Hagenia from the early Miocene of Ethiopia: Evidence for possible niche evolution?

Fossil pollen believed to be related to extant Hagenia abyssinica were discovered in the early Miocene (21.73 Ma) Mush Valley paleoflora, Ethiopia, Africa. Both the fossil and extant pollen grains of H. abyssinica were examined with combined light microscopy, scanning electron microscopy, and transmission electron microscopy to compare the pollen and establish their relationships. Based on this, the fossil pollen grains were attributed to Hagenia. The presence of Hagenia in the fossil assemblage raises the questions if its habitat has changed over time, and if the plants are/were wind pollinated. To shed light on these questions, the morphology of extant anthers was also studied, revealing specialized hairs inside the anthers, believed to aid in insect pollination. Pollen and anther morphology are discussed in relation to the age and origin of the genus within a molecular dated phylogenetic framework, the establishment of complex topography in East Africa, other evidence regarding pollination modes, and the palynological record. The evidence presented herein, and compiled from the literature, suggests that Hagenia was an insect‐pollinated lowland rainforest element during the early Miocene of the Mush Valley. The current Afromontane habitat and ambophilous (insect and wind) pollination must have evolved in post‐mid‐Miocene times.     

Combined LM and SEM study of the middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin,Austria: part IV. Magnoliophyta 2 – Fagales to Rosales

An ongoing investigation of the middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin continues to show that it contains an extremely rich assemblage of angiosperm taxa. The Fagales to Rosales pollen record documented here contains 34 different taxa belonging to the Betulaceae (Alnus, Betula, Carpinus, Corylus, Ostrya), Fagaceae (Castanea, Fagus, Quercus Groups Cerris, Ilex, Cyclobalanopsis, Quercus/Lobatae), Juglandaceae (Engelhardioideae, Carya, Juglans, Pterocarya), Myricaceae (Morrella vel Myrica), Cannabaceae (Celtis), Elaeagnaceae (Elaeagnus), Rhamnaceae, Rosaceae (Prunus) and Ulmaceae (Cedrelospermum, Ulmus, Zelkova). Two of the pollen types represent extinct genera, Trigonobalanopsis and Cedrelospermum, and are also reported for the first time from the Lavanttal Basin along with pollen of Rhamnaceae and Prunus. The different types of Quercus pollen are now affiliated with Groups Cerris, Cyclobalanopsis, Ilex and Quercus/Lobatae based on sculpturing elements observed using scanning electron microscopy (SEM). Köppen signatures of potential modern analogues of the fossil Fagales and Rosales suggest a subtropical (Cfa, Cwa) climate at lower elevation and subsequent subtropical to temperate climate with altitudinal succession (Cfa → Cfb/Dfa→ Dfb; Cwa → Cwb → Dwb) in the Lavanttal area during accumulation of the palynoflora. Most of the fossil taxa have potential modern analogues that can be grouped as nemoral and/or merido-nemoral vegetation elements, and the diversity of Fagales indicates a varying landscape with a high variety of niches.     

Mio-pliocene faunal exchanges and african biogeography: the record of fossil bovids

The development of the Ethiopian biogeographic realm since the late Miocene is here explored with the presentation and review of fossil evidence from eastern Africa. Prostrepsiceros cf. vinayaki and an unknown species of possible caprin affinity are described from the hominid-bearing Asa Koma and Kuseralee Members (～5.7 and ～5.2 Ma) of the Middle Awash, Ethiopia. The Middle Awash Prostrepsiceros cf. vinayaki constitutes the first record of this taxon from Africa, previously known from the Siwaliks and Arabia. The possible caprin joins a number of isolated records of caprin or caprin-like taxa recorded, but poorly understood, from the late Neogene of Africa. The identification of these two taxa from the Middle Awash prompts an overdue review of fossil bovids from the sub-Saharan African record that demonstrate Eurasian affinities, including the reduncin Kobus porrecticornis, and species of Tragoportax. The fossil bovid record provides evidence for greater biological continuity between Africa and Eurasia in the late Miocene and earliest Pliocene than is found later in time. In contrast, the early Pliocene (after 5 Ma) saw the loss of any significant proportions of Eurasian-related taxa, and the continental dominance of African-endemic taxa and lineages, a pattern that continues today.     

