''Smilodectes'' is a genus of

adapiform Adapiformes is a group of early primates. Adapiforms radiated throughout much of the northern continental mass (now Europe, Asia and North America), reaching as far south as northern Africa and tropical Asia. They existed from the Eocene to the M ...

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

that lived in North America during the middle

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

. It possesses a post-orbital bar and grasping thumbs and toes. ''Smilodectes'' has a small

cranium The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

size and the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...

was located at the back of the skull, on the

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobe ...

Named species

There are three named species: ''Smilodectes gracilis'', ''Smilodectes gingerichi'' and ''Smilodectes mcgrewi''.

''Smilodectes gracilis''

''Smilodectes gracilis'' was an

adapiformes Adapiformes is a group of early primates. Adapiforms radiated throughout much of the northern continental mass (now Europe, Asia and North America), reaching as far south as northern Africa and tropical Asia. They existed from the Eocene to the M ...

from the early

, some 55 million years ago. ''S. gracilis'' was found on the land mass of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and based on its dental morphology, ''S. gracilis'' was a

folivore In zoology, a folivore is a herbivore that specializes in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds.Jones, S., Martin, R., & Pilbeam, D. (1 ...

. ''S. gracilis'' had a

dental formula Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...

of and had a relatively short

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...

, with rounded frontal bone as compared to other nothactines. This species lacked symphyseal fusion and this species of primate had comparatively reduced

olfactory bulbs The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC ...

and a more expanded

visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...

. This suggests that ''S. gracilis'' was a diurnal

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. ''S. gracilis'' had a cranial capacity of 9.5 cc. It is thought that ''S. gracilis'' had an average body mass of around 2.1 kilograms. Based upon its postcranial skeleton, ''S. gracilis'' was a vertical clinger and leaper.

References

Bibliography

External links

Mikko's Phylogeny Archive

{{Taxonbar, from=Q4424520 Prehistoric strepsirrhines Prehistoric primate genera Eocene primates Ypresian life Lutetian life Wasatchian Bridgerian Eocene mammals of North America Paleontology in Colorado Paleontology in Utah Paleontology in Wyoming Fossil taxa described in 1903