Earliest thorny bamboo from Pleistocene of Asia characterizing spinescence and paleoclimatic adaptations in bamboos

Abstract

Spinescence—characterized by spines, prickles, and thorns—is a key defensive trait in plants, but is rare among bamboo genera. Its evolutionary history in bamboos remains poorly understood due to limited fossil evidence, with only a single previously documented specimen of a preserved node. Furthermore, the evolutionary ecology and paleoclimatic adaptations of bamboos during the Quaternary in Asia remain unclear due to a lack of fossil records. This study introduces Chimonobambusa manipurensis sp. nov., a well-preserved thorny bamboo fossil from the late Pleistocene of eastern India, marking the first Asian fossil record of thorny bamboo and the first Quaternary record from Asia. The fossil features nodes, internodes, nodal buds, and thorn scars, offering novel insights into bamboo spinescence and nodal morphology. C. manipurensis displays three well-preserved nodes, two complete internodes, prominently conserved nodal buds, and 3–4 thorn base scars along each nodal rim. Morphologically, it shares traits seen in modern Chimonobambusa Makino and is placed within the same genus. Together with a Pliocene–Pleistocene thorny bamboo record from Peru, this discovery suggests spinescence in bamboos likely emerged during the Neogene, with evolutionary adaptations continuing into the Pleistocene potentially as an adaptation to changing climatic conditions and increased herbivory pressures. Furthermore, it suggests that bamboos during Quaternary time in Asia were growing under warm and humid climatic conditions. This finding enhances our understanding of bamboo morphological evolution and paleoclimatic adaptations, filling a critical gap in the global fossil record.