Lecture 3- Primate evolution and diversity I Flashcards
What does primate mean?
- first rank
- primates viewed as the highest rank, the name taken from how we refer to heads of churches and archbishops
- controversial nomenclature as Linnaeus identified similarities between monkeys and humans and has hence classified them together
What does classification mean?
- groups organisms together into phyla, class, order, genus etc based on shared characteristics.
- e.g.: all bats have wings, all mammals produce milk
- knowing that bats have wings and the ancestor didn’t gives us little information as to where the split occured
What does phylogeny mean?
- represents the evolutionary relationships between organisms (it’s an evolutionary tree), based on shared derived characteristics (synapomorphies).
- Shared primitive characteristics (symplesiomorphies) are not considered useful
What are symplesiomorphies?
-shared derived characteristics on which a phylogenic tree is based
What are symplesiomorphies?
-shared primitive characteristics, not considered useful for establishing a phylogenic tree
What is this?
- the mammalian evolutionary tree
- primates are a small portion of the tree (red rectangle)
What are the nearest relatives of primates?
-flying Lemurs (Dermoptera)
What are the Euarchonta?
- means true ancestors, these are three groups that share a common ancestor from which humans have also eveolved
- the groups are:
1. Dermoptera (Flying Lemurs)
2. Primates
3. Scandentia (Tree shrews)= proposed basal link to primates, separated approx. 80 MYA
How old are the earliest primate fossils, where were they found and what were the characteristics of those animals?
- 65-55 MY
- most found in America but also found in Asia and Africa (spread quickly)
- belonged to a now extinct group known as Plesiadapiformes
- small 20-30g, arboreal, insectivorous
- similar in appearance and habits to modern tree shrews -found two species:
1. Purgatorius (c. 64 MYO) - maybe the basal link of primates?
2. Dryomomys (c. 55 MYO) - maybe the ancestor of tree shrews and the basal link?
What are the characteristics of primates in general? (9)
- Grasping hands and feet
- Opposable digits
- Finger nails (instead of claws)
- Hind limb-dominated locomotion (arms less strong)
- Reduced sense of smell (small noses
- Binocular vision
- Extended maternal care
- Large brains
- Relatively small number of teeth
What are the three primate characteristics that are related to arboreal living?
- Grasping hands and feet
- Opposable digits
- Binocular vision
What is this?
- comprehensive primate phylogeny
- 1st split: Plesiadaformes splitting into Strepsirrhines and Haplorrhines
- 2nd split: Haplorrhines split into Anthropoidea and Tarsiiformes (tarsiers)
- 3rd split: Anthropoidea split into Platyrrhines (New World Monkeys) and Catarrhines (Old World Monkeys)
- 4th split: Catarrhines split into Hominoidea and Cercopithecoidea
What was the first split in primate evolution?
- the Plesiadaformes split into Strepsirrhines and Haplorrhines
- this occured approx 78-63 MYA
How many species of Strepsirrhines are there and where do they occur?
- 110 species (about a quater of primate species)
- mostly in Madagascar, few in S Africa, SE Asia
How many species of Haplorrhines are there and where do they occur?
- 280 species
- spread throughout the world, in Africa, Asia, America
In which areas are there differences between Strepsirrhines and Haplorrhines?
- Nose
- Eyes
- Snout
- Teeth
- Hand
How is the nose different in Strepsirrhines and Haplorrhines?
- Strepsirrhines: wet nose, nose pad (rhinarium) and nose slits
- Haplorrhines: dry nose, no nose pad and have nostrils
- Strepsirrhines have better sense of smell & use scent- marking, possibly associated with nocturnal existence
How are the eyes different in Strepsirrhines and Haplorrhines?
