Prosimians

Prosimians are the group of animals who belong to the kingdom of mammals and the order primates. They include most of the animals, whether living or extinct, who belong to the suborder ‘ Strepsirrhines’ and the suborder ‘Haplorhine’. In the suborder Haplorhine, tarsiers are the only group of animals that are included under prosimians.

Prosimians are the most primitive survivors of the order primate and show characteristics that were similar to the ancestors of monkeys or apes. Although they are not similar to apes , monkeys or humans (collectively known as Simiiformes). Tarsiers are more closely related to Simiiformes.Simiiformes were earlier known as Anthropoids.

Prosimians are native to Madagascar but are also found in South east Asia and Africa.

Scientific Classification of Prosimians

The Scientific Classification of any species or organism is presented in an arrangement that is not fixed and can keep on changing based on the new discoveries of fossils, analysis of DNA sequences with new emerging technologies, reanalysis of conventional data etc. Based on the current updated arrangement we can classify Prosimians under the following classification:

The Haplorhini is further classified into the infraorder Simiiformes that is further divided into 6 families of new world monkeys, old world monkeys, apes and humans.

Characteristics of Prosimians

1. Strepsirrhini

• 75% of the species are nocturnal  and others are diurnal.
• They have a tapetum ( shiny, reflective layer in the back of the eyes).
• Most of the prosimians belong to this suborder. The term Strepsirrhini has its origin from Greek, that means ‘curved or bent nose’.  
• The most distinguished characteristic of this order is the presence of ‘wet nose’ that refers to the rhinarium or wet naked area around the nostrils of the nose present in most of the mammals leading to a strong sense of olfaction.
• Moist nose is connected with the upper lip and the upper lip is further connected to the gum leading to restricted facial expressions.
• Their brain is smaller in size with respect to their body leading to a lower intelligence.
• They have  an elongated snout.
• They also have a postorbital bar indicating their primitive nature.
• Their ears can move independently to capture sounds better.
• Most of the strepsirrhines are tooth combed with an exception of Aye-aye. This feature helps them in grooming.
• There is a claw on the second toe and the big toe is separated leading to a vise-like grip for locomotion.
• They can also enzymatically manufacture Vitamin C.
• Females have multiple sets of nipples and Y shaped uterus.
• For reproduction they have a specific breeding season.

2. Tarsiers

• They are nocturnal.
• They have a fovea.
• They are dry nosed primates.
• Their body and head sizes range from 10-15 cm in length.
• Their upper lip is not directly connected with gum thus leading to varieties of expression.
• Thay have a postorbital plate.
• Their vision is the primary sense and they have trichromatic colour vision.
• They cannot manufacture Vitamin C enzymatically.
• They are very small in size.
• They have enormous eyes and long hind limbs, and fingers.
• They have no tooth- comb, but a unique dental formula.
• Their third toe and hind feet have claws for grooming purposes.
• They have soft velvety fur.
• They have a slender tail.

Frequently asked questions about Prosimians

References

1. Smithsonian National Zoological Park (SNZP). 2008. Great apes and other primates: Differences among prosimians, monkeys and apes. Smithsonian National Zoological Park. Retrieved August 29, 2008.
2. Cartmill, M. (2010). “Chapter 2: Primate Classification and Diversity”. In Platt, M.; Ghazanfar, A (eds.). Primate Neuroethology. Oxford University Press. pp. 10–30. ISBN 978-0-19-532659-8.