Eosimias
Encyclopedia
Eosimias was a genus of early primates, first discovered and identified in 1999 from fossils collected in the Shanghuang fissure-fillings of the southern Jiangsu Province, China. It is a part of the family Eosimiidae
, which includes three known species: Eosimias sinensis, Eosimias centennicus, and Eosimias dawsonae. It provides us with a glimpse of a primate skeleton similar to that of the common ancestor of the Haplorrhini
(including all simian
s). The name Eosimias is designed to mean "dawn monkey", from Greek eos
"dawn" and Latin simius "monkey".
Dating has proven this species lived from 40 to 45 million years ago in the middle Eocene
. The genus Eosimias is unique because of the presence of primitive and derived traits. It provides new insight into the phylogenetic relationships
between simians and prosimian
s (especially the phylogenetic position of the haplorrhine prosimian tarsier
s). It can best be described as a likely tree dweller that relied on a steady diet of insects and nectar. It was probably a nocturnal, solitary creature.
Most eosimiid species are documented by unique or fragmentary specimens. This, as well as the strong belief that simians originated in Africa has made it difficult for many to accept the idea that Asia played a role in early primate evolution. Although some continue to challenge the anthropoid resemblances found in Eosiimidae, extensive anatomical evidence collected over the past decade substantiates its anthropoid status.
: 中华曙猿, "dawn monkey of China") was first discovered in China
in 1994 by Christopher Beard. It was found in a mountain near Liyang
City, Jiangsu
province, China
. It is the earliest catarrhine
that has been discovered.
The species is believed to have lived 45 million years before present, in the Eocene
epoch. E. sinensis was tiny, as small as the smallest monkey presently, the Pygmy Marmoset
(Cebuella pygmaea) of South America
, and could fit in the palm of a human's hand. Its teeth are considered more primitive than those of early higher primates known from Africa, including Algeripithecus
. Due to its highly primitive nature, some paleontologists consider E. sinensis to be evidence that higher primates may have originated in Asia
rather than Africa
.
Christopher Beard was the lead member of the team that discovered Eosimias sinensis in 1994. Beard recovered a right mandible
, cataloged as IVPP V10591, which preserved P4-M2 and roots or alveoli for C1, P2-3, and M3. Although it retains primitive characters such as a small body size (mean estimates range from 67–137 g (2.4–4.8 oz)) and an unfused mandibular symphysis
, it appears to be a primitive simian based on its dental characteristics, including a lower dental formula of 2-1-3-3.
in China. Among these recovered fossils is the first complete lower dentition of Eosimias, catalogued as IVPP V11000. All anatomical information yielded from these fossils confirms the anthropoid-like traits found in E. sinensis. Biostratigraphic
evidence also suggests these fossils are younger than E. sinensis, which is consistent with the anatomy of eosiimids because the dentition of E. centennicus is slightly more derived than that of E. sinensis. This species was also found to be a very tiny primate, with mean estimates of body mass ranging from 91 to 179 g (3.2 to 6.3 oz). E. sinesis was originally described on the basis of fragmentary fossils, but with the discovery of E. centennicus and a complete lower dentition, Eosimias can more definitively be described as an early anthropoid
.
in 1999. The new specimen, represented by a right heel bone cataloged as NMMP 23, was found in wash residue in the Pondaung Formation. This specimen is very morphologically similar to the Eosimias discovered in the Shanghuang region of China. The best estimate for NMMP 23 includes an overall mean weight of about 111 grams, which places it in the upper-sized end of Eosimias fossils discovered. The presence of eosimiid in Myanmar, as well as a high species diversity found in China leads to an apparent conclusion that they had a relatively wide distribution.
Eosimiidae
Eosimiidae is the family of extinct primates believed to be the earliest simians....
, which includes three known species: Eosimias sinensis, Eosimias centennicus, and Eosimias dawsonae. It provides us with a glimpse of a primate skeleton similar to that of the common ancestor of the Haplorrhini
Haplorrhini
The haplorhines, the "dry-nosed" primates , are members of the Haplorhini clade: the prosimian tarsiers and the anthropoids...
(including all simian
Simian
The simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
s). The name Eosimias is designed to mean "dawn monkey", from Greek eos
Eos
In Greek mythology, Eos is the Titan goddess of the dawn, who rose from her home at the edge of Oceanus, the ocean that surrounds the world, to herald her brother Helios, the Sun.- Greek literature :...
"dawn" and Latin simius "monkey".
Dating has proven this species lived from 40 to 45 million years ago in the middle Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
. The genus Eosimias is unique because of the presence of primitive and derived traits. It provides new insight into the phylogenetic relationships
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
between simians and prosimian
Prosimian
Prosimians are a grouping of mammals defined as being primates, but not monkeys or apes. They include, among others, lemurs, bushbabies, and tarsiers. They are considered to have characteristics that are more primitive than those of monkeys and apes. Prosimians are the only primates native to...
s (especially the phylogenetic position of the haplorrhine prosimian tarsier
Tarsier
Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes...
s). It can best be described as a likely tree dweller that relied on a steady diet of insects and nectar. It was probably a nocturnal, solitary creature.