Fossil pollen grains of Asteraceae from the Miocene of Patagonia: Nassauviinae affinity

Fossil pollen grains with morphological features unique in the subtribe Nassauviinae (tribe Mutisieae, Asteraceae) occur in Miocene marine deposits of eastern Patagonia, southern South America. A new morphogenus and two morphospecies are proposed to assemble fossil pollen grains characterized by having a complex bilayered exine structure with delicate columellae, separated by an internal tectum. Subprolate specimens with Trixis exine type (ectosexine thinner than endosexine, straight internal tectum) are referred to Huanilipollis cabrerae. This species is similar to pollen of recent Holocheilus, Jungia, and Proustia. Suboblate specimens with Oxyphyllum exine type (ectosexine and endosexine equally thick, zigzag internal tectum) are referred to Huanilipollis criscii. This species is similar to pollen of recent Triptilion. The spore/pollen sequences in which Nassauviinae pollen types occur suggest a wide range of vegetation types varying from forest dominated during the Early Miocene (Chenque Formation) to virtually xerophytic ones during the Late Miocene (Puerto Madryn Formation). The subtribe Nassauviinae comprises 25 genera and ca. 320 species of vines, shrubs and low trees endemic to America with a wide range of ecological preferences; the nearest living relatives of the fossil types being mostly confined to humid landscapes. The unusual occurrence of these groups during the arid characterized Late Miocene time could be attributed to the complex interplay of the mountain uplift and global circulation patterns. These forcing factors would have created a mosaic of different habitats with both patches of forest and dry-adapted species developing in relatively small regions. This is the first fossil record of Nassauviinae and confirms that this subtribe of Asteraceae was already differentiated in the Miocene.     

A history of shifting fortunes for African penguins

Africa is home today to only a single breeding species of penguin, Spheniscus demersus (black‐footed penguin), which is endangered with extinction. Spheniscus demersus has been the only breeding species of penguin to share African coastlines with humans over the last 400 000 years. Interestingly, African penguin diversity was substantially higher before the evolution of archaic humans. The fossil record indicates that a diverse assemblage of penguin species inhabited the southern African coasts for much of the Neogene. Previous excavations have identified four distinct species in Early Pliocene coastal marine deposits. Here we extend this pattern of high diversity and report the oldest record of penguins from Africa. Seventeen penguin specimens were identified from the Saldanha Steel locality, revealing the presence of at least four distinct species in South Africa during the Miocene. The largest of these species reached the size of the extant Aptenodytes patagonicus (king penguin), whereas the smallest was approximately the size of the smallest extant penguin Eudyptula minor (little blue penguin). Recovery of Miocene penguin remains is in accordance with earlier predictions of multiple pre‐Pliocene colonizations of Africa and supports a higher level of ecological diversity amongst African penguins in the past. © 2013 The Linnean Society of London     

Evolution of pollen morphology in Loranthaceae

Earlier studies indicate a strong correlation of pollen morphology and ultrastructure with taxonomy in Loranthaceae. Using high-resolution light microscopy and scanning electron microscopy imaging of the same pollen grains, we document pollen types of 35 genera including 15 studied for the first time. Using a molecular phylogenetic framework based on currently available sequence data with good genus-coverage, we reconstruct trends in the evolution of Loranthaceae pollen and pinpoint traits of high diagnostic value, partly confirming earlier intuitive hypotheses based on morphological observations. We find that pollen morphology in Loranthaceae is strongly linked to phylogenetic relationships. Some pollen types are diagnostic for discrete genera or evolutionary lineages, opening the avenue to recruit dispersed fossil pollen as age constraints for dated phylogenies and as independent data for testing biogeographic scenarios; so far based exclusively on modern-day data. Correspondences and discrepancies between palynological and molecular data and current taxonomic/systematic concepts are identified and suggestions made for future palynological and molecular investigations of Loranthaceae.     

