Miocene Of Kenya Research Articles

Ecometric models of small mammal hypsodonty can estimate paleoprecipitation across eastern Africa

Ecometric analyses use the relationships between functional traits and the environment at the community level to quantitatively estimate past climatic and environmental variables at fossil sites. Hypsodonty (tooth crown height) in North American rodent and lagomorph (Glires) communities is correlated with mean annual temperature and annual precipitation. Here, we examine the community hypsodonty of African Glires to test if this relationship translates to a continent with more extreme climates and to quantify paleoprecipitation at important fossil sites. Categorical hypsodonty values were gathered from the literature and museum collections for 94 modern African taxa (88%). We used maximum likelihood to model the ecometric relationship between hypsodonty and annual precipitation. We then produced trait-based estimates of paleoprecipitation for 26 well-sampled fossil localities from eastern Africa over the last 5.7 Ma. We confirmed other regional studies by identifying increasing aridity and decreasing annual precipitation (824 mm to 480 mm) in the Late Miocene of Kenya. From the Ethiopian Shungura Formation, we estimated temporal fluctuations in precipitation that correspond with the presence or absence of paleolakes and rivers. Small mammal community hypsodonty illustrates that east African communities have converged towards mesodont means and high standard deviations in response to climate change.

Osteology of Crocodylus palaeindicus from the late Miocene–Pleistocene of South Asia and the phylogenetic relationships of crocodyloids

Fossil crocodylian remains have been documented from India and other parts of South Asia since the mid-nineteenth century, but specimens attributed to several extinct and extant species of Crocodylus have largely been neglected in modern taxonomic treatments. Here, we present a detailed anatomical description of the extinct species Crocodylus palaeindicus, which we restrict to the late Miocene to early middle Pleistocene of India. Using an autapomorphy-based approach to species-level identification, we regard Crocodylus sivalensis as a junior synonym of C. palaeindicus and provide taxonomic re-identifications of all specimens previously referred to these two species. We present a new diagnosis for C. palaeindicus that facilitates its distinction from the extant mugger crocodile, C. palustris, which does not unequivocally appear in the fossil record prior to the Pleistocene. The lack of clear spatiotemporal overlap, coupled with the otherwise lengthy ghost lineage implied by their sister-taxon relationship in our phylogenetic analyses, provides tentative support that the extant species either is the descendant of C. palaeindicus or originated via budding cladogenesis. An expanded phylogenetic analysis recovers the late Miocene African C. checchiai and Pliocene South American C. falconensis as species within the Neotropical Crocodylus clade, supporting an African origin for this radiation. We also recover Kinyang, from the early–middle Miocene of Kenya, as a crocodyline, rather than an osteolaemine as originally described, and it is potentially the stratigraphically earliest known member of the Crocodylus lineage. Other notable results from our phylogenetic analyses suggest that crocodyloids might not have been present in North America prior to the late Neogene arrival of Crocodylus, with Albertosuchus knudsenii, Prodiplocynodon langi and ‘Crocodylus’ affinis all recovered outside of Crocodyloidea. Furthermore, we demonstrate that an alligatoroid placement for the recently erected latest Cretaceous–Palaeogene East Asian clade Orientalosuchina is highly labile, with relationships at the ‘base’ of Crocodylia unstable.

Giant dwarf crocodiles from the Miocene of Kenya and crocodylid faunal dynamics in the late Cenozoic of East Africa.

We describe two new osteolaemine crocodylids from the Early and early Middle Miocene of Kenya: Kinyang mabokoensis tax. nov. (Maboko, 15 Ma) and Kinyang tchernovi tax. nov. (Karungu and Loperot, 18 Ma). Additional material referable to Kinyang is known from Chianda and Moruorot. The skull was broad and dorsoventrally deep, and the genus can be diagnosed based on the combined presence of a partial overbite, a subdivided fossa for the lateral collateral ligament on the surangular, and a maxilla with no more than 13 alveoli. Phylogenetic analyses based on morphological and combined morphological and molecular data support a referral of Kinyang to Osteolaeminae, and morphological data alone put the new taxon at the base of Euthecodontini. Some Kinyang maxillae preserve blind pits on the medial caviconchal recess wall. Kinyang co‐occurs with the osteolaemine Brochuchus at some localities, and together, they reinforce the phylogenetic disparity between early Neogene osteolaemine‐dominated faunas and faunas dominated by crocodylines beginning in the Late Miocene in the Kenya Rift. The causes of this turnover remain unclear, though changes in prevailing vegetation resulting from tectonic and climatic drivers may provide a partial explanation.

