ИСТИНА

Morphological differences between miospores with microreticulate and foveolate sculpture often seem to be ambiguous. This is due to the high diversity and variability of sculptural types within and between species. Traditional descriptive morphological terms such as “scrobiculus”, “foveola”, and “lumen” are without strict definition and can be confused. A lack of precise understanding of the morphological variation within some genera and species has resulted in the doubtful taxonomic status of some of these miospore taxa. In order to define quantitative boundaries for qualitative terms (e.g. of sculpture types) a numerical typification has been applied. This approach was introduced by Vezey and Skvarla (1990, 1994) who used image analysis to segregate perforated exines of angiosperm pollen grains. Material for the present study was a monotypic assemblage of miospores of the Microreticulatisporites-type from the Upper Visean of the Moscow Syneclise, Russia. Analysis was carried out using combined methods of optical light microscopy (LM), scanning-electron microscopy (SEM) and confocal laser microscopy (CLSM) for the first time. Observed miospore specimens demonstrate a range of features of the "microreticulate" exospore. There are numerous circular perforations (“scrobiculae”) on the surface of the exospore. LM and SEM photomicrographs show that these perforations have diameters of 0.2 (0.48±0.09) 1.0 µm. The distance between the edges of perforations is 0.54 (0.89±0.16) 1.35 µm. The average diameter of the perforations is less than the average distance between perforation and thus, the studied miospores do not have a microreticulate sculpture. They therefore do not belong within the genus Microreticulatisporites which is defined as microreticulate or reticulate. The SEM photomicrographs show that the polygonal depressions (meshes) are formed by the junctions of tapered muri. The average diameter of the depressions is variable, being 1.3 (1.8±0.27) 2.8 µm wide. The average diameter of the depressions is greater than average width of the muri meaning that the large depressions should be considered as true lumina. Each circular peforation (“scrobiculus”) is enclosed in a polygonal depression (“lumen”). Virtual cross-sections and reconstructions provided by CLSM show the existence of funnel-shaped “tunnels” that are clearly preserved in the deeper part of the exospore bearing the complex sculpture. Differences between the microreticulate and foveolate sculpture patterns have been defined using quantatitive and qualitative parameters. As a results of our studies, a new sculptural type has been identified. This aids in separation of microreticulate and foveolate sculptures.