Abstract Detail

Paleobotany

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

A structurally preserved fin-winged fruit from the Late Cretaceous of western North America.

The initial diversification of angiosperms is well-preserved in the Cretaceous record of North America and captures the appearances of many extant orders, families, and genera in rapid succession. However, less attention has been given to the phylogenetic turnover of extinct lineages, which hinders our understanding of the early angiosperm diversity. In addition, while much of the reported Cretaceous angiosperm diversity comes from the North American western interior and eastern coast, Cretaceous floras of the western coast are relatively undersampled. Here, we report an enigmatic structurally preserved fossil fin-winged fruit from Campanian (Late Cretaceous) deposits on Sucia Island, Washington state, USA. The fossil was studied using light microscopy and X-ray micro-computed tomography. In addition, persistent floral structures preserved on the fruit allowed us to use the phyloscan method to assess the most parsimonious positions of the fin-winged fruit across the angiosperm phylogeny. The fossil fruit is characterized by an inferior unilocular ovary, five fin wings that longitudinally extend along the fruit body, five persistent calyx lobes that alternate with the wings, raised mounds of tissue (possibly nectaries) outside of the androecium, at least four stamen filaments within two whorls, and three styles that are fused for half of their length. The fossil superficially resembles fruits of Combretaceae, but extant members of this family have only one style. Based on the characters above, the described fossil is assignable to the extinct genus Esgueiria, which has three reported species from the Cretaceous of Europe and Japan and has been considered as a potential stem lineage of Combretaceae. Morphological differences such as the degree of fusion at the base of the styles, indicate that the fossil winged fruit represents a new species of Esgueiria. Phyloscan analyses of Esgueiria indicate three most parsimonious positions within the core eudicots and as a stem lineage of core eudicots. However, both the fin-winged fruit and Esgueiria were not recovered within Combretaceae. These ancient plants most likely represent an extinct family of angiosperms. Continuing to recover and describe extinct angiosperm lineages will undoubtedly help us to better understand early evolutionary patterns of flowering plants.

1 - 1334 Rhode Island St., Lawrence, KS, 66044, United States
2 - Department Of Earth & Environmental Sciences, 1100 North University Avenue, Room 2534, NUB, Ann Arbor, MI, 48109, United States
3 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, United States

Keywords:
Cretaceous
fossil fruit
core eudicot.

Presentation Type: Oral Paper
Session: PL1, Paleobotany: Cookson Student Presentations - Session I
Location: /
Date: Monday, July 19th, 2021
Time: 10:45 AM(EDT)
Number: PL1004
Abstract ID:617
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award