A NEW LAGOMORPH FROM THE LATE MIOCENE OF CHAD (CENTRAL AFRICA)

A new species of the genus Serengetilagus, here named S. tchadensis n. sp., is described from Toros Menalla deposits, Late Miocene of Djurab Erg (North Chad, central Africa). It shows primitive features, such as a simple archaeolagine-type p3, with only two main external folds, and upper cheek teeth strongly widened with wear. Its size and skeletal features resemble S. praecapensis from the Middle Pliocene of Laetoli (Tanzania). They differ in several cranial and dental features (choanae width, zygoma, orbits, basicranial-basifacial angle, lack of hypoflexus in P2, short and asymmetric hypoflexus in P3-M2, lack of lingual folds in p3, etc). Individual variations in S. tchadensis n. sp. approach S. praecapensis. The genus Serengetilagus is here assigned to the subfamily Archaeolaginae and related to Hypolagus, namely to H. gromovi from the Late Miocene of Southern Russia. Other related species are Serengetilagus orientieuropaeus and primitive species of the genus Trischizolagus, such as T. maritsae and T. crusafonti. Pliocene leporids from Spain, Ukraine, Russia, Afghanistan and Mongolia have been questionably attributed to Serengetilagus or Trischizolagus. Several features are here proposed to distinguish both genera.Serengetilagus could have a mixed fossorial-cursorial mode of life, as can be inferred by its ecomorphological traits (combining features of hare and rabbit) and taphonomical indications. This new African archaeolagine is contemporaneous of the widespread palaeolagine Alilepus, recorded in the Late Miocene of Kenya. The independence of these two lineages is favoured after revision of previous hypotheses on the phylogeny of the highly diverse Mio-Pliocene peri-Tethysian leporid species.

Ruminant mesowear reveals consistently browse-dominated diets throughout the early and middle Miocene of eastern Africa

The ecological preferences of ruminant artiodactyls are commonly used to reconstruct the paleoenvironment of Neogene fossil localities throughout Africa. However, comparatively little research has focused on the ecology of ruminant artiodactyls from the Miocene of Africa. Here, we contribute new molar mesowear and hypsodonty data for the ruminant artiodactyls from the early and middle Miocene of Kenya and Uganda. Macroscopic dental characteristics of 608 tragulids, stem pecorans, giraffoids, and bovids dated to between 20 and 13.7 Ma were analyzed. Our hypsodonty results reveal that, whereas tragulids remain brachydont throughout the early and middle Miocene, pecoran ruminants experience an increase in hypsodonty due to the appearance of high-crowned bovids and climacoceratids that migrate into eastern Africa in the middle Miocene. Results from dental mesowear analysis suggest that all tragulids and pecorans were likely browsers, with only one taxon showing mesowear values that overlap with both browsers and mixed feeders in both the upper and lower molars (Canthumeryx sirtensis). None of the taxa analyzed had mesowear scores indicative of a grazing diet. Surprisingly, middle Miocene bovids and climacoceratids, despite possessing gross tooth morphologies adapted to abrasive diets, were largely utilizing a browsing diet. Although the early and middle Miocene habitats of eastern Africa were likely very heterogenous, none of the ruminant artiodactyls present in these habitats is interpreted as having incorporated grasses into their diet in significant quantities.

