Athena Review Image Archive ™
Notharctus skull
Skull of Notharctus (YPM cast; photo: Athena Review)
Notharctus tenebrosus was
an early, adapiform, tree-dwelling primate from the Eocene period,
dating from 54-38 mya. Adapids are considered to have been
lemur-like, as contrasted with tarsier-like omomyids, another group of
early primates. Notharctine primates are abundant in early
(Wasatchian) and middle (Bridgerian) Eocene faunal assemblages from
western North America. Early Eocene adapidae forms are dominated by Cantius, which was replaced in the middle Eocene by Notharctus and Smilodectes, both found most commonly in southwestern Wyoming.
First described by Leidy (1870), Notharctus tenebrosus, about 40 cm in length, is considered one of the earliest known primates in the lineage of humans.
The skull of Notharctus had a complete postorbital ring and a cranial crest. Both eyes were directed forwards for binocular vision. The eyes were smaller than those of omomyids such as Tetonius and were higher on the skull. The jawbones fused at the chin, creating a single solid mandible. The incisors and canines were smaller than those of some other early primates such as Vulpavus.
References
Gregory W.K. 1920. On the structure and relations of Notharctus, an American Eocene primate. Memoirs of the American Museum of Natural History.
Gunnell,
G. 2002. Notharctine primates (Adapiformes) from the early to middle
Eocene (Wasatchian–Bridgerian) of Wyoming: transitional species and the
origins of Notharctus and Smilodectes.
Leidy, J. 1870. Descriptions of Palaeosyops paludosus, Microsus cupidatus and Notharctus tenebrosus. Proceedings of the Academy of Natural Sciences, Philadelphia 22:111-114.
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