A new study led by post-doctoral researcher Samuel Costa, from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), in collaboration with an international team of colleagues, shows how fossils can do more than reveal extinct life. By combining a 99-million-year-old amber fossil with plate-tectonic reconstructions, palaeoclimate data, modern species records and ecological niche modelling, the study demonstrates how palaeontology can help explain the biology of living species and even identify groups that may be vulnerable to future climate change.
These relevant findings were recently published in the Proceedings of the Royal Society B.
The research focuses on Tanaupodidae, a rare family of tiny mites with an unusual lifestyle. Like many Parasitengona mites, their larvae are parasites associated with other arthropods, while the later life stages are free-living predators that crawl through soil, litter and wet habitats. However, Tanaupodidae are especially remarkable because their active post-larval stages are mainly found during the coldest months of the year. While many small soil arthropods are most conspicuous in spring and summer, these mites are winter-active and may occur in cold, humid habitats, including wetlands, mountains and even icy environments.
Today, Tanaupodidae are known only from the Northern Hemisphere. Their living representatives occur mainly in temperate and humid regions of Europe, Asia and North America, and some species are restricted to cold mountainous areas. Until now, their fossil record also seemed to tell a northern story: Eocene Baltic amber from the Kaliningrad region, dating to more than 40 million years ago, and Early Cretaceous French amber from Archingeay-Les Nouillers, dating to more than 100 million years ago, had produced the only known fossil members of the family.
The new fossil changes this picture. The specimen, preserved in Kachin amber from Myanmar, belongs to a newly described genus, Calidothrombium gen. nov. Although Kachin amber is found today in Southeast Asia, geological and fossil evidence indicates that it formed on the Burma Terrane, an island-like landmass derived from Gondwana, the ancient southern supercontinent. During the Cretaceous, this terrane was drifting northward before eventually becoming part of Asia.
This discovery therefore represents the first record of Tanaupodidae from a Gondwanan-derived landmass. Together with the Cretaceous record from France, it shows that these mites were already present on widely separated landmasses around 100 million years ago. This raises a striking evolutionary question: if living Tanaupodidae are winter-active mites associated with cold and humid environments, why was a member of the family living in a tropical forest on a drifting island during one of the warmest intervals of the last half-billion years?
To investigate this question, the authors used MaxEnt, a machine-learning-based ecological niche modelling approach, to identify the climatic conditions and geographic areas most suitable for living Tanaupodidae, based on 131 verified modern occurrence records. The model identified cold and humid winter conditions as key factors associated with the present distribution of the family. In particular, the minimum temperature of the coldest month emerged as the most important climatic constraint, with the highest suitability occurring below 0°C and decreasing sharply under warmer winter conditions.
The fossil evidence tells a very different story. Palaeobotanical data indicate that both known Cretaceous amber deposits containing Tanaupodidae — Kachin amber and Archingeay-Les Nouillers amber — formed in warm, wet tropical forests. Palaeoclimate reconstructions conducted by the authors further show that the French Cretaceous locality experienced much warmer winter conditions than those associated with extant Tanaupodidae. By contrast, the Eocene Baltic amber record, which includes the extant genus Eothrombium, comes from a humid warm-temperate forest and shows winter temperatures much closer to those observed in the modern distribution of the family.
Together, these independent lines of evidence support a major ecological shift in Tanaupodidae: from a broader Cretaceous distribution that included tropical forest ecosystems to the restricted cold and humid habitats occupied by living species today. The new fossil does not simply add another extinct mite to the fossil record; it reveals that a lineage now associated with winter may once have included relatives adapted to warm tropical worlds.
The study also raises a cautious modern warning. If living Tanaupodidae are now limited by warm winter temperatures, ongoing climate warming may further reduce suitable habitats for some species, especially those restricted to cold mountains and humid temperate wetlands. The results therefore highlight the value of fossils for conservation biology: ancient amber can help reveal not only where life came from, but also which living lineages may be most sensitive to future environmental change.
This research was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, and the Brazilian National Council for Science and Technology Development (CNPq).
Reference: Costa, S.G.S., Klimov, P.B., Moreira, D.B.P., Wang, H., Assis-Silva, M.H. & Pepato, A.R. (2026) From warm to cold habitats: a Cretaceous Tanaupodidae fossil reveals a major climatic niche shift and wider past distribution in winter-active mites. Proceedings of the Royal Society B: Biological Sciences, 293, 20261497. https://doi.org/10.1098/rspb.2026.1497.
Fig.1 Calidothrombium gen. nov., a 99-million-year-old fossil mite preserved in Kachin amber.
Fig.2 Cretaceous fossil records of Tanaupodidae on widely separated landmasses: French amber from the Armorica plate and Kachin amber from the Gondwanan-derived Burma Terrane.
Fig.3 Climatically suitable areas for living Tanaupodidae inferred with MaxEnt. Warmer colours indicate higher suitability.
Fig.4 From warm to cold habitats: comparison of Cretaceous tropical amber forests, Eocene Baltic amber forests, and the cold-season habitats of extant Tanaupodidae, including modelled mean winter temperatures.
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