Aceroxylon pravalense, 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 : 78-83

Aceroxylon pravalense sp. nov.

Fig. 28, photos a-i.

Material

From two samples of dispersed petrified wood (field numbers 52 and 213), collected from Prăvăleni area from the left side of Prăvăleni valley at the confluence with BodiȘteanu brook and respectively from Ociu area, MarinaȘu Valley, from Mid-Miocene volcano-sedimentary deposits (Late Badenian-Early Sarmatian). The centimetric sized samples representing a silicified wood fragment of whitish-beige color, gray tinted and is kept now in GIR collection at National Geological Museum - Bucharest under the inventory numbers 26374 and 26402 (field numbers: 52 and 213, respectively). Under the magnifying glass, fibrous structure can be seen, distinct annual rings, short thin medullary rays, and vessels, which suggest a dicotyledonate, as wood fragments of trunk and of branch.

Microscopic description

Growth rings distinct, wood semi-ring-porous, the rays are obviously dilated at the ring boundary and darker at the limit of the annual rings. One specimen preserves the axial area where the pith is resorbed suggesting a branch fragment.

The vessels in the cross section are almost exclusively solitary, or as radial or slightly irregular of 2-5 pores, rarely as small tangential groups of 2-3 pores. They have a round, polygonal or radial-oval section and some of them contain dark-brown solid deposits, granular to compact. The radial/tangential diameters for the solitary pores are (25)40-75(128) / (17)30-65(112) µm, the walls are not too thick, of 4-6 μm double wall, the density is 68- 138-146 vessels per mm 2. The vessels have simple perforations on inclined plates, the vertical walls have spiral tickenings, with thick, slightly tilted, nearly horizontal, quite obvious turns. The pitting is shallow, hexagonal, numerous, small (7-8 μm), alternate, with very large chamber (5 μm), sometimes quite badly preserved. The average length of the vascular elements is 88-182 μm. In the lumen, you can see large thin-waled tyloses, and granules or crystals brown colored, dispersed, locally to compact.

The axial parenchyma - is of apotracheal type and appears as few short uniseriate lines or diffuse, as 1-2 cells dispersed among the fibers and paratracheal few also visible especially in the longitudinal sections as large, polygonal cells attached to the vessels, with many opposite pits, or as numerous strands with more than 6 rectangular empty cells, not too thick walled, sometimes bearing solitary crystals.

The medullary rays - thin to thick in cross section show obvious dilation at the growth rings boundary. They are relatively linear and can touch vessels. The ray cells appear pitted on the horizontal walls. In tangential section have 1-12(16) cells thick. The rays of 1-4 cells thick are not very tall, appear relatively numerous around the thick rays and are formed of round or oval or slightly elongated vertical oval cells, (of 12-16-20 µm in diameters), mixed or arranged marginally as incomplete sheats. The thicker rays are frequently dissected by 1-3 fibers and have uniseriate endings of 1-3 rounded cells, the last being triangular and elongated. The body cells tend to be more rounded and more equal in size of 7-11 μm in diameters. The frequency is of 8-10 rays per horizontal tangential mm. Radially the rays have all procumbent cells, with varying height of 11-16-20 μm. On the ray- cells small simple pits of 2 μm punctuation, slightly irregular in 1-2 horizontal rows arranged, quite badly preserved. Sometimes the ray cells have 1-3 large crystals, polygonal to oval-rounded, floating in a dark mass. Sometimes, only their contours are visible.

The fibers have a polygonal section of 10-12 μm in diameter, relatively thick walled 3-6 μm to very thick and with round to point like lumen. Vertical have spiral thickenings and rare small, numerous bordered pits in a single vertical row, slightly irregular, and rare septa.

Affinities and discussions

The comparative study of the xylotomic characters observed in the here studied specimens suggested big similitudes with the typical features of the former Aceraceae family, especially of Acer type, as is described by Hofmann (1952). Now this genus belongs to the Sapindaceae family, the Hippocastanoideae subfamily ( APG IV, 2016).

