Week 5: Primate Evolution Flashcards
1
Q
anthropoid origins
A
- one of the most contested questions in primate evolution
- first remains from north africa (algeripithecus, altiatlasius), but are now disputed
- in the last 25 years more and more material from east and southeast asia (eosimiidae)
- eosimiidae also preserve postcranial material which is anthropoid-like
- eosimiids probably insectivores (very small), diurnal
2
Q
A
3
Q
rafting the atlantic
the origin of platyrrhines
A
- long thought to originate from North American, but there are no plausible ancestors there
- came likely from africa
- rafting on floating islands seems unlikely, but isolated islands are another possibility
4
Q
suprisingly rare
fossil platyrrhines
A
- despite the diversity of present-day platyrrhines, and the in general good fossil record in south america, fossil platyrrhines are very uncommon
- probably due to ecological and taphonomic factors - a lot of their evolution would have been in the amazon basin
5
Q
an endemic fauna
pleistocene platyrrhines from the caribbean
A
- a number of fossil platyrrhines have been found in the caribbean, while there are no present day primates there
- originally interpreted as having been introduced by humans it became clear that they differ from any other recent platyrrhines, and were an endemic radiation
- probable cause of extinction: arrival of humans in the region. one species (xenothrix mcgregori on jamaica) likely surivived until european colonization of the island
- origin unknown, but the earliest fossil is a talus assigned to paralouatta marianae, from the early miocene of cuba
- possibly multiple colonization events
6
Q
early anthropoids and friends
the fayum egypt
A
- one of the richest primate bearing fossil localities
- almost 400 m thick succession, covering several million years near the eocene-oligocene boundry, and up into the miocene
- diverse primate fauna, including omomyoids, probable adapoids, stem anthropoids and stem catarrhines
7
Q
parapithecoids
dentition
A
- dental formula mostly 2.1.3.3/2.1.3.3 but lower incisors reduced/missing in some taxa
- canines large and tusk like in parapithecus grangeri, otherwise platyrrhine-like
- three lower premolars increase i size and complexity from front to back
- upper premolars are broad, usually with three cusps rather than two
- molars with low, rounded cusps
- lower molars with small trigonid (including paraconid in some M1s), wider talonids
8
Q
parapithecoids
cranium and mandible
A
- fused frontas suture
- postorbital closure, except in one species (biretia megalopsis), here the floor of the orbit and the palate are fused, like in tarsius
- mandible fused in most, except in the most primitive genus (biretia megalopis)
- orbits tend to be small, indicating diurnal habits
- in apidium browni and parapithecus grangeri, orbits less converging than in other anthropoids
9
Q
still in the fayum, egypt
the first catarrhines
A
- the two main groups, the propliopithecids and ologopithecids
- tend to be larger than parapithecoids and proteopithecoids, up to about 8000g
10
Q
the best known early anthropoids
propliopithecids
A
- dental formula 2.1.2.3, molars similar to hominoids
- tend to be large 3-8 kg
- in details of cranial and postcranial anatomy significantly more primitive than hominoids or cercopithecoids and so are likely stem catarrhines
11
Q
what makes an ape
A
no tail and unique elbow
12
Q
ape characteristics
A
- appendix
- no tails
- highly mobile arms
- unique elbow joint - can be seen on humerus, radius, ulna
13
Q
dryopithecinae
and other eurasian apes
A
- arrive in eurasia somewhat after the pliopithecoids
- diverse radiation of mostly medium-large species
- with regards to dental, cranial and post cranial morphology in general great-ape like
- taxonomy complex, and further complicated by strong personal opinions - different specimens, and even species move between genera depending on the author
14
Q
the enigmatic ape
oreopithecus bamboii
A
- from the late miocene of italy
- very specialized dentition, with centroconids (accessory cusps in the center of the molars)
- associated with an island fauna that lived in swampy forests
- very long forelimbs, short hindlimbs, but possibly bipedal
- precision grip with thumb and index
15
Q
conflict between cranial and postcranial data
homoplasy in sivapithecus
A
- if the similarities in the crania of sivaputhecus and pongo are homologous, then the similarities in the postcrania of great apes are homoplasies
- if the similarities in the postcrania of great apes are homologous, then the cranial similarities between sivapithecus and pongo are homoplasies
- we could have the case of trait reversal
- either way, reconstructing phylogeny from the morphology is not easy!
16
Q
the largest primate
gigantopithecus
A
- known from numerous isolated teeth and a few mandibles
- gigantopithecus gigantaeus (the smaller species): late miocene of the siwaliks (pakistan)
- gigantopithecus blacki: pliocene - middle pleistocene of south china and vietnam
- very large jaws and teeth with thick enamel, premolars molarized, canines reduced
- based on stable isotope data forest dweller with generalized plant diet
17
Q
in the fossil record
what makes a hominin
A
- bipedal locomotion
- small canines, no honing on first premolar
- thick enamel
18
Q
what is bipedalism
A
walking upright
19
Q
when did bipedalism evolve
A
- evolved many times
20
Q
why did bipedalism evolve
A
- thermoregulation: less direct sun hits the body
- enables transport of food and tools: free arms and hands to do useful things
- better overview in open grassland: easier to spot predators and scout for food
- pair bonding and changes in social behaviour: monogamous - males carry food back to sedentary females
21
Q
what is the ancestral locomotor behaviour
for hominins
A
- hominins comprise humans, their fossil ancestors and fossil relatives
- our closest living relatives are gorillas and chimpanzees which both engage in knucke walking
22
Q
posture and locomotion of our close relatives
A
- locomotor patterns of living hominoids are diverse
- gibbons and orangutans brachiate in trees
- gibbons usually walk upright when on the ground
- gorillas and chimpanees both engage in knuckle walking
23
Q
cranial anatomy of a biped
how to spot an upright walking head
A
- foramen magnum moves forward
- smaller muscle attachments at the neck
- occipital squama changes orientation
