Fossil fruits from the early Paleocene of Patagonia, Argentina reveal west Gondwanan history of Icacinaceae

Phytocreneae (Icacinaceae) are a tribe of climbing plants distributed throughout tropical Afro-Eurasia and Papua New Guinea. There is a rich Cenozoic fossil record of the group with occurrences on all continents except Antarctica. Fossil evidence supports a Cretaceous origin but the biogeographic history of Phytocreneae remains unclear. We examined a silicified endocarp collected from the Danian (early Paleocene) Salamanca Formation at the Estancia Las Violetas locality. We investigated the internal structure using micro-CT scanning and compared the fossil with fruits of other living and fossil species. Finally, we explored the biogeographic history of the tribe graphically and discuss the implications of this discovery. The endocarp belongs to the fossil genus Palaeophytocrene. This new occurrence significantly expands the known geographic range of Phytocreneae in South America. Furthermore, this is the oldest (ca. 63 Ma) unequivocal evidence of the tribe in the southern hemisphere. The presence of Phytocreneae at Estancia Las Violetas confirms that these lianas occurred in mid-latitude forests by the early Paleocene, and it also reveals that the tribe likely survived the end-Cretaceous extinction event in southern South America. Future work on the tribe should include filling gaps in the Gondwanan record to test the hypothesis that Australasian lineages are related to American lineages via high-latitude dispersal.

Automated summary

Phytocreneae is a tribe of climbing plants widely distributed in tropical regions. The fossil record of this tribe spans the Cenozoic era, with occurrences on all continents except Antarctica. This study presents a new silicified endocarp fossil from the early Paleocene period, providing evidence of Phytocreneae's presence in South America and its survival during the end-Cretaceous extinction event. Analysis of the fossil's internal structure and comparison with other species contribute to understanding the biogeographic history of this tribe. Further research should focus on bridging the gaps in the Gondwanan record to examine the relationship between Australasian and American lineages.