Wits Evolutionary Studies Institute (ESI)

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    Molteno Kannaskoppia: Mid-Triassic gymnosperm case study for whole-plant taxonomy
    (Evolutionary Studies Institute, 2023-12) Anderson, John M; Anderson, Heidi M
    The flora from the Upper Triassic Molteno Formation, southern Africa, is the most extensively collected and documented macro-flora in the Gondwana Triassic. The collection includes c. 30 000 catalogue slabs from 100 assemblages in 43 super-localities. Some 61 genera and 211 species have been described in a series of publications from the early 1980s covering most of the plant groups. In this volume, the genus Kannaskoppia and affiliates, in the order Petriellales, are described in greater detail than previously in 2003, and offer the opportunity to explore the question of whole-plant genera and species. The ovulate strobilus, Kannaskoppia, with the single species K. vincularis, occurs in only one assemblage – where it is common with c. 50 specimens, including five with both the foliage and strobili found attached to shoots. This find remains unique for the Gondwana Triassic. The male strobilus, Kannaskoppianthus, with eight species recognized (four described as new), occurs in 12 assemblages; at two of these, both distinct species, it is found attached to shoots. The foliage Rochipteris, with 12 Molteno species recognized (seven described as new), is known from 26 of the 100 Molteno assemblages; at four of these, in three distinct species, the foliage has been found attached to shoots. For each of the these 26 assemblages, geographic and stratigraphic information is provided, plus the associated fl ora and plant/insect records. As in previous Molteno publications, the Palaeodeme approach is followed in the circumscription of species. All the Reference Palaeodemes are illustrated by line drawings and extensive photographs as are the more important Sister Palaeodemes. A comprehensive revision of the Gondwana Triassic records of Rochipteris has resulted in 24 accepted species, of which seven occur only in the Molteno Flora. All previously illustrated material is listed in the hypodigm table and used for comparison and nomenclatural considerations with the Molteno specimens. Whole-plant species from the Molteno have been recognized, based on considerations of affiliation and taphonomy. For each of these the habit and habitat are reconstructed in colour. Each is placed in its most-likely habitat within the Molteno Biome, with the seven primary habitats (ecozones) as recognized previously for the Formation. These plants are typically considered perennials to about one metre high that grew in a variety of habitats and were often associated with Dicroidium/Umkomasia or with Heidiphyllum/Telemachus trees. The current study of Kannaskoppia, and affiliates, supports previous phylogenetic, anatomical and ecological studies that amongst the gymnosperms the order Petriellales constitutes a likely sister group of the angiosperms.
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    New fossil remains of Homo naledi from the Lesedi Chamber, South Africa
    (eLife Sciences Publications Ltd, 2017-05) Hawks, J.; Elliott, M.; Schmid, P.; Churchill, S.E.; de Ruiter, D.J.; Roberts, E.M.; Hilbert-Wolf, H.; Garvin, H.M.; Williams, S.A.; Delezene, L.K.; Feuerriegel, E.M.; Randolph-Quinney, P.; Kivell, T.L.; Laird, M.F.; Tawane, G.; DeSilva, J.M.; Bailey, S.E.; Brophy, J.K.; Meyer, M.R.; Skinner, M.M.; Tocheri, M.W.; VanSickle, C.; Walker, C.S.; Campbell, T.L.; Kuhn, B.; Kruger, A.; Tucker, S.; Gurtov, A.; Hlophe, N.; Hunter, R.; Morris, H.; Peixotto, B.; Ramalepa, M.; van Rooyen, D.; Tsikoane, M.; Boshoff, P.; Dirks, P.H.G.M.; Berger, L.R.
    The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.
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    The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa
    (eLife Sciences Publications Ltd, 2017-05) Dirks, P.H.G.M.; Roberts, E.M.; Hilbert-Wolf, H.; Kramers, J.D.; Hawks, J.; Dosseto, A.; Duval, M.; Elliott, M.; Evans, M.; Grün, R.; Hellstrom, J.; Herries, A.I.R.; Joannes-Boyau, R.; Makhubela, T.V.; Placzek, C.J.; Robbins, J.; Spandler, C.; Wiersma, J.; Woodhead, J.; Berger, L.R.
    New ages for flowstone, sediments and fossil bones from the Dinaledi Chamber are presented. We combined optically stimulated luminescence dating of sediments with U-Th and palaeomagnetic analyses of flowstones to establish that all sediments containing Homo naledi fossils can be allocated to a single stratigraphic entity (sub-unit 3b), interpreted to be deposited between 236 ka and 414 ka. This result has been confirmed independently by dating three H. naledi teeth with combined U-series and electron spin resonance (US-ESR) dating. Two dating scenarios for the fossils were tested by varying the assumed levels of 222Rn loss in the encasing sediments: a maximum age scenario provides an average age for the two least altered fossil teeth of 253 +82/–70 ka, whilst a minimum age scenario yields an average age of 200 +70/–61 ka. We consider the maximum age scenario to more closely reflect conditions in the cave, and therefore, the true age of the fossils. By combining the US-ESR maximum age estimate obtained from the teeth, with the U-Th age for the oldest flowstone overlying Homo naledi fossils, we have constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the later parts of the Pleistocene in Africa, and indicate a much younger age for the Homo naledi fossils than have previously been hypothesized based on their morphology.