APPROACH TO THE CLASSIFICATION OF MESOZOIC " GINKGOALEAN" PLANTS FROM SIBERIA V. A. KRASSILOV Far Eastern Institute of Geology, USSR Academy of Sciences, Vladivostok ABSTRACT plant with the Czekanowskia leaves. The New findings from the Mesozoic of Bureja basin structure of Leptostrobtts is unique among confirm Harris' interpretation of Leptostrobus. Its female flowers of Gymnosperms. The plants capsule is analogous to the ovary of Angiospermae. with such flowers must be removed from the contact surface of valves is verrucose and papil• Ginkgoales. Probably they composed a late and corresponds to the stigma. The leaves of Czekanowskia. Phoenicopsis and allied genera are separate taxa. At the same time Harris assigned to the plants with Leptostrobus type of showed some difficulties in dividing the fructification and mu t be excluded from the Czekanowskia group from Ginkgos: the male Ginkgoales. Three types of female fructifications: reproductive structures are completely un• megastrobili of Ginl~go, Karkenia and Umaltolepis Aretobaiera (a new organ-genus referred to Pseudotorellia) are known and "the position of distinguished within the Ginkgoales, each of them and Sphenobaiera would be doubtful and representing a distinct family. this would be a real disadvantage" (HARRIS, 1951, p. 505). INTRODUCTION Our study of Ginkgoales and allied plants from the Upper J urassic- Lower Cretaceous of the Bureja River basin confirms the Mesozoic(1876)floradescribedas dominatedthe bySiberianGinkgo statements of Oishi, and Harris on the HEERfamily. In this family he included heterogenous nature of fossil "Ginkgoales" besides Ginkgo itself such extinct genera as sensu Heer and others and some new details Baiera, Triehopitys, Czekanowskia, Phoeni• come to light. eopsis, Dieranophyllum, Feildenia and Rhipi• dopsis. Heer's (1876) remarks on the affi• MATERIAL AND METHODS nity of Phoenicopsis are noticeable: he conside red this genus as some sort of a link The material was collected at the outcrops between the Ginkgoalean plants and Paleo• of Upper J urassic- Lower Cretaceous conti• zoic Cordaites. Seward and Gowan (1900) nental beds within the valley of Bureja were perhaps the first to doubt Heer's opi• River and its tributaries. Cleaned leaves, nion on the systematic posit.ion of Phoeni• brachyblasts, capsules, seeds and sporangia copsis-Czekanowskia group. Later Oishi were obtained by means of bulk maceration (1933) separated this group from Ginkgoales and transfer techniques. Some of them on the grounds of cuticular analysis: he were then subj ected to oxidation and mace• emphasized the striking difference in the ration with alkaline solution. epidermal structure of leaves of Phoenicopsis• Czekanowskia on one side and true Ginkgoa• DESCRIPTION les on the other. Oishi also rej ected a coniferous affinity of this group and supposed CZEKANOWSKIALES it to be the order of its own. These very exquisitive ideas were somehow oversha• The name" Czekanowskiales " apparently dowed by the well known works of Florin arrived for the first time in Pant's (1958) (1936a, b) on the Ginkgoales from the Franz classification of Gymnospermous plants. Jozef Land. Florin thoroughly investigated FC(lnale organs - Two species of Leptos• the favourably preserved plants from the trobus and one of Staphidiophora were inves• Phoenieopsis-Czekanowskia group and ex• tigated. The structure of Siberian Leptos• pressed no doubt in their Ginkgoalean trobus ex gr. laxiflorus Heer, is as a whole affinity. identical with those described by Harris Harris' (1951) study of Leptostrobus has from Greenland and Yorkshire: these fructi• thrown a new light on the problem. He fications consist of a long axis bearing fertile found a strong evidence of Leptostrobus capsules composed of two valves. Some being the female reproductive organ of a additional details were observed: 12 KRASSILOV - MESOZOIC" GINKGOALEN •. PLANTS FROM SIBERIA 13 1. A short stalk of the capsule ,,,hich is inflorescence. On this shortened axis only sometimes almost completely reduced• two fertile complexes (simple strobiles or capsules being sessile, and sometimes proli• carpels) had been retained which were united ferated in a comparatively solid structure in a two-valved capsule. The capsule is resembling a cylindrical short shoot, bears analogous to the ovary of Angiospermae somewhat ill defined marks or scars of and the contact surface of valves (carpc1s) is scale-leaves. Identical scars were found on specialized for.pollination (the present author the flattened basal part of the capsule. has no alternative interpretation of the 2. Convex central part of each valve is verrucose and papillate sculpture of this bordered by a flat marginal flange. The surface) and is analogous to the stigma. inner face of