Notharctus

Notharctus Temporal range: Early-Mid Eocene (Wasatchian-Uintan) ~ Pal. Eocene Oligo. Miocene P P
Notharctus tenebrosus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Strepsirrhini
Family:	†Notharctidae
Subfamily:	†Notharctinae
Genus:	†Notharctus Leidy, 1870
Species
†N. pugnax Granger and Gregory 1917 †N. robustiorLeidy 1872 †N. tenebrosusLeidy 1870 †N. venticolus Osborn 1902 †N. robinsoni Gingerich 1979
Synonyms
Hipposyus Leidy 1872 Limnotherium Marsh 1871 Telmalestes Marsh 1872 Thinolestes Marsh 1872 Tomitherium Cope 1872 Synonyms of N. tenebrosus Limnotherium tyrannus Marsh, 1871 Hipposyus formosus Leidy, 1872 Tomitherium rostratum Cope, 1872 Thinolestes anceps Marsh, 1872 Limnotherium affine Marsh, 1872 Notharctus osborni Granger and Gregory, 1917 Synonyms of N. robustior Telmatolestes crassus Marsh, 1872

Notharctus is a genus of adapiform primate that lived in North America during the early to middle Eocene. Known from many geologic formations, including the Bridger Basin and the Devil's Graveyard Formation, Notharctus was wide-ranging throughout North America.

The genus contains at least 4 species. Notharctus is among the first known fossil primates from North America, with the first fossil being collected by Joseph Leidy from the Fort Bridger Basin in 1870. Notharctus has a long classification history involving frequent reassessment and assignment to various mammal groups, including the obsolete Pachydermata and the Mesodonta. Notharctus belonged to an extinct primate group known as Adapiformes.

Adapiform primates were among the first primates to exhibit a set of adaptations for life in the trees, such as grasping hands, binocular vision, and flexible backs. In addition to this, small orbits in the genera indicate that they were diurnal. The diet of Notharctus was likely leaves, and the genus moved similarly to modern day lemurs in life. The fingers of the genus were elongated for clamping onto branches, including the development of a thumb. Its spine is flexible and Notharctus was about 40 centimetres (16 in) in length, excluding the long tail. Notharctus was relatively large for an early primate, with a maximum weight of 6.9 kg (15 lb) being estimated for one species. The genus exhibits sexual dimorphism of the canines and developments of the brain which indicates it relied less on smell than other earlier primates.

Notharctines, including Notharcus, are thought to have gone extinct during the Uintan stage of the middle Eocene due to a cooling climate.