Vertebrate faunas from the Awash Group, Middle Awash Valley, Afar, Ethiopia

ArticleinJournal of Vertebrate Paleontology 2(2):237-258 · September 1982with 63 Reads
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Abstract
We present a preliminary report on vertebrate faunas from the Middle Awash Valley in the Afar Depression, from the newly described Adu-Asa, Sagantole, Matabaietu, and Wehaietu Formations. These units, together with the well-known hominid-bearing Hadar Formation and the Chorora Formation, comprise the Awash Group, which is over one kilometer thick, spans the late Neogene, and contains vertebrate fossils throughout. Significantly, periods are represented—the late Miocene to early Pliocene and Middle to late Pleistocene—that are poorly or incompletely known elsewhere in East Africa.At least 24 mammalian families and 170 species are represented in the Awash Group. In the newly described stratigraphic units, faunal change is documented for a number of mammalian groups. This is especially true for Proboscidea, specifically anancine gom-photheres (Gomphotheriidae: Anancinae) and elephants (Elephantidae: Stegotetra-belodontinae and Elephantinae), the Artiodactyla, particularly suids (Suidae), bovids (Bovidae) and hippopotamids (Hippopotamidae), and Primates (Cercopithecidae: Cercopithecinae and Colobinae).Available radiometric dates and biostratigraphy indicate that the time span represented by the Adu-Asa and Wehaietu Formations is at least 5.0–6.0 m.y. long, making the Middle Awash sequence one of the most extensive faunal records in the African Neogene.

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    The Hominidae probably originated in Africa sometime between 14 my and 4 my ago. Unfortunately the fossil evidence from this time period and region is relatively poor. We regard only 11 specimens as unambiguous hominoids, and none preserves a great amount of anatomy. They come from a very restricted geographical region. Two are from Ethiopia and the rest from Kenya, where most have been found in the Tugen Hills succession west of Lake Baringo. No unequivocal fossil evidence of ancestral Gorilla or Pan has yet been recognised. The oldest hominid yet known—in the sense used here—probably dates to greater than 5.6 my. One especially interesting question in the paleobiology of the hominoidea, as in other taxa, is the relation of extrinsic factors to speciation. To resolve this issue, diagnostic and well-dated specimens are necessary. However, they need not be anatomically spectacular. Fragmentary specimens, although imperfect anatomically, can be just as effective as more complete material in defining taxonomic branching points. The origin of Hominidae, or at least bipedalism, has been conjecturally associated with a regional environmental change from tropical forest to widespread grassland. Evidence accumulating from various parts of Africa, particularly the Tugen Hills, suggests this was not an abrupt transition. The pattern of habitats was probably patchy in space and time. This may have been a factor in the origin and development of the hominid clade. Much progress has recently been made, but further hominoid specimens, coupled with environmental information from well-calibrated sequences, is necessary to elucidate the nature and causes of cladistic branching within the superfamily.
  • Article
    This paper evaluates the potential contribution(s) of faunal analysis to hominin palaeoecology at regional and continental scales, through an explicit investigation of the values, methods and conceptual frameworks of palaeoanthropology and their compatibility with real data structures. It employs a problem‐framing method developed in policy‐relevant science to establish a suitable research design for ‘large scale’ faunal analysis, before testing the method in a pilot study of 48 faunal assemblages from the African Plio‐Pleistocene. Hitherto, taphonomic bias has discouraged attempts to study faunal assemblages on large spatiotemporal scales, and most scientists have restricted their work to the smaller (site or local) scale and/or a subset of the total fauna. Furthermore, palaeoanthropological studies of fauna tend to address pre‐determined questions through analysis of statistical outputs (patterns), rather than investigating the limitations and potential of the data through exploratory work. This paper, despite identifying a number of inherent constraints on palaeocommunity analysis at the large scale—including a clear tendency towards the segregation of faunal assemblages along taphonomic and geographic lines—successfully defines palaeocommunities and identifies systematic variation in their distribution in several regional datasets and at the continental scale. It suggests that the potential viability of faunal analyses for a given project could be made empirically testable, and further work on the lines defined here might provide insight into the impacts of taphonomy and ecology at the large scale. Although there are conceptual and methodological problems associated with large‐scale faunal analyses, this paper suggests that they could provide some insight into hominin environments, evolutionary ecology and biogeography as part of a holistic, multi‐scale approach to our lineages' history. Copyright © 2010 John Wiley & Sons, Ltd.
