Senftenbergia plumosa (Artis) is an abundant Carboniferous fern occurring in the Central and Western Bohemian Carboniferous basins of the Czech Republic.
Its epidermal structures are described in detail for the first time. The abaxial cuticles are very thin. The cells are isodiametric, random, pentagonal or hexagonal in shape.
Stomata occur only on the abaxial side of the pinnules. They are irregularly scattered and more or less oriented in one direction; ca. 200 per mm 2 , of the actinocytic or cyclocytic, flush with the epidermal cells.
The abaxial and adaxial surfaces contain small trichome bases. Sporangia are of the Senftenbergia type with Raistrickia type spores. These are different from those of the previously described fertile specimens of S. plumosa from Bohemia, suggesting a large morphological variability of spores in this species.
The epidermal structures of S. plumosa are important for understanding the systematic position of this Carboniferous fern. Generally, the cuticle of S. plumosa is more similar (especially its irregularly, polygonal cells with straight anticlinal wall and cyclocytic stomata) to that of living species of Marattiaceae than of Schizaeaceae.
The epidermal cells of S. plumosa are very similar to those of the Tedelea glabra. It appears to confirm that S. plumosa is a member of the primitive Carboniferous fern family Tedeleaceae (Jennings and Eggert, 1977; Taylor and Taylor, 1993; Bek and Psenicka, 2001).
Estimates of pCO2 for the early Paleogene vary widely, from near modern-day levels to an order of magnitude greater, based on various proxy measures.
Resolving the relationship between climate and pCO2 during this globally warm period is a key task in understanding climate dynamics in a warmer world.
Here, we use the stomatal frequency of fossil Ginkgo adiantoides from the Okanagan Highlands of British Columbia, Canada to estimate pCO2 during the Early Eocene Climatic Optimum (EECO), the interval of peak warmth in the Cenozoic.
We also examine a dataset of modern Ginkgo biloba leaves to critically assess the accuracy and precision of stomatal frequency as a proxy indicator of pCO2. Early Eocene fossil G. adiantoides has significantly lower stomatal frequency than modern G. biloba, suggesting pCO2 levels > 2× modern pre-industrial values.
This result is in contrast to earlier studies using stomatal frequency of Ginkgo that indicated near modern-day levels of pCO2 in the early Paleogene, though not including samples from the EECO. We also find that levels of pCO2 as indicated by stomatal frequency are correlated with trends in climate (mean annual temperature) over time at the Falkland fossil locality, suggesting that climate and pCO2 were coupled during the EECO hyperthermal.
Fossil plant morphological traits have been used extensively as palaeoenvironment and palaeoclimate indicators. Xeromorphic features are considered to be structural adaptations that reduce water loss (e.g. thick cuticle, sunken stomata, epidermal papillae and trichomes, stomatal papillae and stomata arranged in sunken grooves), and their presence in fossil plants is often used to indicate palaeo-environmental aridity.
However, in living plants, xeromorphic traits are not restricted to plants subjected to water stress and are commonly observed in plants growing in environments with high precipitation, humidity and water availability. These “xeromorphic” features often serve multiple functions such as water-repellence, defence and protection from excess light. The use of “xeromorphic” features as indicators of palaeo-environmental aridity therefore requires reinterpretation.
Here we review the ecological functions of “xeromorphic” adaptations in extant plants and analyse the equivocal nature of these morphological features using the extinct Cretaceous conifer Pseudofrenelopsis parceramosa (Fontaine) Watson.
We track the occurrence of stomatal papillae (waxy lobes over-hanging the stomatal pit) that are commonly considered to have an anti-transpirant function, in P. parceramosa through Valanginian–Barremian sediments deposited in a fresh water lowland environment at Worbarrow Bay, Dorset, southern England.
The presence/absence of stomatal papillae in P. parceramosa does not display a pattern consistent with an anti-transpirant function. In the context of supporting sedimentological, geochemical and climate modelling evidence we hypothesise that the primary function of stomatal papillae may be to repel liquid water, in addition to other functions such as providing structural support, pathogen-defence and as a response to high atmospheric particulate content caused by localised volcanism.
Our review presents a new palaeo-environmental interpretation of a widespread and important mid-Cretaceous conifer but also provides an updated synthesis of palaeo-environmental data that can be interpreted from “xeromorphic” features in fossil plants.
This paper describes 115 parataxa of dispersed leaf fossil cuticle from 120 samples from the Early Miocene of Central Otago (the fluvial-lacustrine Manuherikia Group) and Southland (the coastal deltaic East Southland Group), New Zealand.
The modern affinities include Argophyllaceae (Argophyllum), Atherospermataceae, Casuarinaceae (Gymnostoma), Cunoniaceae-Elaeocarpaceae, Ericaceae, Gnetaceae, Grisseliniaceae (Grisellinia), Meliaceae, Menispermaceae, Monimiaceae (Hedycarya), Myrsinaceae, Proteaceae (incl. Lomatia and Placospermum), Santalaceae (Notothixos), Sapindaceae, Strasburgeriaceae (Strasburgeria), and Winteraceae.
