Two species of Haskinsia Grierson & Banks (Lycopsida) from the Middle Devonian of Xinjiang, China, and consideration of their palaeogeographical significance HONG-HE XU 1 *, YI WANG 1,2 , CHRISTOPHER M. BERRY FLS 3 and CHONG-YANG CAI 1 1 Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing 210008, China 3 School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff CF10 3YE, UK Received 8 January 2008; accepted for publication 14 February 2008 Two species of the Devonian herbaceous lycopsid Haskinsia Grierson & Banks, H. hastata Berry & Edwards and H. sagittata Edwards & Benedetto, are reported from the Hujiersite Formation (Givetian–Middle Devonian), Xinjiang, north-west China. Both species were first described from Venezuela. Haskinsia hastata from Xinjiang has hastate leaves with toothed margins, and a pair of basal narrow lateral segments which curve distally. It is assigned to a new subspecies because of the toothed margins which cannot be demonstrated in Venezuelan material. The scar of the sporangium stalk is observed for the first time in specimens of H. sagittata, on the leaves of which a possible ligule structure is also shown. On the basis of our observations on both Xinjiang and Venezuelan specimens, the diagnosis of Haskinsia is enlarged to accommodate plants whose lamina has entire or toothed margins. The palaeophytogeography of the genus, otherwise known from South and North America, is dis- cussed. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 633–644. ADDITIONAL KEYWORDS: fossil – Kazakhstan plate – leaf morphology – phytogeography. INTRODUCTION The Lycopsida has the longest evolutionary history amongst extant vascular land plants. The group origi- nated in the late Silurian and Early Devonian (Gensel & Berry, 2001) from herbaceous forms, diversified in the Middle Devonian, and peaked in both diversity and abundance in the Carboniferous, when arbores- cent forms dominated tropical coal swamps. Undoubt- edly, the Middle Devonian is the key period to study the evolution of this successful group in the context of the transformation of growth forms and increasing diversity. The morphology of microphylls is an important character for the delimitation of Devonian herbaceous lycopsids (Bonamo, Banks & Grierson, 1988). Among these, Haskinsia Grierson & Banks has petiolate leaves with sagittate or hastate blades (Grierson & Banks, 1983; Bonamo et al., 1988; Berry & Edwards, 1996). The genus is an important member of the Middle Devonian flora, and this type of leaf morphol- ogy has been reported from many Middle to lowermost Upper Devonian terrestrial (non-marine) deposits. The Givetian age Hujiersite Formation in north Xinjiang, China, our study area, from which Cai & Wang (1995) briefly reported Haskinsia sagittata Edwards & Bene- detto, is no exception. In this paper, we give the first full description of H. sagittata from this locality. Haskinsia hastata Berry & Edwards, previously found only in the Middle Devonian of Venezuela (Berry & Edwards, 1996), is reported away from its type locality for the first time. Based on our collections from Xin- jiang, China and new observations of Haskinsia speci- mens from Venezuela, new light is thrown on the leaf morphology of Haskinsia, and a new subspecies is erected. Furthermore, implications for the distribution *Corresponding author. E-mail: honghexu@hotmail.com Botanical Journal of the Linnean Society, 2008, 157, 633–644. With 26 figures © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 633–644 633