Rhinarium

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The rhinarium is present in mammals such as the cat.
The rhinarium is present in mammals such as the cat.
Howler monkeys are examples of haplorrhines, which have simple nostrils and a dry upper lip instead of a wet rhinarium.
Howler monkeys are examples of haplorrhines, which have simple nostrils and a dry upper lip instead of a wet rhinarium.

The rhinarium is the wet, naked surface around the nostrils of the nose in most mammals. Colloquially it might be called a "wet snout".

Primates are phylogenetically divided into Strepsirrhini ("curly-nosed" primates with rhinariums, which is the ancestral condition) and Haplorrhini ("simple-nosed" primates which have replaced the rhinarium with a more mobile, continuous, dry upper lip).

Mammals with rhinariums tend to have a stronger sense of olfaction, and the loss of the rhinarium in the haplorrhine primates is related to their decreased reliance on olfaction, being associated with other derived characteristics such as a reduced number of turbinates.

Note that the traditional paraphyletic "prosimian" division of primates cannot be characterised by the presence of a rhinarium, due to its absence in the tarsiers, and loss of the rhinarium is not a synapomorphy of the simians or anthropoids, but a symplesiomorphy shared with the tarsier outgroup.

[edit] References

  • Fleagle, J. G. (1988). Primate adaptation and evolution. San Diego: Academic Press.