The records of Argophyllaceae, Menispermaceae, Placospermum and Notothixos are the first of these families and genera for New Zealand. For the Argophyllaceae and Notothixos at least, these are the first known fossil records.
With the exception of Cunoniaceae-Elaeocarpaceae, Ericaceae, Grisseliniaceae, Myrsinaceae, and Winteraceae, which occur in the south of New Zealand today, the fossils indicate a more southerly range extension in the Early Miocene than today.
This evidence of extended range along with a previously published high diversity of Lauraceae and conifers is probably the result of warmer conditions despite the fossil localities lying at about 50ºS in the Early Miocene – about 5 degrees further south than today.
Argophyllum and Strasburgeria are evidence of a biogeographical link with New Caledonia, where they are now restricted. The plants were components of rainforest vegetation growing in microthermal to mesothermal temperatures.
End-Triassic fluctuations in atmospheric carbon dioxide (CO2) concentration were reconstructed by the use of stomatal frequency analysis on a single plant species: the seedfern Lepidopteris ottonis (Goeppert) Schimper.
Stomatal index showed no distinct intra- and interpinnule variation which makes it a suitable proxy for past relative CO2 changes. Records of decreasing stomatal index and density from the bottom to the top of the Rhaetian–Hettangian Wüstenwelsberg section (Bavaria, Germany) indicate rising CO2 levels during the Triassic–Jurassic transition.
Additionally, stomatal frequency data of fossil ginkgoalean leaves (Ginkgoites taeniatus(Braun) Harris) suggest a maximum palaeoatmospheric CO2 concentration of 2750 ppmv for the latest Triassic.
New compression leaf material of Ceratozamia (Zamiaceae) has been recognised in the EuropeanCenozoic. A leaflet of Ceratozamia floersheimensis (Engelhardt) Kvaček was recovered among unidentified mate-rial from the Oligocene of Trbovlje, former Trifail, Slovenia, housed in old collections of the Austrian GeologicalSurvey, Vienna. It is similar in morphology and epidermal anatomy to other specimens previously studied fromthe lower Oligocene of Flörsheim, Germany and Budapest, Hungary. A fragmentary leaflet assigned to C. hof-mannii Ettingsh. was recovered in the uppermost part of the Most Formation (Most Basin in North Bohemia,Czech Republic) and dated by magnetostratigraphy and cyclostratigraphy to CHRON C5Cn.3n, that is, the latestearly Miocene. It yielded excellently preserved epidermal structures, permitting confirmation of the generic affin-ity and a more precise comparison with this lower Miocene species previously known from Austria (Münzenberg,Leoben Basin) and re-investigated earlier. Both the Oligocene and Miocene populations of Ceratozamia are basedon isolated disarticulated leaflets matching some living representatives in the size and slender form of the leaf-lets. Such ceratozamias thrive today in extratropical areas near the present limits of distribution of the genusalong the Sierra Madre Orientale in north-eastern Mexico, in particular C. microstrobila Vovides & J.D. Reesand others of the C. latifolia complex, as well as C. hildae G.P. Landry & M.C. Wilson (“bamboo cycad”). Theoccurrence of Ceratozamia suggests subtropical to warm-temperate, almost frostless climate and a high amountof precipitation. The accompanied fossil vegetation of both species corresponds well with the temperature regime.While the Oligocene species in Hungary probably thrived under sub-humid conditions, the remaining occur-rences of fossil Ceratozamia were connected with humid evergreen to mixed-mesophytic forests.
Characterisation of Eostangeria ruzinciniana (Palamarev, Petkova & Uzunova) Palamarev & Uzunova(Middle Miocene – Volhynian, Bulgaria) is augmented. The species is compared with morphologically similar cycads: E. saxonica Barthel (Eocene of Germany), E. pseudopteris Z. Kvacˇek & Manchester (Late Palaeocene and Eocene of western USA), and the extant Chigua D. Stevenson and Stangeria T. Moore. Leaf epidermal anatomy indicates that E. ruzinciniana is closely related to other members of Eostangeria, forming with them a natural unit. Eostangeria slightly differs from Chigua (Zamioideae) in the presence of short dark-staining cells in the lower epidermis, densely toothed margins, and in the case of Eostangeria ruzinciniana by obviously persistent, non-articulated leaflets. In morphological features of the leaflets, Eostangeria resembles Stangeria (Stangeriaceae); however, the latter decidedly differs in entirely cyclocytic stomata lacking ventral lignified lamellae, coarsely striated epidermis with strongly undulate anticlines and an absence of short dark-staining cells. A new subfamily Eostangerioideae is suggested to accommodate Eostangeria within Zamiaceae.