ANT333Y1 Lecture Notes - Lecture 20: Oligocene, Premolar, Apposition
ANT333 Lecture #20 – Adaptive Complexes in Primates – Tarsiers and Aye-Aye
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
Primates have infraorders Strepsirhini (Lorisiformes and Lemuriformes) and Haplorhini (Tarsiiformes
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
Morphological analyses have been unable to resolve tarsier phylogeny.
Some analyses point to strepsirhine or haplorhine clade.
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
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
Five Extant Species of Tarsiers
Found below 300m – bancanus, syrichta
Found above 2000m – pumiucs, dianus
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
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 (22.214.171.124./126.96.36.199) – retained third premolar, lost one incisor
No living primate has same formula
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
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
Many anatomical and behavioral traits show a clinal distribution
T. spectrum complex most generalized, T bancanus being the most specialized, and T syrichta being
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
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 smooth sitting pad on ventral surface
Huge eyes lack tapetum lucidum (reflecting layer behind retina).
Like humans, tarsiers possess retinal fovea which is adaptation for close scrutiny
where depression allows light to fall directly on cones.
Western tarsiers relatively largest eyes among tarsiers, while Sulawesi tarsiers have smallest.
Largest eyes relative to body size of all primates
Tarsiers usually 1-2 meters off ground.
Locomotor morphology specialized for vertical clinging and leaping.
Use leaping between vertical supports as the major means of locomotion (60%-70% of the time)
T. bancanus relies on leaping and climbing almost exclusively whereas T. spectrum, T. dianae, and T.
syrichta greater reliance on hopping, walking, and cantering
Average leaps of tarsiers slightly over 1 meter and only rarely farther than 3 meters.
Only primates whose diet is made up entirely of animal foods (ex. slender loris).
Eat beetles, grasshoppers, cockroaches, butterflies, moths, praying mantis, crickets, dragonflies,
termites, and occassionally ants, spiders, and cicadas.
Most prey captured in leaf litter on ground.
Prey located primarily by sound and only secondarily by sight.