So, the xylotomic details of our studied specimens are mostly similar with those specified in Acer diagnosis: the obvious growth rings marked by some rows of flattened fibers, the diffuse-porous wood with solitary pores spaced or in short multiples, with simple perforations, alternate pitting and spiral thickenings, the apotracheal parenchyma few, diffuse, occasionally paratracheal, rarely terminal, the rays slightly dilated at the ring boundary, 1-3- 5(6)-seriate and of 40-50(60) cells in height, homocellular, cells all procumbent with simple pitting, and rarely square in the marginal rows and with enlarged pitting (after Hofmann, 1952).

Such characters we have also observed in our sections. Only the rays show larger thicknesses, up to 16 cells, and this character appears at some Acer species, such as A. campestre .

The comparison with other fossil forms reveals the same difference, the thickness of the medullary rays. Hofmann (1952), shows that Aceroxylon sp. , described by her, has fine and thick rays, of 5 cells or more, without further specification, and the figuration is deficient. The other xylotomic patterns observed in our specimens, regarding the round to oval shape and the size of the vessels in a diffuse-porous structure, the crystalliferous parenchyma thin-walled and pitted, the fibres are pitted and with spiral thickenings, and the rays are fine to broad of 1-16 cells, the multiseriates are taller and fusiform, the cross fields with small simple pitting increased on the marginals and also the vessels with simple perforations, alternate pitting and the spiral thickenings, show a great similarity with the current species Acer campestre L., which has an European and western Asian life area, both marked by a temperate climate. The species described in this paper: Aceroxylon palaeosaccharinum Greguss, 1943 emend. and A. zarandense sp. nov. are both clearly different, so, after this comparative analysis we think we are in front of a new species, which we named Aceroxylon pravalense sp. nov., after the name of the area where the specimen designed holotype (specimen with inventory number: 26,374) originates.

A similar form was described by us under the same name on some material from another collection ( Iamandei et al, 2004b). Since at that time the name proposed in an unpublished PHD Thesis, so it was not validly published assign also that material to this species Aceroxylon pravalense sp. nov., now correctly published. The studied material is deposited in GIR Collection under the inv. Nos. 26,709; 26,711 and 26,715 (=samples L.22, L.24 and L.28 – Țibuleac Coll.).

Diagnosis of Aceroxylon pravalense sp. nov. (Holotype: inv. no.: 26,374; Paratype: inv. no.: 26,402 - both kept now in GIR collection at National Geological Museum - Bucharest) .

Semi-ring-porous secondary wood with distinct growth rings, rays dilated at the ring boundaries. Vessels almost exclusively solitary or in rare tangential groups of 2-3 or radial multiples of 2-5 pores. The vessels have round, polygonal or radial oval shape, radial/tangential diameters have 40-75 / 30-65 µm, cellular wall thickness is 4-6 μm double wall and density of 68-146 vessels per mm 2. Vertically the vessels have simple perforations, spiral thickenings frequent and slightly tilted to nearly horizontal, alternating, hexagonal bordered pits, numerous, small, of 7-8 µm, with large apertures, of 5 μm. The vascular elements of 88-182 μm length have large thin walled tyloses and colored crystals. The parenchyma is of apotracheal type, diffuse or as short lines and few paratracheal. Vertically it occurs in numerous strands of 6 rectangular cells or more, sometimes crystalliferous, or as large polygonal cells, attached to vessels, with numerous, opposite pitting. The rays have cells pitted on the horizontal walls and are fine to broad of 1-12(16) cells wide. The 1-4- seriates are not very high, and occur grouped around the thick rays of up to 16 cells, which are dissected by fascicles of some fibers, and have short endings of 1-3 cells. Ray frequency is of 8-10 rays on horizontal tangential mm. Radially are homocellular with cells all procumbent with variable height, of 11-20 μm, bearing 1-3 large, polygonal oval-rounded crystals, floating in a dark mass. In the cross-fields with vessels there are numerous, small pits of 2 μm in 1-2 horizontal rows arranged. The fibers with polygonal section, of 10-12 μm in diameter, with wide lumen, round to point like, with thick walls and rare spiral thickenings, small, numerously bordered pitted in a vertical row and sometimes septate.

