Ellen R. Miller

Systematics of early and middle Miocene Old World monkeys

New information about the early cercopithecoids Prohylobates tandyi (Wadi Moghra, Egypt) and Prohylobates sp. indet. (Buluk and Nabwal, Kenya) is presented. Comparisons are made among all major collections of Early and Middle Miocene catarrhine monkeys, and a systematic revision of the early Old World monkeys is provided. Previous work involving the systematics of early Old World monkeys (Victoriapithecidae; Cercopithecoidea) has been hampered by a number of factors, including the poor preservation of Prohylobates material from North Africa and lack of comparable anatomical parts across collections. However, it is now shown that basal cercopithecoid species from both northern and eastern Africa can be distinguished from one another on the basis of degree of lower molar bilophodonty, relative lower molar size, occlusal details, symphyseal construction, and mandibular shape. Results of particular interest include: 1) the first identification of features that unambiguously define Prohylobates relative to Victoriapithecus; 2) confirmation that P. tandyi is incompletely bilophodont; and 3) recognition of additional victoriapithecid species.

CREODONTA AND CARNIVORA FROM WADI MOGHRA, EGYPT

Abstract Six new occurrences of carnivorous mammals from Wadi Moghra, early Miocene, Egypt, are described, and the implications of these taxa for interpreting the biogeography of early Miocene mammals are discussed. The new taxa include two hyaenodontid creodonts (Buhakia moghraensis, gen. et sp. nov., and cf. Teratodon) and four carnivorans: an amphicyonid (Cynelos, sp. nov.), two viverrids s. l. (Herpestides aegypticus, sp. nov., and Ketketictis solida, gen. et sp. nov.), and a stenoplesictid (Moghradictis nedjema, gen. et sp. nov.). Previously only two carnivorous mammals, both large creodonts (Hyainailouros fourtaui, Megistotherium osteothlastes), had been reported from Moghra. Together, the eight carnivorous taxa now known from Moghra include not only some representatives of widespread genera common to localities across Eurasia and Africa, but also a number of unique faunal elements, including three new genera and five new species. Evidence for two alternate hypotheses concerning the timing of carnivore migrations events are discussed: 1) an early Miocene (ca. MN 3) event followed by a slightly later (MN 4-5) one; or 2) an even earlier first migration in the late Oligocene-early Miocene (MN 1 or even MP 30), considered here to be the more likely scenario.

Intra- and interspecific variation in macaque molar enamel thickness

Enamel thickness has played an important role in studies of primate taxonomy, phylogeny, and functional morphology, although its variation among hominins is poorly understood. Macaques parallel hominins in their widespread geographic distribution, relative range of body sizes, and radiation during the last five million years. To explore enamel thickness variation, we quantified average and relative enamel thickness (AET and RET) in Macaca arctoides, Macaca fascicularis, Macaca fuscata, Macaca mulatta, Macaca nemestrina, and Macaca sylvanus. Enamel area, dentine area, and enamel-dentine junction length were measured from mesial sections of 386 molars scanned with micro-computed tomography, yielding AET and RET indices. Intraspecific sex differences were not found in AET or RET. Macaca fuscata had the highest AET and RET, M. fascicularis showed the lowest AET, and M. arctoides had the lowest RET. The latitudinal distribution of macaque species was associated with AET for these six species. Temperate macaques had thicker molar enamel than did tropical macaques, suggesting that thick enamel may be adaptive in seasonal environments. Additional research is needed to determine if thick enamel in temperate macaques is a response to intensified hard-object feeding, increased abrasion, and/or a broader diet with a greater range of food material properties. The extreme ecological flexibility of macaques may prohibit identification of consistent trends between specific diets and enamel thickness conditions. Such complications of interpretation of ecological variability, dietary diversity, and enamel thickness may similarly apply for fossil Homo species.

Brachypotherium minor n. sp., and other Rhinocerotidae from the Early Miocene of Buluk, Northern Kenya

ABSTRACT A new species of Rhinocerotidae, Brachypotherium minor n. sp., from the Early Miocene of Buluk, northern Kenya, is described. The new species shares with other members of the genus large sexually dimorphic incisors, flattened buccal walls on its molars, and a low astragalus, but differs from other species of Brachypotherium Roger, 1904 in its small size, placement of the orbit, having widely separated temporal lines, and more simple molar crown morphology. A comparison of the new species with other brachypotheres suggests that the new species may be present at a small number of other sites, and that the brachypothere group may contain more than one African lineage, adding to our understanding of the diversity of African rhinoceroses.