The middle Miocene palynoflora and palaeoenvironments of Eskihisar (Yatağan basin,south‐western Anatolia): a combined LM and SEM investigation

We investigated a palynological section from middle Miocene sediments at Eskihisar (south‐western Anatolia) to establish biogeographic links of the palynoflora and to infer the palaeoenvironment. Four algal palynomorphs, nine spore taxa, eight gymnosperms, three monocots and 67 dicot pollen types were encountered and investigated using the ‘single grain method’ that combines light microscopy and scanning electron microscopy. Two pollen zones reflect different phases of basin development. Zonal vegetation remained fairly stable across the section and reflects heterogeneous environments including broad‐leaved deciduous forest, subtropical forest and sclerophyllous and semi‐evergreen oak forest. Conifers were accessory elements in the broad‐leaved deciduous forest communities and replaced these at higher elevations. Some herbaceous taxa (Plumbaginaceae) indicate scattered occurrences of sandy and/or rocky soils. Biogeographic affinities are general Northern Hemisphere, North American and East Asian, as also suggested by the macrofossil record. Only two taxa provide potential biogeographic links with the African flora. This suggests that biome shifts of plant taxa between African subtropical/tropical biomes and Anatolian (western Eurasian) temperate forests and shrublands may have been rare in the middle Miocene.     

Diverse fossil Onagraceae pollen from a Miocene palynoflora of north-east China: early steps in resolving the phytogeographic history of the family

The origin and evolution of angiosperms can be unravelled by using fossil records to determine first occurrences and phytogeographic histories of plant families and genera. Many angiosperm families, for example the Onagraceae, have a poor macrofossil record, but are more common in palynological records. Modern Onagraceae produce pollen clearly distinct from that of other angiosperms. Combined morphological features obtained by use of light and scanning electron microscopy have enabled assignment of fossil Onagraceae pollen to extant genera, and therefore tracing of the origin and past distributions of extant Onagraceae lineages. We studied a Miocene palynoflora from the Daotaiqiao Formation of north-east China. Using the single-grain technique, we examined individual Onagraceae pollen/tetrads using both light and scanning electron microscopy. Fossil Onagraceae pollen is more frequent than macrofossil remains, but is still rare, and usually represented by a single taxon in palynological samples. Remarkably, samples from the Miocene of north-east China contain five different species: two of Circaea, one of Epilobium, and two of Ludwigia. Such a large number of Onagraceae taxa from a single palynoflora is unknown elsewhere. Whereas Ludwigia pollen is known from Cenozoic sediments of the northern hemisphere, the Circaea pollen is the first fossil pollen assignable to this extant genus. This is also the first fossil record of Epilobium from China. Although the young geological age of this sample does not enable consideration of time of origin for the genera encountered, the co-occurrence of Circaea, Epilobium, and Ludwigia in the mid to late-Miocene of East Asia sheds some light on their phytogeographic histories.     

Pollen–plant–climate relationships in sub-Saharan Africa

Aim  To demonstrate that incorporating the bioclimatic range of possible contributor plants leads to improved accuracy in interpreting the palaeoclimatic record of taxonomically complex pollen types.
Location  North Tropical Africa.
Methods  The geographical ranges of selected African plants were extracted from the literature and geo-referenced. These plant ranges were compared with the pollen percentages obtained from a network of surface sediments. Climate-response surfaces were graphed for each pollen taxon and each corresponding plant species.
Results  Several patterns can be identified, including taxa for which the pollen and plant distributions coincide, and others where the range limits diverge. Some pollen types display a reduced climate range compared with that of the corresponding plant species, due to low pollen production and/or dispersal. For other taxa, corresponding to high pollen producers such as pioneer taxa, pollen types display a larger climatic envelope than that of the corresponding plants. The number of species contained in a pollen taxon is an important factor, as the botanical species included in a taxon may have different geographical and climate distributions.
Main conclusions  The comparison between pollen and plant distributions is an essential step towards more precise vegetation and climate reconstructions in Africa, as it identifies taxa that have a high correspondence between pollen and plant distribution patterns. Our method is a useful tool to reassess biome reconstructions in Africa and to characterize accurately the vegetation and climate conditions at a regional scale, from pollen data.     

