''Archicebus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of fossil primates that lived in the early

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'', " ...

forests (~55.8–54.8 million years ago) of what is now

Jingzhou Jingzhou () is a prefecture-level city in southern Hubei province, China, located on the banks of the Yangtze River. Its total residential population was 5,231,180 based on the 2020 census, 1,068,291 of whom resided in the built-up (''or metro' ...

in the

Hubei Hubei (; ; alternately Hupeh) is a landlocked province of the People's Republic of China, and is part of the Central China region. The name of the province means "north of the lake", referring to its position north of Dongting Lake. The ...

Province in central China, discovered in 2003. The only known

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 ...

, ''A. achilles'', was a small

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 ...

, estimated to weigh about , and is the only known member of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Archicebidae. When discovered, it was the oldest fossil

haplorhine 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 so ...

primate skeleton found, appearing to be most closely related to tarsiers and the fossil omomyids, although ''A. achilles'' is suggested to have been diurnal, whereas tarsiers are nocturnal. Resembling tarsiers and simians ( monkeys,

ape Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister g ...

s, and

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s), it was a

primate, and it also may have resembled the last

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...

of all haplorhines as well as the last common ancestor of all primates. Its discovery further supports the hypothesis that primates originated in Asia, not in Africa.

Etymology

''Archicebus achilles'' was named for being the oldest-known primate skeleton () and for its distinguishing calcaneus (heel bone). The generic name, ''Archicebus'', was constructed from ''

arche ''Arche'' (; grc, ἀρχή; sometimes also transcribed as ''arkhé'') is a Greek word with primary senses "beginning", "origin" or "source of action" (: from the beginning, οr : the original argument), and later "first principle" or "element". ...

'' (ἀρχή), the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

word for "beginning", and ''cebus'', the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

version of the Ancient Greek ''kêbos'' (κῆβος), which refers to a long-tailed monkey. The species name, ''achilles'', is a reference to

Achilles In Greek mythology, Achilles ( ) or Achilleus ( grc-gre, Ἀχιλλεύς) was a hero of the Trojan War, the greatest of all the Greek warriors, and the central character of Homer's '' Iliad''. He was the son of the Nereid Thetis and Pele ...

, the Greek hero of the

Trojan War In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband Menelaus, king of Sparta. The war is one of the most important events in Greek mythology and ...

from

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities ...

Evolutionary history

''Archicebus achilles'' exhibits similarities with simians with regard to the shape of its calcaneus and the proportions of its

metatarsals The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

, yet its skull, teeth, and

appendicular skeleton The appendicular skeleton is the portion of the skeleton of vertebrates consisting of the bones that support the appendages. There are 126 bones. The appendicular skeleton includes the skeletal elements within the limbs, as well as supporting shou ...

resemble those of tarsiers. According to

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis, all of these traits taken together suggest it is the most basal member of the tarsiiform clade within the suborder Haplorhini. Considering its age, and since simians are a sister group to tarsiiforms, ''A. achilles'' may closely resemble the common ancestor of haplorhines and possibly the last common ancestor of all primates.

Biogeography

The discovery of ''A. achilles'' adds further support to the hypothesis that primates originated in Asia, and not in Africa, with many

simians The simians, anthropoids, or higher primates are an infraorder (Simiiformes ) of primates containing all animals traditionally called monkeys and apes. More precisely, they consist of the parvorders New World monkeys (Platyrrhini) and Catar ...

(a group of them) migrating to the latter continent thereafter.

Anatomy

''A. achilles'' is estimated to have weighed , making it comparable in size to today's smallest living primates,

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 ...

Range and ecology

''A. achilles'' lived in the forests of the warm

epoch, approximately 55.8 to 54.8 million years ago in a part of Asia near what now is

, in the southern

Province of China. Judging from its large

canine teeth In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened howeve ...

and sharp crests on its premolars, ''A. achilles'' was insectivorous. Unlike tarsiers, however, its smaller eyes suggest it was diurnal, a pattern previously suggested by other early haplorhines, such as '' Teilhardina asiatica''. Its hind limbs suggest it did a lot of leaping; however, its hips, shoulders, and feet also suggest that it was not a vertical clinger and leaper such as tarsiers and

galago Galagos , also known as bush babies, or ''nagapies'' (meaning "night monkeys" in Afrikaans), are small nocturnal primates native to continental, sub-Sahara Africa, and make up the family Galagidae (also sometimes called Galagonidae). They are ...

s are, but likely moved through the trees in a more generalized quadrupedal fashion by grasping tree limbs from above.

References

Literature cited

External links

Primate skeleton could give clues about human origins
(

BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broad ...

) * {{Taxonbar, from=Q13421161, from2=Q13418266, from3=Q13421154 Eocene primates Fossil taxa described in 2013 Mammals of China Monotypic prehistoric primate genera Prehistoric primate genera Paleontology in Hubei Tarsiers