This comprehensive macromorphological and cuticular anatomical study investigates Bennettitalean foliage specimens collected from the Yaojie Formation (Middle Jurassic) of the Baojishan Basin, Gansu Province, northwestern China. These fossils were assigned to the genus Nilssoniopteris Natorst, and two new species are formally described: Nilssoniopteris baojishanensis Xin et Zhang sp. nov. and Nilssoniopteris specialis Xin et Zhang sp. nov. N. baojishanensis sp. nov. is characterized by strap-shaped leaves with entire margins, typically straight anticlinal cell walls and subsidiary cells bearing 3–6 papillae. N. specialis sp. nov. exhibits oblong to lanceolate leaves with entire margins, strongly sinuous anticlinal cell walls and is featured by a hollow papilla on the periclinal walls of the abaxial epidermal cells. This is the first macromorphological and cuticular anatomical description of Nilssoniopteris in the Middle Jurassic flora of the Baojishan Basin. Based on cuticular analyses of the two new species, floral composition, and sedimentological data, we infer that the Middle Jurassic Nilssoniopteris from the Baojishan Basin inhabited predominantly warm and humid habitats, albeit with seasonal or intermittent droughts. The two present Nilssoniopteris species may have been adapted to relatively open, high-light, and windy habitats within the basin, potentially including settings such as river terraces and forest margins. The papillate surfaces and trichome bases may have promoted leaf-surface self-cleaning, maintained photosynthetic efficiency, and enhanced defense against herbivorous insects.
Zhang et al. (Fri,) studied this question.