Plant Fragments from Devonian Beds in Central Yunnan, China
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PLANT FRAGMENTS FROM DEVONIAN BEDS IN CENTRAL YUNNAN, CHINA B y J. H su (With 5 Plates, one Map and 5 Text-figures) A bstra ct The paper describes 45 specimens of plants collected from Devonian beds at several localities in the districts Lihsien, Kunming, Ch’iiching and Luch’iian of Central Yunnan, China. It is unfortunate that most of the fossils are -too frag: mentary to furnish specific identifications. They are preserved as casts, moulds and incrustations in various kinds o f sandstones and shales. Specimens referable to Protolepidodendron scharyanum Krejci are the commonest in this collection. Tceniocrada cf. dubia Kr. and W., Asteroxylon cf. elberfeldense. Kr. and W., and cf. Zosterophyllum are o f great Interest and are here recorded for the first time from Asia. Other fossils are provisionally referred to Drepanophycus spinceformis Go ppert, Protopteridium minutum Halle, Barrcmdeina, Hostimella, Protolepidodendron 1 arborescens Sze, Leptophloeum australe McCoy, and Heleniella Theodori Zalessky. Several fragments show the . decorticated, stems of some lepidophytic plants preserved in Jfaoma-state. A new species, ? Sublepidodendron sinensis is described. Attempts at cuticle preparations have been made, but do not yield good results. The-axis of Tceniocrada cf. dubia has revealed a cutinized epidermis, but hardly any details are visible; an interesting fact is that the vascular bundle contains tracheids with bordered pits. It is obvious that the flpra represented at these localities in the four districts in question is of Devonian aspect, and at least in each of the first' three districts it is of Lower to Middle Devonian affinities. Although1 the work is of much interest it is fair from satisfactory owing to the frfl.gmfint.ary nature of the material. However, it strongly suggests a promising field for further, investigations at these localities. I. Introduction Previous records of Devonian plants in Asia Our knowledge of the Devonian flora in Asia is restricted to a few papers. Probably the first paper dealing with the Devonian plants of Asia •was made by Colani (1919). She recorded some specimens from Ta-nong-pou in Southern Yunnan, China, and Sui-mo-koa in Northern Tongking, Indochina. Unfortunately her specimens are too fragment ary to be identified.1 In 1927 Professor Halle, reported Arthrostigma' gracile Dawson from a Lower Devonian bed. at Chanyi. in Eastern Yunnan, China, and in 1936 he again described some interesting specimens of Protolepido-< dendron scharyanum Krejci,-Pro topteridiumjninutum Halle and Drepdnb- phycus spinceformis Goeppert l(= Arthrostigma 'gracile Dawson) 'from the district Ch’uching. 24 340 J. H SV Kryshtofovicli in. 1927 recorded Psilophyton sp., Sporogonites exuberans Halle and Dawsonites arcuatus Halle from Turkestan, Central Asia. .Later on Zalessky (1936) described Psilophyton'princeps from Ufal (Stockmans, 1940, p. 9); Dr. H. C. Sze (1936) reported a Devonian plant, Protolepidodendron ? arborescens Sze from Tiaomachien in Central Hunan. In 1941 he again reported Psilophyton princeps Dawson and ? Hostimella sp. from Chaotung in Eastern Yunnan. From the above summary of the literature it would seem that the Devonian flora of Asia is very poor as compared with that of Europe; but this may- be due only to the fact that very little work has yet been devoted’ to it. I was tempted to take up the present work in the hope of extending our meagre knowledge o.f the subject by describing some collections from China. Occurrence o f the present specimens In 1943 I receiyed 45 specimens of plants collected from Devonian' beds at several localities in the districts'of Lihsien, Kunming, Ch’iiching and Luch’iian of Central and Eastern Yunnan, China (see map). These fossils, like most Devonian material, are also fragmentary; they are preserved as casts, moulds, and incrustations in various . kinds of sandstones and shales. Most of them sire represented only by naked axes of vascular plants but some possess leaves, spines 'or leaf-cushions. The specimens from the district of Lihsien were collected by Professor Y. C. Sun and Mr. C. V. Ku o f the National South-Western Associated University, Kunming, from several localities in the P’oshi region. The fossils labelled T8, Tl5, Tl8f and T1$J. are from a series' of Devonian beds at Itate and Ludouchuan. The different horizons are designated T8’ Tl5l etc. respectively. According to the opinion of the collectors, the bed Tg may be of Upper Devonian and the rest are Middle Devonian (Ku, unpublished paper). The specimens labelled Rs, WH2, CD zp_d, PSW5, PSW8, and PWVia were collected from some Middle Devonian beds at other' localities in P’oshi. The specimens from Kunming were collected by Mr.. P. S. T’shong of the National