科研之友
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摘要
Plant fossil collections from Lower Cretaceous floodplain deposits sometimes provide snapshots of local communities that included early herbaceous angiosperms. Here I describe the plant megafossils in a collection made from the lower part of the Potomac Group near Fairlington, Virginia, USA. The collection includes 123 identifiable plant fossils on 42 hand specimens, comprising nine plant morphotypes: three ferns, five gymnosperms and one angiosperm. All but one of the described morphotypes also occur in other collections from the lower Potomac Group. There is one moderately abundant angiosperm species in this collection that has been found at other Potomac Group sites but was incorrectly identified as a fern. Well-preserved specimens of this morphotype clearly show axillary branching, complex leaves and glandular teeth at the apices of lobes on the leaves; together, these characteristics suggest it was an herbaceous eudicot angiosperm. The one new morphotype in this collection is an enigmatic plant of intermediate abundance and unknown affinity. On the basis of the simple, pinnate stenophyllous leaves with two vein orders, reticulate secondary veins and the attachment of one leaf to a carbonized axis roughly 1 cm across with long internodes, I hypothesize that it was a shrubby riparian gymnosperm. This work represents the first step toward a complete morphotype catalog for the flora of the lower Potomac Group.
- 出版日期2014-10
