Laetoli, Tanzania: Extant terrestrial mollusc faunas shed new light on climate and palaeoecology at a Pliocene hominin site

• Published in: PloS one 2024-05, Vol.19 (5), p.e0302435-e0302435
• Main Authors: Tattersfield, Peter, Rowson, Ben, Ngereza, Christine F, Harrison, Terry
• Format: Article
• Language: English
• Subjects: Animals; Annual precipitation; Arid climates; Aridity; Biodiversity; Biology and Life Sciences; Climate; Climatic classifications; Earth Sciences; Ecology and Environmental Sciences; Ecosystem; Environmental conditions; Environmental factors; Forests; Fossils; Global climate; Grasslands; Habitats; Hominidae - physiology; Indicator species; Indicators (Biology); Mean annual precipitation; Mollusca - classification; Mollusca - physiology; Mollusks; Paleoecology; Paleontology; Pliocene; Precipitation; Reconstruction; Seasonal variations; Semiarid climates; Shells; Stratigraphy; Surveys; Tanzania; Vegetation; Woodlands
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0302435

Laetoli, Tanzania is one of the most important palaeontological and palaeoanthropological localities in Africa. We report on a survey of the extant terrestrial gastropod faunas of the Laetoli-Endulen area, examine their ecological associations and re-examine the utility of Pliocene fossil molluscs in palaeoenvironmental reconstruction. Standardised collecting at 15 sites yielded 7302 individuals representing 58 mollusc species. Significant dissimilarities were found among the faunas of three broad habitat types: forest, woodland/bushland and open (grassland and scattered, xeric shrubland). Overall, more species were recorded in the woodland/bushland sites than in the forest sites. Open sites were less diverse. Environmental factors contributing most strongly to the separation of habitat types were aridity index and elevation. The results are supplemented with new mollusc data from the Mbulu Plateau south of Lake Eyasi, and compared to the list of species cumulatively recorded from the Ngorongoro area. Some regional variation is apparent and historical factors may explain the absence of some fossil taxa from Laetoli today. Differences in seasonality separated upland forest sites on the Mbulu plateau from those at Lemagurut at Laetoli. Indicator species were identified for each habitat. These included several large-bodied species analogous to the Laetoli Pliocene fossil species that were then used for palaeoenvironmental reconstruction. Based on the estimated aridity index, and adopting the widely used United Nations Environment Programme (UNEP) global climate classification, the four stratigraphic subunits of the Upper Laetolil Beds (3.6-3.85 Ma) would be placed in either the UNEP's Dry Sub-humid or Semi-arid climate classes, whereas the Upper Ndolanya Beds (2.66 Ma) and Lower Laetolil Beds (3.85-