Original paper
Gnetophyte assemblage from the Early Cretaceous of Transbaikalia
Krassilov, Valentin A.; Bugdaeva, Eugenia V.
Palaeontographica Abteilung B Band 253 Lieferung 4-6 (2000), p. 139 - 151
25 references
published: Mar 8, 2000
Abstract
The Baisa locality in the upper reaches of the Vitim River east of Lake Baikal (Transbaikalia) has previously yielded a few early angiosperm fossils as well as proangiospermous plants of gnetalean (Eoantha) and bennettitalean (Baisia) affinities (Vakhrameev. Kotova 1977, Krassilov & Bugdaeva 1982, Krassilov 1986). The Hauterivian to Barremian age of the locality is based on faunistic evidence and correlation. New finds in the same plant-bearing horizon provide additional information on the previously described genera and reveal new gnetalean reproductive structures. They include Baisianthus ramosus gen. et sp. nov., a branching axis bearing verticillate cupulate sporangiophores with synangia producing caveate anasulcate pollen grains, and Vitimantha crypta gen. et sp. nov., a flower-like pedicellate structure, with perianth bracts showing reticulate venation and follicle-like gynoecial structures. Polyplicate pollen grains are found stuck to the latter in the area of a papillate adaxial groove. A comparison of the vascular elements described for the newly found reproductive and foliar organs give evidence of the graminoid leaves Praeherba spathulata gen. et sp. nov. belonging to the Eoantha plant. The association of early angiosperms and diverse angiosperm-like plants suggests an innovative nature of this peculiar plant community. It is suggested that environmental changes, indicated by the evidence of mass mortalities of aquatic organisms in the same strata, might have affected terrestrial vegetation as well, promoting herbaceous habit and accelerate development in both the gnetophyte and angiosperm lineages.
Keywords
angiosperm evolution • gnetophytes • graminoid leaves • pollen organs • Transbaikalia