New observations on the Late Miocene–Early Pliocene Lutrinae (Mustelidae: Carnivora,Mammalia) from the Middle Awash,Afar Rift,Ethiopia

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, 5.54–5.77 Ma) and Earliest Pliocene (Kuseralee and Gawto Members of the Sagantole Formation, 5.2 and 4.85 Ma, 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.     

Differential mesowear in occluding upper and lower molars: opening mesowear analysis for lower molars and premolars in hypsodont horses

A new approach of reconstructing ungulate diet, the mesowear method, was recently introduced by Fortelius and Solounias ([2000] Am Mus Novitat 3301:1-36). Mesowear is based on facet development on the occlusal surfaces of the teeth. Restricting mesowear investigation to maxillary cheek teeth would allow mesowear investigation only in assemblages of large numbers of individuals and therefore would generally restrict this method to relatively few assemblages of recent and fossil ungulates. Most of the fossil, subfossil, and recent ungulate osteological assemblages that may be assigned to a single taxon have smaller numbers of individuals. This results in a demand to extend the mesowear method to further tooth positions in order to obtain stable dietary classifications of fossil taxa. The focus of this article is to test if a consistent mesowear classification is obtainable for mandibular as well as for maxillary teeth. For statistical testing, large assemblages of isolated cheek teeth of the Vallesian hipparionine horse Hippotherium primigenium and of the recent zebra Equus burchelli were employed as models. The upper tooth positions P4, M1, M2, and M3 as suggested by Kaiser and Solounias (2003) as the model for the "extended" mesowear method and the lower tooth positions P4-M3 were tested for their consistency in classification of the mesowear variables. We found a considerable shift of the mesowear signature towards the grazing edge of the mesowear continuum in lower cheek teeth. In order to adjust the signal of lower teeth to the signal of the upper teeth, a calibration factor was introduced which allowed incorporation of lower cheek teeth into the same model of mesowear investigation together with upper cheek teeth. We propose that this model is particularly suited for the reconstruction of paleodiets in hypsodont hipparionine and equine equids. We further investigated the functional relation between the mesowear profiles and the distribution of dental tissues along the course of the occlusal contact. We therefore correlated mesowear profiles with enamel distribution profiles and found the mesowear profile to be strongly controlled by the attritional environment encountered by a given apex area. The differential signal observed in cusp apex morphology between upper and lower cheek teeth was found to be more closely related to attrition by the antagonistic tooth than to the distribution of dental tissues in the tooth under consideration. The results suggest a general extension of the mesowear method of paleodiet reconstruction and a basic scenario for the evolution of anisodont dentitions.     

Subnasal alveolar morphology and the systematic position of Sivapithecus

Recent collecting in the Potwar Plateau of Pakistan has produced several new maxillae attributable to Sivapithecus. Since the subnasal region is preserved in most of these specimens, comparisons with early Miocene hominoid and Pliocene hominid maxillae become possible. On the basis of these comparisons, it has become clear that subnasal/premaxillary morphology distinguishes Asian and African hominoids. Ramapithecus and Sivapithecus share with Pongo an "Asian" subnasal pattern. The Proconsul species from the early Miocene of western Kenya and Australopithecus afarensis from the Hadar Formation of Ethiopia present two subsets of an "African" subnasal pattern. We think it likely that Ramapithecus and Sivapithecus represent a lineage that postdates the last common ancestor of African and Asian hominoids.     

A new large Pliocene colobine species (Mammalia: Primates) from Asa Issie, Ethiopia

The Colobinae (Mammalia: Primates) are relatively unknown from the African middle to late Miocene. When they appear in the Pliocene they are unambiguous and already fairly diverse taxonomically, geographically, and ecologically. Discoveries from Pliocene sediments in eastern and southern Africa document a radiation of large-bodied colobines very different from those known today. Paleontological research in Ethiopia has recently led to the discovery and identification of another large-bodied colobine species from the early Pliocene site of Asa Issie, discovered in 2000. This new colobine is larger than but morphologically very similar to its sister taxon Kuseracolobus aramisi, an older taxon also described from the Middle Awash. This new species has significant implications for our understanding of the Pliocene colobine adaptive radiation.     

