The iconic redwood tree (genus Sequoia) was widely distributed across the Northern Hemisphere during the Cenozoic. However, the living species are now confined to a narrow strip along the west coast of the United States. Due to the relatively scarce fossil records in certain regions, particularly East Asia, our understanding of its biogeographic history remains limited.
In a study published in Journal of Palaeogeography, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators reported a new Sequoia fossil record from the Late Palaeogene of southwestern China. The fossil discovery provided crucial evidence to decode the climatic and biogeographic history of this important genus.
The fossil leaves, unearthed in Jianshui County and dating to the Late Eocene–Early Oligocene (approximately 34-30 million years ago), have been identified as Sequoia maguanensis through detailed morphological and cuticular analysis. They show strong similarities to related fossils from nearby basins, featuring an alternate leaf arrangement with a decurrent base, straight epidermal cell walls, and stomata surrounded by four subsidiary cells, very similar to both the living coast redwood (Sequoia sempervirens) and previously described Sequoia fossils from Wenshan, Yunnan.
"This discovery not only enriches the fossil record of Sequoia in East Asia but also provides direct evidence for its distribution in this region during a critical transitional period of global cooling," said LI Shufeng of XTBG.
To reconstruct the historical distribution of Sequoia, the researchers applied species distribution modeling (MaxEnt). Using climate data from the current habitat of the sole living species, Sequoia sempervirens, along with global fossil records, the team reconstructed the genus’s most suitable potential habitats from the Palaeocene to the Pliocene.
The results indicated that Sequoia thrived in warm and humid conditions. As global temperatures declined from the Eocene to the Pliocene, its suitable habitats progressively shifted southward and contracted toward lower latitudes. Sequoia originated in East Asia during the Early Cretaceous, later dispersing to North America via the Bering Land Bridge. During the warmer Palaeocene, its range expanded to Greenland and Svalbard, reaching Western Europe by the Eocene.
Furthermore, the disappearance of Sequoia from southwestern China, including Yunnan, was attributed to the combined effects of global cooling, the intensification of the East Asian winter monsoon, and the genus's own long-term morphological stasis, which limited its ability to adapt to increasingly arid conditions.
"Our study clearly illustrates the origin, dispersal, and climate-driven response patterns of Sequoia, offering an important case for understanding the evolution of Northern Hemisphere flora," said LI Shufeng.
Fossil leaves of Sequoia maguanensis and living Sequoia sempervirens. (Image by YANG Rendan)
Available online 23 December 2025