A new crocodylid from the middle Miocene of Kenya and the timing of crocodylian faunal change in the late Cenozoic of Africa

AbstractBrochuchusis a small crocodylid originally based on specimens from the early Miocene of Rusinga Island, Lake Victoria, Kenya. Here, we report occurrences ofBrochuchusfrom several early and middle Miocene sites. Some are from the Lake Victoria region, and others are in the Lake Turkana Basin. Specimens from the middle Miocene Maboko locality form the basis of a new species,Brochuchus parvidens, which has comparatively smaller maxillary alveoli. Because of the smaller alveoli, the teeth appear to be more widely spaced in the new species. We also provide a revised diagnosis forBrochuchusand its type species,B.pigotti. A phylogenetic analysis supports a close relationship betweenBrochuchusand tube-snoutedEuthecodon, but although relationships among crocodylids appear poorly resolved in the set of optimal trees, this is becauseBrochuchusandEuthecodon, along with early Miocene “Crocodylus”gariepensisfrom the early Miocene of Namibia, jointly adopt two distinct positions—either closely related to the living sharp-nosed crocodile (Mecistops) or to a group including the living dwarf crocodiles (Osteolaemus). Character support for a close relationship withMecistopsis problematic, and we suspect a closer relationship toOsteolaemuswill be recovered with improved sampling, but the results here are ambiguous. In either case,Brochuchusis more closely related to living groups not currently found in East Africa. This material helps constrain the timing of crocodylian faunal turnover in the East African Rift Valley System, with endemic lineages largely being replaced byCrocodylusin the middle or late Miocene possibly in response to regional xerification and the replacement of continuous rainforest cover with open grasslands and savannas.UUID:http://zoobank.org/e6f0b219-5f3e-44e5-bdb9-60a4fae8d126

New insights into the giant mustelids (Mammalia, Carnivora, Mustelidae) from Langebaanweg fossil site (West Coast Fossil Park, South Africa, early Pliocene).

Giant mustelids are a paraphyletic group of mustelids found in the Neogene of Eurasia, Africa and North America. Most are known largely from dental remains, with their postcranial skeleton mostly unknown. Here, we describe new craniodental and postcranial remains of the large lutrine Sivaonyx hendeyi and the leopard-size gulonine Plesiogulo aff. monspessulanus from the early Pliocene site Langebaanweg, South Africa. The new material of the endemic S. hendeyi, includes upper incisors and premolars, and fragmentary humerus, ulna and a complete astragalus. Its postcrania shares more traits with the living Aonyx capensis than the late Miocene Sivaonyx beyi from Chad. Sivaonyx hendeyi could therefore be tentatively interpreted as a relatively more aquatic taxon than the Chadian species, comparable to A. capensis. The new specimens of Plesiogulo comprise two edentulous maxillae, including one of a juvenile individual with incomplete decidual dentition, and a fragmentary forelimb of an adult individual. The new dental measurements point to this form being amongst the largest specimens of the genus. Both P3-4 differs from the very large species Plesiogulo botori from late Miocene of Kenya and Ethiopia. This confirms the existence of two distinct large species of Plesiogulo in Africa during the Mio/Pliocene, P. botori in the Late Miocene of Eastern Africa (6.1–5.5 Ma) and Plesiogulo aff. monspessulanus at the beginning of the Pliocene in southern Africa (5.2 Ma). Lastly, we report for the first time the presence of both Sivaonyx and Plesiogulo in MPPM and LQSM at Langebaanweg, suggesting that the differences observed from the locality may be produced by sedimentation or sampling biases instead of temporal replacement within the carnivoran guild.

Primitive Old World monkey from the earliest Miocene of Kenya and the evolution of cercopithecoid bilophodonty

Old World monkeys (Cercopithecoidea) are a highly successful primate radiation, with more than 130 living species and the broadest geographic range of any extant group except humans. Although cercopithecoids are highly variable in habitat use, social behavior, and diet, a signature dental feature unites all of its extant members: bilophodonty (bi: two, loph: crest, dont: tooth), or the presence of two cross-lophs on the molars. This feature offers an adaptable Bauplan that, with small changes to its individual components, permits its members to process vastly different kinds of food. Old World monkeys diverged from apes perhaps 30 million years ago (Ma) according to molecular estimates, and the molar lophs are sometimes incompletely developed in fossil species, suggesting a mosaic origin for this key adaptation. However, critical aspects of the group's earliest evolution remain unknown because the cercopithecoid fossil record before ∼18 Ma consists of only two isolated teeth, one from Uganda and one from Tanzania. Here we describe a primitive Old World monkey from Nakwai, Kenya, dated at ∼22 Ma, that offers direct evidence for the initial key steps in the evolution of the cercopithecoid dentition. The simple dentition and absence of bilophodonty in the Nakwai monkey indicate that the initial radiation of Old World monkeys was first characterized by a reorganization of basic molar morphology, and a reliance on cusps rather than lophs suggests frugivorous diets and perhaps hard object feeding. Bilophodonty evolved later, likely in response to the inclusion of leaves in the diet.