the flange is verrucose, with Pollination there ",as perhaps of gymnos• pointed or rounded outgrowths. The cuticle permous nature, but it is worth mentioning of inner side of the flange is densely papillate. that in ~ome tropical flowering plants (some The marginal flange gives inside very thin Anonaceae and others) pollen falls through lamellae overhanging the seeds. The cuticle the stigma and does not germinate on it. of lamellae is also papillate. M ale Organs - I consider the organ-genus 3. The inner concave side of the valve has 1xostrobus Raciborski as a male cone of very thin cuticle which differs in its struc• Czekanowskiales. In two localities in the ture from the outer cuticle. Seeds were Bureja basin these cones were found in not embedded in the "fibrous layer" as association with Leptostrotl1s. But in both Harris (1951) supposed them to be. cases 1xostroGus is a rare fossil while Leptos• Another type of LeptostroGus - L. ex troGus is abundant. The association with gr. crassipes Heer differs from the above the leaves attributed to Czekanowskiales described L. ex gr. laxiflorus in its large (see below) is more impressive. Still Raci• and flattened capsules with more dense borski and Heer emphasized the association and occasionally anastomo~ing venation. of I xostrobus (A nthohthcs sdmidtianus in Seeds are more numerous (about eight on Reer's monograph) with Czekanowsln'a or each valve). Inner cuticle of the valve Phoenicopsis. Prynada (1962) analizing the is more robust and clearly differentiated extensive Siberian material had come to on zones of very narrow cells under the the conclusion that I xostrocus belongs to veins and broader cells with slightly sinous Czehanowshia or Sphenobaicra. But male or undulating walls between them. The fructifications of the later are known and axis is pilose - the long unicellulJ.r tri• their structure is different (KR.:\usEL, 1943). chomes are rather frequent. One cone is I found two species of 1xostrobus -I. still attached to the cylindrical short shoot schmidtianus (Heer) Krassilov and I. heeri covered with scale leaves. Prynada. The first occurs in association The fructification closely allied to Sta• with Stephencphylhm in three locdities phidiophora secunda Harris was found in and the second - with both Czekancwskt'a the upper layer of coal-bearing rocks of and Phoenicopsis (Stcphcncphyllum) in four Bureja basin. According to the first inter• localities. Other a~sociated leaves belong to pretation given by Harris (1935) lateral Ctenis, Nilsscnia, Pteropl,yllum and Sphe• appendages of this fructification were seeds. nobaiera. It seems quite unlikely that Later Harris (1951) realized the other possi• one of them is a foliage of I xostrobus. bility - that appendages are fertile capsules. Harris provisionally assigned I xostrobus to This new interpretation is confirmed now Podozamites but the evidence is not very and some resistant to maceration megaspore strong. membranes were found within the capsules. I xostrobus consists of an axis and spirally Megaspore membranes are elliptical, folded attached microsporophylls composed of a and with few small apical protuberances thin stalk and more or less expanded ter• (archegonial necks ?). Staphidiophora is minal cup. This cup is built of five appen• very close to Leptostrobus and differs from dages. The basiscopic appendage is sterile it in much smaller dimensions of capsules and backwardly curved while the others and of fructification as a whole, in more are more or less fused and form a sinangium. regular distichous arrangement of capsules, Cutiele of sinangium is very thin and sto• etc. mata was not observed. Pollen grains are According to the authors' interpretation small, wingless, badly preserved. Micro• the stalk of a capsule is a reduced axis of sporophylls of I xostrobus differ from all 14 THE PALAEOBOTANIST corresponding structures of other gymno• but some abnormal cylindrical shoots with sperms and some points of resemblance to a cluster of Stephenopkyllu1n leaves were a stamen of Angiospermae can be traced. found. The scale leaves on the fertile The Leaves - Harris (1951) put forward and sterile shoots are identical and their a convincing evidence of attribution of cuticles have frequent trichomes which Leptostrob~ts to Czekanowshia. In the Bureja are closc1y similar to trichomes on the cone basin L. ex gr. laxiflor us occurs in three axis of L. ex gr. erassipes. localities and in all of them Czehanowshia I obtained many hand-specimens on is a mostly abundant leaves. In two of which Staphidiophora and Hartzia are asso• them leaves of Pseudotorellia were found in ciated. Other plants in this locality are great number, but in the third (in the lower Nilssonia, Phoenieopsis, Ginkgoites, Pit yo• part of the Azanowshi