a POST ORBITAL WALL (or "Partition")
Post Orbital Bars in Prosimians
More "primitive"primates (closer to earlier forms of primates) did not have a 
an enclosed eye socket. They had a post orbital "BAR". Thus you can ID a lemur 
skull. 
The post- orbital BAR is a strip of bone from the top of the eye to the cheek 
but the back of the eye is open. You can pass a pen through the eye and it you 
would  come out the back! This is not true with your eye. 
Non-Primates
Dogs are not primates.
Non-primate mammals, like dogs, have no post-orbital wall and no post-orbital 
bar.
You can poke into their eyeball from above and a little to the side and there 
is no bone protecting the eyeball (don’t try this at home!).
Dogs have long snouts and good smell. Most primates rely on vision.Prosimian 
primates use smell (e.g. lemurs)
Prominent snouts
A snout is a long muzzle with the nasel passage at the tip.
Prominent snouts are often good if you have a better sense of smell e.g. lemurs 
and dogs and may be related to the diet of foods eaten.
Tooth (or dental) combs
Prosimians (e.g. lemurs) have tooth combs which are very specialized teeth good 
for piercing insects and scraping gum out of trees to eat.
Tooth (or dental) combs stick out prominently forward and do not look like our 
incisors. They are small and look like the small ridges on a  comb (often hard 
to count)
Generalized dentition
Humans have the most generalized dentition of any primate.
All our teeth are approximately the same size and shape.
A saber-toothed tiger had very specialized dentition.
Large canines do not mean the animal is a meat eater 
(e.g. gorillas eat leaves). 
They have large canines for sexual display, etc.
Dental formulas
Old World primates (the Old World includes Africa, Europe and Asia) have 
2-1-2-3 dental formulas
**********
New World primates (Central and South America) have distinctive 
2-1-3-3 dental formulas
Hence you can instantly tell them apart!
Cusps on molars (3,4,5)
Prosimians (e.g.lemurs) have only 3 cusps (high points on the molars).
Monkeys have 4 cusps on their molars. The 4 cusps are in a rectangular shape.
New World Monkeys have 4 cusps with a valley like an X. Old World Monkeys 
have 4 cusps with a sharp ridge between them and this is called 
"bilophodent"
Cusps on molars
Apes (e.g. like us) have a distinctive Y-5 cusp pattern.
The valley on the molar looks like the letter "Y" and there are 5 cusps.
Hence the molars can be used to tell species apart.
Dental Arcades can be used to tell primates apart
Prosimians have a distinctive "V" shaped mandible (lower jaw)that is long.
Monkeys have more of a U to the end of the long V shape.
Apes have a distinctively sharp rectangular shape that is much longer than it 
is wide.
Humans have a distinctively parabolic shape where the overall length and width
of the lower jaw is about the same.
Is the lower jaw fused together?
Our lower jaws (the mandible) are fused together. (Simians are every primate 
except for prosimians. If the mandible is fully fused then the skull is of a 
"simian.")
Prosimian lower jaws (like lemurs) are not fully fused together
Tarsiers also do not have fused mandibles but have some charactersitics that 
may arguably put them in a separate category.
Diet is indicated by tooth size
Narrow incisors relative to molars are indicators of leaf eaters. (Florivores)
Wide incisors relative to molars are typical of fruit eaters. (Frugivores).
Incisors are the fruit "can openers"
Outer Ear shape
Old World Primates have TUBE shaped outer ears.
New World Primates have RING shaped outer ears
They are quite distinctive and can be used to tell skulls apart.
What does your outer ear look like then?
Tail or NO Tail?
Monkeys have tails.
Apes do not.
CHIMPS DON’T HAVE TAILS!!!
New World Monkeys (e.g. Howler monkeys) have prehensile tails (grasping tails 
with dermatoglyphics -  like fingerprints).
Old World Monkeys DO NOT have prehensile (grasping) tails.
Lengths of the arms and legs
Quadrupeds (walk on 4 limbs) have equal lengths of the arms and legs.
Brachiators have longer arms than legs.
Bipeds have longer legs than arms
Knucklewalkers have somewhat longer arms than legs
The Intermembral index
The Intermembral Index is just the ratio of the length of the arm to the leg 
or the humerus + radius / femur + tibia
Are the legs longer than the arms?
Forelimb and rearlimb refer to quadruped directions.(front legs and back limbs).

