''Archicebus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of fossil primates that lived in the early

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 ...

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

Jingzhou Jingzhou ( zh, s=, c=荆州, t=, p=Jīngzhōu) 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 Seventh National Population Censu ...

in the

Hubei Hubei is a province of China, province in Central China. It has the List of Chinese provincial-level divisions by GDP, seventh-largest economy among Chinese provinces, the second-largest within Central China, and the third-largest among inland ...

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

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), ...

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

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 ...

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

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Archicebidae. When discovered, it was the oldest fossil haplorhine primate skeleton found, appearing to be most closely related to

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 and the fossil omomyids, although ''A. achilles'' is suggested to have been diurnal, whereas tarsiers are

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 ...

. Resembling tarsiers and

simian 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 monkey, Platyrrhini (New World mon ...

s (

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes. Thus monkeys, in that sense, co ...

s and

ape Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

s), it was a haplorhine 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. According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonl ...

of all haplorhines.

Etymology

''Archicebus achilles'' was named for being the oldest-known primate skeleton () and for its distinguishing

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the Tarsus (skeleton), tarsus of the foot which constitutes the heel. In some other ...

(heel bone). The generic name, ''Archicebus'', was constructed from ''

arche In philosophy and science, a first principle is a basic proposition or assumption that cannot be deduced from any other proposition or assumption. First principles in philosophy are from first cause attitudes and taught by Aristotelians, and nuan ...

'' (ἀρχή), the

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

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

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

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 () was a hero of the Trojan War who was known as being the greatest of all the Greek warriors. The central character in Homer's ''Iliad'', he was the son of the Nereids, Nereid Thetis and Peleus, ...

, the Greek hero of the

Trojan War The Trojan War was a legendary conflict in Greek mythology that took place around the twelfth or thirteenth century BC. The war was waged by the Achaeans (Homer), Achaeans (Ancient Greece, Greeks) against the city of Troy after Paris (mytho ...

from

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Evolutionary history

''Archicebus achilles'' exhibits similarities with

s with regard to the shape of its

and the proportions of its metatarsals, yet its skull, teeth, and

appendicular skeleton The appendicular skeleton is the portion of the vertebrate endoskeleton consisting of the bones, cartilages and ligaments that support the paired appendages ( fins, flippers or limbs). In most terrestrial vertebrates (except snakes, legless li ...

resemble those of tarsiers. According to

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis, all of these traits taken together suggest it is the most basal member of the tarsiiform

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

within the suborder

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

. Considering its age, and since simians are a

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

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 monkey, Platyrrhini (New World mon ...

(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 and weigh , making them the smallest primates (the smallest sp ...

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, 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 ...

and sharp crests on its

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 ...

s, ''A. achilles'' was

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...

. 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 Paleontology in Hubei Tarsiers