Chamaecyparixylon Khudaiberdyev, 1958

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 : 45-47

Genus Chamaecyparixylon Khudaiberdyev, 1958 Chamaecyparixylon sp.

Fig. 6 , photos a-i.

Material

The sample of petrified wood studied here was collected from Ociu area, the Church brook, from Mid-Miocene volcano-sedimentary deposits (Late Badenian-Early Sarmatian), and has ash-brown color and centimetric size. It is much silicified and displays a regular fibrous texture, and annual rings suggesting a conifer. Some fragments remained after oriented slides cut, are kept now in GIR collection at National Geological Museum - Bucharest under the inventory number 26,340 (740 as field no.)

Microscopic description

Growth rings of 55-78 tracheids high, with gradual transition from early to late wood, ring boundary distinct, marked by the late wood constituted by 20-38 thick walled cells. Normal axial resin ducts are absent, but often there are tracheids full of resin and even traumatic aspects.

Tracheids poligonal with rounded corners in cross section, having radial / tangential lumina diameters 12-20 / 12-28 μm, smaller in the late wood. Sometimes very large ones are intermingled in the early wood (up to 70-80/50- 60 μm). Usually their wall thickness is of 4-8 μm (double wall), thicker in the late wood: up to 12 μm. Between two successive rays there are 1-7-14(21) regular radial rows, with small intercellular spaces, especially in the late wood. The density is 1616-1764 tracheids on mm 2. On the tangential tracheidal walls the pitting is uniseriate, spaced, sometimes slightly irregularly arranged, round pits with 7-8 μm in diameter and with apertures of 3-4 μm. The radial pitting is of abietinean type having pits of 14-16 μm in diameter and round apertures of 4 μm in the early wood and smaller, uniseriate, spaced of 7.5-9-12 μm border pit diameter with aperture of 3 μm in the late wood. Crassulae are not present, in the tracheid lumina granular resin remains appear and the tracheidal walls have striations, inclined or crossed (due to compression), and even fine spirals in the final wood.

The axial parenchyma in cross section appears diffuse, as large isolated polygonal or rectangular thin walled cells (of 1.5 μm simple wall). Vertically the thin walls are smooth and slightly constricted at the end (horizontal) walls, which are also thin and smooth. Inside cells globular resin content is present, having circular empty spaces.

The medullary rays in cross section appear linear and in tangential section appear uniseriate, locally bi- or triseriate, and low, of 6-12 cells high. The ray cells are oval or laterally flattened, have 8-16 μm in diameter, and without lateral intercellular spaces. Their frequency is 5-6 rays on mm tangential millimeter. Radially the rays are homocellular, cells all procumbent of 12-16 μm high, marginal higher, of 22-24 μm. The smooth horizontal walls are thin walled having 1.5-2.5 μm double walls. The tangential wall is straight, vertical, smooth and thin, of 1-1.5 μm. Indentures not observed. The cross fields present 1-2 cupressoid pits (or taxodioid small), round to oval of 3-5 μm in diameter, with circular to elliptic inclined apertures of 1-1.5 μm. In the marginal taller fields appear 2-4 pits in vertical pairs.

Affinities and discussion

The xylotomic characters observed in our specimen, like form, size and distribution of tracheids, of parenchyma and of rays suggest similitudes with those of the Cupressaceae , of which most affinity seems to have with the "Thujidae group" by the clear presence of the axial thin-walled parenchyma which send more to the extant Chamaecyparis not to Thuja (see Greguss, 1955). Anyway Cupressus type is excluded since it has nodular aspects, or even dentate on the parenchyma end (horizontal) walls. Juniperus type is also excluded since our specimen has not juniperoid nodules on the tangential walls of the rays. In addition, the absence of the callitroid thickenings on the tracheidal walls excludes any comparison with members of the Callitroideae ( Greguss, 1955). For the last taxonomy of the Cupressaceae Family, we used Farjon (2005). Using the identification key of Vaudois & Privé (1971), we observed that between Chamaecyparixylon and Thujoxylon is very difficult to do distinction, which is reduced to the presence or the absence of the parenchyma and of the indentures. Since our specimen have relatively abundant axial parenchyma, and the presence of indentures is doubtful we attribute our specimen to Chamaecyparixylon genus. The description of our specimen is in perfect accord with the diagnosis of Khudaiberdyev (1958), as it is commented by Vaudois & Privé (1971). Our specimen, coming from the same geological deposits with the form Chamaecyparixylon cf. polonicum (Kräusel) Khudaiberdyev, 1958 , previously described by us (in Iamandei & Iamandei, 2002b; Iamandei et al., 2013) from which it differs at least by the thin and smooth horizontal walls of axial parenchyma, not nodular, the lower rays, the slightly different cross-fields and the absence of the indentures. Also is different of C. privegilii Iamandei et Iamandei (in Iamandei, E. & Iamandei, S., 2000, p. 192-194), which have also nodular horizontal walls of axial parenchyma and not very similar cross fields.

After this discussion on the possible affinities, we conclude that there are no sufficient observed xylotomic details for a specific identification and we attribute our specimen to Chamaecyparixylon sp.

Figures

Fig. 6 Chamaecyparixylon sp. a, b - cross section: not very distinct growth-ring boundary, since early wood disorganization, very thick-walled tracheids in late-wood - x100; c - detail in the early wood disorganization - x200; d - very thick-walled tracheids in late-wood - x200; e - tangential section: uniseriate rays - x200; f-i – radial section: radial uniseriate pits on tracheids, cross-fields pits - x200.