Zygosporium palaeogibbum sp. nov. (Xylariales, Ascomycota) associated with Cinnamomum Schaeff. (Lauraceae) leaves from the Siwalik (Middle Miocene) of eastern Himalaya

Abstract

Well-preserved remains of a mitosporic fungus were found on leaf cuticles of Cinnamomum sp. (Lauraceae) recovered from the lower Siwalik (Chunabati Formation; Middle Miocene) sedimentary stratum of Darjeeling foothills of eastern Himalaya. Based on the characteristic features (solitary vesicular conidiophores arising directly from a superficial mycelium and strongly curved, darkly pigmented, ovoid to pyriform vesicles with 1–3 celled stalk cells), it is here proposed as a new fossil species, Zygosporium palaeogibbum sp. nov. The in situ evidence of Z. palaeogibbum in appreciable numbers on the host leaf cuticles suggests the probable existence of a host-specific saprophytic relationship in the Darjeeling sub-Himalaya’s ancient warm humid tropical climate during the time of deposition. This conclusion on past climate is in agreement with published qualitative, quantitative, and palaeomycological climatic data obtained from the study of megafossil plant remains from the same fossil locality.