Notharctinae
| Notharctinae Temporal range: Early-Middle Eocene |
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| Notharctus tenebrosus | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Strepsirrhini |
| Family: | †Notharctidae |
| Subfamily: |
†Notharctinae Trouessart, 1879 |
| Genera | |
Notharctinae is an extinct subfamily of primates that were common in North America during the early and middle Eocene (55-34 million years ago). The six genera that make up the group (Cantius, Pelycodus, Copelemur, Hesperolemur, Notharctus, and Smilodectes) contain species that are among the most primitive of the adapiform group, which is one of the most primitive groups of primates. The evolutionary history of this subfamily has been comparatively well documented and has been used to argue for evolutionary gradualism. Though it is generally accepted that adapiforms gave rise to modern day lemurs and lorises, it is not currently known which branch of Adapiformes these living species are most closely related to. Notharctines became extinct in the middle Eocene, most likely because of a combination of factors including climatic change and competition with other North American primates.
Notharctinae is one of the two subfamilies, along with Cercamoniinae, of the Notharctidae family, which is a member of the infraorder Adapiformes along with Adapidae and Sivaladapidae. Compared to other subfamilies, the notharctines were not terribly diverse with only two or three species occurring synchronously. However, notharctines are some of the most common species found in early and middle Eocene deposits. Each genus has between 1 (Hesperolemur) and 11 (Cantius) species for a total of 25 species making up the subfamily. Body size ranges from 1100 grams in early species of Cantius to 6900 grams in late occurring Notharctus with an overall trend of increasing body size.
Overall, each genus was restricted to a small geographic region. Cantius was a northern (Wyoming) early Eocene genus, while the other two early Eocene genera, Pelycodus and Copelemur, occupied more southern habitats (New Mexico). Middle Eocene taxa, Notharctus and Smilodectes. were again found in Wyoming, while Hesperolemur is known only from southern California. This move to the north may be associated with climatic warming between the early and the middle Eocene.
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