A new Elasmotheriini (Perissodactyla, Rhinocerotidae) from the upper Miocene of Samburu Hills and Nakali, northern Kenya

Several rhinocerotid cheek teeth and mandibular fragments from the upper Miocene of the Samburu Hills and Nakali in northern Kenya are described. These specimens show characteristics that place them in the Tribe Elasmotheriini such as a constricted protocone, a developed antecrochet, and coronal cement. The present specimens are compared with other Elasmotheriini species from Eurasia and sub-Saharan East Africa. They are found to be morphologically different from the previously known species of Elasmotheriini. Morphologically, they are most similar to Victoriaceros kenyensis from the middle Miocene of Kenya, but differ from V. kenyensis in having the upper molars with the simple crochet, lingual groove of the protocone and enamel ring in the medisinus. Therefore, the present specimens are assigned to a new genus and species of Elasmotheriini: Samburuceros ishidai. A cladistic analysis tentatively places S. ishidai nov. gen., nov. sp. as a sister taxon of V. kenyensis. However, questions remain regarding a further detailed discussion of the phylogenetic relationship between the African Elasmotheriini and other Eurasian taxa because of the incompleteness of the specimens from Africa, as already noticed by several researchers.

X-rays and virtual taphonomy resolve the first Cissus (Vitaceae) macrofossils from Africa as early-diverging members of the genus.

Fossilized seeds similar to Cissus (Vitaceae) have been recognized from the Miocene of Kenya, though some were previously assigned to the Menispermaceae. We undertook a comparative survey of extant African Cissus seeds to identify the fossils and consider their implications for the evolution and biogeography of Cissus and for African early Miocene paleoenvironments. Micro-computed tomography (µCT) and synchrotron-based X-ray tomographic microscopy (SRXTM) were used to study seed morphology and anatomy. Virtual taphonomy, using SRXTM data sets, produced digital fossils to elucidate seed taphonomy. Phylogenetic relationships within Cissus were reconstructed using existing and newly produced DNA sequences for African species. Paleobiology and paleoecology were inferred from African nearest living relatives. The fossils were assigned to four new Cissus species, related to four modern clades. The fossil plants were interpreted as climbers inhabiting a mosaic of riverine woodland and forest to more open habitats. Virtual taphonomy explained how complex mineral infill processes concealed key seed features, causing the previous taxonomic misidentification. Newly sampled African species, with seeds most similar to the fossils, belong to four clades within core Cissus, two of which are early diverging. Virtual taphonomy, combined with X-ray imaging, has enabled recognition of the first fossil Cissus and Vitaceae from Africa. Early-divergent members of the core Cissus clade were present in Africa by at least the early Miocene, with an African origin suggested for the Cissus sciaphila clade. The fossils provide supporting evidence for mosaic paleoenvironments inhabited by early Miocene hominoids.

A Lower Molar of a Primitive, Large Hippopotamus from the Lower Miocene of Kenya

Abstract. A trigonid of a lower molar of a primitive, large hippopotamus from the upper lower Miocene of Mfwangano Island in southwestern Kenya is described. The molar trigonid is similar in size to that of living hippopotamuses, and is comparable in morphology to that of kenyapotamine hippopotamids (Mammalia, Cetartiodactyla) in having a brachyodont crown, bunodont cusps, an M-like structure on the distal trigonid wall, a single-ridged premetacristid, and a buccolingually bifurcate mesial root, and in lacking a paraconid. On the basis of its size and morphology, the specimen appears to be assignable to Kulutherium, which is a putative kenyapotamine previously known from the upper lower Miocene of Kenya and is so far represented only by the upper dentition. The present specimen provides additional evidence that a hippopotamus-sized, large hippopotamid was already living during the early Miocene. If it proves to be Kulutherium, it provides additional evidence that Kulutherium should be assigned to the Keny...

