Sprecher
Beschreibung
The Eocene collision of Indo-Pakistan into Asia and resulting biotic exchanges contributed to the immense biodiversity of tropical Asia. However, paleobotanical data with robust age controls from pre-interchange Indo-Pakistan are rare, limiting constraints for testing these hypotheses. Previously, mammal assemblages from the early Eocene (ca. 54–50 Ma) Ghazij Formation in Balochistan, Pakistan showed an into-India dispersal pattern. Here, we report the first plant macrofossils, insect damage, and comprehensive palynological data from the Ghazij Formation. The palynofloras indicate an environmental transition from coastal marine settings (lower Ghazij), to freshwater and coastal palm swamps (middle Ghazij), and to increasingly terrestrial ecosystems with persistent marine influence (upper Ghazij). We found palynomorphs typical of modern Southeast Asian forests in the lower and middle Ghazij, an interval of negligible mammalian interchange with Asia, including Podocarpus, Dacrydium, Casuarinaceae, Nypa, Barringtonia, Dipterocarpaceae, and Alangium. Additional pollen taxa from the upper Ghazij include Croton, Malvaceae, Polygonaceae, and Onagraceae. The macroflora is dominated by leaflets similar to Pometia (Sapindaceae), found throughout the Asian tropics today, and multiple Fabaceae and Arecaceae morphotypes. Rarer morphotypes include possible Menispermaceae, Rhamnaceae, Araceae, and the ferns Acrostichum and Salvinia. Insect-feeding damage is diverse and abundant, totaling 42 damage types—some of the highest richness of insect herbivory in the fossil record, when adjusted for sample size. Our finding of several extant Southeast Asian taxa as palynomorphs in the pre-collision lower and middle Ghazij is consistent with established hypotheses. However, pre-collision palynofloras from Southeast Asia are too sparse to entirely rule out a prior presence.