Notes on the Stepsirhines: Lemurs and Lorises

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  • Topic: Primate, Haplorrhini, Simian
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Week Seven Notes:
The Stepsirhines: Lemurs and Lorises
Prosimians(Same thing as Stepsirhines): Lemurs, Lorises, Tarsiers: Most primitive of the primates
Exhibit the fewest derived traits (as a group) of all primates Ancestral Characteristics (ie. Inherited from mammals)
Rely more on olfaction
Moist noise and long snout
Eyes slightly more lateral
Classification of Prosimians: Lemurs, Lorises, and Tarsiers
Order- primates
Suborder: Strepsirhines (used to be Prosimians)
Means “wet-nosed”
Lemurs and Lorises
Strepsirhines: Shared Anatomical Features
1.Postorbital ring/bar (derived)
2.Unfused frontal bone (ancestral)
3.Unfused Mandibular Symphysis (ancestral)
a.Mandibular symphysis at the midpoint of the chin
4.Tooth Comb present (derived)
a.Aka “dental comb”
b.Lower incisors and canines project forward
c.Used in grooming
5.Dental formula is 2 incisors -1 canine-3premolars -3 molars (derived) 6.Tapetum lucidum present (ancestral)
a.Not unique to strepsirhines
7.Bicornuate uterus (ancestral)(almost like a two horned uterus, almost heart shaped) a.For multiple offspring

Strepsirhine Infraorder: Lemuriformes (Lemurs)
Only found on Madagascar and nearby islands
Only nonhuman primates on Madagascar
Found many open niches on arrival
Lemurs:
60 surviving species
Larger Lemurs diurnal-active during day
Smaller lemurs nocturnal
One third of lemurs extinct since AD 500
Lemur Behavior:
Most are arboreal (spends most time in trees)
Most are quadrupeds; some are vertical clingers/leapers
Many live in social groups
Strepsirhine Infraorder: Lorisiformes-Lorises
At least 8 species of Lorises
Found in India, SE Asia, and Africa
Slow arboreal quadrupeds
Nocturnal
Lorisiformes-Galagos
6-9 galago species
Mostly under 1kg
Locomotion is vertical clinging and leaping
Nocturnal

Lorisiformes (Lorises and Galagos)
Some lorises and galagos are entirely insectivorous
Both usually solitary foragers
Tarsiers: Prosimians, but not Strepsirhines
3 recognized genera of tarsiers
Restricted to islands in Southeast Asia
Vertical clingers and leapers
Nocturnal insectivores
Tarsiers
Enormous eyes immobile within sockets
No tapetum lucidum
Different from strepsirhines
Tarsiers: Strepsirhine Traits
1.Unfused frontal (ancestral)
2.Unfused Mandibular symphysis (ancestral)
3.2-1-3-3 Dental formula
4.Bicornuate Uterus
Tarsiers: Traits not shared with Strepsirhines
1.Postorbital ring
2.Dental comb
3.Tapetum Lucidum
Tarsiers more like monkeys in their genetics
Primate Fossil Ancestry: Events Preceding Primates
Ca. 500 MYA: first vertebrates in fossil record
Ca. 250 MYA: Pangea II forms- nearly all land is one big continent Ca. 125 MYA: Pangea is split into Northern and Southern halves

Ca. 125 MYA
Northern continent is Laurasia
oNorth America, Greenland, Europe, Asia (minus India)
Southern Continent is Gondwana
oSouth America, Africa, Antarctica, Australia
Adaptive radiation of angiosperms underway
oAngiosperm-flowering plants
oImportant for later primate evolution (fruits/insects)
Marsupials have recently evolved
Events Preceding Primates cont:
Ca. 70 MYA: first placental mammals in fossil record
Ca. 65 MYA: Mass extinction of most dinosaurs
50% of animal genera go extinct
No land animal over 25 kg survives
Cenozoic Era and the First Primates:
Cenozoic Era (65MYA to present)
Paleocene Epoch (65-55 MYA)
oNo primates yet
oPre-primates(new world)
Eocene Epoch (55-35 MYA)
oFirst primates (strepsirhines)
Oligocene Epoch (35-25 MYA)
oFirst monkeys
Miocene Epoch (25-05 MYA)
oFirst apes
Paleocene Epoch (65-55MYA)
Adaptive radiation of mammals
Environmental change opens up many new ecological niches Plesiadapiformes: pre-primates
Once thought to be primates (but hands differ too much)
No primates were alive during Paleocene

Why aren’t Plesiadapiformes primates?
Dental formula: 3-1-4-3
No postorbital Bar
Claws,...
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