New Plants from the Lower Devonian Pingyipu Group, Jiangyou County, Sichuan Province, China.

Descriptions of Lower Devonian plants from Yunnan, South China, have revolutionized concepts of diversity and disparity in tracheophytes soon after they became established on land. Sichuan assemblages have received little attention since their discovery almost 25 years ago and require revision. With this objective, fieldwork involving detailed logging and collection of fossils was undertaken in the Longmenshan Mountain Region, Jiangyou County and yielded the two new taxa described here. They are preserved as coalified compressions and impressions that allowed morphological but not anatomical analyses. Yanmenia (Zosterophyllum) longa comb nov is based on numerous rarely branching shoots with enations resembling lycophyte microphylls, without evidence for vasculature. The presence of sporangia is equivocal making assignation to the Lycopsida conjectural. The plant was recently described as a zosterophyll, but lacks strobili. These are present in the second plant and comprise bivalved sporangia. The strobili terminate aerial stems which arise from a basal axial complex displaying diversity in branching including H- and K- forms. These features characterise the Zosterophyllopsida, although the plant differs from Zosterophyllum in valve shape. Comparisons indicate greatest similarities to the Lower Devonian Guangnania cuneata, from Yunnan, but differences, particularly in the nature of the sporangium border, require the erection of a new species, G. minor. Superficial examination of specimens already published indicate a high degree of endemism at both species and generic level, while this study shows that Yanmenia is confined to Sichuan and Guangnania is one of the very few genera shared with Yunnan, where assemblages also show a high proportion of further endemic genera. Such provincialism noted in the Chinese Lower Devonian is explained by the palaeogeographic isolation of the South China plate, but this cannot account for differences/endemism between the Sichuan and Yunnan floras. Such an enigma demands further integrated geological, palaeobotanical and palynological studies.

Schmeissneria: a missing link to angiosperms?

BACKGROUND: The origin of angiosperms has been under debate since the time of Darwin. While there has been much speculation in past decades about pre-Cretaceous angiosperms, including Archaefructus, these reports are controversial. The earliest reliable fossil record of angiosperms remains restricted to the Cretaceous, even though recent molecular phylogenetic studies suggest an origin for angiosperms much earlier than the current fossil record. RESULTS: In this paper, after careful SEM and light microscopic work, we report fossils with angiospermous traits of the Jurassic age. The fossils were collected from the Haifanggou Formation (middle Jurassic) in western Liaoning, northeast China. They include two female structures and an associated leaf on the same slab. One of the female structures is physically connected to the apex of a short shoot. The female organs are borne in pairs on short peduncles that are arranged along the axis of the female structure. Each of the female organs has a central unit that is surrounded by an envelope with characteristic longitudinal ribs. Each central unit has two locules completely separated by a vertical septum. The apex of the central unit is completely closed. The general morphology places these fossils into the scope of Schmeissneria, an early Jurassic genus that was previously attributed to Ginkgoales. CONCLUSION: Because the closed carpel is a character only found in angiosperms, the closed apex of the central unit suggests the presence of angiospermy in Schmeissneria. This angiospermous trait implies either a Jurassic angiosperm or a new seed plant group parallel to angiosperms and other known seed plants. As an angiosperm, the Liassic age (earliest Jurassic) of Schmeissneria microstachys would suggest an origin of angiosperms during the Triassic. Although still uncertain, this could have a great impact on our perspective of the history, diversity and systematics of seed plants and angiosperms.

New perspective on the architecture of the Late Devonian arborescent lycopsid Leptophloeum rhombicum (Leptophloeaceae).

A reinvestigation of the previously described Leptophloeum rhombicum trunk from the Late Devonian (Frasnian) Huangchiateng Formation of Hubei, China provides a new perspective on the architecture of this arborescent lycopsid. It is preserved as a flattened, silicified petrification with an unevenly permineralized primary vasculature and spirally arranged rhombic leaf cushions, which agree with the diagnosis of L. rhombicum Dawson distributed worldwide in the Late Devonian. Taxonomically, this plant should be assigned to its own family and within the order Isoëtales sensu lato. The anatomy, from different levels of the trunk, demonstrates that the ontogeny of the plant may conform to a determinate growth pattern. Combining previous data with current architectural analysis, it suggested that the L. rhombicum tree had a pseudomonopodial branching pattern rather than an iso-dichotomous branching crown as previously proposed. New reconstruction of the general habit for this tree is given and consists of three major architectural units: a stigmarian rhizomorph, a main trunk, and lateral branches. When these results are considered with recent cladistic work, L. rhombicum may have developed similar growth architecture to some Famennian and Carboniferous arborescent lycopsids. This growth represents one of the archetypal architectures found in the Isoëtales s.l. extending from the early Late Devonian.

Morphology and affinities of an Early Cretaceous Ephedra (Ephedraceae) from China.

Detailed investigations on Lower Cretaceous Ephedra L. fossils (Gnetopsida) reveal morphological characters similar to those of extant Ephedra rhytidosperma Pachomova, including articulate branches with many fine longitudinal striations, a dichasial branching pattern, uni- or bi-ovulate cones with paired bracts, cones terminal on branchlets, and seeds with a short, straight micropylar tubes, covered by numerous regular and prominent transverse laminar protuberances. Fossils are similar to extant E. rhytidosperma reproductive organs but differ in some vegetative structures and are described and discussed here as Ephedra archaeorhytidosperma Y. Yang et al. Because E. rhytidosperma is currently considered one of the most specialized members in Ephedra L. section Pseudobaccatae Stapf, the occurrence of E. archaeorhytidosperma in the Yixian Formation suggests that Ephedra L. was perhaps a more diverse genus in the Lower Cretaceous. Perhaps the evolution and diversity of Ephedra L. was already in place by the Lower Cretaceous and certainly before the end of the Mesozoic.