Reconstruction of the Early Miocene Critical Zone at Loperot, Southwestern Turkana, Kenya (original) (raw)
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The Kaswanga primate site: An Early Miocene hominoid site on Rusinga Island, Kenya
Journal of Human Evolution, 1988
In 1984 a joint National Museums of Kenya-Johns Hopkins University party began studies on the isolated and unusual site known as R114 or "Whitworth's Pot-hole" at the northwest extremity of Rusinga Island, western Kenya, from which the partial skeleton of Proconsul africanus, KNM-RU 2036 was recovered in 195 1 (Napier & Davis, 1959; Walker & Pickford, 1983). We have published a brief note on the geology and taphonomy of the site and the recovery of additional bones from the skeleton (Walker et al., 1986). Here, we give a preliminary account of remarkably complete remains from several Proconsul individuals found together at site R5 on Kaswanga Point, 3 km east of R114.
Frontiers in Earth Science, 2017
Early Miocene outcrops near Karungu, Western Kenya, preserve a range of fluvio-lacustrine, lowland landscapes that contain abundant fossils of terrestrial and aquatic vertebrates. Primates are notably rare among these remains, although nearby early Miocene strata on Rusinga Island contain a rich assemblage of fossilized catarrhines and strepsirrhines. To explore possible environmental controls on the occurrence of early Miocene primates, we performed a deep-time Critical Zone (DTCZ) reconstruction focused on floodplain paleosols at the Ngira locality in Karungu. We specifically focused on a single stratigraphic unit (NG15), which preserves moderately developed paleosols that contain a microvertebrate fossil assemblage. Although similarities between deposits at Karungu and Rusinga Island are commonly assumed, physical sedimentary processes, vegetative cover, soil hydrology, and some aspects of climate state are notably different between the two areas. Estimates of paleoclimate parameters using paleosol B horizon elemental chemistry and morphologic properties are consistent with seasonal, dry subhumid conditions, occasional waterlogging, and herbaceous vegetation. The reconstructed small mammal community indicates periodic waterlogging and open-canopy conditions. Based on the presence of herbaceous root traces, abundant microcharcoal, and pedogenic carbonates with high stable carbon isotope ratios, we interpret NG15 to have formed under a warm, seasonally dry, open riparian woodland to wooded grassland, in which at least a subset of the vegetation was likely C 4 biomass. Our results, coupled with previous paleoenvironmental interpretations for deposits on Rusinga Island, demonstrate that there was considerable environmental heterogeneity ranging from open to closed habitats in the early Miocene. We hypothesize that the relative paucity of primates at Karungu was driven by their environmental preference for locally abundant closed canopy vegetation, which was likely absent at Karungu, at least during the NG15 interval if not also earlier and later intervals that have not yet been studied in as much detail.
The Colobinae (Mammalia: Primates) are relatively unknown from the middle to late Miocene of eastern Africa. When they appear in the Pliocene fossil record they are unambiguous and fairly diverse taxonomically, geographically, and ecologically. The primate fauna from the late Miocene of Lemudong'o is dominated by colobines and therefore represents one of the richest fossil assemblages yet published of this subfamily at 6 Ma. At least three species of colobine, including a new species of Paracolobus, are represented in this collection. Given the paleoecological reconstruction for Lemudong'o Locality 1, and the postcranial morphology of the cercopithecids, colobines in this area of Africa were occupying a relatively closed or forested habitat, and exhibiting a primarily arboreal habitus, which contrasts with previous hypotheses suggesting that colobines prior to the Pliocene were terrestrial and occupying more open habitats.
Anthropological Science, 2005
One of the major lacunae in our knowledge of African hominoid evolution concerns the origins of the chimpanzee and gorilla. Several thousand specimens from the Plio-Pleistocene of Africa have been attributed to Hominidae (sensu stricto) of which only a few, including Ardipithecus ramidus, have been re-interpreted by some authors as possibly representing an ape rather than a hominid (Senut, 1998). Four recently discovered ape-like specimens from the late Middle Miocene (12.5 Ma) and Late Miocene (5.9 Ma) of Kenya partly fill the gap in the fossil record of African apes, and show some morphological and metric affinities with teeth of chimpanzees and gorillas. If these few specimens from Kenya are indeed more closely related to chimps and gorillas than to hominids, then this implies that the dichotomy between African apes and hominids occurred several million years earlier than is currently estimated by most researchers. Furthermore these ape teeth from Ngorora and Lukeino suggest that extant African apes evolved in Africa, and did not immigrate into the continent from Europe or Asia.
