Early Paleocene flowers confirm a deep history for Cunoniaceae in South America

GANDOLFO, M. A.; IGLESIAS, A.; JUD, N.A.; WILF, P. D.

Texas

Congreso; Botanical Society of America Annual Meeting; 2017

Botanical Society of America

Cunoniaceae comprises 27 extant genera and roughly 300 species of tropical and southern-temperate plants. The current distribution of this family is thought to have resulted from a combination of Gondwanan vicariance and long distance dispersal, but a sparse fossil record limits our ability to test alternate hypotheses. Herein, we report the discovery of two types of cunoniaceous flowers from the early Paleocene (Danian) Salamanca and Peñas Coloradas formations in southern Chubut Province, Argentina. The first has synapomorphies of extant Schizomerieae, including the presence of narrow, incised petals and a nectary disk; however, the fossils are unusual in having a perianth that is 8-10-merous, whereas in extant species the perianth is typically 4-5(6)-merous. The second flower type has features that are typical of the core-Cunoniaceae, including Caldcluvia, Weinmannia, and several other genera. The oldest evidence of Cunoniaceae comes from the Upper Cretaceous of Antarctica, but these represent the oldest Cunoniaceae known flowers and they add to our knowledge of the diversity of Gondwanan floras right after the end-Cretaceous extinction. Together with the recently described Ceratopetalum fruits from the early Eocene of northwest Chubut, these occurrences strengthen the biogeographic connection among Patagonia, Antarctica, and Australasia during the Paleogene.