Angiosperms – Monocots

Order Arecales Bromhead

Family Arecaceae Bercht. & J.Presl, 1820 , nom. cons. (= Arecaceae Schultz-Schultzenst. ); (= Palmae Juss., nom. alt.).

Genus Rhizopalmoxylon (Felix) Gothan, 1942 Rhizopalmoxylon sp. aff. sabaloides

Fig. 19 , photos a-i.

Material

A sample of dispersed petrified wood (field number 814), collected from Basarabasa Hill in Basarabasa village area, from Mid-Miocene volcano-sedimentary deposits (Late Badenian-Early Sarmatian), having centimetric sizes and representing a silicified (opalised) wood fragment of yellowish color. The material remained after the oriented thin sections were realized is kept now in GIR collection at National Geological Museum - Bucharest under the inventory number 26,465 (field numbers: 814). Under the magnifying glass a fascicular structure is guessed, suggesting a monocotyledonate.

Microscopic description

The studied silicified wood fragment appears to originate from a palm tree, with a typical fascicular microscopic structure: it presents in the transversal section a very thin cortical zone and a central cylinder with fibro-vascular bundles and remains of a parenchymal ground tissue. The transverse sections in which the cortical zone appears reveal its development outlining on relatively small portions groups of fibrovascular bundles and ground tissue inside the structure, which is not characteristic of the palm tree trunk, but rather to the root zone.

The cortical zone is marked towards the outside by several rows of thick-walled fibrous cells following an irregular trajectory representing, of course, the irregular contour of a small rootlet developed in competition with the others, numerous in this plant portion. There follows an opaque blanket of parenchyma in which small, dispersed fibrous bundles appear and this aspect similarly appears to the outside of the area, beyond a limit area relatively irregular as thickness of some cells rows, which is probably the rootlet exodermis. The median cortex is marked by the presence of large round elliptical hollow spaces with diameters of 60-168/105-50 μm, tangentially orient- ed, probably representing aeriferous channels, again characteristic of root structures. The inner cortex is hard to delimit as an entity, as it make the transition to the following area.

The outer + intermediate zone (= dermal + subdermal zone) have a thickness of a few millimeters (i.e. 1/3 of the total half-thickness of the structure because they cannot be separated as specific entities here). In this portion appear radially oriented oval-elongated fibro-vascular bundles of 190-220 / 80-112 μm the radial/tangential diameter and the f/v ratio is 0.21 / 1 - 0.27/1 (i.e. part fibrous / vascular part ratio). The fibrous bundles are also present, and the parenchymal tissue comprises dispersed sclerenchymal cells and large round cells most probably representing idioblasts filled with mucilages. It is interesting to note that the fibro-vascular bundles exhibit sclerenchyma cap oriented to the axial part of the structure and not to the external part. The fibro-vascular bundles are relatively few (4-5 per mm 2), are oval-shaped, are of the closed collatersal type, have the sclerenchyma cap of lunaria type (see Stenzel, 1904; Greguss, 1968), the floem plate seems to be undivided, the metaxylem is represented by 5-7 vessels of 16-35 μm in diameter, of circular shape or slightly oval and thick walled (2-3.5 μm simple wall). The protoxylem consists of 9-11 vessels with a narrower lumen (of 4.5-6.5 μm in diameter), circular shape and thick walls (2.5-3.5 μm simple wall), relative to the small diameter of the vessels. In longitudinal section, the complicate trajectory of the fibro-vascular bundles does not provide important anatomical details. Tabular parenchyma not observed. The parenchyma that surrounds the protoxylem has on its outer side two or three layers of cells having thickened and sclerified walls, so completing the protective sheath of the bundle whose growth has ceased. There are also cellular inclusions as long rows of stegmata with spherical silica corpuscles on disperse fibers.

