title: Vegetative characters, growth habit and microsporangiate strobilus of lycopsid Minostrobus chaohuensis.
abstract: Late Devonian Minostrobus chaohuensis is one of the earliest monosporangiate-strobilate isoetaleans. Based on new material of this plant, the vegetative axis and microsporangiate strobilus are studied in detail, and the whole plant knowledge is summarized. The vegetative axis is isotomously branched. The stem is up to 55 mm in diameter with helically arranged leaf cushions. Stems and thick branches bear long fusiform leaf cushions and interareas with vertical linear ornamentations. A ligule pit, oblanceolate leaf scar, and vascular bundle scar appear on the leaf cushion. Distal axes have persistent lanceolate leaves and rhombic leaf bases. The microsporangiate strobilus is cylindrical in shape, possesses sporophyll with alate pedicel and long triangular lamina, uniseriate sporangial wall, subarchesporial pad inside the sporangium, and microspore with cingulum. Based on comparisons with other isoetaleans, the usage of the terms "leaf cushion" and "leaf base" is discussed, and Minostrobus chaohuensis is considered as a tree-like lycopsid. It suggests that arborescent isoetaleans with monosporangiate strobili had appeared and diversified in the Late Devonian. The multi-dichotomous branching system of Minostrobus provides new data on the evolution of growth architecture in rhizomorphic lycopsids.
authors: Ministry of Land and Resources Key Laboratory of Stratigraphy and Paleontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.
authors: Mei-Cen
authors: MC
authors: Meng
authors: Key Laboratory of Orogenic Belts and Crustal Evolution, Department of Geology, Peking University, Beijing, China.
authors: De-Ming
authors: DM
authors: Wang
authors: Ministry of Land and Resources Key Laboratory of Stratigraphy and Paleontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.
authors: Jian-Xin
authors: JX
authors: Yao
mesh_terms: D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D029542:Lycopodiaceae / Q000033:anatomy & histology* / Q000254:growth & development; D058432:Sporangia / Q000033:anatomy & histology*