Ecological change in the lower Omo Valley around 2.8 Ma

Late Pliocene climate changes have long been implicated in environmental changes and mammalian evolution in Africa, but high-resolution examinations of the fossil and climatic records have been hampered by poor sampling. By using fossils from the well-dated Shungura Formation (lower Omo Valley, northern Turkana Basin, southern Ethiopia), we investigate palaeodietary changes in one bovid and in one suid lineage from 3 to 2 Ma using stable isotope analysis of tooth enamel. Results show unexpectedly large increases in C₄ dietary intake around 2.8 Ma in both the bovid and suid, and possibly in a previously reported hippopotamid species. Enamel δ¹³C values after 2.8 Ma in the bovid (Tragelaphus nakuae) are higher than recorded for any living tragelaphin, and are not expected given its conservative dental morphology. A shift towards increased C₄ feeding at 2.8 Ma in the suid (Kolpochoerus limnetes) appears similarly decoupled from a well-documented record of dental evolution indicating gradual and progressive dietary change. The fact that two, perhaps three, disparate Pliocene herbivore lineages exhibit similar, and contemporaneous changes in dietary behaviour suggests a common environmental driver. Local and regional pollen, palaeosol and faunal records indicate increased aridity but no corresponding large and rapid expansion of grasslands in the Turkana Basin at 2.8 Ma. Our results provide new evidence supporting ecological change in the eastern African record around 2.8 Ma, but raise questions about the resolution at which different ecological proxies may be comparable, the correlation of vegetation and faunal change, and the interpretation of low δ¹³C values in the African Pliocene.     

Tooth microwear and premaxillary shape of an archaic antelope

Extant ungulates can be divided into three dietary categories: browsing feeders, grazing feeders, and mixed feeders. Dietary adaptations can be differentiated in extinct ruminants based upon tooth microwear analysis as well as evaluation of premaxillary morphology. Tooth microwear shows that the extinct bovid Kipsigicerus labidotus from the Miocene of Fort Ternan in Kenya (14 million years old) was most likely a grazing feeder, with mixed-feeder tendencies, while morphologically the premaxilla most closely resembles that of a mixed feeder. Because the paleoenvironment at Fort Ternan was likely to have been forested, as shown by paleosol isotopic studies, grazing in this particular ruminant evolved within a forested environment preceding the origin of savanna. □ Tooth microwear, premaxilla, Miocene, Kenya, bovid, paleodiet.     

Coevolution of Tooth Crown Height and Diet in Oreodonts (Merycoidodontidae, Artiodactyla) Examined with Phylogenetically Independent Contrasts

The evolution of increased tooth crown height is considered to be an adaptation for coping with excessive rates of dental wear associated with abrasive herbivorous diets, such as grazing and(or high levels of exogenous grit (e.g. dust, sand, ash). Evolutionary trends in the crown heights of North American ungulates are grossly consistent with a transition from closed forests in the early Eocene to open grasslands in the late Miocene. However, the evolutionary proliferation of hypsodonty (high crowned teeth) in the early and middle Miocene occurs later than the apparent origin of open grassland habitats in North America. The paleoecology of species from the interval between the appearance of grasslands and the evolutionary proliferation of hypsodonty is critical to understanding the role of Cenozoic climate change in mammalian evolution. The paleodiets of late Eocene to middle Miocene oreodonts (Merycoidodontidae) were reconstructed by examining the relative facet development of molars (mesowear). A two-phase diet trend was discovered. Phase 1 suggests either an average reduction in the amount of exogenous grit from the late Eocene to early Oligocene or a decrease in fruit consumption related to the disappearance of more wooded habitats. Phase 2 is a gradual transition from early Oligocene low-abrasion browsing to high abrasion diets similar to mixed feeding and grazing in the Miocene. According to mesowear data, oreodont diets similar to those of modern grazers in terms of abrasion are not seen until the early Miocene (early Hemingfordian land mammal age). The coevolutionary relationship of molar crown height and diet, as represented by mesowear, was examined using phylogenetically independent contrasts. No significant coevolutionary relationship was found. In several instances, diet was found to shift over time despite morphological stasis (i.e. within a single species). These results do not clearly indicate that the overall trend of increasing dietary abrasion imposed sufficient selection to drive crown height evolution in oreodonts. Therefore, direct fossil evidence of dietary abrasion as a causal factor in the evolution of crown height, at least in this clade, is elusive.     

