Omo Basin Research Articles

Diversity and frequency distribution of omo group cercopithecoidea

Approximately 6000 cercopithecoid specimens have been recovered from Omo Group deposits of southwestern Ethiopia since 1967. The specimens range in completeness from fragmentary isolated teeth to nearly complete skeletons. The majority of the specimens consist, however, of isolated tecth, fragmentary jaw parts and limb bones. They range in age from c. 3·0 m.y. to c. 0·9 m.y. Both Colobinae and Cercopithecinae have been recovered, with the cercopithecines predominating. The colobine specimens fall into 4 size groups which probably represent taxonomic units. The smallest of the specimens have been assigned to genus Colobus. Of the two middle-sized groups, the smaller is rare and of unknown affinities, while the larger is probably a new genus and species. The largest of the specimens, similar in size to a modern savannah baboon, probably also represents a new genus and species. Six species of cercopithecines have been recovered. Specimens of Cercopithecus and Papio are rare as are those of two species of small Papionini of uncertain affinities. The majority of the specimens belong to the genus Theropithecus with both T. brumpti and T. oswaldi being represented. Cercopithecoid specimens are not evenly distributed through the deposits and preliminary analysis indicates that the differences in frequencies may be due to changes in the environment of the lower Omo basin through time.

Analysis of an early hominid ulna from the Omo Basin, Ethiopia.

The discovery (in 1971) of a nearly complete right ulna from the Shungura Formation of the Omo basin provides the opportunity to abalyze the forelimb structure of the Australopithecus boisei form of early hominid. Results from multivariate morphometric analyses show that this bone is unique in shape among the extant hominoids although it is most similar to Pan and Homo. Despite its long slender shaft and large distal articular surface the bone's overall morphology is quite unlike Pongo.

Les Voyageurs européens dans le Sud-Ouest éthiopien (1890-1910)

1890-1910 : a course of twenty years when Emperor Menelik II extended his sovereignty over countries which today represent half, if not more, of the national territory. The restoration of the old Christian Empire of Zara Yacob (1434-1468) was made at the expense of French, English, Italian and Russian colonial conquests. In actual fact, the territories conquered by Menelik were coveted by European Powers seeking to control an unknown but supposedly rich land. Exploration and conquest were on the same footing. The Omo basin, unheard of in 1890, was explored, conquered and pacified during the twenty years that followed. The accounts of travellers — either scientists or ofFicers — testify of the fragility of colonial politics, as opposed to Menelik's achievements. Indeed, the few English and Italian attempts to annex South-West Ethiopia failed to stem Menelik's advance, helped, as he was, by the French and Russians. Apart from some exceptions — Bottego for instance — , most travellers were content with giving brief description for the benefit of the prosperous Geographical Societies of the time. In matter, thèse accounts were rather poor, but as a whole they were unintentionally typical of Ethiopian dynamism in baffling impérialiste plots.

Magnetostratigraphy of the Shungura Formation, southwestern Ethiopia: Fine structure of the lower Matuyama polarity epoch

Paleomagnetic measurements are reported for 500 sites in the lower Omo basin of southwestern Ethiopia, an important region for mammalian and hominid fossils. Magnetozones are defined with varying degrees of reliability for more than 700 m of measured stratigraphic section. In a half dozen sedimentary cycles of lower Member G at the locality sampled, we found the concreted basal sand to be normally magnetized and the upper silt to be reversely magnetized. We hypothesize a reversed primary magnetization of all these beds and a hard secondary magnetization of the permeable beds by groundwater. A chronological interpretation is proposed consistent with K/Ar dates on interbedded tuffs, faunal correlation with Bed I at Olduvai Gorge, and the detailed stratigraphy of J. De Heinzelin and P. Haesaerts. The exposed section is found to span the age range 3.2-0.9 m.y. For the lower Matuyama epoch the following suggestions are made about the fine structure of the geomagnetic polarity scale: (1) there are at least two and possibly three Reunion events near 2.0 m.y., (2) the “X” anomaly of J.R. Heirtzler et al. (1968) does represent a normal event near 2.3 m.y., (3) the Gilsa and Olduvai events are the same.

Early hominid ulna from the Omo basin, Ethiopia.

A NEARLY complete right ulna (Loc 40–19) was recovered by G. Eck in 1971 in Member E of the Shungura Formation in the lower Omo basin of Southern Ethiopia. It was found in a locality within unit E5 which immediately underlies Tuff F, the K–Ar age for which is 2.04 Myr1–4. This locality has yielded other vertebrate fossils but no further hominid remains in spite of intensive searching. The lower limb of fossil hominids is much better represented than the upper and the remains that do exist are mostly fragmentary. This is the first early hominid forearm bone to be recovered in a state of completeness that will allow locomotor inferences, based on pelvic and lower limb material, to be correlated with good evidence from the upper limb.

