Abstract Detail


Tang, Keana [1], Matsunaga, Kelly [2], Atkinson, Brian [3].

Crown group Lauraceae in the Late Cretaceous: new evidence from fossil flowers.

The angiosperm family Lauraceae comprises up to 3,500 species within 50 genera that are distributed globally within tropical and temperate regions. While the fossil record of Lauraceae extends into the Turonian of the Late Cretaceous (93-90 Ma) and includes numerous flowers, most of these fossil flowers have yet to be analyzed in a phylogenetic framework. Thus, their evolutionary relationships with living members of Lauraceae remain unclear. We report new fossil flowers assignable to Lauraceae from Coniacian (89.8–86.3 Ma) deposits of the Eden Main locality in British Columbia, Canada that provide new phylogenetic evidence of the emergence of crown group Lauraceae in the fossil record. The fossil flowers were serial sectioned using the cellulose acetate peeling technique and studied using light microscopy. Preliminary phylogenetic analyses were conducted using both the phyloscan method, to assess potential relationships outside of Lauraceae, as well as maximum likelihood in RAxML using a new genus-level morphological dataset of floral characters for Lauraceae, with extensive outgroup sampling in Laurales. The Eden Main flowers are trimerous with two whorls of tepals, three whorls of fertile stamens, an inner whorl of staminodes, and a superior ovary containing a single apically attached ovule. The tepal whorls are unequal in size, with the inner whorl of tepals about four times longer than the outer whorl. The androecium consists of nine fertile tetrasporangiate stamens that dehisce by apically hinged valves. An innermost whorl of sagittate staminodes surround the ovary. The first and second whorls of stamens are introrse while the third whorl of stamens are extrorse. A pair of peltate staminal appendages is present at the base of each stamen in the third whorl. A single apically attached ovule is present in the ovary. Trichomes are present on the adaxial side of the inner tepals, the androecium, and inside the receptacle. These characters indicate the fossil flowers are assignable to the family Lauraceae, a conclusion strongly supported by the phyloscan analysis. The combination of unequal tepal whorl sizes, tetrasporangiate anthers, and peltate staminal appendages associated with the third whorl of stamens suggest the Eden Main fossils represent a new taxon. Preliminary phylogenetic analyses focused on Lauraceae indicate strong support for a position within the crown group, but relationships with any particular clade remain unclear and will be the focus of future analyses. Previously described fossil flowers from the Cretaceous have combinations of characters that indicate affinities with Lauraceae. However, these fossils have not been analyzed in a phylogenetic framework or cannot be confidently placed within the crown group. The Eden Main fossils therefore provide the oldest and only phylogenetically informed evidence for the emergence of crown group Lauraceae in the fossil record so far. Our new morphological dataset provides an important foundation for elucidating the phylogenetic relationships of lauraceous fossil flowers, which will be essential for understanding the early evolutionary and biogeographic history of the family.

1 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Ave, Lawrence, KS, 66045, USA
2 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnysive Ave., Lawrence, KS, 66045, United States
3 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, United States

fossil flowers

Presentation Type: Oral Paper
Number: PB1003
Abstract ID:838
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award

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