The Order Primates has traditionally been divided into two Suborders: Prosimii (lemurs, lorises, galagos, and tarsiers) and Anthropoidea (monkeys, apes, and humans).
Lemuriformes (Lemurs): Ring-tailed lemurs, indris, sifakas, mouse lemurs, aye-ayes. Found only on island of Madagascar, include both nocturnal and diurnal species. Generally longer tails; toilet claw on second toe; have a rhinarium, most have 36 teeth.
Lorisiformes (Lorises): Slow loris, slender loris, potto, galago (or bushbaby). Found in Africa and Asia, are all nocturnal. Have a very short (or no) tail; toilet claw on second toe; have a rhinarium, most have 36 teeth.
Tarsiiformes (Tarsiers): Tarsiers (5 species). Found in Asia, all nocturnal. Huge, immobile eyes (turn whole head); toilet claw on second and third toe; no rhinarium; 34 teeth; unfastened lip; elongated ankle bones.
A newer (BETTER) classification based on molecular and morphological evidence places tarsiers with monkeys, apes and humans in the Suborder Haplorhini (“dry noses”), with lemurs and lorises in the Suborder Strepsirhini (“wet noses”). (**HINT: be sure to use this new classification in filling out your taxonomies)
Strepsirhini Characteristics
The Strepsirhini (and prosimians in general) exhibit some unique features not seen among other groups of primates. Some terminology to consider before looking at these primates.
Hairless rhinarium
The rhinarium is a moist, hairless/furless patch of skin that surrounds the nostrils in many mammals. It is part of the olfactory system (associated with the sense of smell). It is believed that organisms that have a rhinarium have a more acute sense of smell. It is also able to determine wind direction, allowing individuals to determine which direction a smell is coming from. The presence or absence of this feature determines whether an organism is categorized in the suborder Strepsirhini or Haplorhini.
Dental comb (Tooth comb)
A unique trait shared by members of the suborder Strepsirhini (see taxonomic discussion below) the incisors and mandibular canines come together to form a tooth comb. This comb is used by individuals who posses it during oral grooming, and can also be useful as a tool when accessing various food resources. This feature is seen only among the strepsirrhines.
Grooming Claw (Toilet Claw)
While a defining characteristic that separates the order is that all primates have nails instead of claws, prosimians retain an exception to this rule. All prosimians maintain one (or sometimes two) grooming claw that they use for personal grooming needs. This claw serves as a useful tool for individuals that have it. Like a nail, it is also made of keratin. This feature is seen among all members of the suborder Strepsirhini; tarsiers are the only individuals of the suborder Haplorhini who retain a grooming claw.
Instructions: Look at the 3D images below to compare members of the suborder Strepsirhini (Ringtail Lemur and Slow Loris) and the suborder Haplorhini (Tarsier and Capuchin). Be sure to rotate and look closely at these 3D skulls, noting the characteristics described above that distinguish Prosimians from Anthropoids. Please reference the keywords list above (which are all described in the lab instructional video) and the lecture clips for information on these features.
Reflection Question
What overall differences seem most noticeable between the prosimians and anthropoids (or Strepsirhini and Haplorhini)?
