Omomyidae is a group of early

primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...

s that radiated during the

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

epoch between about (mya). Fossil omomyids are found in North America, Europe & Asia, making it one of two groups of Eocene primates with a geographic distribution spanning

holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...

continents, the other being the adapids (family

Adapidae Adapidae is a family of extinct primates that primarily radiated during the Eocene epoch between about 55 and 34 million years ago. Adapid systematics and evolutionary relationships are controversial, but there is fairly good evidence from the ...

). Early representatives of the Omomyidae and Adapidae appear suddenly at the beginning of the Eocene (56 mya) in North America, Europe, and Asia, and are the earliest known crown primates.

Characteristics

Features that characterize many omomyids include large orbits (eye sockets), shortened

rostra The Rostra () was a large platform built in the city of Rome that stood during the republican and imperial periods. Speakers would stand on the rostra and face the north side of the Comitium towards the senate house and deliver orations to t ...

and dental arcades, loss of anterior premolars, cheek teeth adapted for insectivorous or

frugivorous A frugivore ( ) is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance ...

diets, and relatively small body mass (i.e., less than 500 g). However, by the late middle Eocene (about 40 mya), some North American omomyids evolved body masses in excess of and frugivorous or

folivorous 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 ...

diets. The largest omomyids were ''

Macrotarsius ''Macrotarsius'' is an extinct genus of omomyid that inhabited North America and East Asia during the Eocene epoch. Taxonomy ''Macrotarsius'' contains five species: the type species ''M. montanus'', ''M. jepseni'', ''M. macrorhysis'', ''M. ro ...

'' and '' Ourayia'', both at in weight.Rachel H. Dunn.
Additional postcranial remains of omomyid primates from the Uinta Formation, Utah and implications for the locomotor behavior of large-bodied omomyids
. Journal of Human Evolution Volume 58, Issue 5, May 2010, pp. 406-417 Large orbits in genera such as '' Tetonius'', ''

Shoshonius ''Shoshonius'' is an extinct genus of omomyid primate that lived during the Eocene (~56-34 million years ago). Specimens identified as ''Shoshonius'' have been found exclusively in central Wyoming and the genus currently includes two species, '' ...

'', ''

Necrolemur ''Necrolemur'' is a small bodied omomyid with body mass estimations ranging from . ''Necrolemur''’s teeth feature broad basins and blunt cusps, suggesting their diet consisted of mostly Frugivore, soft fruit, though examination of microwear patt ...

'', and '' Microchoerus'' indicate that these taxa were probably

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

. At least one omomyid genus from the late Eocene of Texas (''

Rooneyia ''Rooneyia viejaensis'' is a relatively small primate belonging to the extinct monotypic genus ''Rooneyia''. ''Rooneyia viejaensis'' is known from the North American Eocene of the Sierra Vieja of West Texas; the species is only known from the typ ...

'') had small orbits and was probably diurnal. Like

s alive today, omomyids had grasping hands and feet with digits tipped by nails instead of claws, although they possessed

toilet claw A grooming claw (or toilet claw) is the specialized claw or nail on the foot of certain primates, used for personal grooming. All prosimians have a grooming claw, but the digit that is specialized in this manner varies. Tarsiers have a grooming ...

s like modern lemurs. Features of their skeletons strongly indicate that omomyids lived in trees. In at least one genus (''Necrolemur''), the lower leg bones, the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

and

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

, were fused as in modern

tarsier Tarsiers ( ) are haplorhine primates of the family Tarsiidae, which is the lone extant family within the infraorder Tarsiiformes. Although the group was prehistorically more globally widespread, all of the existing species are restricted to M ...

s. This feature may indicate that ''Necrolemur'' leaped frequently. Most other omomyid genera (e.g., '' Omomys'') lack specializations for leaping, and their skeletons are more like those of living

dwarf Dwarf, dwarfs or dwarves may refer to: Common uses *Dwarf (folklore), a supernatural being from Germanic folklore * Dwarf, a human or animal with dwarfism Arts, entertainment, and media Fictional entities * Dwarf (''Dungeons & Dragons''), a sh ...

and

mouse lemur The mouse lemurs are nocturnal lemurs of the genus ''Microcebus''. Like all lemurs, mouse lemurs are native to Madagascar. Mouse lemurs have a combined head, body and tail length of and weigh , making them the smallest primates (the smallest sp ...

s. Omomyid systematics and evolutionary relationships are controversial. Authors have suggested that omomyids are either: #stem

haplorhines Haplorhini (), the haplorhines (Greek for "simple-nosed") or the "dry-nosed" primates is a suborder of primates containing the tarsiers and the simians (Simiiformes or anthropoids), as sister of the Strepsirrhini ("moist-nosed"). The name is some ...

[i.e., basal members of the group including living

s and anthropoids]. #stem tarsier, tarsiiformes [i.e., basal offshoots of the tarsier lineage]. #stem primates more closely related to adapids than to living primate taxa. Recent research suggests the Omomyiformes are stem haplorhines, making them likely a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

grouping. Attempts to link omomyids to living groups have been complicated by their primitive (

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

) skeletal anatomy. For example, omomyids lack the numerous skeletal specializations of living haplorhines. These haplorhine adaptations - absent in omomyids - include: # significant reduction of the canal for the stapedial branch of the

internal carotid artery The internal carotid artery is an artery in the neck which supplies the anterior cerebral artery, anterior and middle cerebral artery, middle cerebral circulation. In human anatomy, the internal and external carotid artery, external carotid ari ...

