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Lecture 8

Lecture 8 - Prosimians and New World Monkeys - October 30.docx

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University of Toronto St. George
Keriann Mc Googan

October 30, 2012. Lecture 8 - Overview of the living primates: Prosimians and New World Monkeys Outline  Primate adaptations  Survey of the living primates o Strepsirhines  Lemurs  Lorises o Haplorhines  Tarsiers  New World Monkeys Why did primates evolve their particular set of traits? Four Theories:  The Arboreal Hypothesis – The primate pattern represents an adaptation to an arboreal habitat or to life in the trees. o Proposed by Elliot-Smith and Wood-Jones (1920), further supported by Le Gros Clark o Complex 3D environment with high risks o Increased sense of smell o Stereoscopic vision an important asset to perceive depth in trees o Grasping hands an important asset for travel o Objections: Other orders have arboreal species that do not share primate pattern (i.e. opossums, tree shrews, squirrels, raccoons)  i.e. claws are a better adaptation for climbing up and down vertical supports vs. nails  The Visual Predation Hypothesis – The primate pattern represents an adaptation to foraging for insects in the terminal branches of trees o Developed by Cartmill in 1960s and 70s o Grasping hands needed to grab at insects better/more quickly and hold on o Visual advances important for seeing small bugs o Objections: other arboreal insect eating mammals within visual specialization?  Evidence of primitive condition of omnivory  Other modes of detection (some use sound)  The Angiosperm Radiation or Angiosperm Coevolution Hypothesis: Primates co-evolved with flowering plants. o Developed by…? o Refers to the evolutionary process by which a species diversifies to occupy different ecological niches o …. o Early primates were not visually directed predators but rather omnivores o Therefore feeding on all kinds of different fruits and foliage that is appearing o Hands for grasping onto fruits, flowers, leaves o Colour vision to deduce ripeness o Objections: Angiosperms first appear in the fossil record millions of years before the first primates.  Early primates were not nectar specialists  Early marsupials had grasping hands before evolution of flowering plants  Plenty of animals have a varied diet and are nocturnal  Terminal Branch Hypothesis – Primate patterning better explained only in terms of exploitation of….. o ….. o Loco motor traits an advantage for arboreal habitat o Objections: Are surprisingly few – Researchers have essentially agreed upon the “fine- branch nice” for the evolution of early primates  Which is the best hypothesis? o Does watching wild primates shed light on the best theory? o Kind of Geography and Habitat  Most primates live in the tropics and/or below the equator o Some (very few) kinds of primates in Asia will live in very cold regions  Some are arboreal, some are terrestrial  Locomotion o Quadrupedal = walking on all four limbs o Intermembral index of over 70  Measure of the relative length of upper and lower limbs  (humerus length + radius length)/(femur length + tibia length) x 100 o IM Index and Loco motor Pattern  50-80 = Bipedal or VCL  80-100 = Quadrupedal  100-120 = Brachiation o Vertical clinging and leaping  Forced to leap and bounce across gaps in trees  E.g. lemurs, tarsiers o Brachiation: arm swinging as primary/main form of locomotion, longer arms and legs, long curved fingers, often have reduced thumbs  E.g. Gibbons o Bipedalism: walking on two legs  Some nonhuman primates  BUT: humans only habitual bipeds Strepsirhines (suborder Strepsirhini)  Infraorder = Lemuriformes, No Parvorder, Superfamilies = Lemuroidea and Lorisoidea  Most “primitive” living primates o More similar in anatomical structure to early primates, not stupid or worse than other less “primitive” primates  More reliance on olfaction o Rhinarium (moist hairless pad at end of nose) o Long snout  Immobile upper lip, tethered to upper gums  Eyes more to side of head  Less reliance on vision due to this  Some nocturnal species o Larger eyes to better see in the dark o Tapetum lucidem: another layer in retina of eye to better reflect minimal light, gives nocturnal animals that golden shine in the eyes  Dentation: (MOST lemurs and lorises)  Dental comb o Forward projecting lower incisors and canines o Used for grooming and feeding on tree gum  Grooming claw o Second toe used for grooming  Distribution: found in Africa and SE Asia o Lemurs are ONLY found in MADAGASCAR = endemic = highly unique  Lemurs o Range in size  Mouse lemur (~30 grams)… o Both nocturnal and diurnal patterns  Nocturnal solitary or mated pairs  Diurnal more likely to travel/live in groups o Some arboreal, others more terrestrial o Vertical clinging and leaping o Diet  Mainly fruit, flowers, nectar, insects, small fauna, gums, saps, …  ….  Dental formula = o Scent marking  Lots of olfactory communication  Glands in wrists emitting powerful chemical scents  Ring-Tailed Lemur o Lemur catta o Large, diurnal lemur o 2.3-3.5 kilo
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