Carvalho, Monica R., Herrera, Fabiany, Gomez Marulanda, Sebastian, Martinez, Camila, and Jaramillo, Carlos. 2021. "Early Records of Melastomataceae from the Middle-Late Paleocene Rain Forests of South America Conflict with Laurasian Origins." International journal of plant sciences, https://doi.org/10.1086/714053.
Premise of research. Melastomataceae are a diverse and primarily tropical family with a particularly sparse fossil record. Various biogeographic interpretations based on phylogenies, extant distribution, and a limited fossil record have placed the origin of the family in either Laurasia or Gondwana (eastern or western). Methodology. We describe Xystonia simonae M. Carvalho gen. et sp. nov. on the basis of fossil leaves from middle-late Paleocene deposits of the Bogota Formation in central Colombia. These leaves have a characteristic acrodromous venation pattern common among subfamily Melastomatoideae. The leaves are compared with various acrodromously veined fossils and living angiosperms to assess their natural affinities. Pivotal results. The fossil leaves described predate the earliest known occurrence of Melastomatoideae by 5-7 Myr and conflict with previous interpretations that considered Melastomatoideae as Laurasian in origin. In revising the fossil record of Melastomataceae, we reevaluated the age of Melastomaephyllum danielis Huert. to be Miocene (previously Eocene/Oligocene) using pollen obtained from the rock that contained the type specimen. Conclusions. Our findings contribute to the scant early records of Melastomataceae and show that Melastomatoideae was part of a tropical rain forest assemblage by the middle-late Paleocene. Leaf galls and other leaf damage on X. simonae evidence intense and specialized biotic interactions in the early evolution of this lineage.