Strepsirrhines:
- the back of the retina has a layer (the tapetum) that reflects light which allows for more light to be collected at the retina
- this is believed to be a nocturnal adaptation (increases light gathering abilities of the rod cells)
- mostly dichromatic (not colour vision)
Haplorrhines:
-have colour vision and no tapetum, poorer visual acuity in the dark (as they are diurnal)
How is the snout different in Strepsirrhines and Haplorrhines?
Strepsirrhines:
- have larger snout and a better sense of smell
Haplorrhines:
- have a flatter profile and less prominent snouts
How are teeth different in Strepsirrhines and Haplorrhines?
Strepsirrhines:
- incisors and canines modified into thin prominent teeth = toothcomb which is used for grooming and chewing off bark
Haplorrhines:
-comparable mammalian dentition
How are hands different in Strepsirrhines and Haplorrhines?
Strepsirrhines:
- second digit is modified into a longer claw, used for grooming.
eg. Aye-ayes (Daubentonia madagascariensis) have extra long claw for food extraction (eat insect grubs)
Haplorrhines:
-“normal” hands
What is the controversial fossil of a possible early Haplorrhine?
-Darwinius masillae (aka “Ida”)
- Most complete fossil primate ever found
- 47 Mya old - found in Germany
- Lacks toothcomb and second-digit claw (hence Haplorrhine)
- 60cm long - probably 600-900g
- Diet - frugivorous/herbivorous (Fur and stomach contents preserved)
- controversial as the line is there and the time between the find and publishing (1983-2009)
- some say it is a lemur but doesn’t have the basic characteristics!
- probably spread from Siberia then to Europe and then east to the Americas
What was the second split in primate evolution?
- Haplorrhines split into the Anthropoidea and the Tarsiiformes (tarsiers)
- Tarsiiformes: 9 species, all in SE Asia
- Anthropoidea: 270 species, Africa, Asia, Americas
Are there any easily identifiable synapomorphies in Anthropoids?
- genuine synapomorphies for Anthropoids are difficult to identify (many are shared with tarsiers)
- but anthropoids did evolve a single, “simple” uterus, which is typically associated with a decreased litter size, often means an increase in individual maternal investment
What were the earliest Anthropoids like?
- Earliest anthropoids - Tarsier-like (<100g)
- Probably arose in Asia
- Insectivorous and arboreal
- had shearing plates in their dentition= characteristic of species that need to crush the hard exoskeleton of insects
What was the third split in primate evolution?
- the Anthropoids split into the Platyrrhines (New World Monkeys) and the Catarrhines (Old World Monkeys)
- split occurred approximately 43 MYA
- the Platyrrhines consist of about 135 species, all occur in the Americas
- the Catarrhines consist of about 145 species and occur in Asia, Europe and Africa
How is the nose different in Platyrrhines and Catarrhines?
Platyrrhines
- wide flat noses
- nostrils well separated
Catarrhines
- narrow pointed noses
- nostrils close together
How is the tail different in Platyrrhines and Catarrhines?
Platyrrhines
- long,muscular,prehensile
- used to hold onto branches
Catarrhines
- less muscular, shorter
- sometimes absent
How are teeth different in Platyrrhines and Catarrhines?
Catarrhines
- lost a pre-molar (they have 2 incisors, 1 canine, 2 [not 3] pre-molars and 3 molars)
- Upper canine occludes against the first pre-molar
What were the earliest Catarrhines like?
-Aegyptopithecus zeuxis and Propliopithecus (2 species)
- 34 million years ago
- Found in Egypt (African origins)
- Body mass about 6kg
What is the fourth split in Primate evolution?
- the Catarrhines split into the Hominoidea (c. 20 species, Africa and Asia) and the Cercopithecoidea (Old World Monkeys, c. 125 species, Africa and Asia)
- occurred approx. 31 MYA
What was the earliest Hominoid found?
-Proconsul
• Found in East Africa
- at least 3 species
- Earliest fossils ≈ 24 Mya
- Rainforest-dwelling, frugivorous, quadrapedal (not full flexibility of arms)
- Large monkey - about 30kg
