Earliest Swintonia (Anacardiaceae) fossil from the late Paleogene of India suggests its Gondwanan origin

The Anacardiaceae family plays a vital ecological and economic role in tropical and subtropical regions globally. The genus Swintonia Griff. being an evergreen genus is confined largely to Southeastern Asia. This study reports the earliest fossil record of Swintonia from the late Oligocene (∼24–23 Ma) sediments of the Makum Coalfield, Assam, northeast India, offering new insights into the evolutionary history of the genus. The fossil leaf described here represents the species Swintonia floribunda Griff., placing it within the subfamily Anacardioideae. This finding supports the Gondwanan origin of the Anacardiaceae family, where India plays a pivotal role in its early diversification and dispersal. Further, it enriches the Paleogene fossil record of the family and suggests an Indian origin for the genus, followed by its subsequent migration to Southeast Asia. The presence of Swintonia in the late Oligocene indicates that the genus emerged earlier than previously thought, thriving in the warm and humid climate of the Indian subcontinent. This finding enhances our understanding of its evolutionary development and biogeographic distribution.