Abstract
ABSTRACTThe feature distinguishing typical angiosperms from gymnosperms is that their ovules are enclosed before pollination. Bennettitales were formerly related to angiosperms because of the flower-like organisation of the former's reproductive organs. There is little information on how the naked ovules of Bennettitales became enclosed in angiosperms because fossil evidence for such a transition, if it exists, has not been described. Here, we report a reproductive organ,Zhangwuiagen. nov., from the Middle Jurassic of Inner Mongolia, China. Like many Bennettitales, the arrangement of the foliar parts around the female part inZhangwuiademonstrates a resemblance to typical angiosperm flowers. It is noteworthy that the ovule is secluded from the exterior space inZhangwuia, therefore implying the existence of angio-ovuly. Although Bennettitales have been related to angiosperms for more than a hundred years, their way of ovule-enclosing was not previously revealed. The discovery ofZhangwuiaprompts a rethinking of the relationship between Bennettitales and angiosperms, as well as of the origin of angiosperms.
Highlights
Material and methodsThe general morphology and details of Zhangwuia were observed and photographed using a Nikon SMZ1500 stereomicroscope with a digital camera
A bennettitalean plant, Foxeoidea, was reported with its ovules surrounded by interseminal scales, its ovules were not fully enclosed as they are in angiosperms (Rothwell & Stockey 2010)
The fossil material was collected by a local fossil collector, Mr Hongtao Cai, from the outcrop of the Jiulongshan Formation near Daohugou Village, Ningcheng, Liaoning, China (119.236727E, 41.315756N; Fig. 1), and it was donated to the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (CAS)
Summary
The general morphology and details of Zhangwuia were observed and photographed using a Nikon SMZ1500 stereomicroscope with a digital camera. More details were further observed and recorded using a Leo 1530 VP scanning electron microscope (SEM) at the Nanjing Institute of Geology and Palaeontology (NIGPAS), Nanjing, China. Micro-computed tomography (CT) observation was performed using 225 kv micro-CT (developed by the Institute of High Energy Physics, CAS) at the Key Laboratory of Vertebrate Evolution and Human Origin of CAS in the Institute of Vertebrate Palaeontology and Palaeoanthropology, scanning under a cone-beam energy of 130 kV and a flux of 100 mA with an 8.8 mm slice distance. The transmission images of 1536 slices were reconstructed with a 2048 Â 2048 matrix and 8.8 mm pixel size through a 3D image processing software developed by the Institute of High Energy Physics, CAS. To make our description more neutral, we use the terms ‘female part’ and ‘female unit’, instead of ‘gynoecium’ and ‘carpel’ (which are restricted to angiosperms) to describe the morphology of Zhangwuia
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