Abstract
In the abundant material collected from the Middle Jurassic Yima Formation, leafy shoots with helically arranged, elongate, sessile and parallel-veined leaves consisting each of a decurrent base and a spreading free part are found in association with numerous leafy dwarf shoots and isolated leaf fragments of Phoenicopsis and some fructifications of the Ixostrobus type. This type of leafy shoot is very different from all others so far known of Mesozoic gymnosperms and is described under a new name Tianshia patens Zhou et Zhang, gen. et sp. nov. In cuticular structure, leaves of this type of long shoots resemble those of the associated dwarf shoots referred as Phoenicopsis euthyphylla Zhou et Zhang, sp. nov. They are of the Windwardia type and similar to each other in stomatal distribution and orientation, and in some other respects. It is likely that the two types of leafy shoots may belong to the same plant and represent different developmental stages. As compared with other gymnospermous plants known to have both long and dwarf shoots, long shoots of the Tianshia type are believed to be young, while shoots of the Phoenicopsis type may have been mature. If our interpretation is correct, it is so far the first record of young shoots in Czekanowskiales. In the article, both Tianshia patens and Phoenicopsis euthyphylla are described in detail and compared with other known taxa.
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