Eosimias
| Eosimias | |
|---|---|
| |
| Restoration ofE. sinensis | |
Scientific classification
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Family: | †Eosimiidae |
| Genus: | †Eosimias Beardet al., 1994 |
| Species[1] | |
| |
Eosimiasis a genus of earlyprimates,first discovered and identified in 1999 from fossils collected in the Shanghuang fissure-fillings of Liyang, the southern city ofJiangsu Province,China. It is a part of the familyEosimiidae,and includes three known species:Eosimias sinensis,Eosimias centennicus,andEosimias dawsonae.[3]It provides us with a glimpse of a primate skeleton similar to that of the common ancestor of theHaplorhini(including allsimians). The nameEosimiasis designed to mean "dawn monkey", from Greekeos"dawn" and Latinsimius"monkey".[4]
Dating has proven this genus lived from 45 to 40 million years ago in the middleEocene.[4]The genusEosimiasis unique because of the presence of primitive and derived traits. It provides new insight into thephylogenetic relationshipsbetween simians andprosimians(especially the phylogenetic position of the haplorhine prosimiantarsiers). It can best be described as a likely tree dweller that relied on a steady diet of insects and nectar.
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[who?]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.[citation needed]
Eosimias sinensis
[edit]Eosimias sinensis(Chinese:Trung hoa thự viên,lit. 'dawn monkey of China') was first discovered inChinain 1992 by Christopher Beard. It was found in a mountain nearLiyangCity,Jiangsuprovince,China.
The species is believed to have lived 45 million years before present, in theEoceneepoch.[5]E. sinensiswas tiny, as small as the smallest monkey presently, thepygmy marmoset(Cebuella pygmaea) ofSouth America,and could fit in the palm of a human's hand.[6]Its teeth are considered more primitive than those of early higher primates known from Africa, includingAlgeripithecus.Due to its highly primitive nature, some paleontologists considerE. sinensisto be evidence that higher primates may have originated inAsiarather thanAfrica.[5]
Christopher Beard was the lead member of the team that discoveredEosimias sinensisin 1994. Beard recovered a rightmandible,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 grams (2.4–4.8 oz)) and an unfused mandibularsymphysis,it appears to be a primitive simian based on its dental characteristics, including a lowerdental formulaof 2.1.3.3.[4]Eosimias sinensishas incisors which are vertical and spatulate. These creatures are known primarily from lower jaws and teeth, no cranial remains have been able to indicate whetherEosimiaswas diurnal or nocturnal.[7]
Eosimias centennicus
[edit]
Eosimias centennicuswas found in 1995 while doing fieldwork in theYuanqu Basinof the southernShanxi Provincein China.[8]Among these recovered fossils is the first complete lower dentition ofEosimias,catalogued as IVPP V11000. All anatomical information yielded from these fossils confirms the anthropoid-like traits found inE. sinensis.Biostratigraphicevidence also suggests these fossils are younger thanE. sinensis,which is consistent with the anatomy of eosiimids because the dentition ofE. centennicusis slightly more derived than that ofE. sinensis.[8]This species was also found to be a very tiny primate, with mean estimates of body mass ranging from 91 to 179 grams (3.2 to 6.3 oz).E. sinesiswas originally described on the basis of fragmentary fossils, but with the discovery ofE. centennicusand a complete lower dentition,Eosimiascan more definitively be described as an earlyanthropoid.
Eosimias dawsonae
[edit]Eosimias dawsonaeis the newest of theEosimiasspecies. 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.[9]Analysis of these remains has led to the conclusion it was the largest of the known species ofEosimias,yielding a body mass ranging from 107 to 276 grams (3.8 to 9.7 oz). Stratigraphic evidence also showsE. dawsonaeis older thanE. centennicus.
Unidentified fossils
[edit]Additionally, an expedition team discovered evidence of a new, small eosimiid fromMyanmarin 1999. The new specimen, represented by a right heel bone cataloged as NMMP 23, was found in wash residue in thePondaung Formation.[10]This specimen is very morphologically similar to theEosimiasdiscovered 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 ofEosimiasfossils 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.[10]
Eosimias paukkaungensis
[edit]A new species of eosimiid primate,Eosimias paukkaungensis,from the latest middle Eocene of Pondaung, central Myanmar, was discovered in the early 2000s. The specimen consists of left and right mandibular fragments preserving only the M3, so that its generic status is provisional. TheE. paukkaungensisfossil is much larger than homologues of the twoEosimiasspecies from China.[2]
References
[edit]- ^ab"Eosimias".paleobiodb.org.Retrieved2021-07-28.
- ^abTakai, Masanaru; Sein, Chit; Tsubamoto, Takehisa; Egi, Naoko; Maung, Maung; Shigehara, Nobuo (2005)."A new eosimiid from the latest middle Eocene in Pondaung, central Myanmar".Anthropological Science.113(1): 17–25.doi:10.1537/ase.04S003.
- ^Beard, K.C.; Qi, T.; Dawson, M.R.; Wang, B. & Li, C. (1994). "A diverse new primate fauna from middle Eocene fissure-fillings in southeastern China".Nature.368(6472): 604–609.Bibcode:1994Natur.368..604B.doi:10.1038/368604a0.PMID8145845.S2CID2471330.
- ^abc"Tracking Our Extended Family".Carnegie Mellon’s Museum of Natural History. Archived fromthe originalon July 6, 2010.Retrieved2010-08-09.
- ^ab"The Discovery ofEosimias sinensis,the Ancestor of the Human and Their Anthropoid Relative "(in Chinese). Chinese Academy of Sciences. 2002-02-20. Archived fromthe originalon 2007-09-27.Retrieved2010-08-09.
- ^Hendricks, M. (April 2001)."Tales from the Crust".Johns Hopkins Magazine.Retrieved2010-08-09.
- ^John G. Fleagle, Primate Adaptation & Evolution, ch. 10
- ^abGebo, D.L.; Gunnell, G.F.; Ciochon, R.L.; Takai, M.; Tsubamato, T. & Egi, N. (2002). "New eosimiid primate from Myanmar".Journal of Human Evolution.43(4): 549–553.Bibcode:2002JHumE..43..549G.doi:10.1006/jhev.2002.0571.
- ^Beard, K.C.; Tong, Y.; Dawson, M.R.; Wang, J. & Huang, X. (1996). "Earliest complete dentition of an anthropoid primate from the late middle Eocene of Shanxi Province, China".Science.272(5258): 82–85.Bibcode:1996Sci...272...82B.doi:10.1126/science.272.5258.82.S2CID83617771.
- ^abBeard, K. C.; Wang, J. (2004). "The eosimiid primates (Anthropoidea) of the Heti Formation, Yuanqu Basin, Shanxi and Henan Provinces, People's Republic of China".Journal of Human Evolution.46(4): 401–432.Bibcode:2004JHumE..46..401B.doi:10.1016/j.jhevol.2004.01.002.PMID15066378.
