일반명 : 오스트랄로피테쿠스 아에티오피쿠스
학 명 : Australopithecus aethiopicus
시 대 : 2.5 million-year-old
발견지역 : west shore of Lake Turkana in northern Kenya
발견시기 : 1985
발견자 : Walker, Leakey, Harris and Brown in Nature in 1986.
Australopithecus aetheopicus KNM WT 17000, commonly referred to as the "Black Skull," due to it's blue-black color, this specimen was discovered in 1985 on the west shore of LakeTurkana in northern Kenya. Although not considered a direct line to humans, it is a prime example of ancient hominid evolution. Latest dating techniques place it somewhere between A. afarensis and A. boisei.
Australopithecus aethiopicus
The discovery of
The first specimen attributed to this species group is an edentulous mandible (Omo 18) found in southern
Not until the Black Skull discovery was there much interest in the specimen, but once KNM-WT 17000 was discovered, interest was renewed in the Omo mandible. The genus name was dropped in favor of the more traditional Australopithecus designation, but Arambourg and Coppens' species designation of aethiopicus was taken as the species name. This species designation is still debated.
Diagnostic Features
The better known aethiopicus specimen is
- A large palate with a thick roof.
- The broken roots of large rooted (and thus probably large crowned) molars and 4th premolar.
- The very anterior zygomatic process of the maxilla whose size and orientation creates a flat, flaring face (this puts the masseter attachment far forward and lateral, where its leverage in producing grinding motions is best).
- The skull does not retain any teeth, but the size of the roots and the palate indicate that the anterior and postcanine teeth were very large.
Other specimens attributed to aethiopicus show thickened molar enamel (similar to afarensis.) The combination of a very small brain and enlarged masticatory apparatus leads to the development of a well-developed sagittal crest that meets the nuchal crest to form a compound temporonuchal crest similar to A. afarensis at the rear of the vault.
Other features that resemble A. afarensis include:
- Large anterior tooth sockets.
- A flattened cranial base (and flattening of everything on it such as the flat, nonprojecting articular eminence of the mandibular fossa and the shallow palate).
- A posterior foramen magnum position and more sagittal orientation of the petrous pyramid of the temporal bone.
- Extreme development of the nuchal muscles and the more vertical orientation of their attachment of the occiptal bone.
- Extreme facial prognathism.
Other remains were attributed to aethiopicus following
- The temporal lines meet at the middle in an anterior position (there would have been a sagittal crest if the individual had lived long enough).
- A marked development of the superior nuchal line with a strong downward projecting inion at its center.
- A large overlap of the temporal onto the parietal bone.
The earliest known aethiopicus material is probably the 2.7 myr L55s-33 mandible fragment from level C6 in the Omo deposits, north of
Conclusions
Australopithecus aethiopicus became important in phylogenetic considerations soon after the discovery of the Black Skull. The species is generally accepted to have shown that the genus designation Paranthropus is polyphyletic and invalid, though some still vocally argue against that fact. One of the earliest important cladistic analysis was by Walker and Leakey (1988), which they claim shows aethiopicus is at the base of the boisei lineage, is more primitive than robustus, and that aethiopicus is not ancestral to robustus. However, Strait et al. says that this phylogeny requires 39 extra steps above the most parsimonious tree, and most cladists do not favor this phylogeny. Skelton and McHenry (1992) and Lieberman et al. (1996) both came to the same conclusions regarding aethiopicus and Paranthropus using different character traits. Both see aethiopicus as a dead-end side branch and Paranthropus as polyphyletic and invalid. On the other side of the coin, Strait et al. (1997) see all the robusts sharing a recent common ancestor (aethiopicus), with Paranthropus monophyletic.
Bibliography
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Arambourg, C., and Y. Coppens. 1968. "Decouverte d'un Australopithecien nouveau dans les gisements de l'Omo (
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