Dental microwear profilometry of African non-cercopithecoid catarrhines of the Early Miocene

The Early Miocene of Kenya has yielded the remains of many important stem catarrhine species that provide a glimpse of the East African primate radiation at a time of major faunal turnover. These taxa have been subject to innumerable studies, yet there is still no consensus on their dietary niches. Here we report results of an analysis of dental microwear textures of non-cercopithecoid catarrhines from the Early Miocene of Kenya. Scanning confocal profilometry of all available molar specimens with undamaged occlusal surfaces revealed 82 individuals with unobscured antemortem microwear, representing Dendropithecus, Micropithecus, Limnopithecus, Proconsul, and Rangwapithecus. Scale-sensitive fractal analysis was used to generate microwear texture attributes for each individual, and the fossil taxa were compared with each other using conservative non-parametric statistical tests. This study revealed no discernible variation in microwear texture among the fossil taxa, which is consistent with results from a previous feature-based microwear study using smaller samples. Our results suggest that, despite their morphological differences, these taxa likely often consumed foods with similar abrasive and fracture properties. However, statistical analyses of microwear texture data indicate differences between the Miocene fossil sample and several extant anthropoid primate genera. This suggests that the African non-cercopithecoid catarrhines included in our study, despite variations in tooth form, had generalist diets that were not yet specialized to the degree of many modern taxa.

A hoatzin fossil from the middle Miocene of Kenya documents the past occurrence of modern-type Opisthocomiformes in Africa

ABSTRACT The fossil bird Namibiavis senutae from the early Miocene of Namibia was recently identified as an African stem-group representative of Opisthocomiformes (hoatzins). The species is known only from two wing and pectoral girdle bones, however, and the extent to which African Opisthocomiformes resembled their Neotropical relatives in skeletal morphology has remained elusive. I report a hoatzin tarsometatarsus from the middle Miocene of Maboko Island in Kenya, which, except for a peculiar autapomorphic fusion of the first metatarsal, closely matches the tarsometatarsus of the extant Opisthocomus hoazin. Although a well-founded classification on the species level is not possible, the new fossil documents the existence of essentially modern-type Opisthocomiformes in the Miocene of Africa. Being 2–2.5 Ma younger than N. senutae, the specimen further extends the temporal and spatial range of Miocene African Opisthocomiformes.

Lorisine Primate from the Late Miocene of Kenya

The origin of African Lorisidae has been the subject of debate for the past half century, so far without resolution. The matter is complecated by the fact that strepsirrhines (Lorisiformes = Lorisidae + Galagidae) are rare in the African fossil record, with large gaps between occurrences in the Early Oligocene Fayum (Egypy) deposit, the Early Miocene strata of East Africa and the Plio-Pleistocene of the same region. Likewise, the Asian fossil record of this group is spotty, with only a few specimens described from the Late Miocene of Pakistan. In the search for evidence concerning the dichotomy between Lorisidae and Galagidae, authors have tended to focus on the Early Miocene fossils from Kenya and Uganda which is the only region to have yielded a reasonable diversity of forms. Unfortunately, the history of study has been marred by the description and interpretation of non-primate material as strepsirrhines (Lorisiformes spurii). This contrasts with the genuine strepsirrhine (Lorisiformes veri) fossil from the same region which have thrown much light on the group, but which have not yet resolved the issue of the timing or the modality of the dichotomy between the two families. At present, among the described African fossil lorisiformes only the genus Mioeuoticus is accepted by some, but not all, authors (Harrison, 2010) as a Lorisidae (or Lorisinae, all the others generally being classed as Galagidae (or Galginae) Walker (1987). It is thus of interest to put on record the discovery of a lorisid anout from the Late Miocene deposits of the Tugen Hills, Kenya, which is close in dimensions and some aspects of the Far East (Nycticebus, Nycticeboides) and West Africa (Arctocebus). The fossil does not particularly resemble any of the Early Miocene forms described from East Africa, and it is suggested that the lineage entered Africa during the Late Miocene at the same time that several other vertebrate groups spread into the continent from South-East Asia.

