Guwahati, Oct. 7 -- A single fossil leaf buried for nearly 24 million years in Assam's Makum Coalfield has given scientists a new clue to why a plant lineage found today only in the peat swamps of Southeast Asia disappeared from the Indian subcontinent.

The fossil, discovered in the late Oligocene deposits of the Makum Coalfield in Tinsukia district, has been identified as a new fossil species, Tetrameristophyllum makumensis. Researchers say it closely resembles the living Tetramerista glabra, a plant now restricted to freshwater peat-swamp forests of western Malesia.

The discovery, reported in the 2026 Geological Journal, pushes the known history of the Tetrameristaceae family much farther west than its present-day distribution and sug...