Cupressinoxylon sp.

Iamandei, Stănilă & Iamandei, Eugenia, 2017, New Trees Identified In The Petrified Forest Of Middle Miocene From Zarand, Apuseni Mountains, Romania., Acta Palaeontologica Romaniae 13 (2), pp. 37-90 : 41-43

Cupressinoxylon sp.

Fig. 4 , photos a-i.

Material

The three studied samples of petrified wood were collect- ed from Prăvăleni area (on Hoarna Tarnița brook), from Ociu area (on MarinaȘu valley and on Church Brook , respectively), found in Mid-Miocene volcano-sedimentary deposits ( Late Badenian-Early Sarmatian ), ash-brown or whitish color and centimetric size. They represent silicified pieces of wood and display a regular fibrous texture and annual rings, suggesting a conifer. The fragments remained after the oriented slides were cut, are kept now in the Geological Institute of Romania ( GIR) Collection hosted in the National Geological Museum , in Bucharest, under the inventory number: 26,388; 26,392 and 26,474 (i.e.: 114; 107b and 288 as field numbers) .

Microscopic description

The growth rings are distinct, variably sized, with often crushed early wood, where the cells were big lumened gradually passing to the late wood which is formed from 12-20 thick walled cells. Normal axial resin ducts absent.

The tracheids in cross section are polygonal rounded, sometimes deformed, but usually have rounded lumina with radial / tangential diameters of (17)25-45(50) / 20- 30 μm, smaller in the late wood: 7.5-11 / 7.5 μm and the walls have 4-7 μm double wall, thicker in the late wood. Between two successive rays there are 1-7 regular radial rows of tracheids, some intermingled rows being formed from smaller ones. Their frequency is of (900)1380-2050 tracheids on mm 2. Pitting on the tangential tracheidal walls is missing. The radial pitting is in one single vertical row arranged, sometimes as opposite pairs, are spaced or contiguous and seem to be molded by the tangential walls. The pits have round borders of 9-12-16 μm in diameter and apertures of 3-3.5 μm. Sometimes there are obvious crassulae, and the vertical walls radial walls of tracheids frequently have oblique striations ( Fig. 4 ).

The axial parenchyma, probably diffuse, is difficult to observe in cross section, but sometimes it appear in the longitudinal sections as rectangular cells with thin and smooth walls, as the terminal (horizontal) wall also.

The medullary rays in cross section seen are linear, of rows of rectangular cells, slightly crushed. Tangentially appear clearly uniseriate, of 1-15(26) polygonal-rounded cells in height. Sometimes lateral intercellular spaces are present. Their density is 6-12 rays on a mm tangential. Radially seen the rays are homocellular. The parenchyma ray cells are of 13-17.5 μm high, the marginals taller, of 20-24 μm, with wavy outer wall. The horizontal walls are smooth, and 3-3.5 μm double wall. Because of the bad preservation, the tangential walls and the indentures were not observed. The cupressoid cross fields have 1-2(3) cupressoid pits (or small taxodioid) of 6-8 μm in diameter, with slightly elliptic borders, sometime lens like inclined in conformity with the striations of the tracheids. The apertures are unclear. The marginal fields can have 6-8 pits on two horizontal rows.

Affinities and discussions

The xylotomical study of the two samples showed badly preserved coniferous structure, and the absence of resin ducts, scarcity of parenchyma, uniseriate radial pitting and the cross field most probably of cupressoid type suggest for both of the specimens a cupressaceous structure (see Greguss, 1955; Schweingruber, 1990; InsideWood - onward) or how Vaudois & Privé (1971) showed in their key of identification of Cupressaceous wood. Most similar seem to be those of the extant Cupressus and Chamaecyparis genera ( Greguss, 1955; 1969), regarding the tracheidal pitting, the cross field pitting and the aspect of axial and radial parenchyma. Both genera belong now to the Subfamily Cupressoideae Rich. ex Sweet ( Farjon, 2005; Earle, 2017).

The comparison of here studied specimens with other forms described as Chamaecyparixylon (Iamandei & Iamandei, 2000; Iamandei et al., 2013), and also as Cupressinoxylon of Thuja type (see Iamandei et al., 2008a, c; 2011; 2012) shows some general resemblances, but not identity.

The comparison with other cupressaceous structures shows many similitudes with forms of Cupressinoxylon described by Zalewska (1953), Schönfeld (1957), Greguss (1967), Dupéron-Laudouéneix (1979) or by Iamandei et al. (2008a).

Once again, consulting the revised diagnoses of Kräusel (1949) and Vogellehner (1967, 1968), and using the identification key proposed by Vaudois & Privé (1971), we can attribute our studied specimens to Cupressinoxylon genus. The xylotomic details observed in our studied specimens are not identical to those of the already described species and are not sufficient to describe a new species, we attribute our studied material to Cupressinoxylon sp.

Figures

Fig. 4 Cupressinoxylon sp. a, b - cross section: distinct growth-ring boundary, thick-walled tracheids in late-wood - x100- x200; c - tangential section: uniseriate rays, striated tracheids - x100; d - radial section: pits and striations on tracheids, crossfields - x100; e, f - radial section: striations on tracheids, cupressoid cross-fields - x200; g - radial section: 2-3 seriate pits and striations on tracheids, cupressoid cross-fields - x100; h, i - radial section: 2-3 seriate pits with crassulae on striated tracheids, cupressoid cross-fields - x200.