Detecting Inter-Cusp and Inter-Tooth Wear Patterns in Rhinocerotids

Extant rhinos are the largest extant herbivores exhibiting dietary specialisations for both browse and grass. However, the adaptive value of the wear-induced tooth morphology in rhinos has not been widely studied, and data on individual cusp and tooth positions have rarely been published. We evaluated upper cheek dentition of browsing Diceros bicornis and Rhinoceros sondaicus, mixed-feeding R. unicornis and grazing Ceratotherium simum using an extended mesowear method adapted for rhinos. We included single cusp scoring (EM(R)-S) to investigate inter-cusp and inter-tooth wear patterns. In accordance with previous reports, general mesowear patterns in D. bicornis and R. sondaicus were attrition-dominated and C. simum abrasion-dominated, reflecting their respective diets. Mesowear patterns for R. unicornis were more attrition-dominated than anticipated by the grass-dominated diet, which may indicate a low intake of environmental abrasives. EM(R)-S increased differentiation power compared to classical mesowear, with significant inter-cusp and inter-tooth differences detected. In D. bicornis, the anterior cusp was consistently more abrasion-dominated than the posterior. Wear differences in cusp position may relate to morphological adaptations to dietary regimes. Heterogeneous occlusal surfaces may facilitate the comminution of heterogeneous browse, whereas uniform, broad grinding surfaces may enhance the comminution of physically more homogeneous grass. A negative tooth wear gradient was found in D. bicornis, R. sondaicus and R. unicornis, with wear patterns becoming less abrasion-dominated from premolars to molars. No such gradients were evident in C. simum which displayed a uniform wear pattern. In browsers, premolars may be exposed to higher relative grit loads, which may result in the development of wear gradients. The second premolar may also have a role in food cropping. In grazers, high absolute amounts of ingested abrasives may override other signals, leading to a uniform wear pattern and dental function along the tooth row, which could relate to the observed evolution towards homodonty.     

Diversity of hipparionines (Perissodactyla: Equidae) from the late Miocene–Pliocene Siwalik deposits at Haritalyangar,India

The present work is focused on the hipparionine remains from the late Miocene to early Pliocene deposits of the Haritalyangar areas, Himachal Pardesh, India. These remains are taxonomically ranked to five genera (Plesiohipparion, Proboscidipparion, Cormohipparion, Sivalhippus, and Eurygnathohippus) and seven species. The described taxa are predominantly known from China, Africa and the Indian subcontinent. Among these, Proboscidipparion is reported for the first time from the Siwaliks; the material assigned to Plesiohipparion sp. is a potential candidate for a new species. Hipparionines from this area have long been poorly known and are helpful to understand the palaeontological context of the Indian Siwalik mammalian fauna. The hipparionines suggest a wide variety of environmental conditions ranging from grasslands to forests.     

New Eucyon remains from the Pliocene Aramis Member (Sagantole Formation), Middle Awash Valley (Ethiopia)

The Aramis Member (Sagantole formation) includes the Gàala Tuff Complex-Daam Aatu Basaltic Tuff interval which has produced a taxonomically diverse vertebrate assemblage including the primitive hominid Ardipithecus ramidus. New Eucyon remains recovered from this interval come from localities in the Aramis, Sagantole, and Kuseralee catchments. The chronology established for the GATC-DABT interval is 4.4 Ma. These recoveries represent the most abundant available Eucyon assemblage of the eastern African Pliocene. Here, Eucyon fossils from the Kapsomin and Lemudong’o Late Miocene Kenyan sites are compared with the Aramis representatives, showing comparable morphology although with smaller dimensions. E. intrepidus–E. wokari nov. sp., might constitute a single lineage, with increasing size and robusticity, and the derivation of some morphological traits mainly on the lower carnassial. E. wokari represents a new eastern species of the African Pliocene Eucyon lineage.     

Feeding behaviour of middle-size deer from the Upper Pliocene site of Saint-Vallier (France) inferred by morphological and micro/mesowear analysis

In the middle Villafranchian (Late Pliocene) fossil deposit of Saint-Vallier (Drôme, France), the international biochronological reference for the MN17 biozone, deer are the most common species. Two middle-sized taxa, “Metacervoceros” rhenanus [Dubois, E., 1904. On an equivalent of the Cromer Forest Bed in the Netherlands. Koninklijke Akademie van Wetenschappen, 214–222] and Croizetoceros ramosus (Croizet and Jobert, 1828), are particularly abundant. We have performed functional morphology and micro- and mesowear analyses in order to explain if and how the two herbivorous species avoided intra-guild competition. The results of the microwear analysis show a clear difference in the wear pattern of their tooth enamel, demonstrating the two species had different feeding behaviour habits.     