University of Yunnan from some Middle Devonian beds at Chintien, about 12 km. east of the city of Kunming. Specimens from the district Ch’iiching were collected by Professor Y; C. Sun from beds of Middle or Lower Devonian age at several loca lities. There is one specimen from a Devonian bed in Luch’iian. Acknowledgment This work was carried out at Lucknow during the years 1944-46 under the guidance of Professor B. Salmi, F.R.S.; to whom I am extremely grateful. I owe-, valuable criticisms and .suggestions to Professor T. G. Halle of Stockholm and Professor C. A. Arnold of Ann Arbor (Michigan). I wish to express my thanks to Professor DEVONIAN PLANTS FROM CENTRAL YUNNAN 341 Y. C. Sun, Messrs. C. V. Ku, and P. S. T’shong for kindly collecting the specimens for me on my request. I am also grateful to the University of Lucknow for granting me a research scholarship during my stay in India. II. D escription A . Specim ens from P’oshi in the district of Lihsien Some specimens were collected by Professor Y. C. Sun of the National Peking University and Messrs. C. V. Ku, T. S. Han, and L. G. Hu of the Geological Survey of Yunnan from several localities in P’oshi. Most of them are too fragmentary and poorly preserved to be identified. Under careful examination and comparison, the following fossils were determined • Protolepidodendron scharyanum Krejci, Taniocrada cf. dubia Kr. and W., cf. Drepanophycus spincs- formis Goeppert, and cf. Asteroxylon elberfeldense Kr. and W. A somewhat spinous axis probably recalls the thorny branch of Psilo phyton princeps Dawson. Some ribbed axes are referred to the stem of Protopteridium minutum. Several casts and incrustations represent the axes of some unknown plants with branches, spines and long ridged.or short rhombic leaf-cushions. v 1. Protolepidodendron scharyanum Krejci (PI. I, Figs. la, 2-5; PI. Ill, Figs. 25-26; Text-fig. 1) Five specimens referable to Protolepidodendron scharyanum were obtained from four different beds exposed in the P’oshi region,' which shows that this species was probably a common plant at the time in these localities. The shoots of this plant are covered with leaves. Each leaf con sists of a large decurrent leaf base, generally of an oblong shape, from which arises an elongated limb tapering rather rapidly to a slender elongated point. In well preserved leaves this point is seen to be continued into a peculiar delicate minute forked apex (PI. I, Figs. 3-5). When the forked apex is not clearly seen or is not preserved the1 leaf has tthe appearance of a spine. The decurrent leaf base forms a well marked cushion on which the lower end of the free limb is sometimes seen marked by two converging lines.. The degree of decortication and the quality of preservation make it difficult to define the character of the leaf cushions. But generally they have a narrowly oblong outline. In places especially thicker parts of the axis, the leaf limbs appear to have dropped off and the outlines of the cushions are more clearly exposed (PI. I, Figs. la, 5; PI. Ill, Figs. 25-26). They are generally rather crowded together, concealing from view the' entire or almost the entire surface of the stem. The arrangement of the leaves is not always very clearly shown. The main question at issue is whether the arrangement is spiral or whorled. This question being of some little importance from, the point 24a J. HSi) Map showing the localities from which the material here described was collected. of view of the affinities of the genus,'we shall describe this feature in some detail. On the’ narrowest axis*the leaves appear to be spirally placed with their bases contiguous and covering the whole surface of £he stem (PL I, Figs. 3, 5). In the thicker proximal.parts o f the same shoots some leaf cushions are seen separated from each other by DEVONIAN PLANTS FROM CENTRAL YUNNAN 343 narrow strips of the stem (PI. I, Fig. la; PI III, Fig. 25), but the arrange ment is still clearly a spiral one. Still thicker stems show the cushions clearly separated from each other and (at least in one specimen, see PI. I, Fig.. la) there is a vague suggestion of something like a verticillate arrangement, though the verticils (if such they are) are placed obliquely across the stem—a fact which may indicate that here also the arrange ment, may after all be a spiral one. Figs. 2 and 3 of PI. I show two fairly well-preserved young leafy shoots, 2 • 1 cm. and 1 -2 cm. long. PI. I, Figs. 4, 5 show another young leafy shoot, with both ends broken, which is about 1 -5 cm. long. In these slender shoots, the axes are only 0 -5-1 mm. thick and are preserved as thin flattened incrustations in a grey sandstone of the bed Tisr (p. 12). This carbonised crust is raised into a series of ridges which represent the decurrent bases o f the crowded spirally placed leaves and cover the entire surface of the stem.