''Homunculus'' (; "little person") is an extinct genus of

New World monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboi ...

that lived in

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

. Two species are known: ''Homunculus patagonicus'' and ''Homunculus vizcainoi'', which are known from material found in the

Santa Cruz Formation The Santa Cruz Formation is a geological formation in the Magallanes Basin, Magallanes/Austral Basin in southern Patagonia in Argentina and adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with the eponym ...

in the far south of

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. Reaching a latitude of ~ 55°S at the time of it lived, it is the southernmost primate ever recorded.

Taxonomy

Early history

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''Homunculus patagonicus'' (MACN-A 634), a partial skull, was discovered around the

Río Gallegos Rio or Río is the Portuguese and Spanish word for "river". The word also exists in Italian, but is largely obsolete and used in a poetical or literary context to mean "stream". Rio, RIO or Río may also refer to: Places United States * Rio, Fl ...

, though more specific details of its provenance have never been given. It is likely, from its location, that the holotype originates from strata belonging to the

. At some point prior to 1891, it entered the collection of palaeontologist

Carlos Ameghino Carlos Ciriaco Ameghino (16 June 1865 – 12 April 1936) was an Argentine paleontologist and explorer who accompanied his brother Florentino Ameghino throughout Argentina searching for fossils. Scientific career Carlos Ameghino was educated ...

and in that year it was described by his brother, Florentino. At some point, MACN-A 634 was lost. It was, in 2008, replaced with a neotype, MACN-A 575. A second ''Homunculus'', ''H. vizcainoi'', also from the Santa Cruz Formation, was described in 2019.

Synonyms

In the same year as Florentino Ameghino's paper, Swiss geologist and palaeontologist Alcides Mercerat described an incomplete mandibular fragment, bearing part of a molar. He dubbed the specimen ''Ecphantodon ceboides''. However, ''E. ceboides'' was treated by Ameghino as indistinguishable from ''Homunculus'', and he opted to synonymise the two. The type specimen of ''E. ceboides'' has been lost. In the paper describing ''H. patagonicus'', Florentino Ameghino also named ''Anthropops perfectus'', which he distinguished based on purported characteristics of the mandible and lower

canine Canine may refer to: Zoology and anatomy * Animals of the family Canidae, more specifically the subfamily Caninae, which includes dogs, wolves, foxes, jackals and coyotes ** ''Canis'', a genus that includes dogs, wolves, coyotes, and jackals ** Do ...

, and ''Pitheculus australis''. In 1894, he named ''Stilotherium grande'', which he suggested to be a

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

. However, subsequent authors, like Osvaldo A. Reig, disagreed with this assessment, and 1981, Philip Hershkovitz determined that it belonged to ''Homunculus''. Hershkovitz erected a new species, ''H. grandis''. Even in the absence of the holotype, further specimens have been assigned to ''H. patagonicus''. Notable among these is MACN-A 5968, the left side of a partial skull, recovered from Puesto Estancia La Costa. In 2008, a genus-level revision of ''Homunculus'' was carried out, whereupon it was concluded that ''Anthropops'', ''Pitheculus'' and ''Stilotherium'' were all junior synonyms of ''Homunculus''. Some authors consider ''

Killikaike ''Homunculus'' (; "little person") is an extinct genus of New World monkey that lived in Patagonia during the Miocene. Two species are known: ''Homunculus patagonicus'' and ''Homunculus vizcainoi'', which are known from material found in the Santa ...

blakei'' to be a junior synonym for ''H. patagonicus'', but others consider the species distinct. A 2025 study of an associated skeleton of ''Homunculus'' again concluded that ''Killikaike'' is a junior synonym of ''Homunculus patagonicus.''

Classification

Some studies have regarded ''Homunculus'' as a

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...

platyrhine and a member of the family

Pitheciidae The Pitheciidae () are one of the five families of New World monkeys now recognised. Formerly, they were included in the family Atelidae. The family includes the titis, saki monkeys and uakaris. Most species are native to the Amazon region of ...

, possibly belonging to a tribe of its own (Homuncilini), while other studies have regarded it as a stem-group platyrhine outside any modern group. The latter is supported by the morphology of its

nasal turbinates In anatomy, a nasal concha (; : conchae; ; Latin for 'shell'), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of bone that protrudes into the breathing passage of the nose in humans and various other animals. The conc ...

, which are dissimilar to those of crown-group platyrhines.

Description

''H. patagonicus'' was a robustly built, quadrupedal primate, with body mass estimates varying between based on different techniques, with a 2025 study estimating a body mass of around , comparable to a

titi monkey The titis, or titi monkeys, are New World monkeys of the subfamily Callicebinae, which contains three extant genera: ''Cheracebus'', ''Callicebus'', and ''Plecturocebus.'' This subfamily also contains the extinct genera '' Miocallicebus, Homun ...

or a saki monkey. The interorbital region, the portion of the skull between the

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

(eye sockets) was wide, similar to in titi monkeys (Callicebinae). The frontal bone was unvaulted, unlike modern

capuchin monkeys The capuchin monkeys () are New World monkeys of the subfamily Cebinae. They are readily identified as the " organ grinder" monkey, and have been used in many movies and television shows. The range of capuchin monkeys includes some tropical fores ...

(Cebinae). The

maxillary sinus The pyramid-shaped maxillary sinus (or antrum of Nathaniel Highmore (surgeon), Highmore) is the largest of the paranasal sinuses, located in the maxilla. It drains into the middle meatus of the noseHuman Anatomy, Jacobs, Elsevier, 2008, page 209- ...

was relatively large, and the

nasals In phonetics, a nasal, also called a nasal occlusive or nasal stop in contrast with an oral stop or nasalized consonant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. The vast majorit ...

were quite wide. The

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

was fairly procumbent. The main body of the

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, the corpus, was deeper

posteriorly Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

(towards the rear), similar to in douroucoulis (''Aotus''). The tooth rows converged

anteriorly Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...

(towards the front). The

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

were narrow and fairly high crowned. The second

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

is wedge-shaped, compressed transversely (across) and has a large honing facet (wear pattern) from the upper

. The

molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...

have fairly long talonids, and the trigonids were short, especially in the first molar. The postcrania have a few attributes indicating a relatively basal position, such as the form of its nasal turbinates and an epidoncylar foramen. The

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

was similar to modern cebids, and could rotate freely.

Ecology

Its morphology suggests that ''Homunculus'' was a diurnal (day active)

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

primate that spent a significant amount of time climbing and clinging to trees, probably occasionally leaping between them. Although one study suggested that it was primarily

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 ...

based on dental wear, this has been disputed, and other studies suggest the diet of ''Homunculus'' likely consisted of fruit, leaves and seeds, including relatively hard items, with the significant input of abrasive volcanic dust into the environment of the Santa Cruz Formation being the likely cause of the heavy tooth wear observed in adult ''Homunculus'' teeth. The

in which ''Homunculus'' has been found, and from which the remains of many other species of prehistoric animal have been uncovered, is thought to have been relatively warm and humid, including a mix of open

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

gallery forests A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...

and semi-deciduous forests.

References

{{Taxonbar, from1=Q27664287, from2=Q1446235 Miocene mammals of South America Miocene primates of South America Prehistoric mammals of South America Neogene Argentina Fossils of Argentina Fossil taxa described in 1891 Prehistoric monkeys Mayoan Laventan Colloncuran Friasian Santacrucian Taxa named by Florentino Ameghino Golfo San Jorge Basin Sarmiento Formation Austral or Magallanes Basin Santa Cruz Formation