New infant cranium from the African Miocene sheds light on ape evolution

The evolutionary history of extant hominoids (humans and apes) remains poorly understood. The African fossil record during the crucial time period, the Miocene epoch, largely comprises isolated jaws and teeth, and little is known about ape cranial evolution. Here we report on the, to our knowledge, most complete fossil ape cranium yet described, recovered from the 13 million-year-old Middle Miocene site of Napudet, Kenya. The infant specimen, KNM-NP 59050, is assigned to a new species of Nyanzapithecus on the basis of its unerupted permanent teeth, visualized by synchrotron imaging. Its ear canal has a fully ossified tubular ectotympanic, a derived feature linking the species with crown catarrhines. Although it resembles some hylobatids in aspects of its morphology and dental development, it possesses no definitive hylobatid synapomorphies. The combined evidence suggests that nyanzapithecines were stem hominoids close to the origin of extant apes, and that hylobatid-like facial features evolved multiple times during catarrhine evolution.

Suidae and Sanitheriidae from Wadi Moghra, Early Miocene, Egypt

New suid and sanithere material from Wadi Moghra, early Miocene, Egypt, is described and discussed. The new material greatly improves the sample size and diversity of suoids known from North Africa, and includes one species of Sanitheriidae and three species of Kubanochoerinae. The Moghra suoid assemblage most closely resembles that from Gebel Zelten, Libya, suggesting that at least part of the Moghra deposits may overlap in time with part of Zelten, i.e., is equivalent in age to MN 4–5 of the European mammal zonation, or PIII of the East African one. Information from suids and sanitheres is consistent with previous interpretations, that the Moghra deposits were formed under swampy and littoral paleoenvironmental conditions.

A new anthracothere (Artiodactyla) from the early Oligocene, Fayum, Egypt, and the mystery of African ‘Rhagatherium’ solved

Abstract. Recent work on new anthracothere (Mammalia, Artiodactyla) specimens from the Jebel Qatrani Formation, early Oligocene, Fayum, Egypt, has revealed the presence of a new genus. Nabotherium new genus is described on the basis of a partial skull, several mandibular and maxillary specimens, and isolated teeth. The new genus exhibits a distinctive combination of features not seen in other Paleogene anthracotheres. The most noticeable characteristics of the new genus include the presence of large and well-developed upper and lower canines, caniniform third incisors, the presence of only a short diastema between the canine and first premolar, and broad, bunodont cheek teeth. This is in contrast to other contemporary anthracotheres, including other forms from the Fayum, which show a spatulate third incisor, a reduced canine, a much longer canine-premolar diastema, and more narrow, bunoselenodont cheek teeth. The presence of a relatively short rostrum with closely packed incisors, low-crowned and simple premolars, and low-crowned, bunodont molars indicates that members of the new genus would have been more efficient at crushing foods than slicing vegetation, and suggests a more varied herbivorous and frugivorous diet than was favored by other, more bunoselenodont Fayum anthracotheres.

Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye

In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.The fossil taxon Propotto was originally identified as a primate, but is currently widely interpreted as a bat. Here, the authors identify Propotto as a stem chiromyiform lemur and, based on phylogenetic analysis, suggest two independent lemur colonizations of Madagascar.

Patterns of dental emergence in early anthropoid primates from the Fayum Depression, Egypt

Abstract Paleontological field work in the Fayum Depression of Egypt has produced a remarkable diversity of fossil anthropoids, and this, combined with advances in genetic analyses of living anthropoids, has led to establishment of a temporal and phylogenetic framework for anthropoids that is achieving some degree of consensus. Less well understood are the evolutionary mechanisms and selective factors behind the origin and early diversification of anthropoids. One area that has remained under explored is investigation into the life history patterns of early anthropoids, a major omission given that understanding patterns of growth and development is essential for interpreting the paleobiology of fossil species. Here we detail dental emergence sequences for five species in four families of early anthropoid primates from the Fayum, and use these data to test Schultz’s Rule concerning the timing of emergence of molars versus premolars in mammals. Two important results are generated: (1) only one species had a dental eruption sequence identical to that observed among crown catarrhine primates; and (2) in all cases, the permanent canine was the last post-incisor dental element to fully erupt, a finding that may be significant for interpreting early anthropoid behavioral strategies.

Small vertebrates from Khasm El-Raqaba, late Middle Miocene, Eastern Desert, Egypt

Khasm El-Raqaba (KER) (28.451°N, 31.834°E) is a large commercial limestone quarry in Egypts Eastern Desert. The site is best known for cetacean fossils recovered from middle Eocene deposits, but remains of some geologically younger, small fossil vertebrates representing snakes, rodents and bats, have been recovered from karst fissure-fill deposits intrusive into the Eocene limestones. Comparisons with extant and extinct material reveal that the KER snakes represent two different colubrines, the rodents are referable to the ctenodactylid Africanomys, and the bats represent a new species of Hipposideros (Pseudorhinolophus). Together, faunal correlation and geological evidence are in broad agreement with a late Middle Miocene age for this KER fauna, and a palaeoenvironmental reconstruction of mixed subtropical and more arid microhabitats.