Ulmoxylon cf. kersonianum STAROSTIN et TRELEA

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 : 384-385

Ulmoxylon cf. kersonianum STAROSTIN et TRELEA

Pl. 1, Fig. 2, Pl. 4, Fig. 1–4, Text-fig. 11

?1969 Ulmoxylon kersonianum STAROSTIN et TRELEA , p. 450–451, fig. 1–2.

2010 Ulmus sp. ; Sakala et al., p. 623, fig. 5C.

M a t e r i a l: Nechranice 75/04, Vrbice 1/3, 1/4.

D e s c r i p t i o n. Wood is ring-porous ( Text-fig. 11 ); growth rings are distinct, 0.6–(1.6)– 2.9 mm wide.

Vessels: Earlywood vessels in tangential or radial multiples of 2 (occasionally 3), in 1–3 tangential rows, latewood vessels form clusters arranged in tangential to diagonal wavy bands; solitary pores circular in outline. Tangential diameter of earlywood vessels 28–87–140 µm, radial diameter 49–168 µm; tangential diameter of latewood vessels 14–33–49 µm, radial diameter 19–65 µm. Perforation plates exclusively simple; intervessel pits alternate, with polygonal outlines. Helical thickenings present.

Rays: Homocellular, 2–3 (occasionally 4) cells wide, 8– 24 cells high, composed exclusively of procumbent cells.

Axial parenchyma: Scanty paratracheal.

Fibres: Thin-walled.

D i s c u s s i o n. All features, especially the ring porosity and the typical ulmoid latewood vessels arrangement indicate that our wood belongs to the family Ulmaceae ( Wheeler and Manchester 2007) . A ring (or semi-ring) porous wood with latewood vessels in tangentially oriented wavy clusters is typical of deciduous specimens of this family, which are Hemiptelea , Planera , Ulmus and Zelkova ( Wheeler and Manchester 2007) .

Planera has diffuse to semi-ring porous wood, and its earlywood vessels do not form rows . Zelkova has only one row of earlywood vessels, and crystals in axial parenchyma, as well as in enlarged ray cells; Hemiptelea typically has very wide rays ( Wheeler and Manchester 2007). All described features point to the genus Ulmus .

For a correct determination, it is necessary to take into account the preservation of our samples, as well as the fact they probably represent small branches. Therefore, it is possible that some of the measured dimensions are not typical.

The first specimen from the Czech Republic attributed to the Ulmaceae was identified in Bílina by Sakala (2002) as Ulmoxylon marchesonii BIONDI. The same species was also described by Kłusek (2012) from south-eastern Poland, from the village Włoszczowice. Our wood type (see also in Sakala et al. 2010: 623) is similar to both descriptions, but has thinner rays, and no chambered crystalliferous axial parenchyma was observed. However, according to Biondi’s (1981a) definition, there are most frequently tri-seriate rays. The difference of the vessel lumina dimensions can be caused by wood maturity, habitat conditions etc. Our wood is also similar to Ulmoxylon sp. ex aff. Ulmus campestris LINNAEUS (Sacchi- Vialli 1958) and Ulmoxylon cf. carpinifolia ( Greguss 1969) , but they both have wider rays, and the latter also has chambered axial parenchyma with crystals. Both of them are also inadequately described, so it is not easy to present an unambiguous determination.

Ulmoxylon kersonianum ( Starostin and Trelea 1969) is very similar to our fossil: it does not have chambered crystalliferous axial parenchyma; on the other hand, it also has wider rays. Although U. marchesonii more frequently has thinner rays, and its vessel diameter is closer to our wood than that of U. kersonianum , we propose, based on absence of crystalliferous chambered axial parenchyma, to designate this wood type as Ulmoxylon cf. kersonianum STAROSTIN et TRELEA. It was marked “cf.” because of thinner rays and smaller vessels in our wood, possibly caused by its juvenile character.

The genus Ulmus is recorded in the Tertiary of northwestern Bohemia both as foliage and leaves: U. fischeri HEER from Doupovské hory and České středohoří Mts. (e.g., Bůžek et al. 1990, Kvaček and Walther 2004) and U. pyramidalis GÖPPERT from České středohoří Mts. (e.g., Akhmetiev et al. 2009). U. pyramidalis was associated by Sakala (2002) with the wood of U. marchesonii . The fossil leaves found by Kotlaba (1960) at Vrbice were later identified by. Z. Kvaček (personal communication 2014) as U. fischeri . It is therefore possible that the wood of Ulmoxylon kersonianum can be associated with the leaves of Ulmus fischeri .

Figures

Text-fig. 11. Schema of transversal section of Ulmoxylon cf. kersonianum (sample 1/3). v – vessel, r – ray, grb – one growth ring.