Eucaryoxylon lesbium Iamandei et Iamandei, 2024

Iamandei, Stanila, Iamandei, Eugenia, Velitzelos, Dimitrios & Velitzelos, Evangelos, 2024, Palaeoxylotomical Studies In The Cenozoic Petrified Forests Of Greece. Part Three - Dicots, Acta Palaeontologica Romaniae 20 (2), pp. 61-96 : 82-85

Eucaryoxylon lesbium Iamandei et Iamandei , sp. nov.

Fig. 10 , photos a-i; Fig.11 , photos a-i.

Studied material. Other two samples of silicified wood, collected from early Miocene volcano-sedimentary deposits, of Lesbos Island showed a similar special juglandaceous xylostructure of Carya type. They are registered under the field numbers: Lsv 1, Lsv 6, and kept in the Collections of the Faculty of Geol. & Geoenviron., of NKUA .

Microscopic description. The growth rings – are present, with porous to slightly semi-ring-porous structure, showing quite distinct ring boundaries, marked by a few rows of smaller and flattened cells of ground tissue, at the outer border of the growth ring, suddenly followed by normal ground tissue cells, where larger vessels of early-wood appear. Also, in cross-section, the long tangential bands of axial parenchyma, regularly arranged, give the structure a reticulate aspect.

The vessels – appear, in cross sections, as solitary pores and radial multiples of 2-3(-5), in a radial arrangement between two successive rays, defining a porous to semi-porous structure, in which the thick-walled large vessels of the early-wood are slightly diminishing in size to the late-wood. The solitary vessels are round to oval-shaped, having in the early-wood a lumina size of 70-200 / 50- 150 µm the radial / tangential diameter. In the late-wood, the vessels are smaller, of 45-60 / 30-45 μm (r/tg.d). When grouped, the vessels are slightly deformed. Their walls are thick, of 8-12 µm the double wall. In longitudinal view, the vessels show exclusively simple perforation plates and the intervessel pits are numerous, polygonal, of bordered type, small (their mean size of 5-7 µm) and have a contiguous alternate arrangement. The vessel-ray pits are quite similar and have much reduced borders, the cross-fields pits are described below. Helical thickenings in the vessel elements were not observed. The mean tangential diameter of vessel lumina is around 120 µm. Vessels' density is 5-10 vessels per square millimeter. The mean vessel element length is between 300-600 µm. Inside the vessels' lumina rare, big, and relatively thin-walled tyloses sometimes appear.

Tracheids – or vascular fibres or vasicentric tracheids were not observed.

The libriform fibres – represent the major part of the ground tissue and appear minutely pited and not septate.

The axial parenchyma – is present in cross-section, paratracheal fewer, apotracheal more, as long tangential 1-3-seriate bands, quite regularly arranged giving a reticulate aspect. In longitudinal section the parenchyma can be recognized as vertical rows of rectangular cells. Sometimes some cells are chambered, hypertrophied and crystalliferous, appearing as huge solitary and/or in short chains of 2-3 enormous barel-like cells (rarely more: 4 in Lsv6), bearing a singular big polygonal crystal inside.

The rays – appear as fine rays, usually 1-3(-4) seriate. The ray height is usually low to high, sometimes of more than 30 cells. The ray density is between 8-12 rays/mm tangential. As cellular composition, in radial view, the rays are of heterocellular type: the body ray cells are all procumbent, having 1-2 row of upright and/or square marginal cells which have a white or dark content and, sometimes, crystalliferous. In cross-fields with vessels, small polygonal rounded pits, in 1-2 horizontal rows, often not visible due to presence of dark content, or poor preservation.

Storied structures are absent. Secretory elements seem to be absent. Mineral inclusions – appear as large prismatic crystals, solitary or in short vertical chains of 2-3(-4), as a single big crystal inside an enlarged cell (or chamber of axial parenchyma cell). Also, as noted above, crystal sand appears in rays, especially in the upright and/or square marginal ray cells.

Affinities and discussions. From the numerous petrified wood remains with Juglandaceous affinities, studied here, two specimens showed a special xylostructure, showing thick-walled vessels, with exclusively simple perforations and numerous alternate bordered pits; with banded and crystalliferous parenchyma in a reticulate arrangement, vasicentric less; vertically, the axial parenchyma appear as solitary cells or short chains of 2-3 enlarged chambers, each bearing a single big crystal inside.

