Paleobotany and Paleopalynology: new advances.

This special issue, compiling a set of articles dealing with Paleobotany and Paleopalynology recently submitted to Geodiversitas reflects, for the half part, oral presentations delivered at 16th International Congress of the “Organisation Francophone de Paléobotanique” (9–11 September 2009). They allow to focus on some selected aspects of current researches on these topics. New advances dealing with works on fossil woods; macrofloras preserved as impressions, compressions and permineralisations; microfloras and morphometric approach on fossil fruits, with all their implications, are then provided all together to the scientific international community.

In this paper we describe fragments of silicified wood specimens found in “EI Barranquillo” outcrop (Castellote, Teruel, Spain) in the Aragonese branch of the Iberian Range. This new species without any growth ring and with mixed radial pitting could represent an ancestral form of the modern Sequoioideae subfamily. This anatomical study, in association with an observation of the lithological facies, the position and the preservation of the fossil woods, evidences a subtropical climate with abundant precipitation and without seasonal contrasts, during the deposition of the Utrillas Formation.

Reappraisal of Brachyoxylon rotnaense Mathiesen, description of B. serrae n. sp. and stratigraphical implications for South-East Asia Early Cretaceous stratigraphy. The Mesozoic strata of Muang Phalan in southern Laos yielded fossils of terrestrial organisms (vertebrates, molluscs, wood). The latter was assigned to a species known from the Liassic strata of Denmark, Brachyoxylon rotnaense Mathiesen, whereas vertebrates are indicative of a late Early Cretaceous age. A revision of the type material for B. rotnaense and for its putative taxonomical synonym Simplicioxylon hungaricum Andreánszky, of the Lao material and of new material from Thailand allowed to: 1) confirm the taxonomical synonymy; 2) reject the assignment of the Lao material to the European species; and finally 3) to recognize a new species, here described as B. serrae n. sp., encompassing the Lao and Thai materials. This new species of Brachyoxylon is characterized by the occurrence, in the radial pitting, of clusters of much flattened contiguous pits and of pairs of opposite pits in otherwise long araucarian uniseriate rows. Our revision removed the stratigraphical ambiguity and confirmed the biogeographical peculiarity of Indosinian terrestrial biomes during the Early Cretaceous.

The Lower Devonian represents an important episode in plant life history, which was marked by the diversification of land plants. Unfortunately, remains of early Devonian plants in the Iberian Peninsula are scarce. In the present paper, we describe a small assemblage of early land plants from the Lochkovian (Lower Devonian) of the Teruel Province in Spain. The main element consists of Taeniocrada-like sterile stems that are predominandy dichotomous and ribbon-like with a narrow central strand. An unidentified fossil formed by dichotomous axes together with an uncertain globular structure were also observed. This finding increases our knowledge of the palaeogeographical distribution of early land plants.

In the Perdasdefogu Basin (Ogliastra, Sardinia) plants occurring in angular cherts are preserved as siliceous permineralizations. The plant assemblage consists of the genera Sphenophyllum, Arthropitys, Astromyelon, Palaeostachya, Pecopteris, Scolecopteris, Stewartiopteris, Psaronius, Ankyropteris, Anachoropteris; furthermore, probable medullosan wood and ovules, cordaitean stems, leaves and ovules, and Dadoxylon wood have been recorded. Arborescent marratialean ferns are the dominant elements with Pecopteris and Scolecopteris leaves being the most common; the calamiteans are the second in abundance. Generally the chert blocks contain a large number of plant fragments — roots and leaves are being almost equally represented — suggestive of a coal ball-like plant accumulation. More rarely a chert block may consist of a single plant part, for example a piece of wood. The preservation and accumulation of the plants are closely comparable to the silicified plant assemblages described from the Lower Permian of Autun and the upper Pennsylvanian of Grand-Croix (Massif central, France) and from the Early Permian Döhlen Basin (Germany). It is certainly significant that the assemblage from the Perdasdefogu Basin is dominated by tree ferns and calamites like the coeval silicified vegetation from Autun. However, like in Autun, the permineralized flora contrasts with the underlying compression floras dominated by conifers and peltasperms. The Perdasdefogu macroflora record suggest a middle-upper Autunian age which corresponds to the Surmoulin and Millery formations of the Autun Basin. This is in agreement with the Asselian-Sakmarian transition as pointed out by the amphibian species found in the same formation, and perfectly correlatable with the same association found in Gottlob-lake (Thuringian Forest Basin). Because of its rich fossil content, the Perdasdefogu Basin represents a reference succession for the Autunian of the entire westernmost palaeo-Tethyan domain and its macrofloral record.

