Diversity and homologies of corystosperm seed-bearing structures from the Early Cretaceous of Mongolia

Abstract

New discoveries of corystosperm seed-bearing structures from the Tevshiin Govi locality, Mongolia, which is of Early Cretaceous (Aptian–Albian) age, show that the individual seed-bearing units of Umkomasia mongolica were borne in a cone, as also documented for the very similar reproductive units of Doylea tetrahedrasperma. New material from the Tevshiin Govi locality also documents two additional species of Umkomasia – U. corniculata sp. nov. and U. trilobata sp. nov. – that most likely grew in a different environment to U. mongolica. The occurrence of three different Umkomasia species in the Early Cretaceous of Mongolia, together with other records from the Early Cretaceous of the Northern Hemisphere, indicate that previous concepts of corystosperms, based mainly on material from the Southern Hemisphere, need to be revised. The consistent reproductive architecture of the seed-bearing structures in all three corystosperm species, with a bract subtending a variously modified axis bearing ovules, is similar to the situation in Ginkgo and conifers. These underappreciated architectural commonalities among the reproductive structures of major groups of seed plants are likely significant for a deeper understanding of seed plant evolution and require further exploration.

Keywords:

• corystosperms
• Umkomasia
• Early Cretaceous
• Mongolia
• seed
• seed ferns

Acknowledgements

We thank T. Gombosuren, O. Nyamsambuu and S. Crane for assistance with fieldwork in Mongolia; A. M. S. Buiser, B. Cooper, N. Gavin-Smyth and L. Audi for help sorting fossil material; B. Strack for assistance with scanning electron microscopy; and P. von Knorring for the plant reconstruction. We are also grateful to the editors for handling the submission and reviews for this manuscript, and to B. Bomfleur and an anonymous reviewer for their helpful comments and suggestions. Funding for this work was provided by National Science Foundation grant DEB-1348456 and 1748286 to PSH, PRC and FH; the National Natural Science Foundation of China (41772014) and the Youth Innovation Promotion Association, CAS (2017359) to GS; Oak Spring Garden Foundation to FH; and the Grants-in-Aid for Scientific Research (21405010 and 24405015) from the Japan Society for the Promotion of Science to MT.