Gnetophytes are a key group of plant for understanding seed plant phylogeny,partly because of their unique and elusive morphology,such as xylem with vessels,phloem with chaperones,reticular veins,and double fertilizat...Gnetophytes are a key group of plant for understanding seed plant phylogeny,partly because of their unique and elusive morphology,such as xylem with vessels,phloem with chaperones,reticular veins,and double fertilization(Endress,1996).In particular,the ovule bears a membranous integument,the upper part of which extends beyond the seed envelope to form a micropylar tube.Therefore,gnetophytes occupy a unique evolutionary position in the phylogeny of seed plants and apparently represent a transition between angiosperms and other gymnosperms(Ran et al.,2018).Modern gnetophytes consist of only three families:Ephedraceae,Gnetaceae,and Welwitschiaceae,and each family contains only one genus.Ephedraceae(Ephedra L.)are the earliest diverging group of Gnetales,with a total of 70 extant species,and usually occur in cold and arid places in Asia,Europe,northern Africa,western North America and South America(Price,1996;Yang et al.,2017b).展开更多
Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present s...Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures. Leaves are dimorphic, spirally and imbricately arranged. They are scale-like on the main and cone-bearing branchlets, and subulate to falcate-subulate on the juvenile or sterile shoots. The seed cones are singly elliptic, ovate or elongate-ovate and terminally borne on ultimate shoots, bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis, the bracts are broadovate, rhomboidal or hexagonal with entire margins. Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania. Furthermore, geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.展开更多
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0704)the National Natural Science Foundation of China(Grant No.42272029).
文摘Gnetophytes are a key group of plant for understanding seed plant phylogeny,partly because of their unique and elusive morphology,such as xylem with vessels,phloem with chaperones,reticular veins,and double fertilization(Endress,1996).In particular,the ovule bears a membranous integument,the upper part of which extends beyond the seed envelope to form a micropylar tube.Therefore,gnetophytes occupy a unique evolutionary position in the phylogeny of seed plants and apparently represent a transition between angiosperms and other gymnosperms(Ran et al.,2018).Modern gnetophytes consist of only three families:Ephedraceae,Gnetaceae,and Welwitschiaceae,and each family contains only one genus.Ephedraceae(Ephedra L.)are the earliest diverging group of Gnetales,with a total of 70 extant species,and usually occur in cold and arid places in Asia,Europe,northern Africa,western North America and South America(Price,1996;Yang et al.,2017b).
基金conducted under the 973 Program of China (No. 2012CB822003)the National Natural Science Foundation of China (Nos. 41402007, 41602023)the Fundamental Research Funds for the Central Universities (Lzujbky-2014-132)
文摘Fossil Taiwania was discovered from the Lower Cretaceous Yixian Formation of Lingyuan City, western Liaoning Province, Northeast China. It is identified as a new species, Taiwania lingyuanensis sp. nov.. The present specimen is preserved as impressions with well defined leaf shoots system and reproductive structures. Leaves are dimorphic, spirally and imbricately arranged. They are scale-like on the main and cone-bearing branchlets, and subulate to falcate-subulate on the juvenile or sterile shoots. The seed cones are singly elliptic, ovate or elongate-ovate and terminally borne on ultimate shoots, bearing 22–24 scale-bracts complexes imbricately and helically arranged around the cone axis, the bracts are broadovate, rhomboidal or hexagonal with entire margins. Both the leafy shoots morphology and reproductive structures are similar to extant Taiwania. Furthermore, geological distribution and molecular biological evidences support that Taiwania is probably originated from the eastern Asia at least in the Early Cretaceous and widely distributed in the North Hemisphere thereafter.
