Strepsirrhini
A suborder of primates including lemurs, lorises, and extinct adapiforms.
Strepsirrhini is a suborder of primates comprising the living lemuriforms—lemurs of Madagascar, African galagos and pottos, and lorises from India and Southeast Asia—alongside the extinct adapiforms, which flourished across Europe, North America, and Asia during the Eocene before vanishing from most of the Northern Hemisphere as the climate cooled. Though adapiforms are often described as "lemur-like," the diversity of both groups makes that comparison misleading. Strepsirrhines are distinguished by a moist rhinarium, or wet nose, similar to that of dogs and cats, which gives them the informal but imprecise label "wet-nosed" primates. They possess a smaller brain relative to simians of comparable size, enlarged olfactory lobes for enhanced smell, a vomeronasal organ for detecting pheromones, and a bicornuate uterus with an epitheliochorial placenta. Their eyes contain a reflective layer that improves night vision, and their eye sockets feature a bony ring around the eye but lack a thin bone wall behind it. Unlike haplorhines, strepsirrhines can synthesize their own vitamin C. Living lemuriforms are characterized by a toothcomb—specialized lower front teeth used mainly for grooming fur. Many extant strepsirrhines face endangerment from habitat loss, bushmeat hunting, and capture for the exotic pet trade. Both living and extinct groups are behaviorally varied but primarily arboreal; most living lemuriforms are nocturnal, whereas most adapiforms were diurnal. Their diets mainly consisted of fruit, leaves, and insects.
- suborder
- Strepsirrhini
- common_name
- Strepsirrhines
- living_groups
- Lemurs, galagos, pottos, lorises
- extinct_group
- Adapiforms
- defining_feature
- Moist rhinarium (wet nose)
- key_trait
- Produce own vitamin C
- conservation_status
- Many living species endangered due to habitat destruction, hunting, and exotic pet trade
Lore & Background
Strepsirrhini is a suborder of primates that includes the lemurs of Madagascar, the galagos (bushbabies) and pottos of Africa, and the lorises of India and Southeast Asia, collectively known as lemuriform primates, as well as the extinct adapiforms that lived during the Eocene in Europe, North America, and Asia. The defining characteristic of strepsirrhines is their moist rhinarium, or wet nose, which gives them the colloquial but imprecise name "wet-nosed" primates, with sinuous, comma-shaped nostrils. Compared to simians of similar size, they have a smaller brain but large olfactory lobes for a strong sense of smell, and they possess a vomeronasal organ for detecting pheromones. Their eyes have a reflective layer that enhances night vision, and their eye sockets are ringed with bone but lack a bony wall behind the eye. Females have a bicornuate uterus and an epitheliochorial placenta. Unlike haplorhine primates, strepsirrhines can produce their own vitamin C. Living lemuriforms are distinguished by a toothcomb, a specialized set of lower front teeth used mainly for grooming fur. Most living strepsirrhines are nocturnal and arboreal, while most adapiforms were diurnal; both groups primarily ate fruit, leaves, and insects. Many living species are endangered due to habitat loss, hunting, and the exotic pet trade.
Reader's Guide
Strepsirrhines diverged from haplorhine primates near the beginning of the primate radiation, between 55 and 90 million years ago, with older dates based on genetic analysis and younger dates on the fossil record. They include the extinct adapiforms, which were diverse and widespread during the Eocene in Europe, North America, and Asia, but disappeared from most of the Northern Hemisphere as the climate cooled. Living strepsirrhines are primarily arboreal and mostly nocturnal, while most adapiforms were diurnal. Both groups fed on fruit, leaves, and insects. Lemuriform primates are characterized by a toothcomb used for grooming. The lemurs of Madagascar are often inappropriately portrayed as 'living fossils' or 'basal' primates, a view that has historically hindered understanding of mammalian evolution and strepsirrhine traits such as olfaction, skeletal anatomy, and relatively small brain size. Natural selection has driven lemurs to diversify significantly and fill many ecological niches despite their smaller brains compared to simians.
Did You Know?
- Strepsirrhines produce their own vitamin C, whereas haplorhine primates must obtain it from their diets.
- The name Strepsirrhini derives from Greek words meaning 'a turning round' and 'nose', referring to the sinuous nostrils on the wet nose.
- Adapiforms, an extinct group of strepsirrhines, thrived during the Eocene in Europe, North America, and Asia but disappeared from most of the Northern Hemisphere as the climate cooled.
- Lemuriform primates are characterized by a toothcomb, a specialized set of teeth used for combing fur during grooming.
Frequently Asked Questions
What is Strepsirrhini?
Strepsirrhini is a suborder of primates that groups together the 'wet-nosed' primates, as opposed to the dry-nosed simians. It spans both living lineages and a major extinct group that once roamed the Northern Hemisphere.
What makes a strepsirrhine a strepsirrhine?
The defining feature is a moist rhinarium (wet nose), accompanied by a vomeronasal organ and enlarged olfactory lobes for a strong sense of smell. They also share a bicornuate uterus with an epitheliochorial placenta and a smaller brain-to-body ratio than similarly sized simians.
Which living and extinct groups fall under Strepsirrhini?
Living members include lemurs of Madagascar, galagos and pottos of Africa, and lorises of India and Southeast Asia. The extinct adapiforms once thrived across Europe, North America, and Asia during the Eocene.
Why are strepsirrhines so good at seeing in the dark?
Their retinas carry a reflective layer that bounces incoming light back through the photoreceptor cells a second time, effectively doubling the usable light. This adaptation makes them well suited to nocturnal foraging and navigation.
Can strepsirrhines make their own vitamin C?
Yes—unlike most other primates, strepsirrhines retain the ability to synthesize vitamin C internally rather than depending solely on dietary intake. This metabolic trait is one of the ways they differ biochemically from the simian primates.
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