Abstract
The origins of the five groups of living seed plants, including the single relictual species Ginkgo biloba, are poorly understood, in large part because of very imperfect knowledge of extinct seed plant diversity. Here we describe well-preserved material from the Early Cretaceous of Mongolia of the previously enigmatic Mesozoic seed plant reproductive structure Umaltolepis, which has been presumed to be a ginkgophyte. Abundant new material shows that Umaltolepis is a seed-bearing cupule that was borne on a stalk at the tip of a short shoot. Each cupule is umbrella-like with a central column that bears a thick, resinous, four-lobed outer covering, which opens from below. Four, pendulous,winged seeds are attached to the upper part of the column and are enclosed by the cupule. Evidence from morphology, anatomy, and field association suggests that the short shoots bore simple, elongate Pseudotorellia leaves that have similar venation and resin ducts to leaves of living Ginkgo. Umaltolepis seed-bearing structures are very different from those of Ginkgo but very similar to fossils described previously as Vladimaria. Umaltolepis and Vladimaria do not closely resemble the seed-bearing structures of any living or extinct plant, but are comparable in some respects to those of certain Peltaspermales and Umkomasiales (corystosperms). Vegetative similarities of the Umaltolepis plant to Ginkgo, and reproductive similarities to extinct peltasperms and corystosperms, support previous ideas that Ginkgo may be the last survivor of a once highly diverse group of extinct plants, several of which exhibited various degrees of ovule enclosure.
Original language | English (US) |
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Pages (from-to) | E2385-E2391 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 114 |
Issue number | 12 |
DOIs | |
State | Published - Mar 21 2017 |
Funding
We thank T. Gombosuren and O. Nyamsambuu for assistance with fieldwork in Mongolia; I. Glasspool and S. Grant for curatorial assistance; B. Strack for assistance with scanning electron microscopy; Z.-X. Luo and A. I. Neander for permission and assistance with X-ray tomography; G. Bedoya for nomenclatural suggestions; P. von Knorring for the plant reconstruction; P. Knopf, A. B. Leslie, and S. Carlquist for comments on the fossils; and J. M. Hilton and S. McLoughlin for valuable comments on the manuscript. Funding for this work was provided by National Science Foundation Grant DEB-1348456 (to P.S.H. and P.R.C.) and by Grants-in-Aid for Scientific Research (21405010 and 24405015) from the Japan Society for the Promotion of Science (to M.T.).
Keywords
- Cretaceous
- Ginkgo
- Mongolia
- Umaltolepis
ASJC Scopus subject areas
- General