The new genus, Morenoa fertilis from the early Cretaceous beds of the Baqueró Formation (Santa Cruz Province, Argentina) is here described. This conifer is referred to the family Podocarpaceae on account of its vegetative as well as reproductive male organs that include bisaccate pollen grains. The ultrastructure of the leaf cuticle (of the Elatocldus type) and the pollen grains (of the Podocarpidites type) was studied with transmission electron microscopy. Comparision with fossil and extant taxa of the family are also made, including the other three fossil genera known in fertile state from the same formation. The excellent preservation of the closed pollen sacs permitted the recognition of still inmature tetrads and a high inner content of Ubisch bodies. Epiphyllous fungi were also recognized on the leaf epidermis suggesting a mild and humid climatic regime.Some degradation of the leaf cuticles was observed, possibly related in part to fungal activity.
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"There are also slight differences. For example, in Squamastrobus (Archangelsky & Del Fueyo, 1989) and in Morenoa (Del Fueyo, Archangelsky & Taylor, 1990) two Cretaceous genera from Patagonia, the exine is composed of an alveolate ectosexine and a granular endosexine. Trisacocladus, another Patagonian Cretaceous genus, shows such differences more accentuated — a columnar ectosexine, an alveolar endosexine and a non-lamellate nexine (Baldoni & Taylor, 1982). "
[Show abstract][Hide abstract]ABSTRACT: The development of the microsporangium and male gametophyte of three species of Podocarpus was studied with light microscopy (LM) and the morphology of pollen with scanning and transmission electron microscopy (SEM and TEM). During early stages, the male cone is covered with coriaceous scales. The archesporid cells go through a dormant period. Later the pollen mother cells differentiate and undergo meiosis. Callose is detected around the tetrad and between each monad. The microspore nucleus divides several times to give rise to a multicellular gametophyte, which includes the tube cell, the stalk and body cells, and four prothallial cells. The exine of the pollen grain is rugulate in the corpus and quite smooth in the sacci. The ultrastructure of the pollen wall consists of the alveolate sexine, the laminate nexine I and the amorphous nexine II. The intine is very thin. Comparison of the mature grain of some fossils with living members of the Podocarpaceae reveals great similarity.
Full-text · Article · Jun 2008 · Botanical Journal of the Linnean Society
"The studies on the fossil leaf cuticular ultrastructure using transmission electron microscopy started with the pioneer work of Archangelsky et al. (1986). Since then, the leaf cuticular ultrastructure is known for a number of fossil taxa or groups, including pteridosperms (Taylor et al., 1989; Baldoni and Barale, 1996; Labe and Barale, 1996; Maheshwari and Bajpai, 1996; Bajpai, 1997; Guignard et al., 2001), bennettitaleans (Barale and Baldoni, 1993; Villar de Seoane, 2001), cycadaleans (Artabe and Archangelsky, 1992; Villar de Seoane , 1997b), ginkgoaleans (Taylor et al., 1989; Villar de Seoane , 1997a; Guignard and Zhou, in press), czekanowskialeans (Zhou and Guignard, 1998), as well as conifers (Archangelsky and Taylor, 1986; Archangelsky et al., 1986; Del Fueyo et al., 1990; Barale et al., 1992; Guignard et al., 1998; Villar de Seoane, 1998; Zhou et al., 2000). Most of the cuticle is marked [Vol. "
[Show abstract][Hide abstract]ABSTRACT: Sphenobaiera huangii (Sze) Hsü is typical Early Mesozoic fossil foliage of Ginkgoales in China. It has been recorded from the Upper Triassic to the Lower Jurassic. The cuticular anatomy is investigated based on material from the type locality, Lower Jurassic Hsiangchi Formation, Zigui County, Hubei Province. The specimens are similar to S. huangii, but contain new information about leaf morphology and cuticular anatomy. Lower and upper cuticle is investigated using light and electron microscopy (LM, SEM, and TEM). Many features are described for the first time, including general structures of lower and upper cuticle, stomata, papillae, and cuticular ultrastructure. At the ultrastructural level, two layers have been distinguished in both lower and upper cuticle, including a homogeneous outer layer with granules and a heterogeneous inner layer with fibrils. Based on a literature comparison between S. huangii and other relevant species of Sphenobaiera, S. huangii may represent the best-known taxon in the genus Sphenobaiera in both leaf morphology and cuticular structures. This study provides the first detailed ultrastructural data on the leaf cuticle of Sphenobaiera, one of the oldest foliage taxa of Ginkgoales, and offers further evidence for potential discussion on the taxonomic relationships of S. huangii with other ginkgoalean taxa.
Full-text · Article · Apr 2005 · American Journal of Botany
"Leaf cuticle ultrastructure is known for a number of fossil taxa (or groups). Although their cuticles vary in construction, most of them are similar to 'Qpe 1 of Holloway, i.e. they are characterized by an outer polylamellate zone, such as in some pteridosperms , Pachypteris, Rhaphidopteris Cycadopteris and Karinopteris (Taylor et al., 1989; Labe and Barale, 1996), Ginkgoites (Taylor et al., 1989 ), cy- cadaleansArchangels@ and Taylor, 1986; Barale et al., 1992; Del Fueyo et al., 1990). So far, an outer amorphous layer has been reported in only a few fossil taxa. "
[Show abstract][Hide abstract]ABSTRACT: Leaf cuticles of Phoenicopsis and Arctobaiera collected from the Middle Jurassic Yima Formation, Henan Province, Central China were studied with transmission electron microscopy. The upper and lower cuticles are generally similar in ultrastructure. The cuticle is usually composed of two parts. The upper part is finely granular. The lower part is mainly fibrillar. In the upper cuticle there is normally a thin basal granular layer. The structure appears to be close to Type 3 of Holloway, but it has an inner granular layer and the fibrillae are usually more parallel in orientation. This type of cuticle is also different from those of the other fossil plants. This is the first time the ultrastructure of leaf cuticles of the Czekanowskiales has been studied. It is of interest that the two taxa of the same plant group bear a similar cuticular ultrastructure.
Preview · Article · Aug 1998 · Review of Palaeobotany and Palynology