Zavialova N., Markevich V., Bugdaeva E., Polevova S.
В журнале Grana
Год: 2011 Том: 50 Выпуск: 3 Страницы: 182-201
The general morphology, surface sculpturing, and exine ultrastructure have been studied in dispersed monosulcate pollen from the Early Cretaceous of Transbaikalia, Russia. The pollen grains dominate the palynological assemblage extracted from coal deposits of the Khilok Formation in the Buryat Republic, which also contain ginkgoalean leaves of Baierella averianovii as the only constituent of the assemblage of plant megafossils. The relationship between the pollen grains and ginkgoalean leaves from this autochthonous burial is hypothesised on the basis of taphonomical analysis and palaeobiogeographical data. It is shown that the ectexine of the pollen grains includes a thick solid tectum, a thin granular infratectum and a thin foot layer; the endexine is ?ne-grained, slightly more electron-dense than the ectexine, and is preserved only in places. The distal aperture is formed by a thinning of the exine. No analogous ultrastructure has been described so far in fossil pollen grains of this morphotype studied ultrastructurally from in situ material. For comparison, we also studied the exine ultrastructure of Ginkgo biloba pollen grains. The fossil pollen is not identical to pollen of extant G. biloba, but shows several signi?cant similarities in the exineu ltrastructure, which does not contradict the presumable ginkgoalean af?nity of the fossil pollen.