Inventory of remains of Hominidae from Pliocene-Pleistocene formations of the lower Omo basin, Ethiopia (1967-1972).

AbstractSince its initiation in 1966 the Omo Research Expedition has recovered a series of hominid fossils, in association with many vertebrate taxa, from formations of Pliocene/Pleistocene age from the lower Omo basin, southern Ethiopia. These fossiliferous formations span a time range from over 4.2 m.y. to about 1.4 m. y. on the basis of K/A age determination. Hominid remains have been found so far to occur at two localities in the upper part of the Usno Formation (∼ 2.9 m.y.) and in the Shungura Formation at 79 localities from successive Members B through levels postdating J, a time span between 3 m.y. and 1.4 m.y. The remains—inventoried here according to skeletal part, locality and stratigraphic level, age and situation—include numerous isolated and associated teeth, mandibles, partial maxillae, portions of crania, and elements of the postcranial skeleton.

Deciduous teeth of Hominidae from the Pliocene/Pleistocene of the lower Omo basin, Ethiopia

A few deciduous teeth of Hominidae from Pliocene/Pleistocene formations of the lower Omo basin, Southern Ethiopia, are briefly described. They derive from fossiliferous localities dated radiometrically between 2 and 3 million years ago. They show resemblances to homologues of other early hominids, and in particular some australopithecines of Southern Africa. No taxonomic attributions are made, but the deciduous teeth appear to confirm other evidence which would indicate the presence of more than one hominid taxon within this time range.

New Fossil Cercopithecus Material from the Lower Omo Basin, Ethiopia

New fossil Cercopithecus material dated at 1.90 and 2.90 m.y. from the lower Omo basin, southwestern Ethiopia is described and compared to samples of modern C. aethiops and C. nictitans and to several other species discussed in the literature. All of the specimens described belong to the genus Cercopithecus. Assignment to species must await the recovery of further material.

Molluscan assemblages from the Late Cenozoic of the Lower Omo Basin, Ethiopia—Comments

Molluscan assemblages from the Late Cenozoic of the Lower Omo Basin, Ethiopia—Comments

Molluscan Assemblages from the Late Cenozoic of the Lower Omo Basin, Ethiopia

The lower Omo basin, southern Ethiopia, preserves formations of sedimentary and pyroclastic rocks which span a substantial range of later Cenozoic time. These formations are often extraordinarily rich in vertebrate fossils and have also afforded a series of molluscan assemblages from contexts radiometrically dated by K/Ar or 14C. The late Cenozoic molluscan fauna has been previously ill-known in this part of Africa and these assemblages provide a broad faunal zonation for the northern sector of the Eastern Rift valley. The five principal assemblages are here treated as faunal groupings, rather than as formal faunal zones. Three groupings are recognized for the Pliocene/Pleistocene time range, one grouping for the later Pleistocene and one grouping for the subrecent and present.

Contemporary Depositional Environments of the Omo Delta

Geomorphological and sedimentological studies of depositional environments of the modern Omo River delta and floodplain are essential to an understanding of the Pliocene to Pleistocene Mursi, Nkalabong and Kibish Formations of the Lower Omo Basin (southwestern Ethiopia).

Remains of Hominidae from Pliocene--Pleistocene formations in the lower Omo Basin, Ethiopia.

Discoveries by the Chicago contingent of the 1967 and 1968 International Research Expedition to the Omo Valley extend the fossil records of australopithecines back to between 3 and 4 million years ago.

Some Late Cenozoic Sedimentary Formations of the Lower Omo Basin

Geological and geomorphological studies in the lower Omo valley 1967–1968 have established a sedimentary sequence recording much of the late Cenozoic.

Age Determinations on Feldspar from the Lower Omo Basin

Total degassing 40Ar/39Ar age determinations have been made on a concentrate of fresh feldspar from lapilli in a pumice–lapilli-tuff of the Nkalabong Fm., Lower Omo Basin, Ethiopia.

Early Homo sapiens Remains from the Omo River Region of South-west Ethiopia: Geological Interpretation of Two Pleistocene Hominid Sites in the Lower Omo Basin

Early Homo sapiens Remains from the Omo River Region of South-west Ethiopia: Geological Interpretation of Two Pleistocene Hominid Sites in the Lower Omo Basin