Abstract Detail



Paleobotany

Tang, Keana [1], Atkinson, Brian [2], Smith, Selena [3].

Cunonicaceae from the Late Cretaceous of North America and its paleobiogeographic implications.

The family Cunoniaceae consists of over 300 species within 27 genera that are mostly distributed in the Southern Hemisphere. The Cretaceous record of these flowering plants is enigmatic, with the only unequivocal representatives being pollen and wood from Late Cretaceous deposits of Antarctica and South America. Flowers of three Cretaceous taxa that superficially resemble Cunoniaceae have been reported in the Northern Hemisphere, but their affinities to the family remain questionable. However, the Cenozoic record of the family clearly indicates that crown-group Cunoniaceae were present in the Southern Hemisphere by the earliest Paleocene. Here, we report two structurally preserved fossil winged fruits assignable to Cunoniaceae from Campanian (Late Cretaceous) deposits on Sucia Island, Washington state, USA. The fossils were studied using the cellulose acetate peel technique, light microscopy, and microCT scanning. A preliminary Bayesian phylogenetic analysis was conducted using a morphological matrix of fossil and extant Cunoniaceae that was integrated with molecular data of extant species. The Sucia Island fruits are characterized by the presence of a semi-inferior ovary, four to five calyx lobes that resemble wings, annular nectary disk, persistent diplostemonous androecium, and two styles. The sepals are oblong in shape with a rounded apex and constricted base. Five primary veins enter each wing with secondary veins diverging from primary veins at about 90 degrees. An inter-wing vein connects the marginal vascular bundles of each wing to those of adjacent wings. No evidence of petals was observed. Stamens of the outer androecial whorl are opposite of the calyx lobes while those of the second whorl are alternate. Anthers are not preserved. Styles are clearly free at about three-quarters of their length. Internal tissues underwent extensive diagenesis. This combination of characters remarkably resemble extant Ceratopetalum. The phylogenetic analysis recovers the fossils in a monophyletic clade with Ceratopetalum with high posterior support. Extant Ceratopetalum fruits were microCT scanned for morphological comparison. The presence of persistent stamen and the size, shape, and wing venation of these Cretaceous fruits suggest that they represent a new species of Ceratopetalum. These fossils are the first unequivocal evidence of crown Cunoniaceae in the Cretaceous and in the Northern Hemisphere, and extends the geographic distribution of the family beyond the Southern Hemisphere. This newly recovered distribution supports the Cretaceous North American-South American-Antarctic dispersal hypothesis.  


1 - University of Kansas, Ecology and Evolutionary Biology, 1450 Jayhawk Blvd, Lawrence, KS, 66045, United States
2 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, 2041 Haworth Hall, Lawrence, KS, 66045, United States
3 - Department Of Earth & Environmental Sciences, 1100 North University Avenue, Room 2534, NUB, Ann Arbor, MI, 48109, United States

Keywords:
Cunoniaceae
Ceratopetalum
Late Cretaceous
fossil fruits
Sucia Island.

Presentation Type: Oral Paper
Number: PAL1003
Abstract ID:222
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


Copyright © 2000-2020, Botanical Society of America. All rights reserved