Volume 28 1991

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    Palaeontologia africana Volume 28
    (Bernard Price Institute for Palaeontological Research, 1991)
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    A palaeontological model for determining the limits of early hominid taxonomic variability
    (Bernard Price Institute for Palaeontological Research, 1991) Wood, Bernard
    This paper has examined the utility and implications of using Australopithecus boisei as a model for assessing the limits of intraspecific variation in early hominid species. When compared to variation in a sample of lowland gorilla, the coefficient of variation values of the 25 cranial and mandibular, and 44 dental measurements taken on the A. boisei hypodigm were not excessive; the main difference between the two samples was the higher levels of canine variability within gorilla. Levels of variability in A. boisei were compared with those in the hypodigms of A. robustus and A. africanus. In neither case did comparisons demonstrate that those hypodigms were excessively variable. This suggests that if more than one taxon is present within these collections, then any differential diagnosis needs to be based on excessive variation in shape and not size.
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    Alun Rhun Hughes: a tribute after forty four years of companionship in Anatomy and Anthropology
    (Bernard Price Institute for Palaeontological Research, 1991) Tobias, Phillip V
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    Miocene faunal remains from the Burji-Soyama area, Amaro Horst, southern sector of the main Ethiopian Rift
    (Bernard Price Institute for Palaeontological Research, 1991) Suwa, Gen; White, Tim; Asfaw, B; WoldeGabriel, Giday; Yemane, Tesfaye
    The Palaeoanthropological Inventory of Ethiopia is dedicated to the discovery and documentation of palaeoanthropologically significant study areas in the Main Ethiopian Rift and Afar Depression. Fieldwork in the area at the southern end of the Amaro Horst during the 1989 field season was focused on a fossiliferous sedimentary succession with intercalated volcanic horizons. Potassium-argon dating sets a minimum age of 11.1 my for sediments bearing vertebrate remains. The partial skeleton of a fossil proboscidean recovered at Burji is described, illustrated and assessed comparatively. The remains are those of a primitive species of choerolophodont mastodon. Biochronological considerations place this specimen in the time range of 15-17 my. The presence of fossiliferous sediments in the Burji area suggest that a rift-related basin had developed in this part of Ethiopia by Middle or Early Miocene times.
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    The stratigraphy of the Sterkfontein hominid deposit and its relationship to the underground cave system
    (Bernard Price Institute for Palaeontological Research, 1991) Partridge, T C; Watt, I B
    A programme of orientated core drilling was carried out during 1989 to elucidate stratigraphic relationships within the Sterkfontein Formation and to obtain a representative suite of samples for palaeomagnetic analysis. The cores have revealed that the hominid-bearing cave deposits occur as a continuous succession comprising 6 Members and extending to a maximum depth of about 30 m below present surface. Of these Member I (comprising a sterile, residual fill) and Member 3 are the most extensive. This sequence has been displaced vertically downwards within a zone of decalcification coinciding with the central part of the deposit. This zone has been the focus of recent deep excavations at the site. The results of the drilling, in conjunction with recent surveys of the underground cave system, confirm that a dolomite floor existed at an average depth of about 20 m at the time offirst cave filling. Subsequent cavern development down to depths in excess of 50 m caused the local collapse of some lower units of the Sterkfontein Formation and, as new openings developed to the surface, permitted the ingress of younger fills below the base of the hominid-bearing succession.
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    Palaeo-ecology of the Sterkfontein hominids: a review and synthesis
    (Bernard Price Institute for Palaeontological Research, 1991) McKee, Jeffrey K
    Excavations at the Sterkfontein hominid fossil site have yielded a rich and revealing faunal assemblage. Evolutionary transitions are evident in early hominids and associated fauna between the times represented by Members 4 and 5. Member 4 has yielded a large and variable sample of Australopithecus africanus as well as evidence of considerable species diversity among the artiodactyls, carnivores and primates. The appearance of early Homo along with stone and bone tools in Member 5 coincides with a reduction of species representation in the orders of larger mammals as well as with the occurrence of new derived species and apparent extinctions. Three hypotheses have been suggested to account for the trends seen in the hominid-bearing members of the Sterkfontein Formation. The 'Climatic Change Hypothesis' accounts for the evolutionary trends by the causal factors of global and local cooling and aridification with evidence of savanna-grasslands supplanting an earlier environment with a denser cover of vegetation. The 'Taphonomic Hypothesis' explains changes in relative species representation at Sterkfontein in terms of the bone-accumulating agents; in Member 4 primary carnivores were largely responsible for the deposition of large mammalian fauna, whereas the scavenging activities of early Homo would have accounted for much of the bone and all of the artefacts found in Member 5. A third proposition is the 'Species Interaction Hypothesis', a derivative of the ' Red-Queen Hypothesis'; here the dynamics of species interaction, including competition and commensalism among hominids, carnivores and cercopithecids, propel the evolutionary changes and cause the extinctions. These hypotheses are not mutually exclusive, but the relative effects of the factors involved must be verified or refuted with better chronological controls and further analyses of the African fossil sites. The Sterkfontein Formation represents a microcosm in which various scenarios of African mammalian evolution can be tested.