俄罗斯阿穆尔河东部上泽亚坳陷始新统孢粉

报道一个产于上泽亚(Uupper Zeya)坳陷(东经129-130°,北纬54-55°)东南部,保存良好的化石孢粉植物群.孢粉组合中裸子植物花粉居统治地位,占总数的53.4%,其中Taxodiaceae占36.3%,松科仅占5%.被子植物花粉占39.9%,多为葇荑花序类,如胡桃科、桦木科、山毛榉科等;同时还有不少反映温暖气候的分子,如Liquidambar,Balsaminaceae,Magnoliaceae,Nyssaceae等.孢子植物占21%.这样的孢粉植物群代表了潮湿温暖的温带气候.孢粉学至今在坳陷区内仍是人们用以确定地层时代的唯一依据.Pistillipollenites macgregorii,Anacolosiditessuplingensis,Ulmoideipites tricostatus及U. crempii等的出现可以确定含孢粉地层的地质时代属于中-晚始新世.斯涅日诺戈斯克产煤区中晚始新世沉积中的孢粉层位与普里阿姆尔耶,雅库提亚和亚洲东北部的同期沉积相当.     

New fossil anthropoids from the middle Miocene of East Africa and their bearing on the origin of the oreopithecidae

Recent paleontological collections at the middle Miocene locality of Maboko Island in Kenya, dated at 15-16 million years, have yielded numerous new specimens belonging to at least five species of fossil anthropoids. The most common species of ape at the site, a medium-sized primate with a very distinctive dental morphology, clearly represents a previously undescribed taxon. When compared with other Miocene anthropoids from East Africa, it has its closest affinities with the poorly known species Rangwapithecus vancouveringi from the early Miocene locality of Rusinga Island. The species from Maboko Island is described here as belonging to a new genus of fossil anthropoid, to which "Rangwapithecus" vancouveringi is also referred. The new genus has a highly distinctive suite of derived characters of its molars and premolars, which it shares with Oreopithecus bambolii from the late Miocene of Europe. These synapomorphies indicate a close phyletic relationship between the East African species and Oreopithecus and form the basis for the inclusion of these taxa in a single family, the Oreopithecidae Schwalbe, 1915. In many respects, however, the East African forms are more conservative than Oreopithecus, and in a general sense they can be regarded as an intermediate grade between Oreopithecus and the more generalized early Miocene catarrhines, the proconsuloids. There is, therefore, good fossil evidence to indicate that the origins of the Oreopithecidae can be traced back to the early Miocene of Africa.     

Enters the shrew,some considerations on the Miocene palaeobiogeography of Iberian insectivores

The fossil record of the Iberian insectivores forms a subset of those found in central Europe. Comparison of the late early to early late Miocene record of the two areas shows that, particularly during the late Early Miocene, central European taxa have transient occurrences in Spain. Most taxa appear earlier and survive longer in central Europe. A notable exception is the gymnure Galerix, which extirpates earlier in central Europe, except for a transient occurrence in Germany just prior to its extinction. The main period of insectivore migrations is the late middle Miocene, although some of the taxa that enter remain restricted to the coastal areas. Overall, the pattern of distribution in time and space is best explained by the preference of insectivores for humid environments, as were found during the early Miocene and re-appeared at the end of the middle Miocene.     