  • Chapter
    A review of the middle Pleistocene vertebrate faunas of Africa is presented. After a summary of the climate and conditions prevalent during the middle Pleistocene, a regional approach is taken to the evidence, focusing in turn on northern Africa, eastern Africa, and southern Africa. Western Africa is not discussed due to the lack of faunal remains from the region. The changes in geographic range of some species and the composition of the evolving African fauna are emphasized, and modern African terrestrial faunas are shown to be archaic in comparison with those of Eurasia and the Americas.
  • Article
    The authors of this note met to discuss the chronology of certain Miocene biologic events and their implications concerning palaeogeographic reconstructions. Two topics in particular were examined. The first was that the collision of the Afro-Arabian Plate into mainland Asia appears to have had a gradual effect on the mammalian and marine faunas. The marine evidence suggests a progressive diminution in exchanges between the Mediterranean Sea and the Indian Ocean from the Chattian/Aquitanian boundary onwards (Adams et alii 1983) whereas the continental mammalian faunas do not indicate the occurrence of faunal interchanges prior to the Burdigalian. The period between 18 and 20 Ma seems to be the key moment for the establishment of intercontinental pathways permitting faunal exchanges between the two land masses. The second subject examined concerned the «Hippariondatum. Analysis of available geochronological evidence and biostratigraphical correlations do not confirm the date of 12.5 Ma attributed to the earliest known Mediterranean Hipparions. On the contrary, it seems that the radiometric dates obtained from tuffs at Höwenegg (Germany) and Bou Hanifia (Algeria) on which this early date was founded, are not closely associated with the fossils they purport to date. New radiometric dates allied with magneto- and biostratigraphy allow us to suggest an age about 11.5 Ma to the earliest records of Hipparion in Europe and North Africa.
  • Article
    The most diverse collection of fossil elephantoids from a single area, are contained in the 1-km-thick hominid-bearing Awash Group. These deposits range from late Miocene to Holocene in age and are found in the Awash Valley of the Afar Depression, Ethiopia. Uniquely, the Afar elephantoids inhabited a series of internal lake basins splayed out across an evolving, subaerial triple junction created by the separation of the African, East African and Arabian plates. The spatial and temporal distribution of elephantoids in these basins demonstrates that these animals were progressively drawn into the central Afar with the divergence of the three plates. As such, the elephantoids moved from the higher margins of the East African and African plates to the depressed lowlands of the triple junction, where subsiding and migrating lake basins served as ideal habitats for large herbivores with high water requirements. This pattern of migration serves as a model for the migration of animals into intercontinental areas and for their dispersal across plate boundaries.
  • Article
    Late Miocene to early Pliocene gomphothere proboscideans (Family Gomphotheriidae: Subfamily Anancinae) from the Middle Awash Valley, Ethiopia, were recovered throughout 350 m of strata, representing some 1½ to 2 my. Specimens referred to the genus Anancus from the Adu-Asa and Sagantole Formations are more complete and more extensive than any described previously from sub-Saharan Africa. Three evolutionary stages referable to A. kenyensis, as well as a much more derived new form of Anancus, are recognizable from dental remains.
