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 (188.8.131.52./184.108.40.206) – 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