Comparing ungulate dietary proxies using discriminant function analysis

A variety of tooth‐wear and morphological dietary proxies have been proposed for ungulates. In turn, they have been applied to fossil specimens with the purpose of reconstructing the diets of extinct taxa. Although these dietary proxies have been used in isolation and in combination, a consistent set of statistical analyses has never been applied to all of the available datasets. The purpose of this study is to determine how well the most commonly used dietary proxies classify ungulates as browsers, grazers, and mixed feeders individually and in combination. Discriminant function analysis is applied to individual dietary proxies (hypsodonty, mesowear, microwear, and several cranial dietary proxies) and to combinations thereof to compare rates of successful dietary classification. In general, the tooth‐wear dietary proxies (mesowear and microwear) perform better than morphological dietary proxies, though none are strong proxies in isolation. The success rates of the cranial dietary proxies are not increased substantially when ruminants and bovids are analyzed separately, and significance among the three dietary guilds is reduced when controlling for phylogenetic relatedness. The combination of hypsodonty, mesowear, and microwear is found to have a high rate of successful dietary classification, but a combination of all commonly used proxies increases the success rate to 100%. In most cases, mixed feeders bear the greatest resemblance to browsers suggesting that a morphology intermediate to browsers and grazers may represent a fitness valley resulting from the inability to exploit both browse and graze efficiently. These results are important for future paleoecological studies and should be used as a guide for determining which dietary proxies are appropriate to the research question. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Creodonts and carnivores from the Middle Miocene Muruyur Formation at Kipsaraman and Cheparawa,Baringo District,Kenya

The Middle Miocene Muruyur Formation (ca 14.5 Ma), Tugen Hills, Kenya, has yielded a huge creodont and a variety of carnivores ranging in size from mongoose-sized viverrids and herpestids to lion-sized amphicyonids. The fauna partly fills what used to be a major gap in our knowledge of Neogene African carnivores, spanning the period between the better known Early Miocene assemblages of western Kenya and eastern Uganda, and the Late Miocene and Plio–Pleistocene faunas of East Africa. Present in the deposits are Megistotherium, two species of Hecubides, one species of Agnotherium, Herpestes, Vishnuictis, and one or two undetermined felids.     

A New Rhinoceros, Victoriaceros kenyensis gen. et sp. nov., and Other Perissodactyla from the Middle Miocene of Maboko, Kenya

The middle Miocene site of Maboko (Lake Victoria, Kenya), dated to ca. 15 Ma, has yielded one of the best collection of rhinos in Africa. The most common taxon, Victoriaceros kenyensis n.gen., n.sp., is represented by an almost perfect skull (whose main features are the large nasal horn, an orbit located very anteriorly and with a prominent border, and very broad zygomatic arches) and numerous limb bones, probably belonging to only a few individuals. Characters of the teeth and skull support an assignment to the subfamily Elasmotheriinae, a group best known in the middle and upper Miocene, but whose monophyly is disputable, as some of their tooth characters could be adaptations to a grazing diet (in agreement with their distribution in the Maboko beds). In any case, Victoriaceros clearly differs from other East African middle Miocene rhinos, whose diversity is far greater than currently assumed. A few other specimens attest to the occurrence at Maboko of at least one other species, perhaps close to the brachypotheres; a single calcaneum is tentatively assigned to the Chalicotheriidae.     

Mid-Pliocene Carnivora from the Woranso-Mille Area,Afar Region,Ethiopia

The Woranso-Mille paleontological study area, located in the central Afar region of Ethiopia, is one of the most important Pliocene sites in eastern Africa. Since the Woranso-Mille Research Project began its investigation in 2005, more than 7,500 mammalian fossils, including hominins, have been collected from 80 vertebrate localities. This paper provides a preliminary assessment of the Woranso-Mille carnivoran record, a record that is of great interest given the high level of species richness of African carnivorans during the middle Pliocene. Craniodental and postcranial material of canids, lutrine mustelids, viverrids, herpestids, machairodontine and feline felids, and hyaenids has been recovered. Thus, this diverse fauna includes not only the largest carnivorans from this time period (e.g., Enhydriodon and Homotherium), but also some of the smallest, including mongooses, civets, genets, and felids, some of which represent new species. However, the diversity of small taxa does not yet approach that found in the roughly contemporaneous Upper Laetolil Beds of Tanzania. In contrast, lutrine mustelids are better represented at Woranso-Mille than at Kanapoi (Kenya) or Laetoli (Tanzania), which is to be expected given the diversity of habitats represented at these sites. While more material from these sites and others are necessary to truly understand the increased diversity within the early to middle Pliocene eastern African carnivoran guild, it is clear that the material from Woranso-Mille has the potential to fill many of the gaps in our knowledge of carnivorans during this time period.     

