Trimerous flowers with a unique set of floral and pollen traits from the Late Cretaceous of Southern Bohemia (Czech Republic)
- Author(s)
- Xieting Wu, Maria von Balthazar, Fridgeir Grimsson, Zuzana Heřmanová, Jiri Kvacek, Jürg Schönenberger
- Abstract
New, exceptionally well-preserved charcoalified flower fossils from the Late Cretaceous of Southern Bohemia, Czech Republic, were examined in detail using scanning electron microscopy and high-resolution X-ray computed tomography. The numerous specimens
exhibit a unique combination of floral traits. Flowers are small, bisexual or female, trimerous, and actinomorphic. In bisexual flowers, the perianth is clearly differentiated into two types of organs. The calyx consists of three free and broadly triangular sepals with valvate aestivation. While in most flowers, the corolla comprises one or two whorls of three free, scale-like petals each, petals are absent in a few specimens and are apparently replaced by stamens. The androecium comprises one to three whorls of three stamens each. Filaments are narrow and very short; the basifixed anthers are slightly longer than the filaments and have four pollen sacs each. Each pollen sac contains a single spherical polyad comprising 32 pollen grains. The gynoecium is tricarpellate-syncarpous with a semi-inferior ovary. The three styles are short and apparently free from each other but place the wet stigmas in close proximity likely forming an extragynoecial compitum. The superior carpel surfaces are densely covered by glandular hairs. The ovary is trilocular and each locule contains at least three ovules inserted
on axile placentae. One of the specimens represents a female flower, which is similar in size to the bisexual flowers and has three sepals, six scale-like petals, and six carpels. The numerous specimens found so far, clearly all belong to the same taxon based on the structure of their individual organs. However, the specimens differ not only in the number of perianth organs,
stamens, and carpels (at least five morphotypes) but also in their sexual system (bisexual vs. unisexual). We discuss systematic affinities based on a detailed comparative investigation of floral morphology and an angiosperm-wide phylogenetic analysis.- Organisation(s)
- Department of Botany and Biodiversity Research
- External organisation(s)
- National Museum Prague
- Pages
- 824
- Publication date
- 2024
- Austrian Fields of Science 2012
- 106008 Botany, 106042 Systematic botany, 106012 Evolutionary research
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/9d54921b-4f49-4ec3-b5ff-d965664d56e5