CZEKANOWSKIA FROM THE JURASSIC OF INNER MONGOLIA, CHINA Chunlin Sun, 1, * , y David L. Dilcher,* , y Hongshan Wang, y Ge Sun,* and Yuhui Ge* *Key Lab for Evolution of Past Life and Environment in Northeast Asia, Ministry of Education, 6 Ximinzhu Street, Changchun 130026, Jilin, China; and y Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611-7800, U.S.A. The genus Czekanowskia is an important member of the Mesozoic flora and is widespread in the Northern Hemisphere. In China, it is found mostly in Late Triassic and Early and Middle Jurassic sediments of North China. With the exception of a few specimens, all the reports of this genus from China have been based on gross leaf morphology. Abundant Czekanowskia leaves, preserved as compression fossils, were collected from the Middle Jurassic, Zhaogou Formation of Inner Mongolia, China. In this article, two subgenera of Czekanowskia, Harrisella and Vachrameevia, are recognized from Inner Mongolia, China, on the basis of leaf morphology and epidermal characters. Two new species, Czekanowskia chinensis sp. nov. (subg. Harrisella) and Czekanowskia shiguaiensis sp. nov. (subg. Vachrameevia), are described. The occurrence of these species in the Middle Jurassic of Inner Mongolia significantly extends the stratigraphic and geographic distribution of Czekanowskia in the Northern Hemisphere. Analysis of the epidermal characters of material presented here along with consideration of other associated plants of the flora and sedimentology of the plant-bearing strata suggests that the two species described in this report grew in an area with a warm and humid climate in a warm temperate zone. Biostratigraphic correlation of the plant-bearing strata indicates that the specimens described here are Middle Jurassic in age. Keywords: Czekanowskia, Middle Jurassic, Inner Mongolia, China. Introduction Czekanowskia, an important member of Late Triassic and Early and Middle Jurassic floras, is common and widely dis- tributed in the Northern Hemisphere. It has been reported from Eastern Greenland (Harris 1926, 1935), England (Harris and Miller 1974), Sweden (Nathorst 1906; Johansson 1922), Romania (Popa and van Konijnenburg-van Cittert 2006), Kazakhstan, Eastern Ural, Central Asia, Siberia (Doludenko and Rasskazova 1972; Samylina and Kiritchkova 1991, 1993; Kostina 1999, 2004), China (Sze et al. 1963; Ye et al. 1986; Li et al. 1988; Mi et al. 1993, 1996; Sun 1993; Li 1995), Japan (Kimura and Ohana 1979), the United States, and Canada (Ash and Basinger 1991; Ash 1994). Czekanowskia was first described by Heer (1876) on the basis of material from the Irkutsk Jurassic coal-bearing basin of Eastern Siberia. Since then, many fossil leaves have been discovered throughout the Northern Hemisphere. Most of them were assigned to Czekanowskia setacea Heer and Cze- kanowskia rigida Heer on the basis of leaf morphology. The cuticle of C. setacea Heer from the type locality in Siberia and C. rigida Heer also from Siberia, but not the type locality, was studied by Florin (1936) and Vachrameev and Doludenko (1961). Cuticle of C. rigida Heer found in other areas was also described from the basal Liassic of Sweden (Nathorst 1906; Johansson 1922) and the Lower Cretaceous of Franz-Joseph- Land (Florin 1936). Cuticular material belonging to other species of Czeka- nowskia was studied from other areas of the world, for ex- ample, from Yorkshire by Seward (1900, 1919), Black (1929), and Harris and Miller (1974); from Eastern Green- land by Harris (1926, 1935); from Japan by Oishi (1932) and Kimura and Ohana (1979); and from the United States by Ash (1994). Samylina and Kiritchkova (1991, 1993) studied well- preserved cuticle of the genus Czekanowskia collected from more than 170 localities in the former Soviet Union. They di- vided the genus into three subgenera on the basis of leaf epidermal characters, that is, Czekanowskia (leaves amphis- tomatic with stomata arranged in files), Harrisella (leaves amphistomatic with stomata arranged in bands, at least on the lower epidermis), and Vachrameevia (leaves hypostomatic with stomata arranged in files or bands). So far, ;80 species of the genus Czekanowskia have been established on the basis of differences of cuticular features. Sixty-five species were assigned to the subgenus Czekanow- skia, including two species from Eastern Greenland (Harris 1926, 1935), four species from Yorkshire (Harris and Miller 1974), one species from the United States (Ash 1994), one species from Sweden (Johansson 1922), one species from Ja- pan (Kimura and Ohana 1979), and 56 species from the for- mer Soviet Union (Samylina and Kiritchkova 1991, 1993). Eight species were assigned to the subgenus Harrisella and seven species to the subgenus Vachrameevia from the former Soviet Union (Samylina and Kiritchkova 1991). Fossils of the subgenus Vachrameevia were reported from the Jurassic of Northwest China (Wu et al. 2002). Czekanowskia was thought to belong to the order Gink- goales (Florin 1936). Pant (1957) established the order Cze- kanowskiales, but he did not provide a diagnosis. After fruits of Leptostrobus were studied (Harris 1935, 1951; Krassilov 1 Author for correspondence; e-mail: clsun@mail.jlu.edu.cn. Manuscript received April 2009; revised manuscript received June 2009. 1183 Int. J. Plant Sci. 170(9):1183–1194. 2009. Ó 2009 by The University of Chicago. All rights reserved. 1058-5893/2009/17009-0006$15.00 DOI: 10.1086/605869