Thorax shape
The thorax is the area enclosed by the ribs.
Looking down from the top of the body (overhead looking down) some animals have 
a more pointed chest shape to the ribs (like quadrupeds like dogs and baboons) 
and some have more of a cylinder shape (like us). 
From the front, chimp rib cages flare out and are a good shape for overhead 
reaching.
Rib shape
If you are hanging from your arms all day and moving by using your arms mostly 
they tend to be long and powerful e.g. gibbons with permanently curved fingers 
or orangutans who live almost their entire lives in the trees.
The scapula (shoulder blade)
Humans are very good at lifting their arms over their heads and throwing things.

Our scapula is away from the vertebrae and closer to the shoulder and is flat 
against the ribs (largely behind our rib cage in the "coronal" plane)
Dogs have a scapula that is closer to the middle of their body and tilted.
The Glenoid Fossa
The glenoid fossa is the bowl shaped depression on the scapula (shoulder blade)
 that articulates (attaches) with the proximal humerus (upper arm).
The glenoid fossa points cranially (toward the cranium) on a dog and laterally 
(toward the side) on a human
The vertebrae (bones of the spine)
The cervical spine is the neck
The thoracic vetrebrae are attached to the ribs
The lumbar vertebrae is the low back
In upright humans the lumbar or low back vertebrae are much thicker than the 
cervical or neck vertebrae
Mammals have 7 neck vertebrae. The others vary.
The Pelvis
Humans walk upright and have short, thick, bowl shaped (curved around the sides)
 pelvic bones to support the weight of the internal organs, and to habitually 
walk upright, etc.
Other primates like chimps and apes have long flat pelvic bones that lie flat 
against the back
The Foot
Humans have arched feet in two planes that acts as a shock absorber for 
habitual bipedalism.
Our big toes are in-line and are non-grasping as opposed to a chimp or 
orangutan. 
Pronograde and Orthograde
Pronograde primates are "prone" such as down on all fours walking. The trunk 
is parallel to the ground.
Orthograde primates are upright. They may hang from branches, move by 
knucklewalking, walk short distances on 2 feet, etc.
Prosimians (lemurs)
V shaped dental arcades, specialized dentition like dental combs, nonfused 
mandible (lower jaw), partial stereoscopic vision, prominent snout, 
post-orbital bar instead of a post-orbital wall (or partition) etc. 
Tarsiers
Their eyes are larger than their brains.
Their eyes are neither fully enclosed but they have more bone behind the eye 
than just a post orbital bar.
A unique 1-1-3-3 dental formula
Unfused mandibular sympheses (a no-fused lower jaw
Sharp insect crunching cusps.
No toothcomb
Howler Monkeys
Fully enclosed eyes and fully stereoscopic vision
2-1-3-3 dental formula (a New World Monkey)
a monkey shaped jaw (more U shaped than a sharp V)
A fused lower jaw
A shorter snout
A prehensile (grasping) tail
Baboons
Quadrupedal
Males are 50% larger than females.
Old World Monkeys - tails, 2-1-2-3 dental patterns
Diet
folivores eat foliage
gumivores eat gum
frugivores eat fruit
insectavores eat insects
herbivores eat plants
carnivores eat meat
omnivores eat everything (omni)
Todays Lab
Move from station to station following the directions in the lab manual (on 
pp. 62-65) Do the the observations and measurements.
There are calipers for measuring teeth and arm alnd leg length where needed.
BE CAREFUL WITH THESE DELICATE SPECIMENS!!!! Work with them OVER the green 
padded tubs. Don’t fumble them!
What not to do
Don’t even touch the articulated specimens or they may fall apart!
Don’t pull apart articulated specimens to count teeth.
Don’t bump tables and shake the articulated specimens or the glue may give way.
1000 students a year use these skeletons so Be careful!
Todays lab
Try to identify the  Suborder and Superfamily (and species if you can) without 
looking at the info card inside the brown paper bag

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