A Review of the Fossil Record of the Genus Itea (Iteaceae, Saxifragales) with Comments on its Historical Biogeography

Itea is a genus of about 20 species of trees and shrubs that are today native to southeastern North America, eastern Asia, and eastern Africa. In this paper, I review the fossil record of Itea, which is based on four types of fossils: diporate, psilate pollen attributed to Itea or the dispersed pollen genus Iteapollis; carpofossils representing fruits and seeds attributed to Itea europaea; flowers preserved in amber and assigned to Adenanthemum iteoides; and leaf impressions attributed to Itea. The distributions of these fossils indicate that Itea was present in western North America from the early Eocene to Miocene, in eastern North America beginning no later than the early Miocene, and in western Eurasia from the late Eocene to Pliocene. Only one datapoint is known from eastern Asia; it is early Miocene in age. Based on the fossil record, it can be inferred that Itea crossed between continents over both the Bering Land Bridge and North American Land Bridge, and that it reached Africa from Europe via Anatolia. Thus, it is predicted that the sole extant North American species, I. virginica, may be most closely related to the sole extant African species, I. rhamnoides. The potential application of Itea fossils to calibrating phylogenetic trees generated from molecular sequence data is also discussed.     

中国桑寄生科花粉形态研究

本文报道用光学显微镜和扫描电镜观察中国桑寄生科45个分类群的花粉形态,综合分析其外部特征,参考内部结构及化学成分方面的资料,探讨本科各属的分类和系统发育。 研究结果表明,中国桑寄生科植物花粉明显区分为两种类型,而且各自有其演化规律。我们也支持将我国的桑寄生科区分为两个独立的科,即 Loranthaceae A.Juss.(1808)和Visca-ceae Miers(1851),使其更全面反映自然系统发育。 过去国产桑寄生亚科种类,发表的新分类群往往当作桑寄生属(Loranthus)植物,据花粉形态研究表明,它们在花粉粒的大小,萌发器官的细微结构以及外壁纹饰方面,可以区分成几个类型,支持应将我国原隶于 Loranthus Linn.属的植物分成6个属的观点。而桑寄生属(Lo-ranthus Jacq.)与梨果寄生属(Scurrula Linn.)这二属的花和花粉形态彼此有明显的区别,是不应将 Scurrula Linn.视作 Loranthus Jacq.(保留属名)的异属名的。     

Origines du peuplement mammalien en Afrique du Nord durant le miocène terminal

The late Miocene North African mammalianassemblage is considered here from three viewpoints: survivals, extinctions, and immigrations. The Eurasiatic affinities of the large mammals slightly prevail over the Ethiopian affinities. Amongst the North African large mammals, 4 to 8 taxa are Eurasiatic immigrants, while 4 to 6 are of Subsaharian origin. Contrarily, the micromammalian fauna is highly endemic, with only one species, a murid (Paraethomys miocaenicus), considered here as being related to an Asiatic form (Karnimata darwini). Our study of Eurasian and African Miocene faunas reveals that during the late Astaracian-early Turolian interval, the Saharo-Arabic belt permitted very little latitudinal faunal exchanges. However, during the middle and late Turolian such faunal exchanges became frequent. The micromammal record unequivocally indicates that a brief period of faunal exchange occurred between Africa and western Europe at the end of the Miocene, corresponding with the Messinian Salinity Crisis. The increased intercontinental faunal exchange between Africa and Eurasia during the late Miocene coincides with, and counterbalances the extinction of more than 10 taxa at the Mio/Pliocene boundary.     