  • Article
    Full-text available
    The tridactyl horse Hipparion (s.l.) has long attracted the attention of paleontologists and geologists alike for its potential use as a stratigraphic and paleoenvironmental index. A central dogma surrounding this horse's record is that it first occurred abruptly and instantaneously throughout the Old World ca. 12.5 Ma, heralding a general late Miocene environmental shift from forest to savanna ecosystems. We present data on the oldest known Central European hipparions, “Hipparion” primigenium (s.s.), that bear on these issues. Our analysis of the local Vienna Basin stratigraphie sequence and Paratethys geochronology suggests that hipparion's first provincial occurrence was ca. 11.0–11.5 Ma. We falsify the hypotheses of an Old World “Hipparion Datum” and the purported initial association of this horse with savanna habitats. An explicit cladistic analysis of “Hipparion” primigenium (s.s.), its North American sister taxon Cormohipparion occidentale, and several Old World primitive hipparions (“Group 1”) suggests that several distinct lineages may have been derived from “Hipparion” primigenium (s.s.). We attribute trans-Eurasian and North African speciation of “Group 1” horses to provincial environmental change which fragmented species ranges (environmental vicariance), and adaptations to newly emergent ecosystems.
  • Article
    Recent revalidation of the species Mammuthus rumanus influences several interrelated aspects of mammoth evolution. European material referred to M. rumanus might provide a useful background for the identification of finds from Africa and the Middle East. It seems plausible that M. rumanus originated in Africa c. 3.5 Ma and migrated to Eurasia via the Levant. While remaining poorly known, M. rumanus apparently played a significant role in the dispersal of mammoths to Eurasia, and any additional information on that species might elucidate problems of the earlier stages of mammoth evolution in Africa and their subsequent dispersal.
  • Article
    L'étude des restes de proboscidiens récoltés dans les sites à vertébrés du secteur fossilifère de Kollé (Nord Tchad) permet de définir un nouveau taxon d'Elephantidae. L'analyse des caractères et leur traitement cladistique permettent de placer ce taxon au voisinage des Stegotetrabelodontinae. Cette découverte montre, une fois de plus, la remarquable biodiversité des proboscidiens. L'association de proboscidiens récoltés à Kollé et leur degré évolutif dentaire permettent d'attribuer à ce secteur un âge biochronologique de la base du Pliocène.
  • Article
    As the most diverse collection of Elephantoidea from one area and a single stratigraphic sequence, fossils from the Middle Awash Valley, Ethiopia, add significantly to our current knowledge of the morphology and systematic phylogeny of late Neogene proboscideans. Abundant specimens of the late surviving “gomphothere” (in the informal sense), Anancus, reveal two species, an earlier more plesiomorphic form in our cladistic analysis and a later, more derived form. The former is tetralophodont on the M2 and is similar to the poorly preserved A. kenyensis from Kenya; also this earlier form is likely to be the immediate ancestor of a more derived tetralophodont Anancus from South Africa. In turn, these two species are clearly ancestral to pentalophodont sister taxa, one from North Africa (A. petrocchii) and a second from the Middle Awash. Both the South African and Ethiopian derived Anancus are apparently new species. All known African genera of the family Elephantidae are also present in the Middle Awash including the three “stegomorphs”, Stegotetrabelodon, Stegodibelodon and Stegodon, all of which form a monophyletic group with the subfamily, Elephantinae, comprising Primelephas, Loxodonta, Mammuthus, and Elephas. In our cladistic analysis, the stegomorphs form a series of paraphyletic taxa that are clearly plesiomorphic to the more widely known elephantines. Finally, the abundant Middle Awash elephants add to our belief that the loxodonts and the remaining elephants (Primelephas, Mammuthus, Elephas) form separate clades that are sister groups to one another.
  • Article
    The period from 14 to four million years is poorly known in Africa, but during this time the Ethiopian fauna became established and hominids originated. The sedimentary sequence of the Tugen Hills in the Baringo area of Kenya provides important geological, environmental and plaeontological data concerning this interval. Concordant radiometric and palaeomagnetic determinations within the type section of the Ngorora Formation show that it spans more than 2 m.y., from 13 m.y.a. to less than 10 m.y.a., and from chrons 14 to 9. Other dates refine the calibration of the Younger Mpcsida, Lukeino and Chemeron units. Palaeontological results include the collection from the Ngorora Formation of one of the best Neogene macrofloras in Africa, and more fauna, including hominoids. No equids have been recorded older than 10 m.y.a. We also report new fauna from the more recent units.
