Robust capuchin monkeys are

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

s in the genus ''Sapajus''. Formerly, all capuchin monkeys were placed in the genus ''

Cebus Gracile capuchin monkeys are capuchin monkeys in the genus ''Cebus''. At one time all capuchin monkeys were included within the genus ''Cebus''. In 2011, Jessica Lynch Alfaro ''et al.'' proposed splitting the genus between the robust capuchin ...

''. ''Sapajus'' was erected in 2012 by Jessica Lynch Alfaro et al. to differentiate the robust (tufted) capuchin monkeys (formerly the ''C. apella'' group) from the

gracile capuchin monkey Gracile capuchin monkeys are capuchin monkeys in the genus ''Cebus''. At one time all capuchin monkeys were included within the genus ''Cebus''. In 2011, Jessica Lynch Alfaro ''et al.'' proposed splitting the genus between the robust capuchin ...

s (formerly the ''C. capucinus'' group), which remain in ''Cebus''.

Taxonomy

Based on the

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

and

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

proposed by Groves in 2001 and 2005, robust capuchin monkey taxa include: ''S. flavius'' was only rediscovered in 2006. The specific species and subspecies within ''Sapajus'' are not universally agreed upon. For example, Silva (2001) proposed a slightly different species and subspecies split in which, for example Azara's capuchun, ''Sapajus libidinosus paraguayanus'', is considered a separate species, ''Sapajus cay'', as are the large-headed capuchin and the crested capuchin.

Taxonomic history

Philip Hershkovitz Philip Hershkovitz (12 October 1909 – 15 February 1997) was an American mammalogy, mammalogist. Born in Pittsburgh, he attended the Universities of Pittsburgh and Michigan and lived in South America collecting mammals. In 1947, he was appointed ...

and

William Charles Osman Hill William Charles Osman Hill FRSE FZS FLS FRAI (13 July 1901 – 25 January 1975) was a British anatomist, primatologist, and a leading authority on primate anatomy during the 20th century. He is best known for his nearly completed eight-volume ...

published

taxonomies image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

of the

s in 1949 and 1960, respectively. These taxonomies included all robust capuchins, described then as the tufted group, in the single species ''Cebus apella'', while three gracile (untufted) capuchin species were recognized. Over time, the original ''C. apella'' was split into the additional species of robust capuchin monkeys recognized today. In 2001, Silva published a study in which he found greater genetic diversity among robust capuchins than among gracile capuchins. Silva's study also concluded that due to the differences between robust and gracile capuchins, the two groups should at least be placed in separate subgenera within the genus ''Cebus'', offering ''Sapajus'' as the

subgenus In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...

name for robust capuchins. After further studies of the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

and

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...

of the capuchin monkeys, Lynch Alfaro, Silva and Rylands proposed elevating ''Sapajus'' to a separate genus in 2012.

Evolutionary history

The genetic studies led by Lynch Alfaro concluded that robust and

genera diverged about 6.2 million years ago. This is approximately the same time that

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s and

chimpanzee The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...

s are believed to have diverged. In contrast, capuchins diverged from their nearest common relative,

squirrel monkey Squirrel monkeys are New World monkeys of the genus ''Saimiri''. ''Saimiri'' is the only genus in the subfamily Saimiriinae. The name of the genus is of Tupi origin (''sai-mirím'' or ''çai-mbirín'', with ''sai'' meaning 'monkey' and ''mirím' ...

s, over 13 million years ago. Lynch Alfaro suggested that the formation of the Amazon River may have caused the split that led to separation of robust and gracile capuchins. The robust capuchins then evolved in the Atlantic forest, while the gracile capuchins evolved in the

Amazon Amazon most often refers to: * Amazon River, in South America * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon (company), an American multinational technology company * Amazons, a tribe of female warriors in Greek myth ...

. In the late

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

, about 400,000 years ago, robust capuchins began to expand their range northwards into the

Cerrado The Cerrado () is a vast ecoregion of Tropics, tropical savanna in central Brazil, being present in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Maranhão, Piauí, Bahia, Minas Gerais, São Paulo (state), São Paulo, Paraná ...

and the Amazon. In some of these areas robust capuchins outcompeted gracile capuchins, and are now the only capuchin monkeys in the area, while particularly in the north Amazon, robust capuchins are

sympatric In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

with gracile capuchins. In areas of sympatry, robust capuchins achieve higher population densities than gracile capuchins. This is thought to reflect the advantage of the adaptations for

durophagy Durophagy is the eating behavior of animals that consume Seashell, hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including ...

in the robust forms, which allow them to exploit hard nuts, palm fruit and unripe fruit, while gracile forms are more restricted to ripe fruit. In general, robust capuchins seem to be more flexible in their diet.

Morphology

Robust capuchins differ in morphology from gracile capuchins in a number of respects. Some of these are related to behavioral differences between the two genera. Robust capuchins have shorter limbs relative to body size than gracile capuchins. There are significant differences between the skulls of robust and gracile capuchins, particularly among males. These differences include the shape of the nasal aperture and the shape 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

canine teeth In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, eye teeth, vampire teeth, or fangs, are the relatively long, pointed teeth. In the context of the upper jaw, they are also known as '' fangs''. They can appear more fl ...

are also different; robust capuchins' canines are shorter and more robust than those of gracile capuchins. Male robust capuchins also have a

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...

, which is lacking in gracile capuchins, and larger, thicker mandibles than gracile capuchins. Some of these differences, such as the sagittal crest, the mandibles and teeth reflect robust capuchins' diet, which includes hard nuts and

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera **Palm oil * Several other plants known as "palm" Palm or Palms may also refer to: Music ...

fruits that are difficult for gracile capuchins to consume. Robust capuchins also have some uniformly consistent features of their fur. All robust capuchins have a tuft of fur on their head, at least to some extent, while no male gracile capuchins have such a tuft. They also all have a

beard A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, beards are most commonly seen on pubescent or adult males, though women have been observed with beards ...

to some degree, which gracile capuchins lack. All robust capuchins have dark fur along their "

sideburn Sideburns, sideboards, or side whiskers are facial hair grown on the sides of the face, extending from the hairline to run parallel to or beyond the ears. The term ''sideburns'' is a 19th-century corruption of the original ''burnsides'', named ...

s" and above their eyes.

Tool use

Some robust capuchins species are known to use stone tools in the wild. These are used to habitually crack open nuts and other shelled fruits, seeds and even

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but no ...

s. Male capuchins use tools to crack open nuts more frequently than females and body mass is the best predictor of efficiency, but the sexes do not differ in terms of efficiency. Some populations have also been known to use stone tools for digging soil and stick probing tools to flush out prey or dip liquid. Robust capuchins are also known at times to rub defensive secretions from

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s over their bodies before eating them; such secretions are believed to act as natural

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

References

{{Taxonbar, from=Q11703605 ^ Taxa named by Robert Kerr (writer)