The microsporangiate cone Classostrobus amealensis sp. nov. with in situ pollen from the Lower Cretaceous (lower Hauterivian) of Portugal: pollen ultrastructure and implications for frenelopsid species diversity

A new cheirolepidiaceous conifer pollen cone, Classostrobus amealensis sp. nov., is described from the Lower Cretaceous of Lusitanian Basin, in the Estremadura region of western Portugal. The new microsporangiate cone was collected in the Vale Cortiço open cast clay pit complex, near the small village of Ameal, from sedimentary deposits belonging to Santa Susana Formation and considered to be early Hauterivian in age. The new species is based on a single well-preserved, coalified microsporangiate cone, ca. 27 mm long and 14 mm wide, ovoid in shape, bearing ca. 20 helically arranged, imbricate microsporophylls. The microsporophyll bears four pollen sacs abaxially and it is smooth or finely papillate showing an acute apex fringed with short trichomes. The new microsporangiate cone is morphologically different from all Classostrobus species previously described, and we compare it with all other frenelopsid microsporangiate cones known to date. Pollen grains in situ show close similarity to dispersed pollen of the species Classopollis martinottii Reyre 1970. Pollen details were studied using LM as well as scanning electron (SEM) and transmission electron microscopy (TEM). Pollen grains are spheroidal, ca. 26.1 μm in LM and 23.8 μm in SEM, characterized by an equatorial band with six to eight striations, a distal cryptopore, and a proximal tetrad scar. The exine sculpture is distinctly microechinate. The new microsporangiate cone is associated with fragments of vegetative shoots of Frenelopsis teixeirae Alvin et Pais 1978 and Pseudofrenelopsis dinisii M.M.Mendes et J.Kva�cek 2023.