Hominoid primates from a new Miocene locality named Meswa Bridge in Kenya
Journal of Human Evolution, 1981
The remains of a species of Proconsul from early Miocene deposits at Meswa Bridge are described. Associated dental, mandibular, maxillary and cranial specimens represent several immature individuals. They are equivalent in size to Proconsul nyanzae but differ morphologically, particularly in the greater breadth and degree of flare of the deciduous and permanent molars, but lack of adult individuals from Meswa Bridge makes it difficult to compare them adequately with existing species. They are therefore left unassigned as an indeterminate species of Proconsul.
New Fauna from Loperot Contributes to the Understanding of Early Miocene Catarrhine Communities
International Journal of Primatology
The site of Loperot in West Turkana, Kenya, is usually assigned to the Early Miocene. Recent discoveries at Loperot, including catarrhine primates, led to a revision of its mammalian fauna. Our revision of the fauna at Loperot shows an unusual taxonomic composition of the catarrhine community as well as several other unique mammalian taxa. Loperot shares two non-cercopithecoid catarrhine taxa with Early Miocene sites near Lake Victoria, e.g., Songhor and the Hiwegi Formation of Rusinga Island, but Loperot shares a cercopithecoid, Noropithecus, with Buluk (Surgei Plateau, near Lake Chew Bahir). We use Simpson's Faunal Resemblance Index (Simpson's FRI), a cluster analysis, and two partial Mantel tests, to compare Loperot to 10 other localities in East Africa representing several time divisions within the Early and Middle Miocene. Simpson's FRI of mammalian communities indicates that Loperot is most similar in its taxonomic composition to the Hiwegi Formation of Rusinga Island, suggesting a similarity in age (≥18 Ma) that implies that Loperot is geographically distant from its contemporaries, i.e., Hiwegi Formation of Rusinga Island, Koru,
New information about African late middle Miocene to latest Miocene (13-5.5 Ma) Hominoidea
HAL (Le Centre pour la Communication Scientifique Directe), 2022
In Africa, relatively few hominoid fossils are known from the late middle Miocene and late Miocene periods corresponding to the time span 13-5.5 million years ago, compared to the preceding and subsequent periods from which several thousand specimens have been reported from many different localities. In Eurasia, in contrast, many hominoid fossils are known from the Late Miocene period from diverse localities scattered from Spain in the west to China in the East. The scarcity of hominoid fossils from this period in Africa lent support to the hypothesis that the ancestors of extant African Apes and hominids may have evolved in Eurasia and then dispersed to Africa during the late Miocene where they gave rise to the extant Gorilla, Pan and Homo lineages. We herein document additional hominoid fossils from Berg Aukas, Namibia, aged ca 12-13 Ma, and rectify the locality data concerning the Niger proto-chimpanzee fossil. The new data indicate that Africa was not devoid of hominoids during the period under discussion, and they support the hypothesis that the extant African Apes and hominids may have evolved autochthonously within the continent.
Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes
Nature, 2013
Apes and Old World monkeys are prominent components of modern African and Asian ecosystems, yet the earliest phases of their evolutionary history have remained largely undocumented 1. The absence of crown catarrhine fossils older than 20 million years (Myr) has stood in stark contrast to molecular divergence estimates of 25-30 Myr for the split between Cercopithecoidea (Old World monkeys) and Hominoidea (apes), implying long ghost lineages for both clades 2-4 .Here we describe the oldest known fossil 'ape', represented by a partial mandible preserving dental features that place it with 'nyanzapithecine' stem hominoids. Additionally, we report the oldest stem member of the Old World monkey clade, represented by a lower third molar. Both specimens were recovered from a precisely dated 25.2-Myr-old stratum in the Rukwa Rift, a segment of the western Branch of the East African Rift in Tanzania. These finds extend the fossil record of apes and Old World monkeys well into the Oligocene epoch of Africa, suggesting a possible link between diversification of crown catarrhines and changes in the African landscape brought about by previously unrecognized tectonic activity 5 in the East African rift system.