Week 4: Functional Morphology Flashcards
bonobo
pan paniscus
- live in central africa, south of the zaire river in relatively forested habitat
- locomotion - knuckle walking on the ground, some climbing and suspensory behaviour, most suspensory of the african apes
- mostly frugivorous and foliovorous, but both vertebrates and invertebrates are eaten if available
- social system : fission-fusion, frequent use of sexual behaviour (male-female, f-f, rarely m-m) in social interaction
comparative morphology of apes
cranium
- hylobates: much smaller than other apes
- pongo: tall, narrow oval orbits with “supraorbital costae”; small interorbital distance; airorhynchy (upward bent face); teeth with wrinkled, thick enamel
- gorilla: large supraorbital torus; sagittal and occipital crests in males; sharp crests on teeth and thin enamel
- pan: smaller and more gracile; supraorbital torus curved; usually no sagittal/occipital crests
comparative morphology of apes
orbital region
relationship between form and function
functional morphology
- two main factors influencing morphology (phylogeny and function)
- similarities in morphology can be either homologous (similarity due to common descent) or homoplasies (similarity due to similar function)
- studies the relationship between function/behaviour and morphology
- allows to use morphology to reconstruct behaviour of extinct taxa
homoplasy
independent evolution of streamlined shape
functional morphology
teeth
main function of teeth
* biting
* chewing
* defense
* social functions (display, tooth comb, etc.)
functional morphology
biting
different foods need to be bitten in different ways
* frugivores: broad incisors
* foliovores: narrow incisors
* massive and strong incisors can indicate that the animal bites hard things - wood to get insects (daubentonia) or sap (some callitrichines)
functional morphology
chewing
different foods need to be chewed in different ways
* frugivores: low, rounded cusps, frequently thick enamel
* foliovores: teeth with sharp longitudinal and transverse crests, thin enamel
* insectivores: teeth with sharp, pointy cusps to pierce chitin
* morphology of course always a compromise between different functional constraints
morphological indicators of diet
frugivores
fruit eaters
- broad incisors
- low rounded molar cusps
- small long intestine
morphological indicators of diet
foliovores
leaf eaters
- small incisors
- well developed molar shearing crests
- large caecum
- complex stomach
- enlarged large intestine
morphological indicators of diet
gummivores
gum eaters
- stout incisors
- claws for clinging
- long caecum
morphological indicators of diet
insectivores
insect eaters
- sharp cusps
- short, simple gut
diet and body mass
- smaller primates tend to eat less leaves, but the regression only explains 27.7% of the variance
- no primates below about 500g body mass is primarily foliovorous
- smaller primates tend to eat higher quality food, however a lot less variability
functional morphology
teeth and social behaviour
- canine size correlates well with social system (at least in catarrhines)
- papio: very strong sexual dimorphism, males with large, dagger-like canines ; polygenous (one male with many females)
- hylobates: monomorphous canines (same size in males and females) ; monogamous
functional morphology
locomotion
- locomotion very closely correlated to postcranial morphology
- should allow to reconstruct locomotion/positional behaviour easily
- not so easy when only fragementary material
locomotion adaptations
arboreal quadrupedalism
- long tail
- narrow thorax
- laterally places scapula
- long olecranon process
- deep ulna
- grasping foot
- short similar length forearms
locomotion adaptations
terrestrial quadrupedalism
- narrow thorax
- reduced tail
- short digits
- restricted shoulder joint
- posteriorly extended olecranon process
- robust radius
- short digits
- long similar length forelimb and hindlimd
locomotion adaptations
vertical clinger and leaper
- long lumbar regions
- short femoral neck
- deep femoral condyles
- long hindlimb
- narrow tibia
locomotion adaptations
suspensory or brachiating locomotion
- long curved fingers
- rotary wrist joint
- long forelimbs
- short olecranon process
- broad thorax
- mobile hip joint
- often no tail
- short lumbar region
- dorsally placed scapula
locomotion adaptations
bipedalism
- lumbar curve
- short, broad illium
- short ischium
- relatively long hindlimbs
- short toes
- adducted great toe
- affucted knee
- large head of femur
plesiadapiforms
primate-like mammals
- widely distributed in the palaeocene and eocene of north america and europe
- probably not the ancestors of the primates, as most of them are too specialized in their dentition, could have occupied the ecological niche of the rodents
- but probably close relatives of the ancestors of the primates
- about 45 genera with more than 100 species widely accepted, many more described
plesiadapiforms
morphology
- no postorbital bar or closure
- dental formula of 3.1.4.3 in pergatorius, later strongly reduced
- procumbent incisors, with diastema between canines and incisors
- many arboreal quadrupeds, with hallux in most cases not opposable
main reason
ecological scenarios for the origin of primates
- “arboreal hypothesis”
- grasping extremities were seen as having value for more secure climbing, and the distinctive primate orbital features were explained as being useful for judging distances in the trees during leaping
hypothesis for the origin of the primates
arboreality hypothesis
szalay 1973
- arboreality is plesiomorphic for the archonta (group including primates, scandentia, dermoptera, chiroptera, and plesiadapiformes)
- derived behaviour of primates: herbivory, acrobatic jumping and climbing
- jumping from branch to branch, need to be “securely anchored”
