REVISION OF ACHATINA LEAKEYI (ORDER GASTROPODA, FAMILY ACHATINIDAE) AND ITS PALEOENVIRONMENTAL SIGNIFICANCE

Gastropod assemblages are important paleoenvironmental indicators that can reveal subtle differences in environment among localities, such as water availability. For example, the Giant African Land Snail, genus Achatina (family: Achatinidae), is frequently found in regions of eastern Africa with perennial water availability and a rainy/dry seasonal cycle. At the Miocene (~19 ma) East African Rift Valley site of Legetet, faunal dominance of Achatina leakeyi has been used to infer a seasonal climate, fluctuating between humid and dry conditions. Since identification of gastropods in the paleontological record relies primarily on shell morphology, which can be highly convergent among taxa, caution necessitates that only the most complete specimens are used for taxonomic identification. Close examination of the Legetet gastropod specimens in the National Museums of Kenya reveals several shells filled with the pea-sized, calcareous ova characteristic of Limicolaria, a viviparous genus within the family Achatinidae. Additionally, gross shell morphology can be characterized by apomorphis of the genus Limicolaria. Although Limicolaria and Achatina share achatinid synapomorphies in shell morphology and are superficially similar, their biology and reproductive behavior are vastly different. This taxonomic reassessment has profound implications for the paleoenvironmental reconstruction of Legetet, as the genus Limicolaria is not an indicator of more humid environments, instead employing vivipary as a mechanism to endure and reproduce in lengthy dry seasons. As a result, the paleoenvironmental interpretation of Legetet should be revised to reflect a much more arid environmental setting. It is also recommended that the nomenclature of Achatina leakeyi be revised to Limicolaria leakeyi.