526


Journal of Paleontology 92(4):525–545 Geological setting, material and methods


Since the late 1990s, SHD and his colleagues have been systematically collecting plant fossils at several coal mines near Hami City, Xinjiang Uygur Autonomous Region, NW China, and the plant fossils described in this study are from the Sandaoling Opencast Coal Mine, ~90km west of Hami City (Fig. 1). Gymnospermous fossil leaves collected from those mines often occur as compressions with well-preserved cuticles that are readily applied for precise identification. The Jurassic strata exposed in theHamiDepression comprise


only the Lower Jurassic Badaowan Formation and Sangonghe Formation, as well as the Middle Jurassic Xishanyao Formation, which is disconformably covered by the Late Cretaceous– Paleocene ShanshanGroup. The upper part of theMiddle Jurassic and the Upper Jurassic have been eroded. The formation consists of grayish white, grayish green, or light red fine-grained sandstone and siltstone alternating with grayish to dark gray mudstone intercalated with conglomerate and coal seams or beds (Fig. 1). Plant fossils fromtheXishanyao Formation yielded anAalenian to Bajocian age (Deng et al., 2010). The specimens studied here are preserved as impressions


and compressions. The hand specimens were first photographed using a Canon EOS 5D Mark III digital camera. When clean cuticles were needed, pieces of leaf fossil compressions were removed using a blade, then dissolved in hydrofluoric acid. The isolated fossil pieces were then macerated in sodium hypo- chlorite for oxidation until they became yellow in color. The cuticles then were washed in distilled water and treated with drops of ammonia to remove impurities before being thoroughly rinsed with distilled water. The adaxial and abaxial clean cuticleswere separated by a silver needle under a light microscope.


Cuticles were mounted on microscope slides for observation and photographing with a Leica DMLB light microscope equipped with a Leica DFC450C digital camera, or mounted on scanning electron microscope (SEM) sample stubs, coated with gold, and then observed and photographed through a TESCAN VEGA II LMU SEM.


Repository and institutional abbreviation.—All illustrated specimens are deposited in the Research Institute of Petroleum Exploration and Development (SDL), Beijing, China.


Systematic paleontology


Order Bennettitales Engler, 1892 Family unknown


Genus Nilssoniopteris Nathorst, 1909


Type species.—Nilssoniopteris solitaria (Phillips, 1829) Cleal and Rees, 2003 from White Nab near Scarborough (Yorkshire), Yorkshire, UK (Pott and Van Konijnenburg-van Cittert, in press).


Diagnosis.—Emended from Pott et al. (2007) and Pott and Mcloughlin (2009). Leaves falling from stem at maturity, petiolate. Lamina mostly entire-margined, or undulate, lobed, to completely dissected down to the rachis in the middle portion with at least basal or apical portion entire-margined, attached laterally or to adaxial surface of midrib, leaving part of the upper surface of the midrib exposed. Veins simple or forked, or occasionally anastomosed, ending at margin. Cuticle with syndetocheilic stomata; epidermal cell walls straight or usually sinuous.


Figure 1. Location of the Sandaoling Coal Mine and the stratigraphic column.


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