Middle Miocene dispersals of apes

The earliest record of fossil apes outside Africa is in the latest early Miocene of Turkey and eastern Europe. There were at least 2, and perhaps 4, species of ape, which were found associated with subtropical mixed environments of forest and more open woodland. Postcranial morphology is similar to that of early Miocene primates and indicates mainly generalized arboreal quadrupedal behaviours similar to those of less specialized New World monkeys such as Cebus. Robust jaws and thick enamelled teeth indicate a hard fruit diet. The 2 best known species of fossil ape are known from the site of Pa?alar in Turkey. They have almost identical molar and jaw morphology. Molar morphology is also similar to that of specimens from Germany and Slovakia, but there are significant differences in the anterior teeth of the 2 Pa?alar species. The more common species, Griphopithecus alpani, shares mainly primitive characters with early and middle Miocene apes in Africa, and it is most similar phenetically to Equatorius africanus from Maboko Island and Kipsaramon. The second species is assigned to a new species of Kenyapithecus, an African genus from Fort Ternan in Kenya, on the basis of a number of shared derived characters of the anterior dentition, and it is considered likely that there is a phylogenetic link between them. The African sites all date from the middle Miocene, similar in age to the Turkish and European ones, and the earliest emigration of apes from Africa coincides with the closure of the Tethys Sea preceding the Langhian transgression. Environments indicated for the African sites are mixtures of seasonal woodlands with some forest vegetation. The postcrania of both African taxa again indicate generalized arboreal adaptation but lacking specialized arboreal function. This middle Miocene radiation of both African and non-African apes was preceded by a radiation of arboreal catarrhine primates in the early Miocene, among which were the earliest apes. The earliest Miocene apes in the genus Proconsul and Rangwapithecus were arboreal, and because of their association with the fruits of evergreen rain forest plants at Mfwangano Island, it would appear that they were forest adapted, i.e. were living in multi-storied evergreen forest. The same or similar species of the same genera from Rusinga Island, together with other genera such as Nyanzapithecus and the small ape Limnopithecus, were associated with plants and animals indicating seasonal woodland environments, probably with gallery forest forming corridors alongside rivers. While the stem ancestors of the Hominoidea were almost certainly forest adapted, the evidence of environments associated with apes in the later part of the early Miocene and the middle Miocene of East Africa indicates more seasonal woodlands, similar to those reconstructed for the middle Miocene of Pa?alar in Turkey. This environmental shift was probably a requisite for the successful emigration of apes out of Africa and made possible later movement between the continents for much of the middle Miocene, including possible re-entry of at least one ape lineage back into Africa.     

Lauraceae fossils from a volcanic Palaeocene oceanic island,Ninetyeast Ridge,Indian Ocean: ancient long‐distance dispersal?

Aim Geological and fossil records are critical for historical biogeography studies. A plant fossil assemblage from a small, well‐dated, transient late Palaeocene island was re‐investigated with regard to regional geology and vicariance versus dispersal hypotheses. Location Deep Sea Drilling Program Leg 22, Site 214 on the Ninetyeast Ridge (NER) in the mid‐Indian Ocean region. Methods Leaf cuticular material was recovered from residues from a previous palynofloral study of Site 214 sediments during the 1970s and identified. The palynoflora was reassessed. Results The only leaf cuticular material recovered with stomata can be placed in crown‐group Lauraceae. It is confirmed that the palynoflora reflects the presence of a low‐diversity island flora in the late Palaeocene, comprising ferns and mostly herbaceous angiosperms with readily dispersible propagules, and perhaps austral podocarps. Other pollen taxa of almost certain local origin were arecoid palms and taxa related to Chloranthaceae. The strong overall similarity of the palynoflora to Australo‐Antarctic and New Zealand assemblages is also confirmed. Main conclusions Foliar fossils of Lauraceae demonstrate the occurrence of one of the world’s largest, most widely distributed woody plant families on a late Palaeocene island. The presence of plants on this island could be explained by vicariance via a vegetated Upper Cretaceous Kerguelen Plateau, in part because crown‐group Lauraceae may be at least this old. However, there are records of other taxa in the Kerguelen region that are anomalous with vicariance, plus evidence for a catastrophic biotic extinction event centred in the area in the latest Cretaceous. Plants were therefore most likely to have reached the island by means of dispersal. This suggests either the presence of presently unknown vegetated land nearby in the Kerguelen region in the late Palaeocene, or long‐distance dispersal, probably from the Australian region. The dispersal of viable seeds could have been facilitated by birds or perhaps by ocean‐surface drift with or without the assistance of ocean‐going animals. The fossils allow that even small, short‐lived islands could have acted as ‘stepping stones’ for biotic interchange between Australia and Africa, and perhaps other regions.     

