Browsing Volume 36 2000 by Issue Date
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ItemEunotosaurus africanus and the Gondwanan ancestry of anapsid reptiles(Bernard Price Institute for Palaeontological Research, 2000) Modesto, Sean PatrickPhylogenetic analyses confirm that the turtle-like Late Permian reptile Eunotosaurus africanus is a parareptile (sensu deBraga & Reisz 1996) and identify it as the sister taxon of Procolophonomorpha. The tree topology for anapsid reptiles suggests that a distribution in Gondwanan Pangaea is ancestral for anapsids (sensu Gauthier, Kluge & Rowe 1988). Minimum divergence times (MDTs) determined from stratigraphic calibration of anapsid phylogeny suggest that anapsids were diversifying in Early Permian Gondwana as early as the Sakmarian. MDTs also support the idea that a preservational bias was operating on terrestrial vertebrates in Gondwana prior to the onset of continental sedimentation in the Late Permian. ItemSedimentology and taphonomy of Late Permian vertebrate fossil localities in southwestern Madagascar(Bernard Price Institute for Palaeontological Research, 2000) Smith, Roger M HThis is the first report of a project that tests the accuracy of the currently accepted palaeoposition of southern Madagascar during the late Permian in juxtaposition to the coast of Tanzania. This is done by comparing the sediments and fossils that accumulated in a series of rift valleys, each around 25 km wide, that formed in this part of Gondwana at the beginning of pull-apart some 250 million years ago. The study reported here on the Madagascan side of the rift system will be followed by a similar study of the Tanzanian portion. Field data on the sedimentology and vertebrate taphonomy of three separate fossil localities in the Late Permian, Lower Sakamena Formation of southwestern Madagascar are used to reconstruct the subenvironments of the Sakamena axial rift valley lake. 1. Ranohira: dominated by microlaminated mudrocks with three horizons of fossil bearing micrite nodules. The fossils are mostly complete articulated skeletons of an ?aquatic procolophonid reptile, Barasaurus, which inhabited the offshore epilimnion of a deep, thermally-stratified closed lake. 2. Zavoloa River: alternating cross-bedded conglomeratic sandstone and laminated siltstone are interpreted as braided delta deposits entering the linear margin of the lake from the passive side of the half graben. These deposits contain some fully articulated skeletons and numerous winnowed bonebeds of a supposedly semi-aquatic reptile, Claudiosaurus, that may be related to sauropterygians. 3. Mount Eliva: is dominated by the younginiform reptile, Hovasaurus, which occurs as articulated skeletons inside micritic siltstone nodules in the mudrocks of a sub-lacustrine deltaic sequence. Pebble masses in the abdomen of Hovasaurus are interpreted as ballast to facilitate swimming. The taphonomic style and sedimentary environment of the host strata confirm this interpretation. Thermal shock from periodic overturn and poisoning from algal blooms are the most likely causes of mass mortality among the aquatic fauna. Hydrogen sulphide released from anaerobic bacterial decay of soft tissue and girdle cartilage formed reduction halos around the newly buried reptile carcasses. At least 3 “micritization episodes” led to the precipitation of calcium cabonate in the reduction halos forming nodules around the vertebrate fossils. They are interpreted as periods of extended lowstand when thermal stratification could not be maintained and oxygenated waters came into contact with previously anoxic sediments. If such lowstand events were climatically controlled, they may be useful timelines to accurately correlate strata within and between these ancient rift valley lakes in both Madagascar and Tanzania. ItemSuperior cervical vertebrae of a Miocene hominoid and a Plio-Pleistocene hominid from southern Africa(Bernard Price Institute for Palaeontological Research, 2000) Gommery, DominiqueThe Miocene hominoid and Plio-Pleistocene hominid vertebral record is poor. In 1994, a complete atlas of a hominoid was found in breccia at Berg Aukas in Namibia. Its age was estimated to be middle Miocene (13 myr) on the basis of microfauna. This locality yielded the holotype of Otavipithecus namibiensis and the atlas could belong to the same genus. The specimen exhibits clear hominoid traits such as a weakly salient retroglenoid tubercle at the superior articular facet of the lateral mass, and a horizontal transverse process. This morphology of the transverse process is close to that of pygmy chimpanzees, gibbons and African colobines, suggesting that Otavipithecus was arboreal. This confirms the conclusions drawn from other parts of the skeleton. From the size of the atlas, a body weight of 15-20 kg is estimated for the Berg Aukas hominoid, which accords with previous estimates based on its teeth. The second fossil considered in this paper is an axis from Swartkrans, SK 854, dated to nearly 1,8 myr. This axis is compared with another Plio-Pleistocene axis from Ethiopia, AL 333.101. SK 854 shows a morphology different from that of humans and AL 333.101, and also of apes. The South African axis was attributed to Paranthropus by Robinson (1972), and its morphology is probably typical of bipedalism associated with climbing. ItemAfrican chelonians from the Jurassic to the present: phases of development and preliminary catalogue of the fossil record(Bernard Price Institute for Palaeontological Research, 2000) de Lapparent de Broin, FranceThe five major phases in the palaeontological history of African chelonians are presented: 1) autochthonous development of the north Gondwanan pleurodires from a Pangean source group; 2) littoral expansion of a member of this group (Bothremydidae), accompanied by the arrival of Laurasian marine turtles; 3) in situ development of pleurodires and the immigration of Eurasian cryptodires (Oligo-Miocene) traversing the Tethys in several waves; 