Two Brachyphyllum species from the Lower Cretaceous of Jiuquan Basin,Gansu Province,NW China and their affinities and palaeoenvironmental implications |
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| Institution: | 1. Key Laboratory of Western China''s Environmental Systems of the Ministry of Education and School of Earth Sciences, Lanzhou University, Lanzhou 730000, China;2. Department of Paleontology, University of Vienna, A-1090 Vienna, Austria;1. Museo Argentino de Ciencias Naturales-CONICET, Av. Ángel Gallardo 470 Ciudad de Buenos Aires, 1405, Argentina;2. Centro de Investigaciones Científicas y Transferencia Tecnológica (CRILAR), Entre Ríos y Mendoza S/n Anillaco, La Rioja, 5301, Argentina;3. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (IGEBA), Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Guiraldes 2620 Ciudad de Buenos Aires, 1428, Argentina;1. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;2. University of Science and Technology of China, Hefei 230026, China;3. School of Geography, Queen Mary University of London, Mile End Road, London E1 4NS, UK;4. Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;1. Division of Geology, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200e, 3001 Leuven, Belgium;2. Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, 4001 Discovery Drive, 80303, United States of America;3. Department of Ocean Systems, NIOZ-Royal Netherlands Institute for Sea Research and Utrecht University, Den Burg, the Netherlands;4. Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8A, 3584 CB, Utrecht, the Netherlands;5. Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussels, Belgium;1. Key Laboratory of Mineral Resources in Western China (Gansu Province), School of Earth Sciences, and College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China;2. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China |
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| Abstract: | Conifers are common in the Lower Cretaceous Zhonggou Formation of Jiuquan Basin, Gansu Province, NW China. The excellent preservation of plant fossils allows detailed investigations of the leaf epidermis by light microscope (LM) and scanning electron microscope (SEM). Based on the leaf morphology and epidermal features, two Brachyphyllum species, B. ningshiaense and B. obtusum are described. They closely resemble one another in foliar morphology and epidermal features, but have different leaf apices, cuticle features, stomatal shape and the number of subsidiary cells. The specimens consist of leafy axes with imbricate, spirally arranged, scale-like leaves. Epidermal analysis shows rectangular, pentagonal or rhomboidal unspecialized epidermal cells and abaxially longitudinally arranged stomatal rows except for the marginal areas, as well as well-developed papillae, sunken stomata and Florin rings of subsidiary cells with papillae on the inner surfaces. The imbricate and spirally arranged leaves with rather thick cuticle in both species indicate an Araucariaceae (Araucaria) or Cheirolepidiaceae affinity. However, epidermal features and the presence of Classopollis pollen in the sediments indicate a cheirolepidiaceous affinity. The morphological and anatomical characters of both taxa are interpreted as adaptations to a warm seasonally and temporarily dry palaeoclimate. |
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