Early Miocene catarrhine dietary behaviour: the influence of the Red Queen Effect on incisor shape and curvature

The early Miocene catarrhine fossil record of East Africa represents a diverse and extensive adaptive radiation. It is well accepted that these taxa encompass a dietary range similar to extant hominoids, in addition to some potentially novel dietary behaviour. There have been numerous attempts to infer diet for these taxa from patterns of dental allometry and incisor and molar microwear, however, morphometric analyses until now have been restricted to the post-canine dentition. It has already been demonstrated that given the key functional role of the incisors in pre-processing food items prior to mastication, there is a positive correlation between diet and incisal curvature (Deane, A.S., Kremer, E.P., Begun, D.R., 2005. A new approach to quantifying anatomical curvatures using High Resolution Polynomial Curve Fitting (HR-PCF). Am. J. Phys. Anthropol. 128(3), 630-638.; Deane, A.S., 2007. Inferring dietary behaviour for Miocene hominoids: A high-resolution morphometric approach to incisal crown curvature. Ph.D. Dissertation. The University of Toronto.). This study seeks to re-examine existing dietary hypotheses for large-bodied early Miocene fossil catarrhines by contrasting the incisal curvature for these taxa with comparative models derived from prior studies of the correlation between extant hominoid incisor curvature and feeding behaviour. Incisor curvature was quantified for 78 fossil incisors representing seven genera, and the results confirm that early Miocene fossil catarrhines represent a dietary continuum ranging from more folivorous (i.e., Rangwapithecus) to more frugivorous (i.e., Proconsul) diets, as well as novel dietary behaviours that are potentially similar to extant ceboids (i.e., Afropithecus). Additionally, early Miocene fossil catarrhine incisors are less curved than extant hominoid incisors, indicating a general pattern of increasing mesio-distal and labial curvature through time. This pattern of morphological shifting is consistent with the Red Queen Effect (Van Valen, L., 1973. A new evolutionary law. Evol. Theory 1, 1-30), which predicts that taxa that are removed from one another by geological time, although potentially having similar diets, may exhibit differing degrees of a similar dietary adaptation (i.e., differing degrees of incisal curvature).     

The phylogenetic affinities of Otavipithecus namibiensis

The middle Miocene hominoid Otavipithecus namibiensis is the first and most complete fossil ape from sub-equatorial Africa and represents a significant addition to the taxonomically sparse African middle Miocene hominoid fossil record. The Otavipithecus hypodigm comprises the holotype mandible, which presents a unique mosaic of dental and gnathic characters, and several attributed cranial and postcranial elements which resemble the stem hominoid Proconsul. Contrary to initial hopes that this discovery would provide new insights into hominoid morphological diversity and phylogenetic relationships, a variety of conflicting phylogenetic hypotheses have been advanced suggesting ties to virtually every major large-bodied hominoid group (Conroy et al., 1992; Andrews, 1992 a; Conroy, 1994; Pickford et al., 1994; Begun, 1994 a). Cladistic analysis of a matrix of 22 qualitative and ten quantitative characters of the mandible and mandibular dentition found no support for a close phylogenetic relationship between Otavipithecus and either the African ape or great ape clades, or with any of the Eurasian fossil hominoids with which it has previously been compared. A close relationship between Otavipithecus and Kenyapithecus cannot be ruled out, but is deemed unlikely on the basis both of morphological comparisons and the absence of support within a cladistic framework. The present analysis indicates that Otavipithecus is most closely related to Afropithecus, as previously suggested by Andrews (1992 a) among others. Due to lack of statistical support for this result, a conservative interpretation, that these taxa represented related but divergent lineages of a late early Miocene hominoid radiation, is currently favored. Findings are consistent with the allocation of Otavipithecus to Andrews' (1992 a) tribe Afropithecini which represents the sister group to Kenyapithecus and the extant ape clade.