Early Miocene small mammals from Harta 2 (western Anatolia) and their implications for systematics and biostratigraphy
The newly discovered Early Miocene small mammal assemblage from Harta 2 in western Anatolia, dominated by rodents and assigned to local zone D (MN3), provides critical data for refining the region's biochronology, extending the stratigraphic range of *Vasseuromys duplex*, and reconstructing subhumid paleoenvironmental conditions.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Deep time leaves its most intimate signatures not in the bones of giants, but in the tiny, scattered teeth of creatures that scurried through the undergrowth. For scientists studying the history of life, these small mammals—rodents, shrews, hedgehogs, and bats—are invaluable timekeepers. Because they evolve quickly and leave behind distinct dental patterns, their remains act as precise markers that allow researchers to date rock layers and track how environments changed over millions of years. In the region surrounding the Mediterranean, these tiny fossils have helped build a timeline of the Early Miocene epoch, a warm period roughly 20 million years ago when the continents were shifting and new ecosystems were taking shape. However, the record in western Turkey has long had gaps, with many fossil sites known only from brief mentions or incomplete lists, leaving a blurry picture of how life evolved in this specific corner of the ancient world.
A team of researchers has now filled in a significant piece of that puzzle by describing a newly discovered site called Harta 2, located in the Manisa region of western Turkey. By carefully washing thousands of kilograms of sediment through fine screens and sorting the resulting concentrate under microscopes, the team recovered a rich collection of small mammal fossils. The assemblage is dominated by rodents, specifically a species of mouse-like creature called Eumyarion aegeaniensis, which makes up the vast majority of the finds. Alongside this dominant species, the site yielded other rodents, including a dormouse named Vasseuromys duplex and a squirrel relative called Palaeosciurus feignouxi. The collection also includes insect-eating mammals such as a hedgehog (Galerix uenayae), a mole-like creature (Theratiskos), and a shrew (Oligosorex), as well as a single bat tooth. Notably, the researchers found no remains of rabbits or hares, which are common in other similar ancient sites.
The specific mix of animals found at Harta 2 allows the scientists to place the site firmly within a known time window, which they identify as a local zone called "D," corresponding to a broader European time marker known as MN3. This dating is supported by the presence of three key rodent species that are characteristic of this period in western Anatolia. However, the site also holds a surprise that challenges a simple, linear view of how these animals evolved. One of the dormice found there, Vasseuromys duplex, was previously known only from older, earlier sites. Its presence at Harta 2 suggests that this species did not vanish immediately when the younger time period began; instead, it persisted alongside the newer species for a while. This finding indicates that the transition between these ancient time periods was not a sudden swap of entire communities, but rather a more complex overlap where older and newer species coexisted.
The combination of species at Harta 2 also offers clues about the ancient landscape. The abundance of rodents with complex tooth ridges, which are typically associated with eating seeds and living in trees, along with the presence of a bat and a hedgehog, points to a subhumid environment with a fair amount of vegetation. It was likely a place with some forest cover and lush undergrowth, rather than an open, dry plain. While the fossil record from this specific site is too small to reconstruct the exact layout of the forest, the evidence strongly suggests a thriving, green ecosystem.
This new discovery does more than just add a list of names to a database; it provides a clearer picture of how life in western Anatolia changed during the Early Miocene. By showing that older species could survive alongside newer ones, the Harta 2 site reveals that the evolution of these small mammals was a gradual and regionally varied process. The researchers emphasize that while the site fits into the established timeline, it also highlights the unique and mixed nature of local faunas, reminding us that the history of life is often written in overlapping chapters rather than distinct, separate pages. Through the careful study of these tiny, broken teeth, the team has helped refine the timeline of the region and offered a glimpse into a lost world that was both familiar and distinct from the one that followed.
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