Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL

Koutecký, Vít & Sakala, Jakub, 2015, New Fossil Woods From The Paleogene Of Doupovské Hory And České Středohoří Mts. (Bohemian Massif, Czech Republic), Acta Musei Nationalis Pragae Series B 71 (3 - 4), pp. 377-398 : 381

Taxodioxylon gypsaceum (GÖPPERT) KRÄUSEL (root wood)

Pl. 1, Fig. 1, Pl. 2, Fig. 6–9, Text-fig. 7

1971 Sequioxylon sp.; Prakash et al., pl. 32–34, fig. 10–25.

M a t e r i a l: Bečov 98/04.

D e s c r i p t i o n. Growth rings distinct, 1.5–2.3 mm wide, with earlywood zone distinctly wider than latewood; transition from earlywood to latewood is gradual.

Tracheids: Outline polygonal to hexagonal. Radial diameter of earlywood tracheids 70–87–105 µm; radial diameter of latewood tracheids is 35–49–70 µm; tangential diameter of tracheids ranges from 23 to 63 µm; number of tracheids between two rays ranges from 1 to 12, most frequently 2 (Tab. 3). Pitting in radial tracheid walls biseriate to triseriate; bordered pits circular in outline ( Text-fig. 7 ), 10–17 µm in diameter.

Rays: Exclusively uniseriate, with very low (1–2 cells) average height. Total range of height between 1 and 5 cells (Text-fig. 6); 3–5 rays per tangential mm and 23–38 rays per square mm tangentially. Individual ray cells 21–42 µm high, horizontal and end walls thin and smooth (thickness of double wall: 3–6 µm horizontal and 3–9 tangential). Ray tracheids absent. Cross-fields pits taxodioid, occasionally cupressoid, 10–15 µm in diameter, 3–4 pits per cross-field arranged in 1–2 horizontal rows.

Axial parenchyma: Diffuse. Transverse walls not observed.

D i s c u s s i o n. Generally, this wood shows features that are typical of Taxodioxylon gypsaceum ( Kräusel 1949) , but it presents also several differences from the previous wood type 2, labelled T. gypsaceum (stem wood). Both types have opposite arrangement of bordered pits in radial tracheid walls, taxodioid and cupressoid pits in the cross-fields, similar diameter of the bordered pits, pits in cross-fields, and thin and smooth horizontal and end walls of the ray-parenchyma cells, but there is a difference in the transversal dimensions of the tracheids, and height of rays and individual ray-parenchyma cells.

After comparing our fossil with those published earlier (e.g., Prakash et al. 1971, Selmeier 1972, Gottwald 1992, Van der Burgh and Meijer 1996, Teodoridis and Sakala 2008, Dolezych 2011), we think our wood is similar to Selmeier’s (1972) samples from Waldkirch ( Germany), except for the ray height. A similarity was also noted to Sequoioxylon sp. ( Prakash et al. 1971): tracheids are smaller in Prakash’s et al. specimen, but very low rays, bordered and cross-fields pits, and walls of the ray-parenchyma cells are similar. The authors described the tracheid outline as rounded, but the samples from Mikulovice have rather polygonal tracheid outline, as we can see in the published photos ( Prakash et al. 1971: pl. 34, fig. 21 and 25). It is possible that these characteristics, which are different from the typical form T. gypsaceum , are related to the anatomical variation of the wood. Therefore, we think both our wood and the material described by Prakash et al. (1971) can be attributed to T. gypsaceum , but they probably come from a root. As demonstrated by several authors (e.g., Bailey and Faull 1934, Falcon-Lang 2005, Denne and Gasson 2008), the tracheids in root wood are up to two times larger than in stem, also the rays are generally lower, and individual ray cells higher in the root than the stem. Broadly oval outlines of ray-cells in tangential section

Figures

Text-fig. 7. Schema of radial section of T. gypsaceum (sample 98/04). t – tracheid, r – ray, bp – bordered pit, tp – taxodioid pit, cp – cupressoid pit.