The central zone represents about 2/3 of the half-thickness of the structure, and is constituted from the parenchymal fundamental mass with rare fibrous or fibro-vascular bundles and comprising probably also, aeriferous spaces.

Affinities and discussions

Based on the typical anatomical characters of our studied specimen representing a monocotyledonous woody structure of Palm type ( Arecaceae, APG IV, 2016 ), especially of the basal part where the root system appears (or the rhizotillic part, after Cook, 1941 - in Tomlinson, 1961), by having fascicular structure of the central cylinder, with closed collateral fibro-vascular bundles, typical for a palm, and on the particularities observed indicating a radicular pattern determined us to attribute it to Rhizopalmoxylon organ-genus.

This fossil taxon created by Felix (1883), including such woody root structures, usually difficult to assign to a taxon comparable to a current genus. It was revised by Gothan (1942), who described a material from the Tertiary coals from Bohlen, Germany as R. glasseli and R. bohlenianum ( Gothan, 1942) . Few other forms were described from European area, by Grambast, L. (1962) as Rhizopalmoxylon sp. , and by van der Burgh & Meulenkamp (1966) as R. pilosum . From Africa is reported by Koeniguer (1970) a R. libycum .

From the New World, Tidwel et al. (1972), reported some palm woods and described some forms of Rhizopalmoxylon (as R. behuninii , R. blackii and R. scotii ) from the Tertiary of Redmond, Utah, US. The forms R. huepaciense and R. teguachachiense described by Cevallos Ferriz & Ricalde-Moreno (1995) and interpreted as Palm rhizomes, represent another plant-part.

Much more forms were described from India as R. indicum Sahni, 1938 ; R. sundaram Mahabale & Rao, 1973 ; R. borassoides Awasthi et al., 1996 ; R. macrorhizon (= Palmoxylon macrorhizon Stenzel, 1904 ) Bonde et al., 2008; Rhizopalmoxylon angiorhizon (= Palmoxylon angiorhizon Stenzel, 1904 ) Bonde et al., 2009 and Rhizopalmoxylon singulare Bonde et al., 2009 and recently Kathal et al. (2017) described a new species identified as R. nipoides , clearly sending to the extant mangrove palm rhizome of Nypa Wurmb.

In the specimen studied here, we observed fibro-vascular formations that are distributed to some "central cylinders" separated by an epidermal area that probably means a thin cortical zone, a structure found only in the basal part of the palm-stem where the root system appears as a basal pillow of rootlets, or rhizotil (Tomlinson, 1961, quoting Cook), in which the adventitious rootlets are inserted, a relatively common aspect of many palm-trees. The presence of the aeriferous spaces observed in the structure of these "central cylinders" is also specific to the root Piranheoxylon perfectum sp. nov., Aceroxylon zarandense sp. nov., Aceroxylon pravalense sp. nov., Aceroxylon palaeosaccharinum (Greguss) emend. Iamandei and a sample with structure of monocotyledon attributed to Rhizopalmoxylon sp. aff. sabaloides, as a very important element with palaeoclimatic significance. The absence of elements of sclerophyllous vegetation excludes a typical subtropical paleoclimate, and the occurrence of some termophillic elements in the identified association excludes a cold palaeoclimate. The growth conditions are further confirmed by the absolute thickness of the growth rings, which is generally quite high in the studied flora. False growth rings rarely appear, due to probable frosts outside the winter or drought during vegetation season. The ratio of early / late wood indicates an increased level of summer precipitation. The ratio of arctotertiary / palaeotropic taxa is 84 / 16 and it is included in the known parameters of the Middle Miocene vegetation representing a mixed mesophytic forest with conifers and deciduous dicots. Some evergreen types also occur, similar to the warm temperate climate forests in eastern China and in southern United States. This association indicates that during the Late Badenian in Zarand basin the average annual temperatures ( MAT) were between 12 and 17 degrees Celsius. Taking into account the island palaeogeographic distribution of the Carpathian land within the Middle-Miocene Paratethys, the relatively uniform palaeoclimate was marked by a low mean annual rainfall ( MAR), and by a mean annual precipitation regime ( MAP) of 1100-1500 mm per year. These parameters suggest a humid subtropical toward warm-temperate climate, fairly damp of mediteranean type: Cfa to Csa in Köppen classification (Geiger, R., 1954) according to the island mountainous relief ( Fig. 20 ), where the altitudes probably did not exceed 1200 m (Iamandei, 2002). After this short palaeoecological analysis we conclude: 1. Obviously, the vegetal assemblage defines for the Late Badenian time, a Mixed Mesophytic

