Guwahati: A tiny mammal collected more than seven decades ago from Nagaland has sparked a breakthrough in evolutionary biology. Preserved in a museum since 1950, the shrew specimen has now been identified as a completely new genus and species—Nagasorex albidens—marking one of the most significant mammal discoveries from India in recent memory.
The discovery, published in the Bulletin of the American Museum of Natural History, is rewriting scientific understanding of shrew evolution. This one-of-a-kind animal shows a striking mix of ancient and modern features, with skeletal and dental characteristics previously thought to have vanished millions of years ago.
The authors of the study are Rainer Hutterer, Mark T. Swanson, Jacob A. Esselstyn, and Lawrence R. Heaney.
“A unique specimen of unidentified shrew from Nagaland, that had remained unstudied in hold-up collections of the Field Museum, first received our attention more than three decades ago. Because this specimen contains a unique mix of traits not seen in any other living taxa, it expands the known morphological diversity of shrews and may provide a key for a better understanding of the relationships among the Soricidae,” the authors state.
What makes this shrew extraordinary is that it doesn’t fit into any existing genus. Its tooth structure—34 in total—is unmatched among all living shrews. Such dental patterns were last seen in fossil genera from the Miocene and Pliocene epochs, including species believed to have gone extinct 5 to 10 million years ago. This unique blend of traits makes Nagasorex albidens not just a new species, but the representative of a brand-new genus altogether.
The specimen was originally collected by Walter N. Koelz in 1950 from Jakhama, a village nestled in the Naga Hills of northeastern India. It had remained unidentified in a museum collection for over 70 years until recent scientific techniques—including advanced genetic analysis and 3D skull imaging—were used to study it in detail. Despite its age, DNA was successfully extracted from the preserved skin, enabling comparisons with both modern and fossil shrews.
The mountains where Nagasorex albidens was found are part of the Burmese Arc, a relatively narrow but prominent geological feature that extends from the northeast border of India with Myanmar and China, south through eastern India (including Nagaland and Manipur) and western Myanmar (including Chin), to the Andaman and Nicobar Islands.
Genetic analyses revealed surprising connections. While the exact placement of Nagasorex within the shrew family tree remains tentative, its closest modern relatives appear to be African shrews from the subfamily Myosoricinae. This unexpected relationship suggests a profound evolutionary connection between African and Asian lineages, potentially indicating ancient migration events across continents. Furthermore, the new shrew shares affinities with fossil genera from Europe and Asia, suggesting that it retains primitive features once thought extinct.
Its physical appearance is equally distinct. Small in size, with soft brown fur, a narrow tail, and almost naked ears, the shrew’s external features are deceptively ordinary. However, a detailed examination of the skull and teeth reveals a different story. One particularly unique feature is a Y-shaped tooth pattern in its lower premolar, a trait considered diagnostic of certain fossil forms. The animal’s skull also shows a mix of modern and ancient cranial features, further confirming its unique evolutionary status.
The generic name combines the place of origin (Naga Hills) with the Latin sorex (shrew); the gender is masculine. The specific epithet combines the Latin albus (white) and dens (tooth).
In the vicinity of the type locality of N. albidens are two reserves—Intanki Sanctuary in southern Nagaland near Mt. Japvo, and Sirui National Park in northeastern Manipur. The largest park in the mountainous portion of the general region is Namdapha National Park in southern Arunachal Pradesh. “N. albidens may occur in one or more of these parks, but surveys are needed to determine whether this is so and whether the populations are stable,” the authors note.
“We suggest that N. albidens should be sought not only in Nagaland but throughout the high mountains of northeastern India, and consider it possible that it might occur in northern Myanmar and southern China, and perhaps along the eastern Himalayan front as well. We especially recommend thorough sampling in the moderate and high-elevation areas that produce voucher specimens of small mammals for morphological studies and tissue samples for genetic studies. These areas are often especially poorly represented in current collections, and specimens are necessary for definitive study of the diversity and phylogenetic relationships and for determining conservation priorities for the many little-known species,” the authors add.
Shrews are small insectivorous mammals that rarely attract public attention, but they play a crucial role in ecological food webs. With nearly 500 known species across 29 genera, they are one of the most diverse families of mammals. Yet this discovery proves that much remains unknown about their origins and evolutionary history.
As conservation challenges mount and natural habitats shrink, the discovery of Nagasorex albidens serves as a powerful reminder: the natural world still holds surprises—and some of its most important clues are already collected, simply waiting to be recognised.
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