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    The palaeontology of Haasgat a preliminary account
    (Bernard Price Institute for Palaeontological Research, 1991) Keyser, Andre W
    Haasgat is a cave on the steep western slope of the upper reach of the Witwatersrand Spruit, on the farm Leeuwenkloof 480 lQ, in the Brits District. It was heavily mined for flowstone (calcite). The cave contains a deposit offossiliferous cave silt and breccia that was partially removed by the miners and dumped on the steep slopes of the valley. The original entrance was probably a shallow inclined pit, leading into an upper chamber and then into the preserved depository. Both porcupines and carnivores served as accumulating agents for the bones. Fossils of the primates Parapapio and Cercopifhecoides, hyaena (Chasmaporthetes), fox, porcupines, several species of bovids and two species of Hyrax have been recovered. An insufficient number of fossils have been prepared to determine the age of the deposit with certainty. The deposit was provisionally thought to be of Pliocene age because of the occurrence of Parapapio. At this stage it would be unwise to correlate this occurrence with any other caves in this age range. It is concluded that the cave silts were deposited by flash floods, under a wetter climatic regime than that of the present.
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    Computed tomography and the measurement of enamel thickness in extant hominoids: implications for its palaeontological application
    (Bernard Price Institute for Palaeontological Research, 1991) Grine, Frederick E
    Isolated permanent lower molars of Homo sapiens, Pan troglodytes and Gorilla gorilla were imaged by computed tomography (CT) using a 1,5 mm thick section through the mesial cusps. The teeth were examined dry and immersed in water. Measurements of enamel thickness were made on enlargements of hard copy images. Following CT examination, the crowns were sectioned in the same plane, and the cut faces with maximum dentine content were micrographed for measurement using a scanning electron microscope (SEM). Enamel thickness measurements from the CT images were noticeably exaggerated compared to the ideal (sectioned) values, and the CT values for dry specimen images were even larger than those for wet specimen images. These results indicate that CT cannot be employed to measure enamel thickness with any degree of reliability in modem specimens. There is no close correspondence between the SEM and CT values; therefore, the latter cannot even be used to predict the actual values. Thus, the application of CT in the measurement of enamel thickness in fossils is rather dubious.
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    Dinofelis barlowi (Mammalia, Carnivora, Felidae) cranial material from Bolt's Farm, collected by the University of California African expedition
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1991) Cooke, H B S
    The collections made by the University of California African Expedition in 1947-48 at Bolt's Farm, near Sterkfontein, included some fine cranial and postcranial material of Dinofelis barlowi, associated with baboon skeletons and crania suggestive of a natural trap situation. The Dinofelis crania are described and compared with other species of this genus, generally lending support to Hemmer's view of a lineage D. diastemata, D. harlowi, D. piveteaui. The age of the deposit is estimated to be in the vicinity of 2 Ma.
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    Enamel thickness in South African australopithecines: noninvasive evaluation by computed tomography
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 1991) Conroy, Glenn C
    Until recently, it has not been possible to systematically study enamel thickness in fossil hominids except by physically sectioning the teeth. Because sectioning studies destroy original specimens, sample sizes will always be low. For this reason, anthropologists have had to devise other methods for acquiring these data such as by measuring enamel in naturally fractured teeth or where it is exposed in worn teeth. It is clearly important to develop and apply non-invasive techniques to augment and expand the data base of early hominid enamel thickness. This is a first attempt to provide such data for a sample of South African australopithecines by utilizing high-resolution computed tomography (CT). This study is based on over 130 CT scans taken at 1 mm slice thickness on a sample of 22 original Australopithecus africanus and A. robustus lower molars from Sterkfontein, Kromdraai, Makapansgat, Swartkrans and Taung. Mean values of absolute and relative enamel thickness between A. africanus and A. robustus are significantly different, confirming that robust australopithecines have thicker enamel than their gracile counterparts. CT sections were taken in the buccolingual plane through the mesial cusps (protoconid, metaconid). While the mean value of enamel thickness at the buccal cusp (protoconid) is greater in A. robustus than in A. africanus, the difference is not statistically significant. The difference in enamel thickness at the lingual cusp (metaconid) is statistically significant, however. This study represents an important, albeit preliminary, first step in establishing a methodology for the non-invasive evaluation of enamel thickness in fossil hominids by computed tomography. It demonstrates the viability of the technique and the type of problem oriented approach that can be tackled using computed tomography in modem anthropological research. Measurements derived from CT cannot, of course, be expected to have the same degree of precision as those taken directly from sectioned teeth; nevertheless, important insights into the functional morphology of early hominid teeth are still easily decipherable from the CT data. Given that the alternative to CT is the physical destruction of original hominid fossils, the slight loss in mensurational accuracy seems well worth the price.