This paper deals with the systematic and botanical description of the microfloral elements from the Pliocene S. Pedro da Torre section (NW Portugal) and the description of the palaeoenvironment and palaeoclimate, for use as a correlation attempt with other Pliocene deposits. The S. Pedro da Torre section represents one of the main sites which may help us to understand the vegetation and the paleoenvironment of the Pliocene north-western Iberian Peninsula. Nearly 70 different taxa were indentified (including bryophytes, ferns, gymnosperms and angiosperms), which indicate a palaeowetland setting, dominated by arboreal vegetation that developed under humid and warm climatic conditions.

The Choshi Group, which crops out in the Outer Zone of south-west Japan, has been extensively studied for its rich macroflora by Makoto and Harufumi Nishida, among others, and was attributed to the Ryoseki-type Floristic Province by Kimura (1987). New microfloras were discovered in muddy, very fine-grained sandstones and mudstones of the marine Ashikajima and Kimigahama formations, representing the base of the Choshi Group. The authors provide a palynological inventory for these lithological units, which have been dated as Barremian on the basis of the ammonites recorded from them, and compare them with the paleofloristic associations of the South-Laurasian Province (Brenner 1976) and Euro-Sinian Region (Vakhrameev 1991). The studied assemblages yielded 53 genera and 89 species of spores and gymnosperm pollen grains, and also marine or freshwater algae and some epiphyllous fungi. No angiosperm pollen grain was observed. Four new species are described: Manumia japonica n. sp., Foveosporites ryosekiensis n. sp., Nodosisporites choshiensis n. sp. and N. makotoi n. sp. Other forms, probably new species, are described here in detail, but the scarcity of the specimens has led us to place them temporarily in open nomenclature. The spatio-temporal distributions of the genus Manumia Pocock, reported for the first time in Asia, and Cicatricosisporites sinuosus Hunt, 1985 are plotted on paleogeographical maps. With this palynological study, we add new data to the present knowledge of Barremian floras. This assemblage probably corresponds to a taphocenose. The authors suggest that the climate indicated had marked dry and more humid seasons, in accordance with the hypothesis of a moderate migration of the oceanic islands of the Outer Zone before their collision with the Eurasian continent, or moderate climatic change during the Early Cretaceous in Japan.

Detailed records of spore-pollen assemblages from four sites located in the Aliaga and Oliete Sub-basins provide new insights into the palaeoclimatic and palaeogeographic settings during the Albian-Cenomanian transition in the Maestrazgo Basin (northeastern Spain). Palynological taxa such as Afropollis jardinus Doyle, Jardiné & Doerenkamp, 1982, Elaterosporites klaszii(Jardiné & Magloire) Jardiné, 1967, Equisetosporites ambiguus (Hedlund 1966) Singh, 1983, Gabonisporis pseudoreticulatus Boltenhagen, 1967, Senectotetradites varireticulatus Dettmann, 1973, Stellatopollis barghoornii Doyle, 1975, and the dinoflagellate cyst Cyclonephelium chabaca Below, 1981 indicate a latest Albian age for this unit. Abundance of Gondwanan elements such as Afropollis Doyle, Jardiné & Doerenkamp, 1982, Elaterosporites Jardiné, 1967 and Stellatopollis Doyle, 1975 indicates a northward extension of the paleogeographic distributions of those taxa during this time. Comparison between the studied microflora of the Iberian Range and microfloras from Tethyan and Gondwanan realms allows better understanding of the Tethyan paleogeographic setting.

Several Cenozoic endocarp remains from the northern hemisphere have been described with strong affinities to either Menispermum L. or Sinomenium Diels, a monophyletic group of menispermous vines. It has been proposed that all of these fossil species are synonymous and should be included within Sinomenium. In order to evaluate this suggestion, we have studied the morphological variation ranges in the menispermous endocarps with geometric morphometrics, and then the ranges of the selected fossil endocarps is compared to the ranges of modern endocarps. The shape of each endocarp is described using eight landmarks and 17 semilandmarks, accounting for the outline and the positions of lateral ridge and foramen on the endocarps. Endocarp ornamentation is studied by statistical comparisons of the number of transverse ridges. It is concluded that the ranges of variation within the fossil genera, all morphologically related to horseshoe-shaped endocarps in Menispermaceae, are found not to be greater than that in the only extant species of Sinomenium, S. acutum (Thunb.) Render & Wilson. Sinomenium macrocarpum Liu & Jacques, 2010 differs from the other fossil species of Sinomenium by its higher number of transverse ridges. All other fossil species of Sinomenium, except S. macrocarpum, and Wardensheppeya Eyde, 1970 are synonymous. Menispermum? taylori Chandler, 1964 is transferred to Sinomenium. The fossil genus Palaeosinomenium Chandler, 1961 is confirmed through the obliquity of its endocarp, but all species are found to be synonymous. Menispermicarpum rariforme Chandler, 1961 is also included in Palaeosinomenium.