A novel lycopsid from the Upper Devonian of Jiangsu, China

Abstract

ABSTRACT. A new lycopsid, Monilistrobus yixingensis gen. et sp. nov., is described from the Wutung Formation (Famennian, Upper Devonian) of Jiangsu, China. The plant has many features typical of other Upper Devonian lycopsids, including dichotomous branching, helically arranged obovate expanded leaf bases, linear leaves with spiny appendages along the lateral margins, sporophylls widened proximally, and one elliptical sporangium attached to the adaxial surface. The most distinctive novel feature of the plant is that the modi®ed sporophylls are arranged tightly into fertile zones or cone-like structures that are separated by lengths of axes with more lax sterile microphylls only: therefore the cone-like structures are strung along the branches like beads on a necklace.

A new species of Lepidostrobus from the Upper Devonian of Xinjiang, China and its bearing on the phylogenetic significance of the order Isoëtales

“…The presence of L. xinjiangensis in Upper Devonian deposits, in addition to contemporaneous diverse reproductive forms (Chaloner, 1968; Chitaley & Mcgregor, 1988; Chitaley & Pigg, 1996; Pigg, 2001; Wang, 2001; Cai, Chitaley & Dou, 2002; Xu & Wang, 2002; Wang & Berry, 2003; Berry et al ., 2003), suggests that arborescent lycopsids might have undergone incipient adaptive radiations by the Frasnian Upper Devonian or even the Givetian Middle Devonian. Longostachys latisporophyllus (Cai & Chen, 1996) and Mixostrobilus givetensis (Senkevitsch, Jurina & Arkhangelskaya, 1993) are two heterosporous lycopsids from the Givetian of China and Kazakhstan, respectively, that show close affinities to arborescent lycopsids, possibly representing ancestral groups to the subsequent bisporangiate‐strobilus clade.…”

Periodicity of reproductive growth in lycopsids: An example from the Upper Devonian of Zhejiang Province, China

“…However, the possible underlying development mechanisms and/or environmental factors for periodicity of reproductive growth are still far from well-understood. Wang and Berry (2003) considered that the alternate reproductive growth in Monilistrobus may reflect interrupted growth of the apex, perhaps being controlled by some sort of climate stimulus. Gola (2008) concluded that, in Huperzia, some environmental factors like temperature, altitude, etc., may switch the genes that are responsible for the transition between vegetative and reproductive developmental phrases, resulting in production of either sporangia or vegetative propagules.…”

“…In the present specimens, fertile and vegetative axes are 1.7-4.1 mm wide, comparable to the described axes of M. yixingensis (1.2-3.5 mm wide) . Chamaedendron, which were reconstructed as small trees (Cai and Chen, 1996;Schweitzer and Li, 1996), Wang and Berry (2003) suspected that Monilistrobus may represent part of the crown of a small tree-shaped lycopsid.…”

“…Monilistrobus is unique as a Late Devonian fossil lycopsid in the presence of intercalary cone-like structures. The morphological comparisons between Monilistrobus and other taxa, such as the Protolepidodendrales, Sublepidodendron Nathorst, Longostachys Zhu, Hu et Feng, and Chamaedendron Schweitzer et Li, have been provided byWang and Berry (2003), which remain valid. Monilistrobus seems more similar to the Middle-Late Devonian Longostachys and Chamaedendron than to other taxa in the dichotomous axes, shape of leaf bases, and morphology of vegetative leaves and sporophylls.…”

A new homosporous, arborescent lycopsid from the Middle Devonian of Xinjiang, Northwest China

“…The sporangia arrangement of Chamaedendron is described as 4–6 megasporangia on the adaxial surface of megasporophyll and 12 microsporangia on the microsporophyll. A more reasonable interpretation was argued that those mega‐/microsporangia are actually megaspores (see Wang and Berry 2003). Chamaedendron is similar to Hoxtolgaya in having unspecialized fertile zones.…”