Abstract Detail

Paleobotanical Section

Benedict, John C. [1], Smith, Selena Y. [2], Specht, Chelsea [3], Pigg, Kathleen B. [4], Devore, Melanie L. [5], Parkinson, Dilworth Y. [6].

A reexamination of the enigmatic North American zingiberalean fossil fruit and seed record.

The large monophyletic order Zingiberales has a fossil record of both vegetative remains and fruits and seeds spanning the Cretaceous through Neogene of the Americas, Eurasia, and Greenland. However, many of these taxa are not assigned confidently to a family and are considered Zingiberales incertae sedis. This is particularly true for fossil seeds and fruits from North America, where Ensete oregonense Manchester & Kress from the Eocene of Oregon, USA, is the only uncontested member of an extant family (Musaceae) based on its thick sclerified seed coat, conspicuous hilar rim, and Musa-type chalazal chamber. Specimens from three Cretaceous and one Paleocene sites of North America have uncertain taxonomic affinities. Spirematospermum chandlerae Friis from the Cretaceous of North Carolina, USA, was originally assigned to Zingiberaceae and later transferred to Musaceae, however, reinvestigation does not support an assignment Musaceae. Fruits of Tricostatocarpon silvapinedae Rodriguez-de la Rosa & Cevallos-Ferriz from the Cretaceous of Coahuila, Mexico, were shown to belong in Zingiberales, but clear affinities with any living family were not found. Fruits of Striatornata sanantoniensis Rodriguez-de la Rosa & Cevallos-Ferriz, also from the Cretaceous of Coahuila, Mexico, were placed in Musaceae because of the presence of a chalazal chamber, but the presence of chalazal chambers in Musaceae, Costaceae, and also recently found in some Zingiberaceae weakens this assignment, along with the presence of other characters not exclusive to Musaceae (e.g., hilar rim, chalazal mesotestal proliferation of cells). Seeds from the late Paleocene of North Dakota, USA, showing features similar to Zingiberaceae and Musaceae, have yet to be formally described and placed to family. Here we re-examine these North American fossils using light microscopy and 3D synchrotron X-ray tomographic microscopy data, to infer the systematic placement of these enigmatic taxa in the context of an expanded dataset of over 200 extant taxa within Zingiberales. Preliminary analyses suggest a close relationship between the fossils Spirematospermum, Striatornata sanantoniensis, and the North Dakota specimens, and affinities of these taxa to Zingiberaceae. Tricostatocarpon differs from all other North American fossils in lacking a chalazal chamber, but may also be closely related to Zingiberaceae because of the presence of mesotestal proliferations of cells in the micropylar and chalazal regions. A more confident placement of these taxa in a systematic context will provide insights into the evolutionary and biogeographic history of this diverse group of tropical and subtropical monocotyledonous plants.

1 - University of Michigan, Earth and Environmental Sciences, 2543 C.C. Little Building, 1100 North University Avenue, Ann Arbor, MI, 48109-1005, USA
2 - University of Michigan, Department of Earth and Environmental Sciences, 2534 CC Little Building, 1100 North University Avenue, Ann Arbor, MI, 48109-1005, USA
3 - University of California at Berkeley, Plant and Microbial Biology, Integrative Biology, 431 Koshland Hall, Berkeley, CA, 94720, USA
4 - Arizona State University, School Of Life Sciences Faculty & Admin, Box 874501, Tempe, AZ, 85287-4501, USA
5 - Dept Of Biology & Env. Science, GC & SU Campus Box 81, Milledgeville, GA, 31061-0001, USA
6 - Advanced Light Source, Lawrence Berkeley National Labs , 1 Cyclotron Road, Berkeley, CA, 94720, USA

Keywords:
Anatomy
morphology
permineralized
systematics
taxonomy
fossil
SRXTM.

Presentation Type: Oral Paper:Papers for Sections
Session: 28
Location: Salon 13/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 9:00 AM
Number: 28005
Abstract ID:846
Candidate for Awards:None