Nelson, Chris W. , Jud, Nathan A .
A new species of Mammea (Calophyllaceae) from the lower Miocene of Panama with comments on biogeography and phylogeny.
Calophyllaceae (formerly part of Clusiaceae) is an important pantropical family of trees and shrubs comprising approximately 500 species. Here we present the earliest neotropical fossil evidence of Mammea, one of the largest genera in the family, in the form of a permineralized stem from the lower Miocene (19 Ma) of Panama. The fossil specimen is characterized by axial canals in the secondary phloem and pith, radial canals in the secondary xylem, ubiquitous pitting in the fibers and parenchyma, vasicentric tracheids, simple perforation plates, and narrow rays. The only other fossil evidence of Mammea is a permineralized wood from the Mio-Pliocene of Ethiopia, and the modern center of diversity for the genus is Madagascar. The distribution and phylogeny of extant Mammea species suggest an old-world origin for the genus, and the new fossil provides a minimum date for dispersal to the Neotropics. Previous molecular-clock analyses of the larger clusioid clade as a whole were calibrated using a single fossil (Paleoclusia) and estimated the origin of crown-group Calophylleae between 40 and 16 Ma. The presence of anatomically-recognizable Mammea in Panama by the early Miocene suggests the origination of the crown-group Calophylleae was probably closer to the former date. The biogeographic history of Mammea can be compared and contrasted with that of other taxonomic groups represented by fossils at the same locality, such as Parinari (Chrysobalanaceae), which likely dispersed from Africa, and Humiriaceae, which likely originated and diversified in the Neotropics. Finally, a new morphological phylogenetic analysis incorporating the new fossil and 15 new wood characters yields a topology broadly similar to that of recent molecular analyses while also highlighting some alternative hypotheses concerning the closest relatives of Mammea. The new Mammea fossil is thus only the most recent example of a growing number of paleobotanical studies that enrich our understanding of the diversification, evolution, and biogeographic history of Neotropical plant families.
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1 - Florida Museum of Natural History, Dickinson Hall, 1659 Museum Rd., Gainesville, FL, 32611, USA
2 - University of Florida, Dickinson Hall, 1659 Museum Rd., Gainesville, FL, 32611, United States
Presentation Type: Oral Paper
Session: 5, Paleobotany Student Awards
Location: 204/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 11:15 AM
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award