Credit: Geodiversitas (2025). https://sciencepress.mnhn.fr/en/periodiques/geodiversitas/47/20
Research teams from the Academia Sinica and National Taiwan University have documented the first discovery of five freshwater mollusk species in the Early Pleistocene Tananwan Formation of northern Taiwan. This pivotal finding, which demonstrates that some present-day freshwater snail lineages were established in Taiwan more than a million years ago, immediately establishes biogeographical connections with East Asia.
The discovery includes only the second known global fossil evidence of a juvenile snail shell preserved within its mother’s shell, a rare find that reveals ancient viviparous (live birth) and nurturing behavior in these prehistoric snails. The research is published in the journal Geodiversitas.
Dr. Chien-Hsiang Lin of Academia Sinica, one of the study’s authors, stated that these are the oldest known freshwater fossil organisms in Taiwan. The research team compared fossil assemblages in Taiwan with those across East Asia and Japan, confirming a crucial role for the Taiwan Strait land bridge during glacial periods. The land bridge acted as a key migratory corridor for freshwater species, underscoring its importance in East Asian species dispersal and evolution.
These ancient fossils provide a vital baseline for comparison with modern freshwater ecosystems, which are now threatened by human destruction and invasive species, serving as a solemn reminder to cherish and maintain these fragile natural systems.
Dr. Chun-Hsiang Chang from the Department of Geology at the National Museum of Natural Science, Taiwan, says, “This study represents a significant advance in understanding Taiwan’s freshwater paleontology. Whereas over 99% of the island’s molluscan fossil record is marine, the authors document the first well-described Early Pleistocene freshwater assemblage from the Tananwan Formation.
“Through integrated stratigraphic control, detailed morphological analyses, and comparative taxonomy, the team establishes a robust framework for reconstructing northern Taiwan’s paleoecology. The discovery of juvenile shells within adult Sinotaia quadrata—only the second fossil evidence of viviparity among viviparids worldwide—provides rare insight into ancient reproductive strategies.
“Equally noteworthy is the biogeographic interpretation: the early presence of S. quadrata in Taiwan implies an earlier faunal exchange with continental East Asia, likely via recurrent Pleistocene land appearance.
“By linking paleontology, stratigraphy, and island biogeography, this work moves beyond taxonomy to address broader evolutionary and environmental questions. It is a landmark contribution that fills a key gap in Taiwan’s Quaternary record and deepens our understanding of freshwater biodiversity evolution in the western Pacific.”
More information:
Fossil freshwater mollusks from the Early Pleistocene (Calabrian) of northern Taiwan, Geodiversitas (2025). DOI: 10.5252/geodiversitas2025v47a20. sciencepress.mnhn.fr/en/period … /geodiversitas/47/20
Citation:
Fossil of a baby sea snail inside a mother’s shell discovered (2025, November 7)
retrieved 8 November 2025
from https://phys.org/news/2025-11-fossil-baby-sea-snail-mother.html
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