  • Article
    In the Djurab Desert (Chad), the fossiliferous sectors of Kossom Bougoudi, Kollé and Koro Toro have yielded a great amount of fossil hippo remains aged between ca. 5 and 3 Ma. Hippos from the first two areas represent a distinct lineage evolving in Chad during the early Pliocene. Indeed, a new species from Kollé is described (Hexaprotodon mingoz sp. nov.) and the Kossom Bougoudi fossils may constitute its ancestral stem. At Koro Toro, a different but very rare form occurs, and its affinities remain unclear. These hippopotamids testify to a more complex family history than previously recognized, and reinforce the idea of using this group for biochronology. The hippos underscore relative endemism of the Chadian fossil faunas and would indicate a greater and earlier aridity of this region in contrast to East Africa.
  • Article
    The origin of the African hominoid clade is a matter of current debate, with one hypothesis proposing that chimpanzees, humans, and gorillas originated in tropical Africa, while another suggests they originated in Eurasia. Support for the latter hypothesis includes biogeographical patterns inferred from the fossil record and proposed Miocene hominoid phylogenetic relationships. The absence of fossil apes from the African Late Miocene has been used as evidence that crown hominoids were not present in Africa during this period. An alternative explanation for the paucity of these hominoids is that biases in collection and preservation have affected the African Miocene fossil record. A survey of currently known African Later Miocene sites and their faunas shows that these sites generally do not contain hominoids because of small sample sizes, poor preservation, or inappropriate habitat sampling. These preservation biases have important implications for evaluating the origins of the Homininae. To cite this article: S.M. Cote, C. R. Palevol 3 (2004).
  • Article
    New fossil remains of the proboscidean genus Anancus are described. Among them, a complete skull allows us to revisit for the first time the entire Chadian Anancus fossil record. This genus occurred in the Old World from the late Miocene up to the early Pleistocene. The analysis of dental and cranial characters was allowed individual variations from specific characters to be distinguished. In this study we show that Anancus kenyensis and Anancus osiris are very likely synonym taxa which leads us to emend the diagnosis of A. kenyensis. In addition, this study shows that dental characters in anancines lineage are of little significance for biostratigraphical inference, by contrast to previous works. This study brings new data about the phylogenetical and palaeobiogeographical history of the African anancines.
  • Article
    The study of the cheek teeth of the proboscidean species Anancus arvernensis from the early Pliocene of Dorkovo (Bulgaria) shows an important intraspecific variation. Different dental morphs are described and a method for quantifying the complexity of the molars is suggested. A short review of the dental criteria used by different authors in their study of earlier or contemporaneous African species is given. It leads to question the biostratigraphic value of what is sometimes conceived as “evolutionary stages”. On the basis of the study of the molars from Dorkovo, one emphasizes the necessary consideration for statistic variations in important samples, so that the biostratigraphic distribution of morphs can be evaluated.
  • Article
    New observations on the Late Miocene and Earliest Pliocene mustelids from the Middle Awash of Ethiopia are presented. The Middle Awash study area samples the last six million years of African vertebrate evolutionary history. Its Latest Miocene (Asa Koma Member of the Adu-Asa Formation, 5.54–5.77Ma) and Earliest Pliocene (Kuseralee and Gawto Members of the Sagantole Formation, 5.2 and 4.85Ma, respectively) deposits sample a number of large and small carnivore taxa among which mustelids are numerically abundant. Among the known Late Miocene and Early Pliocene mustelid genera, the Middle Awash Late Miocene documents the earliest Mellivora in eastern Africa and its likely first appearance in Africa, a new species of Plesiogulo, and a species of Vishnuonyx. The latter possibly represents the last appearance of this genus in Africa. Torolutra ougandensis is known from both the Late Miocene and Early Pliocene deposits of the Middle Awash. The genus Sivaonyx is represented by at least two species: S. ekecaman and S. aff. S. soriae. Most of the lutrine genera documented in the Middle Awash Late Miocene/Early Pliocene are also documented in contemporaneous sites of eastern Africa. The new observations presented here show that mustelids were more diverse in the Middle Awash Late Miocene and Early Pliocene than previously documented.
