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Mummified fossils of Keteleerioxylon (Pinaceae) from the late Eocene of Maoming, South China and its phytogeographical, paleoecological implications
Mummified fossils are extraordinarily important for understanding both biotic evolution and ecology in the geological time, by uniquely providing a far more detailed source of information in comparison to impression materials. In this paper, new species Keteleerioxylon maomingensis is described on the basis of mummified fossil wood from the late Eocene Huangniuling Formation of the Maoming Basin, South China. Detailed anatomical study of well-preserved fossil wood confirmed its close affinity to the extant conifer genus Keteleeria comprising three species distributed in central, southern, and southeastern China, northern Laos and in Vietnam. K. maomingensis is the most ancient fossil evidence of the occurrence of taxon closely related to Keteleeria from the modern distribution area of this genus. This finding strongly suggest that the ancestors of extant Keteleeria were ranged in the late Eocene much further south than it has been indicated by previous fossil records. Unlike more ancient fossil woods known from the Youganwo Formation of Maoming Basin (Chadronoxylon maomingensis and Myrtineoxylon maomingensis), K. maomingenis has distinct growth rings confirming a progressive increase in rainfall seasonality in southern China from the middle to late Eocene. The analysis of growth-rings in the fossil wood in comparison with those of modern Keteleeria davidii suggest that in the late Eocene of Maoming Basin there was humid subtropical monsoon climate with less prominent rainfall seasonality than that in modern northeastern Vietnam.