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Paper Number: 1031

Palaeoclimatic implications of summer breeding frog taxa from Langebaanweg at 5.1 Mya at the south-western tip of Africa

Matthews, T. 1 and Measey, G. J. Measey2

1Iziko South African Museum, 25 Queen Victoria Street, Cape Town, South Africa, Email:tmatthews@iziko.org.za
2John Measey, Centre of Excellence for Invasion Biology, Department of Botany and Zoology, Natural Sciences Building, University of Stellenbosch, South Africa

Frogs are highly sensitive to fluctuations in moisture levels and temperature and fossil frog assemblages may thus potentially provide information on rainfall, seasonality, the types of water bodies available, and also the terrestrial environment (vegetation and substrate) as a great number of frog species are independent of water during various periods of their lifecycles. Until recently no direct palaeo-climatic proxies have been available to indicate the seasonality or amount of rainfall on the west coast of southern Africa during the Early Pliocene as the Neogene terrestrial fossil record is sporadic and incomplete due to the lack of preservation of terrestrial organic materials [1,2]. The Langebaanweg frog population has however provided evidence for substantial rainfall at 5.1 Mya at the south-western tip of Africa[3].

The Benguela Upwelling System (BUS) is today one of the main factors responsible for the present-day summer aridity on the west coast of southern Africa and the initiation of BUS (at ~10.5 – 10 Mya [4,5]) is frequently linked in the literature to the entrenchment of aridity, and the establishment of the current winter rainfall pattern on the west coast. However, marine proxies are inconclusive regarding the effects of past fluctuations in the BUS and sea surface temperatures (SSTs) on the rainfall regime. Neither the fossil evidence, nor the fact that plants using the C3 photosynthetic pathway predominate at this time, provides direct evidence of winter rainfall at Langebaanweg. The recent identification of two species of frog from the genus Ptychadena from Langebaanweg provides new and compelling evidence for a summer rainfall regime, or of at least significant summer rainfall, some 5.1 Mya on the west coast of South Africa in the Langebaanweg region.

References:

  1. Chase BM Lim S, Chevalier M Boom A and Carr AS Meadows ME Reimer PJ (2015) Influence of tropical easterlies in southern Africa's winter rainfall zone during the Holocene Quaternary Science Reviews 107: 138-148

  2. Neumann FH and Bamford MK (2015) https://www.researchgate.net/publication/281116241_Shaping_of_modern_southern_African_biomes_Neogene_vegetation_and_climate_changes?ev=prf_pub Shaping of modern southern African biomes: Neogene vegetation and climate changes Transactions of the Royal Society of South Africa

Matthews T van Dijk E Roberts DL Smith RMH (2015) An early Pliocene (51 Mya) fossil frog community from Langebaanweg south-western Cape South Africa African Journal of Herpetology 64(1): 39-53

  1. Heinrich S Zonneveld KAF Bickert T Willems H (2011) The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: Evidence from calcareous dinoflagellate cysts Paleoceanography: 26: PA3209 doi: http://dx.doi.org/10.1029/2010PA002065

  2. Rommerskirchen F Condon T Mollenhauer G Dupont L Schefuss L (2011) Miocene to Pliocene development of surface and sub-surface temperatures in the Benguela Current System Paleoceanography 26 (PA3216): 15 pp doi:101029/2010PA002074