Strepsirrhini or Strepsirhini is a suborder of primates that includes the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") and pottos from Africa, and the lorises from India and southeast Asia. Collectively they are referred to as strepsirrhines. Also belonging to the suborder are the extinct adapiform primates which thrived during the Eocene in Europe, North America, and Asia, but disappeared from most of the Northern Hemisphere as the climate cooled. Adapiforms are sometimes referred to as being "lemur-like", although the diversity of both lemurs and adapiforms does not support this comparison.
Notharctus tenebrosus was an early primate from the early Eocene, some 54–38 million years ago. Its fossil was found by Ferdinand V. Hayden in 1870 in southwestern Wyoming. When first found, Notharctus tenebrosus was thought to be a small pachyderm due to the concentration of pachyderm fossils in the area. However, after Walter W. Granger's discovery of a nearly complete skeleton, also in Wyoming, it was firmly established as a primate. Notharctus tenebrosus most resembles modern-day lemurs, although they are not directly related.
Europolemur klatti was a medium to large size adapiformes primate that lived on the continent of Europe from the middle to early Eocene. One possible relative to this species is Margarita stevensi, whose type specimen is about the size of a white-footed sportive lemur. Characteristic of most adapines are the reduced or absence of a paraconid and morphology of the paracristid. These and a few other features are synapomorphies that were used to link E. klatti with Leptadapis priscus and Microadapis sciureus, as well as Smilodectes.
Smilodectes is a genus of adapiform primate that lived in North America during the middle Eocene. It possesses a post-orbital bar and grasping thumbs and toes. Smilodectes has a small cranium size and the foramen magnum was located at the back of the skull, on the occipital bone.
Notharctinae is an extinct subfamily of primates that were common in North America during the early and middle Eocene. The six genera that make up the group 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.
Hesperolemur is a genus of adapiform primate that lived in the middle Eocene of southern California. It is an immigrant taxa which appears to be most closely related to the earlier European forms of Cantius. It was approximately 4.5 kilograms (9.9 lb) in weight and was the last surviving notharctine species, probably because of its position in the refugia that existed in southern California during the climate deterioration at the end of the middle Eocene. There are no later taxa that appear to have derived from Hesperolemur.
Altanius is a genus of extinct primates found in the early Eocene of Mongolia. Though its phylogenetic relationship is questionable, many have placed it as either a primitive omomyid or as a member of the sister group to both adapoids and omomyids. The genus is represented by one species, Altanius orlovi, estimated to weigh about 10–30 g (0.35–1.1 oz) from relatively well-known and complete dental and facial characteristics.
Pelycodus is an extinct genus of adapiform primate that lived during the early Eocene (Wasatchian) period in Europe and North America, particularly Wyoming and New Mexico. It is very closely related to Cantius and may even be its subgenus. It may also have given rise to the Middle Eocene Uintan primate Hesperolemur, although this is controversial. From mass estimates based on the first molar, the two species, P. jarrovii and P. danielsae, weighed 4.5 kg and 6.3 kg respectively and were frugivores with an arboreal, quadrupedal locomotion.
Catopithecus is an early catarrhine fossil. It is known from more than 16 specimens of a single species, Catopithecus browni, found in the Jebel Qatrani Formation of the Fayum Province, Egypt. The Jebel Qatrani Formation has been divided into two main faunal zones based on the fact that the fauna found in the lower portion of the quarry appear to be more primitive than those found in the upper section. The upper zone has been dated to older than 31 ± 1 myr based on the dating of a basalt layer that lies immediately above the formation and Nicolas Steno’s Law of Superposition. The lower zone contains the late Eocene green shale unit called Locality-41 (L-41) in which all the specimens of Catopithecus browni have been found. The relative dating of L-41 based on paleomagnetic correlations places it at 36 Myr according to Simons et al (1999), but Seiffert (2006) suggests this should be revised to 34.8-33.9 Myr.
