Omomyidae is a group of early

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 ...

s that radiated during the

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

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.

Etymology

The Omomyidae are named after the type genus '' Omomys''. While the etymology of this genus is uncertain, it most likely derives from the Ancient Greek ὠμός (ōmós), "raw, crude" + μῦς (mûs), "mouse".

Characteristics

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

rostra The rostra ( it, Rostri, links=no) 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 de ...

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 an ...

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'' 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'' (named after the Shoshone tribe) 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 c ...

'', ''

Necrolemur ''Necrolemur'' is a small bodied omomyid with body mass estimations ranging from 114 grams to 346 grams. ''Necrolemur''’s teeth feature broad basins and blunt cusps, suggesting their diet consisted of mostly soft fruit A berry is a small, p ...

'', and '' Microchoerus'' indicate that these taxa were probably nocturnal. 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 (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

and

fibula The fibula 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. Its upper extremity i ...

, were fused as in modern tarsiers. 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 or dwarves may refer to: Common uses *Dwarf (folklore), a being from Germanic mythology and folklore * Dwarf, a person or animal with dwarfism Arts, entertainment, and media Fictional entities * Dwarf (''Dungeons & Dragons''), a humanoid ...

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 less than , making them the smallest primates (the smallest spe ...

s. Omomyid systematics and evolutionary relationships are controversial. Authors have suggested that omomyids are either: #stem haplorhines tarsiers_and_anthropoids.html" ;"title=".e., basal members of the group including living tarsiers and anthropoids">.e., basal members of the group including living tarsiers and anthropoids #stem

tarsiiformes Tarsiiformes are a group of primates that once ranged across Europe, northern Africa, Asia, and North America, but whose extant species are all found in the islands of Southeast Asia. Tarsiers (family Tarsiidae) are the only living members o ...

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

of the temporal bone, i.e. "perbullar" (rather than across the promontory of tympanic cavity, "transpromontorial") . # contact between the

alisphenoid The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward. Structure The greater wi ...

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 auditory ...

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

rhinarium The rhinarium (New Latin, "belonging to the nose"; plural: 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 ...

and

philtrum The philtrum ( la, philtrum from Ancient Greek ''phíltron,'' 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 tubercl ...

to channel fluids into the vomeronasal 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 (;Entry "foramen"
in

for an anastomosis 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 *** Tribe Trogolemurini **** '' Trogolemur'' **** '' Sphacorhysis'' **** '' Walshina'' *** Tribe Anaptomorphini **** '' Arapahovius'' **** '' Tatmanius'' **** '' Teilhardina'' **** '' Anemorhysis'' **** '' Chlororhysis'' **** '' Tetonius'' **** '' Pseudotetonius'' **** '' Absarokius'' **** '' Anaptomorphus'' **** '' Aycrossia'' **** '' Strigorhysis'' **** '' Mckennamorphus'' **** '' Gazinius'' ** Subfamily Microchoerinae *** '' 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 ''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 ...

**** ''

'' *** Tribe Steiniini **** '' Steinius'' *** Tribe Uintaniini **** '' Jemezius'' **** '' Uintanius'' *** Tribe Hemiacodontini **** '' Hemiacodon'' *** Tribe Omomyini **** '' Chumachius'' **** '' Omomys'' *** Tribe Macrotarsiini'' **** '' Yaquius'' **** '' Macrotarsius'' *** Tribe Washakiini **** '' Loveina'' **** ''

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

References

External links

“Adapidae and Omomyidae”
{{Taxonbar, from=Q134979 Prehistoric primates Eocene primates Oligocene primates Paleocene first appearances Primate families Oligocene extinctions Prehistoric mammal families Paraphyletic groups