Abstract Detail

Paleobotany

Liu, Xiaoyan [1], Wang, Yongdong [2], Jin, Jianhua [1].

Eocene Osmunda L. fossil fronds, sporangia and spores from South China and their implications for biogeography.

Osmunda L. is well known from the Mesozoic to Cenozoic of both hemispheres. So far, the vast majority reports for the genus have focused on the numerous rhizomes, leaf venation and dispersed spores, with fewer studies on fronds, sporangia and spores in situ. Additionally, previously described taxa are mainly from high latitude regions in the northern and southern hemispheres with no relatively documents in lower latitude of tropical and subtropical areas of South China. In this study, we firstly studied Osmunda lignita (Giebel) Stur. recovered from the Eocene of Changchang Basin, Hainan Island and Maoming Basin, Guangdong based on the leaf cuticles, sporangia and spores in situ. Sterile fronds are up to 18 cm long and 1–2 cm wide, slightly or deeply pinnatifid. The pinna rachis ranges from 0.5 to 1 mm in width. Pinnules are 0.7–1.2cm long and 0.3–0.8 cm wide. Branching of the pinnae occurs at the angle of 45º–65º. Pinnule veins usually branch once dichotomously with 6–9 and 5–7 veins on the basal and apical side, respectively. The first branch on the basal side generally starts from the rachis. The cuticle is hypostomatal. The regular epidermal cells between veins on both sides are jig-saw-puzzle-shaped, consistently in size of 53–89 µm in diameter. Those on the veins are linear with the length of 80–120 µm. Stomata are rounded or elliptical, 39–42 µm long and 25–34 µm wide, consisting of two subsidiary cells. Sporangia are elliptical with average diameter 500 µm. Spores in situ are rounded, about 42 µm in diameter. Spores are characterized by trilete with strumae or tuberculate sculptures on the surface. The comparison between fossil and living species in morphology and anatomy suggests that the present species is assignable to Osmunda subgenus Plenasium and closest to extant Chinese species, O. banksiifolia (Presl) Kuhn. This is the first record of Osmunda with cuticle, sporangia and spores in situ in China; furthermore, our Osmunda specimens occurring in South China indicates that the genus has reached to the lowest latitude of the northern hemisphere at least in the Eocene.

1 - Sun Yat-sen University, State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, No.135 Xingangxi Road, Guangzhou, Guangdong, 510275, China
2 - Chinese Academy Of Sciences, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, No. 39 East Beijing Road, Nanjing, Jiangsu, 210008, China
3 - Sun Yat-sen University, State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, No.135 Xingangxi Road, Guangzhou, Guangdong, 510275, China

Keywords:
Eocene
Osmunda
Biogeography
fossil fern
South China.

Presentation Type: Oral Paper
Session: 5, Paleobotany Student Awards
Location: 204/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 11:00 AM
Number: 5011
Abstract ID:267
Candidate for Awards:Isabel Cookson Award