Thus, the xylotomy of the studied specimens is comparable with that of the current Carya Nutt. (known as hickory, or pecan) which has also, besides the typical juglandaceous xylotomy with thick-walled vessels, the apotracheal parenchyma as long continuous bands in cross section and, the crystalliferous parenchyma appears with big solitary crystals in some enormous „ barrel-like “ solitary cells which, in vertical view, appear solitary or in short chains of 2-3.

The fossil correspondent of the current Carya Nutt. is Eucaryoxylon (Müller-Stoll et Mädel) Dupéron, 1988 . Its emended diagnosis shows that „the wood- structure is porous, with solitary vessels or short multiples, with thick to very thick walls, has simple perforations, alternate intervascular pitting rather big, paratracheal and apotracheal banded parenchyma, 1-2(4)-seriate, long and rather regular; has crystalliferous parenchyma as large idioblasts, with solitary crystals in such barrel-like idioblasts, which appear isolated or in short vertical chains of 2-3 cells; has rays 1-3(5)-seriate, and septate pith“.

This discussion and the critical overview of the features of our studied specimens strongly suggest that we are facing to a Eucaryoxylon species, since the observed details are perfectly consistent with the generic diagnosis, especially by the presence of the enormous crystalliferous cells, barrel-like (see Dupéron, 1988, citing Manning, 1978).

Comparing the xylotomy of our studied specimens with some valid fossil species described till now, as: Eucaryoxylon boureaui Dupéron, 1977 ; E. budense Greguss, 1969 ; E. crystallophorum Müller-Stoll et Mädel, 1960 ; E. guembelii Müller-Stoll et Mädel, 1983 ; E. moenanum Müller-Stoll et Mädel, 1983 ; E. protojaponicum (Watari) Müller-Stoll et Mädel, 1960 and E. zarandense Iamandei et Iamandei, 2002 , we observed many similar features, but not identical. Thus, the here studied specimens show some specific features as follows: semi-ring-porous structure with thick-walled vessels, solitary or in short radial multiples of 2-3(-5), with perforations exclusively simple and intervessel pitting alternate; long banded parenchyma with a reticulate arrangement, crystalliferous, as solitary or short vertical chains of 2-3(-5) enlarged chambers with big crystals; rays 1-3(-4) seriate, heterocellular, with 1-2 rows of square or upright marginal cells with crystalsand.

All these xylotomical features, described in the studied specimens, compared with previous studied species, allow us to define a new species that we name Eucaryoxylon lesbium Iamandei et Iamandei , sp. nov., after the name of the provenance place (Lesbos Island). It could be a possible ancestor of some disappeared types of Carya , that lived, during the Cenozoic time in Europe, as shown by the identifications of Dupéron (1977), Greguss (1969), Müller-Stoll & Mädel (1960, 1983), Iamandei & Iamandei (2002).

So, we designate the specimen Lsv1 as holotype and, the specimen Lsv6 as paratype, and this is the diagnosis of the new species: “Growth rings present, with porous to semi-ring-porous structure and with long tangential bands of axial parenchyma giving a reticulate aspect; vessels are solitary or in short radial multiples of 2-3(-5), thick-walled, circular to oval, 50-150 µm tg.d., 5-10(-20) vessels on sq. mm; exclusively simple perforations plates, alternate intervascular pitting; parenchyma banded reticulate, with solitary or vertical chains of 2-3 enormous crystals; rays 1-3(-4) seriate, heterocellular, with 1-2 rows of square or upright marginal cells sometimes crystalliferous; cross field small, few simple pits, in 1-2 rows”.

Figures

Fig. 10. Eucaryoxylon lesbium Iamandei et Iamandei sp. nov. (Specimen Lsv1). a–c. Cross section – semi-ring porous structure, quite indistinct growth-rings, reticulate axial parenchyma; d–f. Tangential section –, solitary or short vertical chains of crystals (2-2-3), 1-3 seriate rays; g–i. Radial section – simple perforations, solitary or short vertical chains of crystals; heterocellular rays with crystalliferous marginal cells. photos a-i (graphic scale).

Fig. 11. Eucaryoxylon lesbium Iamandei et Iamandei sp. nov. (Specimen Lsv6). a–c. Cross section – semi-ring porous structure, quite indistinct growth-rings, reticulate axial parenchyma; d–f. Tangential section –, solitary or short vertical chains of 2-3 huge crystals, 1-3 seriate rays; g–i. Radial section – simple perforations, solitary or short vertical chains of 2-3(4) huge crystals; heterocellular rays with marginal cells, sometimes, crystalliferous. photos a-i (graphic scale).