Paraphyllanthoxylon botarii, Iamandei & Iamandei, 2017

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 : 70-72

Genus Paraphyllanthoxylon Bailey, 1924 Paraphyllanthoxylon botarii sp. nov.

Fig. 14 , photos. a-i.

Material

A sample of silicified wood, of 8/8/ 6 cm was collected from a petrified tree stump of 70 cm in diameter and 40 cm tall, which seemed to be in growing position, found in Ociu village on MarinaȘu Valley, the left side, in middle Miocene volcano-sedimentary deposits (Late Badenian-Early Sarmatian). Although the rest of the trunk, representing the basal part, as a tree stump which suggest to have thick roots and it seems to be preserved in a natural (erect) position, it is unlikely that the trunk is in situ, because we have not observed any traces of fossil soil, and the host volcanic-sedimentary formation presents many other arguments, indicating the movement of the material from which it is constituted a lahar. The color of the silicified wood is beige-white with some dark gray areas, and are kept now in GIR collection at National Geological Museum - Bucharest under the inventory number 26,352 (field number: 109). Under the magnifying glass fibrous structure, annual rings, vessels and not too thick rays are visible, suggesting dicotyledonate wood.

Microscopic description

The growth rings are distinct, with the boundary marked by few rows of radially thick-walled flattened fibers and terminal parenchyma. The structure of the wood is semi-ring-porous, the diameter of the vessels gradually decreasing to the late wood, and in the late wood the pores are very small and solitary.

The vessels are predominantly solitary and in radial multiples of 2-3(7), sometimes as tangential pairs. The solitary pores have a polygonal oval shape, with moderately thick walls, of 2-3 μm (5-8 μm the double wall). The lumen of solitary pores has that is 140-200(260) / 80- 120(165) µm radial/tangential diameters (average values 156 / 87 μm). The size of the pores gradually decreases to µm. The density is 2-7 pores per mm 2. The vessels have simple perforations on tilted plates, and intervascular bordered pitting as sub-opposite to alternate, hexagonal pits with small apertures, sometimes only as horizontal slits. The length of the vascular elements is 234-406 μm. On the vessels ends fine spiral thickenings appear.

Axial parenchyma - in cross section is of the apotracheal type, diffuse, in short, uniseriate bands, more obvious in the late wood, when presents a dark matter. Sometimes, few cells touch the vessels suggesting even incomplete sheaths (parenchyma of scanty-paratraheal type). In longitudinal section, the parenchyma occurs in strands of 4-8 rectangular vertical cells or nearly square, with thin walls, showing a slight constriction at the level of the horizontal walls. Some cells contain dark gums and 1-3 crystals.

Medullary rays - in cross section show radially elongated rectangular cells and linear trajectory, sometimes touching vessels, and having dark content in the late wood. In tangential view the rays show the 1-3(4)-seriate aspect. The uniseriates are low, of 3-10 cells tall (i.e. 38-136 μm), the bi- triseriate have 17-26 cells in height (i.e. 117- 273 μm). The frequency is (2)4-6 rays per tangential horizontal mm. The ray cells appear round, oval or slightly polygonal and uneven in size. In the radial view the rays are heterocellular, made up of cells all procumbent in the ray body (of 10-15 μm high), with 1-2(4) marginals high- er, or even upright (of 10-13-15 μm in height). In the cross-fields of the ray cells with vessels sometimes small simple pits appear and small gum remains, often granular.

The fibers - have a polygonal cross section, uneven lumina, with rare, horizontal or slightly inclined septa, and fairly thick walls (of 5-8 μm double walls). Vertical the fibers have simple, rare, very small pitting, relatively irregularly arranged on an irregular vertical row and rare, horizontal or slightly inclined septa.

Affinities and discussions

Some xylotomic features observed in our sample similar to the "euphorbiaceous" wood structures of phyllanthoideuos type as it was known in the former taxonomy. Today such taxa belong to Family Phyllantaceae , not to Euphorbiaceae , both family being now inside the Malpighiales order ( APG IV, 2016).

The fossil genus Paraphyllanthoxylon was created by Bailey (1924), to define a tree belonging to phyllanthaceous structures in which the perforations of the vessels are simple as the genera Antidesma , Hymenocardia, Bishoffia , Phyllanthus or Securinega (some other cited forms belong today to other taxa). Some representatives having only a shrub character (Metcalfe et Chalk, 1950, p.1221; Mädel, 1962, pp 284-288). The collective genus Paraphyllanthoxylon has a series of xylotomic characters that allowed the inclusion by synonymy of Phyllanthinium Ogura, 1932 and Glochidioxylon Ramanujam, 1956 genera. Otherwise Glochidion is included now in Phyllanthus ( Gregory et al., 2009) .