  • Article
    Full-text available
    The Middle Awash palaeontological study area in Ethiopia is widely known for the recovery of abundant faunal remains including the recently discovered hominid Ardipithecus ramidus. In this paper, we describe eleven new fossil wood specimens from three distinct units of the Pliocene Sagantole Formation. The anatomical (xylotomical) characters of the silicified woods were studied using thinsections. The material has been assigned to five species of five genera and five (botanical) families. These species are Anogeissus cf. leiocarpus (Combretaceae) and Vitex cf. simplicifolia (Verbenaceae) from the Haradaso Member (4.85 Ma), Syzygium cf. guineense (Myrtaceae) from the Aramis Member (4.4 Ma), Ficus sp. (Moraceae) and Rothmannia cf. whitfieldii (Rubiaceae) from the Adgantole Member (4.3 Ma). Our comparison of the Middle Awash wood with the fossil record is mainly focused on African records and their stratigraphic and palaeogeographic data. The distribution of the respective nearest living relative species provides remarkable palaeoenvironmental information. Ficus sp. and Rothmannia whitfieldii have modern representatives in the riparian forest along the Awash River. Anogeissus leiocarpus, Vitex simplicifolia, and Syzygium guineense are not present in the present-day steppic vegetation at low elevations but can be found in different forests on the Ethiopian plateaux. They indicate wetter palaeoclimatic conditions at the Middle Awash area during the lower Pliocene. ©2012 E. Schweizerbartsche Verlagsbuchhandlung, Stuttgart, Germany.
  • Chapter
    Comparisons of the Manonga Valley faunas with those from other East African localities for which radiometric dates have been obtained allow the Manonga Valley sequence to be placed within a broader chronological framework. The results of a biochronological analysis produce consistent estimates of the age range of the sequence, and indicate that the fossiliferous sediments were laid down during the late Miocene and early Pliocene. Nevertheless, it should be noted that there are several constraining factors that limit the degree of precision of such correlations, as follows: (1) There are few late Miocene and early Pliocene sites that have been dated radiometrically, and these are restricted geographically to the East African Rift valley (i.e., the Turkana basin, the Baringo basin, the Samburu Hills, and the Middle Awash Valley); (2) with the exception of Lotha-gam in northern Kenya and Langebaanweg in South Africa, the mammalian faunas from this time period are either poorly known or have not been the subject of detailed study; and (3) few researchers have made detailed firsthand comparisons between late Miocene and early Pliocene faunas from fossil localities in North, East, and South Africa.
  • Article
    A new species of Hippopotamidae, Hexaprotodon dulu nov. sp., was discovered in the Middle Awash valley, Afar, Ethiopia. It was found in the Sagantole Formation, within volcaniclastic beds aged between 5.2 Ma and 4.9 Ma (40Ar/39Ar). It is therefore the oldest hippo species described as yet from Ethiopia. This hexaprotodont hippo exhibits a general morphology that is primitive, close in that respect to other Mio-Pliocene forms. However, its cranium and dentition display a distinctive association of measurements and features. This new species increases the hippo fossil record in East Africa. It also reinforces the hypothesis of hippo endemism in each African basin as early as the basal Pliocene.
  • Chapter
    Old World monkeys are some of the most common and visible components of the modern mammalian fauna of Africa, and are the dominant nonhuman primates in Africa today with respect to the overall numbers of species present and the number of ecological zones inhabited. What is rarely appreciated is that Old World monkeys have risen to a position of ecological dominance among primates only recently in geological time. During the early and middle Miocene, the Cercopithecoidea were well established in Africa, but not taxonomically diverse. The absence or near absence of monkey fossils from prolific early Miocene sites like Rusinga Island suggests that the animals were genuinely rare elements of the mammalian fauna at the time. The earliest African cercopithecoids belong to the Victoriapithecidae, an extinct family from the early to middle Miocene of eastern Africa that exhibit a mosaic of basal catarrhine and modern Old World monkeylike morphological features. This chapter describes the systematic paleontology of Cercopithecoidea.