A review of the Cenozoic fossil record of the genus Zamia L. (Zamiaceae, Cycadales) with recognition of a new species from the late Eocene of Panama – evolution and biogeographic inferences

Erdei, Boglárka and Calonje, Michael and Hendy, Austin and Espinoza, Nicolas (2018) A review of the Cenozoic fossil record of the genus Zamia L. (Zamiaceae, Cycadales) with recognition of a new species from the late Eocene of Panama – evolution and biogeographic inferences. Bulletin of Geosciences, 93 (2). pp. 185-204. ISSN 1214-1119 (print); 1802-8225 (online)

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Abstract

Modern Zamia L. is the second largest genus among cycads, however reliably identified fossil occurrences of the genus have so far been missing. Previously, fossil “Zamia” species were established in large numbers on the basis of macromorphological similarity of foliage fragments to living Zamia species. However, a reinvestigation of specimens assigned formerly to Zamia and the relevant literature provided no clear-cut evidence for their assignment to this genus. We investigated a newly recovered fossil specimen from marine sediments of the Gatuncillo Formation, near Buena Vista, Colon Province, Central Panama. It represents the first unequivocal fossil record of the genus confirmed by epidermal as well as macromorphological characters and it is described as Zamia nelliae Erdei & Calonje sp. nov. Foraminiferal and nannoplankton biostratigraphy of the locality indicates a late Eocene to earliest Oligocene age. Morphometric comparison of epidermal features of Z. nelliae with those of modern Zamia species suggests similarity with those of the Caribbean Zamia clade. The fossil record of Zamia from Panama implies that the genus appeared by the end of the Eocene or earliest Oligocene in the Central American–Caribbean region, however, the origin of the genus is still unresolved. The record of Z. nelliae may challenge former concepts on the evolution of Zamia and raises an “intermediate” hypothesis on its origin in the Central American–Caribbean region and its subsequent dispersal south- and northwards. • Keywords: cycad, Zamia, cuticle, morphometry, Paleogene, Panama.

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