Most eosimiid species are documented by unique or fragmentary specimens. This, as well as the strong belief that simians originated in Africa has made it difficult for many to accept the idea that Asia played a role in early primate evolution. Although some continue to challenge the anthropoid resemblances found in Eosiimidae, extensive anatomical evidence collected over the past decade substantiates its anthropoid status.
Eosimias sinensis
Eosimias sinensis (ChineseChinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
: 中华曙猿, "dawn monkey of China") was first discovered in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
in 1994 by Christopher Beard. It was found in a mountain near Liyang
Liyang
Liyang is a city in the southwest of Jiangsu province of Eastern China. It is administratively a county-level city under the administration of Changzhou City, and in 1999 had a population of 781,430.-Administration:...
City, Jiangsu
Jiangsu
' is a province of the People's Republic of China, located along the east coast of the country. The name comes from jiang, short for the city of Jiangning , and su, for the city of Suzhou. The abbreviation for this province is "苏" , the second character of its name...
province, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. It is the earliest catarrhine
Catarrhini
Catarrhini is one of the two subdivisions of the higher primates . It contains the Old World monkeys and the apes, which in turn are further divided into the lesser apes or gibbons and the great apes, consisting of the orangutans, gorillas, chimpanzees, bonobos, and humans...
that has been discovered.
The species is believed to have lived 45 million years before present, in the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epoch. E. sinensis was tiny, as small as the smallest monkey presently, the Pygmy Marmoset
Pygmy Marmoset
The pygmy marmoset or dwarf monkey is a New World monkey native to the rainforest canopies of western Brazil, southeastern Colombia, eastern Ecuador, eastern Peru, and northern Bolivia. It is one of the smallest primates, and the smallest true monkey, with its body length ranging from...
(Cebuella pygmaea) of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, and could fit in the palm of a human's hand. Its teeth are considered more primitive than those of early higher primates known from Africa, including Algeripithecus
Algeripithecus
Algeripithecus is a genus of primates. Its status as an antherpoid or strepsirrhine is under debate.150 to 300 grams extinct primate of 50 to 46 million years ago; fossils found in Algeria; considered by some authorities the leading candidate for the first anthropoid...
. Due to its highly primitive nature, some paleontologists consider E. sinensis to be evidence that higher primates may have originated in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
rather than Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.
Christopher Beard was the lead member of the team that discovered Eosimias sinensis in 1994. Beard recovered a right mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
, cataloged as IVPP V10591, which preserved P4-M2 and roots or alveoli for C1, P2-3, and M3. Although it retains primitive characters such as a small body size (mean estimates range from 67–137 g (2.4–4.8 oz)) and an unfused mandibular symphysis
Symphysis
A symphysis is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint.1.A symphysis is an amphiarthrosis, a slightly movable joint.2.A growing together of parts or structures...
, it appears to be a primitive simian based on its dental characteristics, including a lower dental formula of 2-1-3-3.
Eosimias centennicus
Eosimias centennicus was found in 1995 while doing fieldwork in the Yuanqu Basin of the southern Shanxi ProvinceShanxi
' is a province in Northern China. Its one-character abbreviation is "晋" , after the state of Jin that existed here during the Spring and Autumn Period....
in China. Among these recovered fossils is the first complete lower dentition of Eosimias, catalogued as IVPP V11000. All anatomical information yielded from these fossils confirms the anthropoid-like traits found in E. sinensis. Biostratigraphic
Biostratigraphy
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
evidence also suggests these fossils are younger than E. sinensis, which is consistent with the anatomy of eosiimids because the dentition of E. centennicus is slightly more derived than that of E. sinensis. This species was also found to be a very tiny primate, with mean estimates of body mass ranging from 91 to 179 g (3.2 to 6.3 oz). E. sinesis was originally described on the basis of fragmentary fossils, but with the discovery of E. centennicus and a complete lower dentition, Eosimias can more definitively be described as an early anthropoid
Simian
The simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
.
Eosimias dawsonae
Eosimias dawsonae is the newest of the Eosimias species. It is categorized by the type specimen IVPP V11999, which includes a left dentary fragment and roots of the alveoli. It was collected by Christopher Beard in 1995. Analysis of these remains has led to the conclusion it was the largest of the known species of Eosimias, yielding a body mass ranging from 107 to 276 g (3.8 to 9.7 oz). Stratigraphic evidence also shows E. dawsonae is older than E. centennicus.Unidentified fossils
Additionally, an expedition team discovered evidence of a new, small eosiimid from MyanmarMyanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....
in 1999. The new specimen, represented by a right heel bone cataloged as NMMP 23, was found in wash residue in the Pondaung Formation. This specimen is very morphologically similar to the Eosimias discovered in the Shanghuang region of China. The best estimate for NMMP 23 includes an overall mean weight of about 111 grams, which places it in the upper-sized end of Eosimias fossils discovered. The presence of eosimiid in Myanmar, as well as a high species diversity found in China leads to an apparent conclusion that they had a relatively wide distribution.