Chororapithecus
| Chororapithecus Temporal range: Tortonian,
| |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Infraorder: | Simiiformes |
| Family: | Hominidae |
| Subfamily: | Homininae |
| Tribe: | Gorillini |
| Genus: | †Chororapithecus Suwa et al., 2007 |
| Species: | †C. abyssinicus
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| Binomial name | |
| †Chororapithecus abyssinicus Suwa et al., 2007
| |
Chororapithecus is an extinct great ape from the Late Miocene of Ethiopia roughly 8 million years ago, comprising one species, C. abyssinicus. It is known from 9 isolated teeth discovered in a 2005–2007 survey of the Chorora Formation. The teeth are indistinguishable from those of gorillas in terms of absolute size and relative proportions, and it has been proposed to be an early (and the only other) member of Gorillini; however this is unconfirmed given the paucity of remains. The Kenyan ape Nakalipithecus has also been proposed to be an ancestor or at least closely related. If correct, they would be the only identified fossil members of any modern non-human great ape lineage, and would push the gorilla–human last common ancestor from 8 million years ago (identified by molecular analysis) to 10 million years ago. The teeth are adapted for processing tough plant fibres as well as hard, brittle food, and the formation is thought to represent a forested lakeside habitat.
Taxonomy
Chororapithecus teeth were discovered in Ethiopia in a 2005–2007 survey in the Beticha locality of the Chorora Formation, hence the name, and the formation itself is named after the Chorora village about 8 km (5.0 mi) south of the locality. The species name, abyssinicus, is in reference to Abyssinia, the former name of Ethiopia.[1]
| Hominidae |
| Family tree showing Chororapithecus and Nakalipithecus as stem gorillas[2] |
The remains represent at least 3, perhaps over 6, different individuals. The holotype specimen, CHO-BT 4, is a right upper second molar, and the paratypes are a left lower canine, 3 right upper third molars, a left lower third molar, a left lower first molar, and a left and a right lower molar fragment. The discoverers noted the teeth have several features in common with those of gorillas, and classified it as the first fossil member and the only other genus of the tribe Gorillini. Because the Chororapithecus teeth have several unique specializations (they are derived), they did not consider it as ancestral to the gorilla.[1] However, the discovers also conceded it is possible that Chororapithecus and gorillas instead convergently evolved the same teeth due to a similar diet.[1]
The teeth were originally dated to 10.5–10 million years ago (mya), and the discoverers then concluded that the gorilla–human last common ancestor (LCA) existed about 12 mya, but they were re-dated to about 8 mya, which, if Chororapithecus is indeed a stem gorilla, is more consistent with the timing of 8 mya for the LCA according to molecular data. Based on the revised date and similarly large premolar size, the 10 million year old Kenyan Nakalipithecus has been proposed to have been the ancestor to Chororapithecus, which would move the LCA to 10 mya if correct.[2] Nonetheless, because there are so few remains known, its relations to modern great apes is unclear. No other Miocene ape has been proposed to be a member of any modern great ape lineage.[3]
It is debated if great apes evolved in Africa or Eurasia given the abundance of early fossil apes species in the latter and the paucity in the former, despite all modern great apes except the orangutan being known from Africa. The first Miocene African great ape was discovered in 1997, Samburupithecus, and the only others known are Nakalipithecus and Chororapithecus. If Chororapithecus is indeed an early gorilla, then it would point to an African origin for great apes.[2][3]
Anatomy
The teeth, both in absolute size and relative proportions, are the same as in gorillas, and the molars range in size from the largest and smallest of what is normally seen in gorillas. Like in gorillas, the upper molars have a long protocone crest, and the lower molars have a correspondingly long trigonid crest, which increasing shearing efficacy. Compared to gorillas, the cusp tips are relatively peripheral, are not well pronounced, and the enamel is thicker especially at the side cusps where the tooth borders other teeth. This causes a wide basin on the middle of the molar. The upper molars are elongated and narrow.[1]
Palaeobiology
The teeth exhibit adaptations for shearing, but the low cusp height indicates the teeth likely folded and pulverised tough plant fibres rather than cut through them as gorillas and other folivores with higher cusps do. The thick enamel is more similar to that of orangutans, and may indicate the consumption of hard, brittle foods. Chororapithecus and Oreopithecus are the only known folivorous Miocene apes.[1]
The Chorora Formation represents a braided river system, possibly a forested area alongside a lake in a forest-savanna mosaic environment.[1] The formation also records the earliest known occurrences of cercopithecine monkeys, hippos, and rabbits in Africa. Two different horses, a colobine monkey,[4] the elephant Stegotetrabelodon, a giraffe, and a hippo are also known.[1]
See also
References
- ^ a b c d e f g Suwa, G.; Kono, R. T.; Katoh, S.; Asfaw, B.; Beyene, Y. (2007). "A new species of great ape from the late Miocene epoch in Ethiopia". Nature. 448 (7156): 921–924. doi:10.1038/nature06113. PMID 17713533.
- ^ a b c Katoh, S.; Beyene, Y.; Itaya, T.; et al. (2016). "New geological and palaeontological age constraint for the gorilla–human lineage split". Nature. 530: 215–218. doi:10.1038/nature16510. PMID 26863981.
- ^ a b Dalton, Rex (2007). "Oldest gorilla ages our joint ancestor". Nature News. 448 (7156): 844–845. doi:10.1038/448844a. PMID 17713490.
- ^ Suwa, G.; Beyene, Y.; Nakaya, H.; et al. (2015). "Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia". Anthropological Science. 123 (1): 19–39. doi:10.1537/ase.150206.
External links
New fossils from 10 million year old ape found in Ethiopia at Wikinews
Data related to Chororapithecus abyssinicus at Wikispecies- Researchers find fossils of 10 million-year-old ape at Reuters