Lorisine Primate from the Late Miocene of Kenya

The origin of African Lorisidae has been the subject of debate for the past half century, so far without resolution. The matter is complecated by the fact that strepsirrhines (Lorisiformes = Lorisidae + Galagidae) are rare in the African fossil record, with large gaps between occurrences in the Early Oligocene Fayum (Egypy) deposit, the Early Miocene strata of East Africa and the Plio-Pleistocene of the same region. Likewise, the Asian fossil record of this group is spotty, with only a few specimens described from the Late Miocene of Pakistan. In the search for evidence concerning the dichotomy between Lorisidae and Galagidae, authors have tended to focus on the Early Miocene fossils from Kenya and Uganda which is the only region to have yielded a reasonable diversity of forms. Unfortunately, the history of study has been marred by the description and interpretation of non-primate material as strepsirrhines (Lorisiformes spurii). This contrasts with the genuine strepsirrhine (Lorisiformes veri) fossil from the same region which have thrown much light on the group, but which have not yet resolved the issue of the timing or the modality of the dichotomy between the two families. At present, among the described African fossil lorisiformes only the genus Mioeuoticus is accepted by some, but not all, authors (Harrison, 2010) as a Lorisidae (or Lorisinae, all the others generally being classed as Galagidae (or Galginae) Walker (1987). It is thus of interest to put on record the discovery of a lorisid anout from the Late Miocene deposits of the Tugen Hills, Kenya, which is close in dimensions and some aspects of the Far East (Nycticebus, Nycticeboides) and West Africa (Arctocebus). The fossil does not particularly resemble any of the Early Miocene forms described from East Africa, and it is suggested that the lineage entered Africa during the Late Miocene at the same time that several other vertebrate groups spread into the continent from South-East Asia.

Early Neogene environments in East Africa: Evidence from dental microwear of tragulids

Environmental reconstructions of early Miocene sites are important for understanding the remarkable diversity and abundance of African mammals today. These provide essential context for the faunal interchange that occurred with the appearance of land bridges between Afro-Arabia and Eurasia. Tragulids, for example, were ecological precursors of some bovids, and an appreciation of their habitats during the early Miocene can provide insights into both their adaptive radiation and the environmental backdrop of the larger faunal turnover that followed. Here we reconstruct the diets of four tragulid species from early Miocene of Kenya, Dorcatherium parvum (n=11), D. pigotti (n=7), and D. chappuisi (n=4) from Rusinga Island, and D. songhorensis (n=13) from Songhor, using dental microwear texture analysis. Results indicate that all were likely mixed feeders, though there is variation in the sample. The Songhor species and D. chappuisi are inferred to have been variable grazers, D. pigotti is closer to browsers/generalists in microwear textures, and D. parvum is intermediate. This implies that, despite reconstructions of forested settings, especially at Songhor, at least some grass was available at both sites. It also suggests that the adaptive radiation of tragulids was more diverse in Africa in the past, and that we cannot assume an ancestral diet dominated by fruit and other browse items, as seen in chevrotains today.

Hind limb of the <i>Nacholapithecus kerioi</i> holotype and implications for its positional behavior

