Ancient Assam Fossil Reveals Why Rare Plants Vanished from India

Guwahati: Scientists discovered a 24-million-year-old fossil leaf in the Makum Coalfield of Assam, India. This specimen represents a previously unknown species, Tetrameristophyllum makumensis. It closely matches the modern Tetramerista glabra, a plant now found only in the peat swamps of western Malesia. The find, documented in the 2026 Geological Journal, shifts the history of the Tetrameristaceae family significantly westward.

Harshita Bhatia and Gaurav Srivastava of the Birbal Sahni Institute of Palaeosciences led the study. They pulled the fossil from the Tikak Parbat Formation at the Tirap colliery. Researchers date the leaf to the late Oligocene. Back then, the area featured a complex mix of river systems, deltas, and wetlands. It was humid. It was warm.

Bhatia noted, "Our new study provides a glimpse into such a story from the late Oligocene, around 24-23 million years ago. We discovered a fossil leaf from the Makum Coalfield in Assam that represents a Tetramerista-like plant. Today, Tetramerista is restricted to freshwater peat-swamp forests of Southeast Asia. Our findings show that this plant group once occurred much farther west, in the Indian subcontinent, when suitable wetland habitats were present here."

The team analyzed 18 climatic variables across 151 modern sites to determine why the plant vanished from India. They concluded that climate shift was not the primary driver. The plants still thrive in similar conditions elsewhere today. Instead, the researchers point to the loss of specialized freshwater peat-swamp habitats. Tectonic shifts and the development of the Himalayan monsoon likely dried up these vital wetlands. Bhatia added, "The fossil record therefore offers a striking perspective on a process that remains relevant today: when specialised habitats disappear, the species that depend on them may disappear from those regions as well."

This discovery highlights how environmental degradation forces regional extinctions. While the plant survived in Southeast Asia, its removal from India highlights the fragility of specialized ecosystems. Modern peat-swamp forests face similar threats from logging and drainage today.