Dietary adaptations in an ungulate community from the late Pliocene of Greece

The dietary morphological methods of mesowear and microwear were applied to ungulates of the late Pliocene fauna of Sésklo (Thessaly, Greece). The results provide evidence for the predominance of open grassland in the area, as the most common species, Equus stenonis, was a strict grazer. The rare cervid cf. Croizetoceros ramosus was the only browser. The antelopes (genera Gazella and Gazellospira) yielded discrepant microwear and mesowear results. This is interpreted as an indication of regional or seasonal dietary resource differentiation, inferring that the antelopes were probably mixed feeders that grazed occasionally or periodically.     

Historical distribution,habitat requirements and feeding ecology of the genus Equus (Perissodactyla)

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The fossil turtles of Greece: An overview of taxonomy and distribution

Turtle remains are common in the Miocene-Holocene deposits of Greece, and are a key focus of the growing research interest in Neogene herpetofaunas from the Aegean region. Some of the most important finds include one of Europe's stratigraphically youngest pleurodiran taxa, Nostimochelone lampra, from the Early Miocene of Macedonia, together with arguably the richest record of fossil tortoises from the Eastern Mediterranean. This incorporates the presently oldest definitive representatives of the quintessential genus Testudo sensu stricto from the Late Miocene of Attica and Macedonia, and numerous specimens of the colossal (carapace ∼2 m-length) testudinid Cheirogaster from Late Miocene-Late Pliocene sediments in southern and northern Greece, as well as on the eastern Aegean islands of Samos and Lesvos. Tantalising, but as yet unconfirmed Miocene accounts of the geoemydid Mauremys in Macedonia, and indeterminate emydid-like remains from Euboea, also provide potentially significant range extensions. Although hampered by a historically sparse documentation, the fossil turtles of Greece are a significant resource that record both assemblage changes and the origin of modern lineages.     

<Emphasis Type="Italic">Anchitherium aurelianense</Emphasis> (Equidae,Mammalia): a brachydont “dirty browser” in the community of herbivorous large mammals from Sandelzhausen (Miocene,Germany)

The Anchitheriinae are an extinct subfamily of Equidae that first appeared in North America near the base of the Miocene. Anchitheriinae are found in subtropical to warm temperate habitats and were long considered to be adapted to eating browse. In Europe the genus Anchitherium first occurred in the MN3 mammal zone and became extinct in MN9. The assemblage from Sandelzhausen (Early/Middle Miocene, boundary MN5) is one of the best dental samples known of Old World Anchitherium. The mesowear method was applied to reconstruct the dietary regime of A. aurelianense from Sandelzhausen. Hierarchical cluster statistics and principal component analysis was performed on mesowear variables. Thirty-five upper cheek teeth of A. aurelianense were analysed, and mesowear signatures compared with those of five ruminant species from Sandelzhausen. The extant analogue species indicate that A. aurelianense at Sandelzhausen had a diet similar in abrasiveness to that of extant mixed feeders and that the Sandelzhausen ruminants all occupied a browsing niche with little or no abrasives in their diet. Knowing now that brachydont anchitheres were able to cope with rather abrasive diets, it is assumed that hypsodont North American equids of the Cormohipparion clade, arriving in Europe successively with the extinction of anchitheres shortly after the “hipparion datum” in the MN9, introduced a new component of competition in their dietary niche. The extinction of the Anchitheriidae can now be better understood as response to this competition.      

Afrochoerodon nov. gen. kisumuensis (MacInnes) (Proboscidea,Mammalia) from Cheparawa,Middle Miocene,Kenya

A proboscidean skull from Cheparawa, (Muruyur Formation, Kenya), differs markedly from those of Eurasian Choerolophodon (C. pentelici, C. dhokpathanensis). It is morphologically and metrically close to the holotype of Choerolophodon kisumuensis (MacInnes) a partial skull from Maboko, much of which has been reconstructed in plaster of Paris. The more complete remains of this species now available indicate that it should be placed in a genus separate from Choerolophodon. The new genus Afrochoerodon is erected for it. Choerolophodon ngorora from Ngorora and Fort Ternan (Kenya), Choerolophodon zaltaniensis from Gebel Zelten (Libya) and Choerolophodon chioticus from Chios, Greece, should be transferred to the genus Afrochoerodon. Late Miocene specimens from Nakali, Kenya are probably referrable to the genus Choerolophodon. Fossils from Burji-Soyama (Ethiopia) hitherto assigned to Choerolophodon sp. are excluded from the subfamily Choerolophodontinae.