- A taxonomic suborder within the order Primates – the clade of primates other than the tarsiers and true simians.
2007, Ankel-Simons, F., Primate Anatomy, ISBN 978-0-12-372576-9, page 394–395:
- Those primates with a philtrum and wet rhinarium have therefore been classified together as Strepsirrhini (Geoffroy, 1812) because of the structural similarity of these two characters in the nasal area. (Strepho means 'turned inward' in Greek and rhinos is Greek for 'nose.') In those primates whose snout is reduced in length and whose incisors are positioned close to each other, the rhinarium disappears. This is the case for tarsiers and anthropoids among primates, and therefore they were labeled together as Haplorhini (haplo means 'simple, single' in Greek).