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Lecture 20

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Shawn Lehman

ANT333 Lecture #20 – Adaptive Complexes in Primates – Tarsiers and Aye-Aye Tarsiers (Tarsius)  May be derived from or are sister taxon of Eocene omomyids.  Omomyids often placed with tarsiers in infraorder Tarsiiformes  In Eocene, great variety of omomyids existed in North America & Europe.  Omomyids ~ 30 g animals (similar to smallest extant primates) to 2500 g (Cebus). Tarsiers & Omomyids  However, omomyids lack number of distinguishing features that characterize modern tarsiers.  Thus, other researchers, such as Fleagle (1999) now believe that omomyids are not simply Eocene tarsiers. Tarsier Taxonomy  Primates have infraorders Strepsirhini (Lorisiformes and Lemuriformes) and Haplorhini (Tarsiiformes and Anthropoidea).  Anthropoids may have arose from a tarsier-like, omomyid prosimian.  Still a great deal of debate concerning the relationships of these taxa and their evolution.  Morphology versus DNA Morphology  Morphological analyses have been unable to resolve tarsier phylogeny.  Some analyses point to strepsirhine or haplorhine clade. DNA  DNA sequences in tarsiers, strepsirhines and anthropoids consistently point to tarsiers as a sister group to anthropoids; so we should classify them in the haplorrhine suborder Fossil Tarsiers  Very rare.  Mandibular fragment of tarsier-like primate from early Oligocene deposits in Africa.  Single tarsier molar from Miocene of Thailand.  Recent discovery: fossil Tarsius from middle Eocene in China indicates Tarsiidae part of earliest primate radiation. Five Extant Species of Tarsiers  Tarsius bancanus  Tarsius syrichta  Tarsius pumilus  Tarsius diana Tarsius spectrum  Found below 300m – bancanus, syrichta  Found above 2000m – pumiucs, dianus 1 Tarsier Natural History  All living tarsiers are small, nocturnal, vertical clinging and leaping, faunivorous animals.  They are anatomically and ecologically distinctive with regard to other primates. Distribution of 5 Extant Tarsier Species  Sumatra and Broneo  Island bound Tarsier Dentition & Crania  Resemble those of anthropoids in overall proportions.  Large upper central incisors, small lower incisors, and large canines.  High-cusped, simple molar teeth with conules on upper molars superficially look very primitive, but indications of modifications from more complex molar type in their ancestry.  Dental formula ( – retained third premolar, lost one incisor  No living primate has same formula Tarsier Crania  Unfused mandibular symphasis – strepsirhine characteristic (primitive)  Tympanic ring external to auditory bulla – derived  Postorbital plate rather than bar or full closure – not fully closed - unique Tarsier Postcrania  Striking in many of its proportions.  Hands and feet are relatively enormous, reflecting both clinging abilities and predatory habits.  Extremely long legs and many more specific adaptations for leaping  Fused tibia and fibula and the very long ankle region responsible for their name.  Tarsiers lack grooming claw. Tarsier Reproductive Physiology  Similar to higher primates, except tarsiers have multiple nipples. - primitive  Females have monthly swellings. – similar to homonids  Tarsiers have hemochorial placenta (anthropoid-like) in which maternal blood comes in direct contact with chorion (outermost, protective layer of fetal membranes) – for large brains  Prosimians have epitheliochorial placenta, in which uterine epithelial lining has not eroded but simply lies in apposition to chorion. Hemochorial versus Epitheliochorial Placentas  Strepsirhines have a epithellochorial placenta, which is a placenta in which the wutherine epithelial lining has not eroded but simply reduced Hemochoria versus Epitheliochorial Placentas  Hemochorial placentas provide greater flow of blood and nutrients to fetus  Mother will eat placeneta because it is nutrient rich 2 Interspecific Variation  Many anatomical and behavioral traits show a clinal distribution  T. spectrum complex most generalized, T bancanus being the most specialized, and T syrichta being intermediate.  Other differences: body weight, intermembral indices, finger pads, locomotor behavior, habitat selection, nesting sites, communication, and social and ranging behavior. Tarsier Fingers & Toes  Fingers & toes end in large terminal pads.  Relatively largest pads are found on T bancanus; and smallest on T pumilus, in which pad is almost non-existent, and long, keeled, claw-like nails protrude beyond the end of the fingers and toes.  T pumilus lives at very high altitudes in montane forests, where vertical surfaces are covered with moss. Speculated that digits & toes of this species adapted for clinging to moss covered branches in montane forest Tarsier Tails  Tail twice body length  Used for: support on vertical substrates & to control momentum & direction during leaps.  Sulawesi tarsiers have tail lightly haired along its length.  T syrichta & T bancanus tails nearly naked except for tuft.  Tail has developed smoot
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