Guwahati, March 12: Researchers from the Geological Survey of India (GSI) have documented Miocene-era shark teeth from the South Garo Hills District of Meghalaya for the first time. This study, published in the Arabian Journal of Geosciences, provides valuable insights into the prehistoric marine ecosystem of the region and expands the knowledge of ancient sharks in India during the Miocene epoch.

The Miocene Epoch is a geological time period that lasted from 23 million to 5.3 million years ago. It is part of the Neogene Period and was a time of major environmental changes. During this period, Earth’s climate cooled, grasslands spread across continents, and ocean life, including sharks, thrived in warm, shallow seas.

According to the study done by Bashisha Iangrai and Vinod Kumar, K. B., Palaeontology Division, Geological Survey of India, North Eastern Region, Shillong and published in the Arabian Journal of Geosciences, these fossils closely resemble Miocene shark assemblages previously found in the Baripada beds of Odisha and the Surma Basin of Mizoram. This finding reinforces the idea that during the Miocene epoch, northeastern India was connected to an expansive ancient sea, rich in marine biodiversity.

Researchers unearthed fossilized teeth from four shark families: Lamnidae (mackerel sharks), Hemigaleidae (weasel sharks), Carcharhinidae (requiem sharks), and Sphyrnidae (hammerhead sharks). These specimens, preserved in the Baghmara and Chengapara formations dating back approximately about 15 to 23 million years ago, suggest that this region was once part of a shallow, nearshore marine environment.

Among the most striking discoveries were teeth from Isurus (mako sharks), Carcharhinus (requiem sharks), and Sphyrna (hammerheads). These sharks, apex predators of their time, dominated the prehistoric oceans much like their modern descendants. The teeth, though fragmented and worn, provide valuable insights into the region’s paleoenvironment and its evolutionary past.

The presence of Isurus suggests an open-sea habitat, while Carcharhinus and Hemipristis serra (a snaggletooth shark) point to coastal, tropical waters with abundant prey. The discovery of Sphyrna teeth, albeit rare, indicates that hammerheads once roamed these waters, their distinctive heads giving them an advantage in hunting along the ocean floor.

Along with shark teeth, the site contained fossilized mollusks, crabs, crocodile teeth, barnacles, plant remains, amber, and tiny fossilized spores and pollen. These suggest a rich, diverse coastal environment.

The presence of open-water and coastal shark species suggests that this region was once a warm, shallow sea with strong ocean currents and periodic changes in sea level.

Lead researcher Bashisha Iangrai and co-author K. B. Vinod Kumar emphasized that this discovery not only adds to India’s fossil record but also encourages further research in Meghalaya. Future studies may use isotope analysis to estimate the ancient ocean’s temperature and salinity, and strontium isotope dating to pinpoint the exact age of the fossil-bearing sediments.

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