Don’t Call Them Basic: A Review of Strepsirrhini Primates

Figure 1: Various Strepsirrihini species

 

 

Strepsirrhini.  A word that you may not be familiar with, although you may already know of or seen the primates that make this suborder.  They include all species of lemurs, lorises, and galagos (Figure 1).  They are found in a very small section of the world, specifically on the island of Madagascar, small pockets of Africa, and throughout southern and eastern Asia.  They are also incredibly unique primates, which is what will be discussed in today’s blog post.

 

Strepsirrhini species are classified as being primitive primates.  This refers to the fact that they most resemble ancestral primates, not that they are simple (or basic, in the colloquial sense), unintelligent, or incapable.  It could be argued that they are anything but because they have not evolved (changed) much over time and manage to survive to this day.

 

While there is a great deal of diversity in the types of species that make up the Strepsirrhini suborder there are some specific morphological features that all species have in common.  They are often compared appearance wise to various types of rodent species, which is reflected in their body sizes and shapes.  Overall, they are small bodied.  Also, they have the smallest brain to overall body size ratio, meaning their brains are not very big.  They all have small and moist noses, prominent pointed ears, and very large eyes that lack of a postorbital bar.  They also tend to have very long tails (again, relative to body size).  A tapetum lucidum is present within their eyes.  This is tissue at the back of the eye that causes the eye to have a reflective quality when light shines into it, which you can more easily see at night.  They also retain a dental comb, which are protruding lower incisors and canines.  The dental comb is used to aid in self grooming and grooming of others.  While their hands maintain generalized primate characteristics (i.e., they have prehensile, grasping, hands and opposable thumbs), they use their hands in pairs, not one at a time like other primates.  Their hind legs are longer than their forearms.  They also have a grooming claw, which is just as it sounds like-a long claw on one of their toes that serves the purpose of brushing their fur or the fur of others.  The remainder of their fingers and toes have nails, which is a generalized primate characteristic. 

 

Behaviorally, there remains some diversity.  Lemurs tend to be diurnal, meaning they are active during the day, whereas lorises and galagos are nocturnal, active at night.  All strepsirrhini species are arboreal, meaning they live in the trees.  They also share similar locomotive patterns, which are typically vertical leaping and clinging.  This is an adaptive feature of their arboreal lifestyle.

 

Strepsirrhini species are unique compared to other primate species, which are classified as haplorhini species, but a discussion on these primates will come in a future post.  Again, these species have not seen a need to evolve over time despite various changes over time, but they are facing serious threats due to human interventions.  Because of popular culture attitudes they are at great risk of extinction, and it is important to save these species for various reasons.  Without them ecosystems risk collapse and we lose out on fully understanding our own (human and primate) evolution.

 

References

Fleagle, John G. Priamte Adaptation and Evolution. San Diego: Elsevier, 1999. Print.

Haviland, William, Gary Crawford and Shirley Fedorak. Human Evolution and Prehistory. Toronto: Thomson-Nelson, 2005. Print.

Welsch, Robert L., Luis A. Vivanco and Agustin Fuentes. Anthropology: Asking Questions About Human Origins, Diversity, and Culture. New York: Oxford University Press, 2020. Paper.