A toothcomb is a dental structure found in some mammals, comprising a group of front teeth arranged in a manner that facilitates grooming, similar to a hair comb. The toothcomb occurs in lemuriform primates, treeshrews, colugos, hyraxes, and some African antelopes. The structures evolved independently in different types of mammals through convergent evolution and varies both in dental composition and structure. In most mammals the comb is formed by a group of teeth with fine spaces between them. The toothcombs in most mammals include incisors only, while in lemuriform primates they include incisors and canine teeth that tilt forward at the front of the lower jaw, followed by a canine-shaped first premolar. The toothcombs of colugos and hyraxes take a different form with the individual incisors being serrated, providing multiple tines per tooth.
Adapis is an extinct adapiform primate from the Eocene of Europe. While this genus has traditionally contained five species, recent research has recognized at least six morphotypes that may represent distinct species. Adapis holds the title of the first Eocene primate ever discovered. In 1821, Georges Cuvier, who is considered to be the founding father of paleontology, discovered Adapis in fissure fillings outside of Paris, France. Given its timing and appearance in the fossil record, Cuvier did not recognize the primate affinities of Adapis and first described it as a small extinct pachyderm; only later in the 19th century was Adapis identified as a primate.
Europolemur is a genus of adapiform primates that lived in Europe during the middle Eocene.
Algeripithecus is an extinct genus of early fossil primate, weighing approximately 65 to 85 grams. Fossils have been found in Algeria dating from 50 to 46 million years ago.
Lemurs, primates belonging to the suborder Strepsirrhini which branched off from other primates less than 63 million years ago, evolved on the island of Madagascar, for at least 40 million years. They share some traits with the most basal primates, and thus are often confused as being ancestral to modern monkeys, apes, and humans. Instead, they merely resemble ancestral primates.
Azibiidae is an extinct family of fossil primate from the late early or early middle Eocene from the Glib Zegdou Formation in the Gour Lazib area of Algeria. They are thought to be related to the living toothcombed primates, the lemurs and lorisoids, although paleoanthropologists such as Marc Godinot have argued that they may be early simians. It includes the genera Azibius and Algeripithecus, the latter of which was originally considered the oldest known simian, not a strepsirrhine.
Azibius is an extinct genus of fossil primate from the late early or early middle Eocene from the Glib Zegdou Formation in the Gour Lazib area of Algeria. They are thought to be related to the living toothcombed primates, the lemurs and lorisoids, although paleoanthropologists such as Marc Godinot have argued that they may be early simians. Originally described as a type of plesiadapiform, its fragmentary remains have been interpreted as a hyopsodontid, an adapid, and a macroscelidid. Less fragmentary remains discovered between 2003 and 2009 demonstrated a close relationship between Azibius and Algeripithecus, a fossil primate once thought to be the oldest known simian. Descriptions of the talus in 2011 have helped to strengthen support for the strepsirrhine status of Azibius and Algeripithecus, which would indicate that the evolutionary history of lemurs and their kin is rooted in Africa.
Plesiopithecus is an extinct genus of early strepsirrhine primate from the late Eocene.
The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.
Sivaladapis is a genus of adapiform primate that lived in Asia during the middle Miocene.
Afradapis is a genus of adapiform primate that lived during the Late Eocene. The only known species, Afradapis longicristatus, was discovered in the Birket Qarun Formation in northern Egypt in 2009. While its geographic distribution is confined to Afro-Arabia, Afradapis belongs to the predominantly European adapiform family Caenopithecidae. This taxonomic placement is supported by recent phylogenetic analyses that recover a close evolutionary relationship between Afradapis and adapiforms, including Darwinius. While adapiforms have been noted for their strepsirrhine-like morphology, no adapiform fossil possesses the unique anatomical traits to establish an ancestor-descent relationship between caenopithecids and living strepsirrhines. It ate leaves and moved around slowly like lorises.
