Upper Carboniferous seed fern (Pteridospermophyta) pollen organs from Silesia (Poland) and related evolution considerations

Abstract

Extinct seed ferns (Pteridospermophyta) fill a key position in the evolutionary tree of seed plants. Their reproductive structures enable to recognition of the interrelationship within seed ferns and other seed plants descending from them. Seed fern reproductive structures from Poland are very rarely found and very poorly known, especially the pollen organs to which this paper is dedicated. A new genus and species Silesiatheca formosa Pacyna & Zdebska, gen. et sp. nov. of lyginopteridalean aggregated synangia was recognized based on specimens preserved within sideritic nodules from Sosnowiec. The genus Codonotheca is recognized from European Carboniferous for the first time. The least evolutionarily advanced species of Codonotheca − Codonotheca silesiaca Pacyna & Zdebska sp. nov., is described based on specimens with weakly expressed radial symmetry and slight fusion of the sporangia. this species matches the hitherto hypothetical simplest species of Codonotheca very well, constituting the initial form for all the more compound pollen organs of Medullosales. For the first time in the European Carboniferous the North American species Aulacotheca campbellii (White, 1900) Halle, 1933 is recognized. A new emended diagnosis for the typical species Boulayatheca fertilis (Kidston, 1914) Taylor & Kurmann, 1985 is proposed, based on specimens from Poland. Two new species of genus Boulayatheca Taylor & Kurmann, 1985 are recognized. Boulayatheca ciliata Pacyna & Zdebska, sp. nov. with a synangium surface covered with hairs (a feature hitherto unknown in the Boulayatheca genus) and Boulayatheca saganii Pacyna & Zdebska, sp. nov. with a markedly elongated synangium. Occurrence of Whittleseya Newberry, 1853a emend. Halle, 1933 typical species − Whittleseya elegans Newberry, 1853a was confirmed in Lower Silesia based on new specimens. Some specimens referred to earlier in the literature as W. elegans were ascribed here to the new species W. silesiaca Pacyna & Zdebska, sp. nov., which differs from typical species in synangium shape and sporangia clustering into groups. The new species Whittleseya campanulata Pacyna & Zdebska, sp. nov. has a large synangium and sporangia clustering into groups. Heterogeneity within the genus Whittleseya is recognized, where some species, including those new described here, probably formed compound synangia. The aggregated synangia of Medullosales are recognized in thecompression state of preservation for the first time they are the base for establishing a new genus and species Kotasotheca annaeadamii Pacyna & Zdebska, gen. et sp. nov. The genus Dolerotheca Halle, 1933 was recognized in the Polish Carboniferous for the first time and a new species Dolerotheca migierii Pacyna & Zdebska, sp. nov. was described. T.N. Taylor’s model of evolution of medullosalean pollen organs was confirmed, and the new taxa described were included within it.