. # route of the canal to house the promontory branch of the internal carotid artery through the

auditory bulla The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic b ...

of the temporal bone, i.e. "perbullar" (rather than across the

promontory of tympanic cavity The promontory of the tympanic cavity, also known as the cochlear promontory is a rounded hollow prominence upon - and most prominent feature of - the medial wall of the tympanic cavity formed by the underlying first turn of the cochlea. The surfac ...

, "transpromontorial") . # contact between the

alisphenoid The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone, positioned in the skull behind each eye. There is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, ...

and zygomatic bones. # presence of an anterior accessory cavity confluent with the

tympanic cavity The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external audit ...

. Omomyids further demonstrate a gap between the upper central incisors, which presumably indicates the presence of a

rhinarium The rhinarium (Neo-Latin, "belonging to the nose"; : rhinaria) is the furless skin surface surrounding the external openings of the nostrils in many mammals. Commonly it is referred to as the tip of the ''snout'', and breeders of cats and dogs s ...

and

philtrum The philtrum (, from Ancient Greek , lit. 'love charm') or medial cleft is a vertical indentation in the middle area of the upper lip, common to therian mammals, extending in humans from the nasal septum to the tubercle of the upper lip. Toget ...

to channel fluids into the

vomeronasal The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapods. T ...

organ. Omomyids as a group also lack most of the derived specializations of living tarsiers, such as extremely enlarged orbits (''

'' is a possible exception), a large supra- meatal

foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...

for an

anastomosis An anastomosis (, : anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal (su ...

between the posterior auricular and middle meningeal circulation (again, ''Shoshonius'' is a possible exception, but the contents of the foramen in this extinct taxon are unknown), and extreme postcranial adaptations for leaping. Among primates, omomyids have a uniquely derived characteristic. This is the presence of an aphaneric (not visible or readily distinguishable, due to its position), or "intrabullar" (within the bullae),

ectotympanic The ectotympanic, or tympanicum, is a bony structure found in all mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In catarrhine primates (including humans), it takes a tube-shape. ...

bone, connected to the lateral wall of the auditory bulla by an unbroken annular bridge.

Classification

* Family Omomyidae ** '' Altanius'' ** '' Kohatius'' ** Subfamily

Anaptomorphinae Anaptomorphinae is a pre-historic group of primates known from Eocene fossils in North America and Europe and later periods of Paleocene Asia, and are a sub-family of omomyids. The anaptomorphines is a paraphyletic group consisting of the two t ...

*** Tribe Trogolemurini **** '' Trogolemur'' ** Subfamily Microchoerinae **** '' Sphacorhysis'' **** '' Walshina'' *** Tribe Anaptomorphini **** '' Anaptomorphus'' **** '' Absarokius'' **** '' Anemorhysis'' **** '' Arapahovius'' **** '' Aycrossia'' **** '' Chlororhysis'' **** '' Gazinius'' **** '' Mckennamorphus'' **** '' Pseudotetonius'' **** '' Strigorhysis'' **** '' Tatmanius'' **** ''

Teilhardina ''Teilhardina'' (, ) is an extinct marmoset-like omomyid primate that lived in Europe, North America and Asia during the Early Eocene epoch, about 56-47 million years ago. The paleontologist George Gaylord Simpson named it after the French pale ...

'' **** '' Tetonius'' *** '' Indusomys'' *** '' Nannopithex'' *** '' Pseudoloris'' *** ''

'' *** '' Microchoerus'' *** '' Vectipithex'' *** '' Melaneremia'' *** '' Paraloris'' ** Subfamily Omomyinae *** '' Brontomomys''Amy L. Atwater; E. Christopher Kirk (2018). "New middle Eocene omomyines (Primates, Haplorhini) from San Diego County, California". Journal of Human Evolution. in press. doi:10.1016/j.jhevol.2018.04.010. *** '' Diablomomys'' *** '' Ekwiiyemakius'' *** '' Gunnelltarsius'' *** '' Huerfanius'' *** '' Mytonius'' *** '' Palaeacodon'' *** Tribe Rooneyini **** ''

'' *** Tribe Steiniini **** '' Steinius'' *** Tribe Uintaniini **** '' Jemezius'' **** '' Uintanius'' *** Tribe Hemiacodontini **** '' Hemiacodon'' *** Tribe Omomyini **** '' Chumachius'' **** '' Omomys'' **** '' Saskomomys'' *** Tribe Macrotarsiini'' **** '' Yaquius'' **** ''

'' *** Tribe Washakiini **** '' Loveina'' **** ''

'' **** '' Washakius'' **** '' Dyseolemur'' *** Tribe Utahiini **** '' Asiomomys'' **** '' Utahia'' **** '' Stockia'' **** '' Chipetaia'' **** '' Ourayia'' **** '' Wyomomys'' **** '' Ageitodendron''

References

External links

“Adapidae and Omomyidae”
{{Authority control Haplorhini Prehistoric primates Eocene primates Oligocene primates Paleocene first appearances Primate families Oligocene extinctions Prehistoric mammal families Paraphyletic groups