We present the definitive description of the hind limb elements of the Nacholapithecus kerioi holotype (KNM-BG 35250) from the middle Miocene of Kenya. Previously, it has been noted that the postcranial (i.e. the phalanges, spine, and shoulder girdle) anatomy of N. kerioi shows greater affinity to other early/middle Miocene African hominoids, collectively called ‘non-specialized pronograde arboreal quadrupeds,’ than to extant hominoids. This was also the case for the hind limb. However, N. kerioi exhibits a unique combination of postcranial characters that distinguish this species from other early/middle Miocene African hominoids. The femoral neck has a high angle, but is relatively short, though the adaptive meaning of this form is not readily understood. In the distal femur, the shape of the patellar surface and symmetry of the femoral condylar widths suggest that the knee was not typically abducted but assumed more variable movements and/or postures. Whereas the morphologies of the talocrural and intertarsal joints are generally similar to those of the other fossil hominoids, the tibial malleolus is extremely thick and asymmetry of the talar trochlea groove is more emphasized due to a more prominent lateral trochlear rim than in Proconsul and other African fossil hominoids. The distal foot segment is more elongated. The (non-hallucal) metatarsals appear relatively gracile due to the elongation. The proximal joints of these metatarsals are, nonetheless, large. Ligamentous attachments of the tarsal/metatarsal bones are generally well developed. The distal tarsal row, which is represented only by the medial cuneiform, though, is extremely large for the presumed body mass. In terms of function, the femur, ankle, and tarsal joints are interpreted behaviorally to represent a slow-moving arboreal quadruped. However, the foot of N. kerioi appears to be more specialized for inverted grasping and subvertical support use. All of these foot features are suggestive of a greater role for antiprono-grade activities in N. kerioi relative to other Miocene ‘pronograde arboreal quadrupeds.’

<i>Morotochoerus</i> de Uganda (17.5 Ma) y <i>Kenyapotamus</i> de Kenia (13-11 Ma): implicaciones sobre el origen de los hipopotámidos

El objetivo de este trabajo es describir e interpretar los dientes suiformes de Moroto, Uganda, y Ngorora, Kenia, que contribuyen al debate sobre las relaciones hipo-anthracothere-whale. Las primeras etapas de la evolución de los hipopotámidos son relativamente poco conocidas a causa de la escasez de su registro fósil en edades superiors a los 7 Ma. Nuevos ejemplares de Morotochoerus en Uganda revelan que no están estrechamente relacionados con Hippopotamidae, las semejanzas superficiales de los dientes de la mandíbula con los de los hipopótamos representan convergencias y no homologías. Algunas muestras de Palaeopotamus ternani aparecen en el Medio Mioceno de Kenia {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma}, mientras que desde la base del Mioceno tardío, Kenyapotamus coryndonae aparece en Kenia {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9,5 Ma}, {Ch’orora Etiopía, ca 10.5 Ma} {y Túnez Beglia Formación ca 11-10 Ma}. La obtención de especímenes de Kenyapotamus de la Formación Ngorora, Kenya, con edad ca 11 Ma, es de interés porque incluye dientes bien conservados, incluyendo un m/3 en buenas condiciones. Estos ejemplares apoyan la hipótesis de que los hipotámidos descienden de paleoquéridos y no de antracotéridos.

A New Genus of Tragulid Ruminant from the Early Miocene of Kenya

We re-describe the type material of the tiny African tragulid “Dorcatherium” moruorotensis from the early Miocene of Kenya, and erect the new genus Afrotragulus, the first African Miocene tragulid that does not belong to Dorcatherium. This new taxon is characterized by its elongated and stretched lower molars with a unique morphological dental pattern that strongly contrasts with that of Dorcatherium. We additionally include the former “Dorcatherium” parvum, also a small species from the early Miocene of Kenya, into the new genus Afrotragulus as Afrotragulus parvus, figuring it for the first time. We discuss the usefulness of body size as the main taxonomical criterion for studying the Tragulidae. And finally we comment on the taxonomical and morphological diversity of tragulids in the moment of their sudden early Miocene re-apparition and expansion in the Old World.

New proconsuloid postcranials from the early Miocene of Kenya

New early Miocene forelimb fossils have been recovered from the Songhor and Lower Kapurtay localities in southwestern Kenya. We describe four specimens that are similar in size and functional capabilities. Their specific allocation is problematic but these forelimb specimens must belong to either Rangwapithecus gordoni or Proconsul africanus. If these new postcranial specimens should belong to R. gordoni, on the basis of size and common dental specimens found at Songhor, they represent a new elbow complex. The morphology of these fossils is anatomically and functionally similar to that of Proconsul. The proconsuloid elbow complex allows extensive forelimb rotations and is capable of performing arboreal quadrupedalism and climbing activities. No suspensory adaptations are apparent. The proconsuloid elbow complex remains a good ancestral condition for hominoid primates.