4) great diversification and endemism (Pliocene to Holocene); 5) important faunal reduction due to climatic changes at the end of Holocene times (cooling, aridification); elsewhere, great speciation and arrival during the Present of the last European immigrant in the north. Throughout the period under consideration there were several reductions in taxonomic diversity and emigrations from Africa. A preliminary catalogue of the fossil record of African chelonians is given, presented country by country followed by a taxonomic listing. ItemNotes on the systematics of micromammals from Sterkfontein, Gauteng, South Africa(Bernard Price Institute for Palaeontological Research, 2000) Avery, D MThe micromammalian fauna from Sterkfontein Members 4 , 5E and 6 comprises 34 species. These include six insectivores, three bats, three elephant shrews and 22 rodents. Most of these taxa, or their equivalents, have been previously recorded. Four or five new additions were recovered from deposits probably belonging to Late Pleistocene Member 6, which have previously received little or no attention. Some previously recorded taxa were not found, but this was probably due to differences in identification rather than to the absence of these forms from the sample. ItemEquus capensis (Mammalia, Perissodactyla) from Elandsfontein(Bernard Price Institute for Palaeontological Research, 2000) Eisenmann, VeraThe skull and limb bones collected at Elandsfontein, Cape indicate that E. capensis was different from a Grevy's zebra. The body proportions were similar to those of an extant draft horse (E. caballus) and the skull resembled those of true Cape quaggas and a fossil Algerian plains zebra, E. mauritanicus. ItemA captorhinid with multiple tooth rows from the Upper Permian of Zambia(Bernard Price Institute for Palaeontological Research, 2000) Gow, Chris ECaptorhinids are some of the best known early amniotes. They range throughout the Permian and occur in North America, Europe, India and Africa. There are several small forms with single rows of marginal teeth, medium sized multiple-rowed forms typified by Captorhinus, and large forms most of which possess numerous rows of marginal teeth. As a group, captorhinids are extremely conservative in cranial morphology in most other respects. A small Late Permian, single rowed form has been recorded from the Madumabisa Mudstone of Zambia, equivalent in age to the Cistecephalus Assemblage Zone of the Karoo Basin of South Africa. This paper records a multiple-rowed form from these rocks similar in size to Captorhinus, but with distinctive dentition ItemExtinct equids from Limeworks Cave and Cave of Hearths, Makapansgat, Northern Province, and a consideration of variation in the cheek teeth of Equus capensis Broom(Bernard Price Institute for Palaeontological Research, 2000) Churcher, C S RufusDental specimens of Hipparion libycum from Limeworks Cave, and Equus capensis from Cave of the Horse’s Mandible in the Limeworks Cave entrance and from Cave of Hearths on the farm Makapansgat in the Makapansgat Valley are described. The concept of restricted local formations within each cave is discussed. Qualitative variation in the cheek teeth of E. capensis, based on a sample of 40 upper and 60 lower permanent premolars and molars from Cave of Hearths, demonstrates that there appears to be no correlation in the occurrence of one enamel feature with another between teeth of presumed different individuals. Teeth within a molar row show similar development of features between teeth, whether premolar or molar, as shown by plis, progressive migration of the protocone isthmus along the row, and penetration of the buccal valley to between the enamel loops of the metaconid and metastylid. Consequently, earlier descriptions of species of large Pleistocene Equus in Southern Africa founded on isolated teeth and, using such qualitative variation, are inept, unsuitable and inappropriate, and modem taxonomies synonymising them under E. capensis are supported. The Cave of Hearths ‘loose breccia’ (Beds 1-3 of Mason, 1988) containing earlier Stone Age/Later Acheulean artifacts, is circumstantially dated between 300 000 and 200 000 years BP. ItemA new procolophonid (Parareptilia) from the Lystrosaurus Assemblage Zone, Beaufort Group, South Africa(Bernard Price Institute for Palaeontological Research, 2000) Gow, Chris EThis paper describes the skull of a new genus and species of procolophonid from the Lystrosaurus Assemblage Zone. It is strikingly different from its contemporaries, Procolophon trigoniceps and Owenetta rubidgei, but has a mosaic of characters of each. ItemThe Neogene rhinoceroses of Namibia(Bernard Price Institute for Palaeontological Research, 2000) Guerin, ClaudeSince 1991 the Namibia Palaeontology Expedition has excavated four Miocene sites in the Sperrgebiet, three of which (Arrisdrift, Fiskus and Auchas Mine) are new. Only the material from Arrisdrift and a single bone from Langental are specifically determinable. All but one of the 81 rhinocerotid fossils from Arrisdrift constitute a homogeneous sample pertaining to a very large species of cursorial rhino. The exception is an isolated magnum which suggests a small to medium-sized short legged form, perhaps Chilotheridium pattersoni. A magnum from Langental probably represents Brachypotherium heinzelini. The large form from Arrisdrift seems to be the largest of the Miocene African Rhinos; the size and proportions of the metapodials and the other limb bones suggest an analogy with Diceros gr. pachygnathus-neumayri of the Upper Miocene of the Near East; the type of construction of the upper cheek teeth, namely die fourth premolar, is of Dicerotine type and presents, as do the dimensions, close resemblances with Diceros douariensis of the Upper Miocene of North Africa and Italy; the mandible shows analogies with the Dicerotines, especially the apparently short symphysis. This Rhino is Diceros australis nov. sp., so far the oldest known species of the subfamily.