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The Baripada Beds, exposed along the Budhabalanga River in Odisha, India, represent a remarkable window into the late Miocene, roughly 12.6 to 8.3 million years ago. First studied over a century ago, these fossil-bearing marine deposits have yielded an extraordinary diversity of vertebrates, invertebrates, and microfossils. Among the vertebrates, sharks and rays have dominated, offering a detailed snapshot of Miocene elasmobranch diversity in the Indian Ocean. Fossil collections from Mukurmatia and Itamundia between 2017 and 2022 have expanded this record, with several species reported for the first time from the region. Now, a new study aims to reconstruct the paleoenvironment of the Baripada Beds to fill gaps in our understanding of Miocene marine life in India, particularly the diversity and distribution of sharks and rays. By collecting over 200 new shark and ray teeth from Mukurmatia and Itamundia, researchers were able to identify several species previously unrecorded in India, including some entirely new to the Miocene deposits of the subcontinent.
Geologically, the Baripada Beds rest atop the Precambrian Singhbhum Granite and are composed of greenish to yellowish shales, soft sandstones, and limestones. The limestone layer, which is around 5 feet (1.5 meters) thick, is particularly fossil-rich, containing remains of what once roamed the seas: oysters, gastropods, foraminifera, and sharks and rays (leaving behind only teeth). The beds show a sequence from limestone to sandstone and then shale, capped by much younger Quaternary deposits. Fossil evidence suggests these sediments formed near river mouths and shallow coastal seas, under tropical to subtropical conditions; tiny sea creatures in the rocks indicate the water was probably less than 131 ft (40 m) deep and connected to the open ocean.
And where there sharks? Oh yes, there definitely were. Sharks of the Baripada Beds were found to be dominated by the family Carcharhinidae, with seven genera including Carcharhinus, Galeocerdo, Glyphis, Negaprion, Physogaleus, Rhizoprionodon, and Scoliodon. Lamnidae is represented by three genera, while other families, including Sphyrnidae, Alopiidae, and Odontaspididae, contribute a single genus each. Not to mention there were also rays (or batoids), as well! And they show similar diversity, represented by eight families and numerous genera such as Dasyatis, Myliobatis, and Aetobatus. This biodiversity extends to bony fishes, reptiles, and mammals, here as well, including early representatives of Suidae, Bovidae, and Rhinocerotidae. The variety of species suggests a complex food web where predators, prey, and scavengers all interacted, much like modern tropical coasts. And the presence of mammals, likely nearshore or river-dwelling species, indicates that these habitats were not just marine, but included areas where land and sea met.
Many of the sharks and rays in the Baripada Beds had adaptations similar to species alive today. For example, Carcharhinus and Sphyrna species are circum-tropical, occupying habitats ranging from shallow coastal waters to offshore regions under tropical, subtropical, and temperate conditions. Certain species, such as bull sharks (Carcharhinus leucas), display remarkable freshwater adaptability, while others, including tiger sharks (Galeocerdo cuvier) and thresher sharks (Alopias spp.), thrive in open ocean conditions. Rays like the spotted eagle ray (Aetobatus narinari) and Taeniurops are generally benthic or shallow-water inhabitants, often associated with estuaries and river mouths. This range of adaptations confirms that the Baripada Beds were nearshore seas with a variety of microhabitats, including tidal flats, lagoons, estuaries, and open shallow waters. Essentially, these ancient seas provided shelter, food, and breeding grounds for a wide variety of species, much like modern tropical coasts in the Indian Ocean.
Paleobiogeographically, the Baripada Beds offer a fascinating glimpse into how sharks and rays moved across ancient oceans during the Miocene. Comparisons of the fossils with other Indian Miocene sites, including Kutch on the west coast, Bhavnagar in Gujarat, and Mizoram in northeast India, reveal strong similarities at the genus level; this suggests that elasmobranchs were not confined to a single region but frequently migrated along the subcontinent’s coasts, likely following food sources and suitable habitats. When researchers expand the comparison globally, the Baripada fauna shows a surprising resemblance to Upper Miocene sites across the Circum-Pacific region, including Borneo, Panama, Japan, and even parts of South America. This pattern indicates that seaways through the Indian Ocean and the Tethys Sea were open at the time, enabling these marine animals to travel long distances and colonize multiple regions. In contrast, fossils from the Mediterranean and Atlantic show much lower similarity, highlighting how geography and shifting landmasses gradually isolated marine populations. But, interestingly, while genera were widely shared across regions, species-level comparisons tell a different story. Many species appear unique to the Indian Ocean, demonstrating endemism and what seems to be a localized evolution. This suggests that even though sharks and rays could travel long distances, local environmental conditions (such as water temperature, depth, and coastal geography) shaped distinct regional communities.
This new article also pinpoints that several new species were recently discovered, including Carcharhinus amblyrhynchoides, C. brevipinna, C. perezi, and Physogaleus hemmooriensis. The newly reported species from Mukurmatia and Itamundia, including Carcharhinus amblyrhynchoides, C. brevipinna, C. perezi, and Physogaleus hemmooriensis, underscore the need for taxonomic revision of Miocene elasmobranchs in India. These new fossil discoveries highlight just how much we still have to learn about Miocene sharks in India. Even in areas that have been studied for over a century, like the Baripada Beds, careful excavation and modern techniques continue to uncover species that were previously unknown! The Baripada Beds clearly represent shallow coastal seas, interspersed with lagoons and estuaries, where saltwater mixed with freshwater from nearby rivers. This kind of habitat would have been rich in nutrients, supporting a wide range of life — a dynamic, highly productive ecosystem where diverse species interacted, competed, and coexisted.
By bridging local discoveries with broader global patterns, the Baripada Beds do more than simply document a list of species. These fossils will now allow scientists to trace how sharks, rays, and other marine animals adapted to changing coastlines, shifting sea levels, and new habitats over millions of years. They also have revealed ancient migration pathways, showing how seaways connected distant regions and allowed species to disperse across vast oceanic distances. Studying these patterns allows scientists to better understand the processes that have influenced the modern distribution of species in the Indian Ocean and beyond. But as we piece together the pieces of what our oceans used to be, it makes one wonder how these species responded to environmental pressures that we can barely imagine today. And if we put a modern lens on it all: What can the rise and fall of these Miocene marine communities teach us about the resilience (or vulnerability) of modern marine ecosystems in the face of climate change? Could the ancient migration patterns of sharks and rays inform conservation strategies for species whose ranges are now shrinking or shifting?
For anyone captivated by the lives of sharks, rays, and other denizens of ancient seas, the Baripada Beds tell a story of survival. Of adaptation. It will be interesting to see with the advancements of technology what hidden stories still lie buried beneath our oceans and riverbeds, waiting to challenge our understanding of life on Earth.
