Grewioxylon ortenburgense SELMEIER

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 : 385

Grewioxylon ortenburgense SELMEIER

Pl. 4, Fig. 5–8, Text-fig. 12–13

1985 Grewioxylon ortenburgense SELMEIER , p. 125–129, pl. III, fig. 4, pl. IV, fig. 1–4, pl. V, fig. 1–2.

2000 Grewioxylon ortenburgense SELMEIER , p. 467–476, fig. 2–9 and 11–14.

2010 aff. Craigia sp. Sakala et al., p. 623, fig. 5D–G.

M a t e r i a l: Nechranice 70/03, 78/04, 84/04, 89/04, 90/04.

D e s c r i p t i o n. Wood is semi-ring porous (Text-fig. 12); growth rings are distinct, 1–1.4 mm wide, clearly observed.

Vessels: Rarely solitary (11–19%). Earlywood vessels in tangential or radial multiples of 2–3 (occasionally 4), latewood vessels in radial multiples of 2–3 (occasionally 6), sporadically in clusters; solitary pores circular in outline. Tangential diameter of earlywood vessels 140–253–363 µm, radial diameter 112–372 µm; tangential diameter of latewood vessels 47–91–167 µm, radial diameter 37–149 µm; earlywood pore density 5–7–11 per square mm, latewood 8–14– 18. Perforation plates exclusively simple; intervessel pits alternate, with hexagonal outlines, 12–14 µm in diameter.

Rays: Two types of rays ( Text-fig. 13 ): 1) uniseriate rays; and 2) 4–8 cells (78–196 µm) wide, heterocellular rays, composed of procumbent cells and tile cells of Pterospermum type. They slightly widen tangentially at growth ring boundaries in cross-section, their height ranges from 441 to 1274 µm. Ray density 3–4 rays per tangential mm.

Axial parenchyma: Diffuse and scanty paratracheal.

Fibres: Not observed.

D i s c u s s i o n. The presence of tile cells points clearly to the family Malvaceae s.l., or some species of the genus Hopea from the family Dipterocarpaceae ( Manchester et al. 2006) .

Our samples with “tile cells of Pterospermum type ” according to Manchester and Miller (1978), together with the sample 72/03 from the locality Kadaň-Zadní vrch Hill (Doupovské hory Mts.) were attributed to the family Malvaceae s.l. by Sakala et al. (2010). The authors put the wood closer to Craigia , but did not observe helical thickenings in vessels ( Sakala et al. 2010), which are typical of modern wood ( Manchester et al. 2006).

Among the fossil representatives described so far, our wood is most similar to Grewioxylon ortenburgense SELMEIER , Grewioxylon auctumnalis GOTTWALD , Chattawaya paliformis MANCHESTER and Triplochitioxylon oregonensis MANCHESTER. There is also Wataria TERADA et SUZUKI , which is rather similar to our wood, except for ring porous wood and chiefly solitary earlywood vessels (Tereda and Suzuki 1998). G. ortenburgense has lower tangential dimensions of vessels and more (up to twice as many) rays per tangential mm than our wood ( Selmeier 1985). A possible explanation of the later difference can be due to the fact that we counted only multiseriate rays, since uniseriate rays were not well preserved. Concerning the vessel dimensions, a clue for understanding the variability in this species was presented by Selmeier (2000). On the other hand, G. auctumnalis has prismatic crystals, and its axial parenchyma forms discontinuous tangential bands ( Gottwald 1997). Similarly, both T. oregonensis and Ch. paliformis have prismatic crystals and reticulate axial parenchyma ( Manchester 1979, 1980). The anatomical comparison of our wood with similar woods is given Tab. 6. We designate it as Grewioxylon ortenburgense SELMEIER.

According to Sakala (2007), it is possible that fossil woods of Grewioxylon can be associated with the fossil fruit remains of Craigia . In fact, numerous fossil fruit remains of Craigia bronni (UNGER) KVAČEK, BŮŽEK et MANCHESTER and the accompanying leaves Dombeyopsis lobata UNGER in many localities in the České středohoří Mts. and the Most, Sokolov and Cheb Basins (Kvaček 2004) support this hypothesis about the association of Grewioxylon and Craigia .

Figures

Text-fig. 13. Schema of typical rays in G. ortenburgense (sample 89/04 and 90/04).