Cladostrobus and the systematics of cordaitalean leaves

Abstract

Cladostrobus Zalessky, 1918, is a male strobilus with spirally arranged microsporophylls, having a rhomboid lamina and a long stalk. The sporangia occur in groups. Microspores are of monosaccate type and are without a haptotypic mark. The name Cladaitina dibnerae gen. et sp. nov. is introduced for isolated spores of this kind. Cladostrobus may be a male strobilus of plants that bore Rufloria leaves. The group Cordaitales, as known now, comprises a heterogeneous assemblage of incompletely known plants, mostly sterile leaves. An artificial classification is proposed for sterile leaves, similar to the one already in vogue for dispersed spores and pollen. This classification is in fact a key for identification and cataloguing, and is not meant to show natural affinities.

A new species of Cladaitina Maheshwari & Meyen, 1975 (cordaitalean pollen) from Uppermost Permian deposits of the Famatina Range, Central Western Argentina

“…According to Meyen (1987, p. 191) in the pollen grains of the Cladaitina type "the saccus bears inner polygonal projections with narrow slits in between, so that negative reticulum (intrareticuloid) appears", therefore, should not be considered saccate lacking of a true three-dimensional endoreticulum. The genus Reticulatina established originally by Koloda (1996) seemed to have similar morphology with the genera Cladaitina (Maheshwari & Meyen, 1975) and Cordaitina (Zavialova et al, 2004) and they were considered previously rather similar and eventually conspecific but differing in details of their morphologies and ultrastructures (Zavialova & Gomankov, 2009). The main feature differentiating the surface morphology of Reticulatina as observed under LM and SEM by Zavialova & Gomankov (2009) is the reticulate sculpture by contrast to verrucate ornament in Cladaitina.…”

“…R. Potonié & Kremp, 1954 Genus Cladaitina Maheshwari & Meyen, 1975 Type species. Cladaitina dibnerae Maheshwari & Meyen, 1975, p. 114, figs.…”

“…Maheshwari & Meyen (1975) Balme (1995, p. 221) commented that originally, the pollen of the Cladostrobus cone was illustrated and described as verrucate. According to Meyen (1987, p. 191) in the pollen grains of the Cladaitina type "the saccus bears inner polygonal projections with narrow slits in between, so that negative reticulum (intrareticuloid) appears", therefore, should not be considered saccate lacking of a true three-dimensional endoreticulum.…”

“…Remarks and discussion. The genus Cladaitina was not considered as true monosaccate pollen by Maheshwari & Meyen (1975), because the sexine (the sac) of these pollen grains lacks a true three-dimensional endoreticulum (Balme, 1995, p. 221). On the contrary, as above was mentioned, Taylor et al (2009, p. 803) consider that the pollen assigned to the sporae dispersae genus Cladaitina has a weakly developed saccus that covers the central body, except for a small region on the distal surface.…”

“…Thus, Maheshwari & Meyen (1975) compared them of Ginkgocycadophytus-type, differing in lacking grana-verrucae type of ornamentation.…”