| Micropithecus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Parvorder: | Catarrhini |
| Genus: | †Micropithecus Fleagle & Simons, 1978 |
| Species | |
Micropithecus is an extinctgenus ofprimates that lived inEast Africa about 19 to 15 million years ago, during the earlyMiocene. The genus and itstype species,Micropithecus clarki, were first scientifically described in 1978.[1]
The generic name,Micropithecus, is derived from theGreek Words μικρός (ancient Greek pronouncedmikrós, "small") and πίθηκος (pronouncedpíthēkos, "monkey").Micropithecus thus means "small ape", referring to the fact that thefossils of this genus are among the smallest fossil apes discovered.[1]
Theholotype of both the genus and type species,Micropithecus clarki, is anupper jaw, which is approximately 19 to 17 million years old, with largely preservedpalate bones, and remains of bones of theskull. Also preserved in the upper jaw are three left large molars (M1 - M3), as well as onepremolar, and three large molars (M1 - M3) on the right side. In addition, about 20 individually found teeth, amandible fragment and fragments of a skull dome from the same locality were designated asparatypes.[1]
Micropithecus was distinguished fromLimnopithecus,Dendropithecus,Dryopithecus andPliopithecus by the characteristics of its dentition and its small size. Furthermore, in the initial description of the genus and type species, it was pointed out that themorphology of the face of these fossil finds most closely resemblesgibbons living today. The head-torso length is roughly equivalent to thewhite-fronted capuchin monkeys, which are only about 35 centimetres tall, and is slightly smaller than that of the fossil ofAeolopithecus, now considered a junior synonym ofPropliopithecus.[2]
In 1989, a second species was attributed to the genusMicropithecus,Micropithecus leakeyorum.[3] These are finds from theMaboko Main excavation site onMaboko Island inLake Victoria,Kenya, dating from 16 to 15 million years ago. This species was placed in the genusMicropithecus based on several mandibular fragments with preserved large molars and on the basis of the characteristics of these teeth, but at the same time it was distinguished from the type species because of the spatial and temporal distance.
In 2021, as part of a revision of the small-bodied anthropoids from Kenyan sites, some finds placed since 1982 withMicropithecus clarki were separated from them asMicropithecus chamtwaraensis;[4] the epithet,chamtwaraensis, refers to the name of theChamtwara Formation (seeList of fossiliferous stratigraphic units in Kenya) in the area of 'Site 34' near the locality ofKoru. The holotype is a largely preserved dentate mandible (archive number KNM CA 380).[1]
In the first description ofMicropithecus leakeyorum, it was discussed that there is no other example in East Africa in the Miocene besidesNyanzapithecus andMicropithecus for a genus of primates existing over several million years whose species could be documented in chronological succession. However, it cannot be concluded from this sequence that the younger species evolved from the older one. The preserved remains ofMicropithecus clarki show numerousoriginal features of theOld World monkey, but also variousyounger features, such as relatively small molars in relation to the jawbone and very large incisors compared to the molars; features that overall suggest afruit-rich diet.[3]Micropithecus leakeyorum also has features indicative of a fruit-rich diet, but these features are less pronounced than in its older sister species. This has been interpreted as a presumed consequence of less specialisation on a particular diet, giving this species a morphological proximity to the more primitive, much older, Old World monkeys from East Africa.[3]
An explanation for these different characteristics can be found if one considers thepalaeoecology: About 19 million years ago, what is nowUganda and western Kenya were predominantly covered by forests, fostered by a warm and humidtropicalclimate. Later, the climate in this region changed and the forests became thinner and drier. The cause of these changes was probably tectonic processes, which also had a local influence on the extent of precipitation. For the excavation sites on Maboko Island, detailed studies of theplant world have shown that open, sparsely forested landscapes existed there in the Middle Miocene with densegallery forests along the rivers, comparable to thevegetation of today'sNyika National Park. In suchbiotopes, it was concluded, the ancestors ofMicropithecus leakeyorum gradually adapted to a broader diet that included harder plant fibres.[3]