The xylotomycal characters described in the species on which Bailey created the genus (i.e. Paraphyllanthoxylon arizonense Bailey, 1924 ), have many similarities to those of the here studied specimen. However, our specimen has an obviously semi-ring-porous structure, with distinct growth rings, solitary vessels and in small radial multiples, or irregular groups, with medium to big sized lumina, and are frequently accompanied by rows of narrow vessels, vascular tracheids or fibro-tracheids. Vessel density is higher, and inter-vascular pitting is sub-opposite to alternate. The axial parenchyma is scanty-paratracheal, diffuse, poor and has gums and crystals. The rays have dilations at the boundaries of annual rings, are 1-3(4)- seriate and 3-26 cells in height, radially all body cells procumbent, and 1-4 marginals slightly higher or even upright, with simple pitting, small and larger, visible especially on marginal cells. The fibers are septated and have simple pitting.

It is clear that the species of Glochidioxylon (described by Ramanujam (1956) and Prakash (1959) in the Indian Tertiary and revised by Mädel (1962), as Paraphyllanthoxylon sahnii , is different, by having narrower, shorter, thinner-walled, and more numerous vessels, parenchyma absent, two sized rays very high, of 75-80 cells in height.

Paraphyllanthoxylon pfeferi and P. capense of Mädel (1962) have small vessels distributed in large multiples of up to 10 pores, giving a high density of vessels. Besides this, the rays are higher, and they have 1-6 upright marginals, so is different of our specimen.

P. teldense (Privé, 1975) has short vessels with simple perforations but also scalariform, so is different. P. yvardi (Koenigueur, 1970) has the porous structure without obvious rings, small vessels in short multiples and unsepted fibers, so is different.

The American species are also different: P. idahoense Spackman, 1948 which has metatracheal parenchyma which forms concentric lines or bands seen in cross-section; P. keriense Dayal, 1967 and P. alabamense Cahoon, 1972 , have 2-3 seriate rays, rarely uniseriate and with 1-(2-3) marginal rows of upright cells.

P. lignitum ( Daniou & Duperon-Laudoueneix, 1978) has some affinities with our specimen but presents small vessels and high rays of up to 50 cells and unpitted fibers but abundantly septated.

P. romanicum Petrescu (in Petrescu at al., 1978), has large vessels to very large, and almost exclusively grouped, so is different too.

The comparative analysis of the described species and the structural particularities shown by our Mid-Miocene specimen from the Southern Apuseni, lead us to believe that it represent a new species, that we named: Paraphyllanthoxylon botarii sp. nov. in honor of the owner of the land where the trunk was found, Mr. Remus Botariu.

Diagnosis of Paraphyllanthoxylon botarii sp. nov.: Distinct growth rings, wood semi-ring-porous, usually with solitary vessels and radial multiples of 2-3(7). Solitary pores oval-polygonal, thick-walled, of 2-3 μm simple wall or 5-8 μm double wall, and radial / tangential mean diameters 156 / 87 μm, density 2-7 pores/mm 2. Simple perforations on tilted plates, bordered pitting, oppositesubopposite to alternate, pits hexagonal and with small apertures sometimes as horizontal slits. The length of the vascular elements is 234-406 μm. Fine spiral thickenings appear on the vessel ends. Axial parenchyma few, apotracheal diffuse, as short tangential uniseriate bands, and paratracheal few, as vertical strands of 4-8 cells, sometimes with dark gum remains and 1-3 crystals. Medullary rays 1-3(4)-seriate, of 3-26 cells in height (i.e. 38-273 μm), and with frequency of 4-6 rays/mm tangential. Ray heterocellular with cells all procumbent, and 1-4 marginal higher or even upright. Cross fields of ray cells with vertical elements having sometimes small simple pits and small gum remains, often granular. Fibers polygonal in cross-section, having uneven lumina, with rare, horizontal or slightly inclined septa, and fairly thick walls of 5-8 μm double wall, with simple, rare, and very small pits on an irregular vertical row.

Figures

Fig. 14 Paraphyllanthoxylon botarii sp. nov. a, b - cross section: semi-ring-porous wood, solitary and grouped vessels, 1-3- seriate rays, parenchyma as short tangential lines - x50; c - cross-section: solitary vessels, thick-walled fibres - x100; d-f - tangential section: 2-3-seriate fusiform, parenchyma, septate fibers, alternate, numerous intervascular pitting - x100; g, h, i - radial section: simple perforations, cross-fields with numerous simple pitting - x200.