A fossil of the austral tree fern genus Lophosoria (Dicksoniaceae) from mid-Cretaceous Myanmar amber

The occurrence of taxa typically associated with Gondwana, in what is now the Northern Hemisphere, remains an intriguing subject in paleobiogeography. We describe an unusual tree fern from mid-Cretaceous amber in Myanmar, classified in the genus Lophosoria (Dicksoniaceae, Cyatheales). Its classification within the extant genus Lophosoria is supported by distinctive morphological features of the fertile pinnule, notably its unique flanged spores. Currently, Lophosoria is restricted to the Neotropics and southern South America, with prior paleopalynological and megafossil data indicating its exclusive presence in the Southern Hemisphere, particularly in Eastern Australia, the Falkland Plateau, South America, and the Antarctic Peninsula, suggesting a Gondwanan origin. The identification of the new species in mid-Cretaceous Northern Hemisphere deposits marks the genus's earliest confirmed occurrence in this region, broadening our understanding of its historical distribution and early evolution. This discovery contributes to the recognized diversity of Lophosoria, which has largely been based on spore fossils linked to the genus Cyatheacidites. We also discuss the paleobiogeographic and paleoclimatic implications for the evolutionary history of Lophosoria.