Forest living, very possibly, in an insular palaeogeography of Carpathian Mountains and in a region marked by an intense local volcanism. 2. The palaeovegetational and palaeoclimatic reconstruction made on the basis of the reconstructed vegetation from Zarand area shows the possible zonal climate during the Late Badenian in Carpathians: Zonal Paleoclimate is Warm

Temperate (see Scotese, 2002,

http://www.scotese.com/miocene1.htm). 3. Palaeoecologically evaluating the Late Badenian vegetational assemblage of arboreal plants from

Zarand, through the presence of some taxa with

16% typical thermophilic extant correspondents is suggested: a warm temperate paleoclimate of

Mediterranean type, with MAT = 120 - 170 and

MAP = 1100-1500 mm annual precipitations. 4. Evaluating the ecological requirements of the paleotropical taxa present in the fossil association, and taking into account another paleogeo-

graphic and latitudinal reconstructions, we can say that the Badenian arboreal vegetation from

Zarand represents an altitudinally storied Mixed

Mesophytic Forest with Lauracee and Conifers with Sequoioxylon the dominant taxon, living in an insular mountainous environment and a Warm Temperate Palaeoclimate of Mediterrane- an type.

Figures

Fig. 19 Rhizopalmoxylon sp. aff. Sabaloides. a, b - cross-section: fascicular structure, with fibrous and fibro-vascular bundles, parenchymal ground-mass, aeriferous tissue - x50; c - cross-section: fibro-vascular bundle, fibrous bundles, parenchyma, aeriferous canal - x100; d - cross-section: median cortex between radicular areas - x50; e-h - cross-section: fibrovascular bundles with obvious metaxylem and protoxylem vessels, undivided floem plate, sclerenchyma cap of "lunaria" type, aeriferous canals, parenchymal ground-mass, cortex, - x100; i - cross-section: fibro-vascular bundle with sclerenchyma cap of "lunaria" type, destroyed floem plate, apparently undivided, metaxylem and protoxylem areas partially destroyed, protoxylematic parenchyma appear slerified, ground-mass with undirected parenchyma - x200x

Fig. 20 A transect by the reconstructed Badenian forest of Zarand (from Iamandei, S., 2002). identified tree species allow a phytoecological analysis, structure. Also, the structure of fibro-vascular bundles revealing the plants’ thermal tolerance, the soil and air may suggest the current group of palm trees as extant relatives (Tomlinson, 1961, 1990). humidity, the palaeoaltitude, the relationships and inter- The sclerenchyma cap of "lunaria" type (Stenzel, 1904), actions within the biocoenosis, the palaeophytocoenosis the f/v ratio less than 1, the sieved plate of undivised itself, the succession of phenophases in a mixed conifertype, the metaxylem vessels in number of 5-7, of which ous forest, and the dynamics of the local vegetation durtwo are larger and laterally arranged, the group of 7-11 ing the Late Badenian. The paleoclimate analysis is relatsmaller protoxylem vessels with thickened walls, protect- ed to the neighborhood of the Paratethys, where the ed by a sheath of parenchyma whose the marginal cells Zarand Basin evolved. That forest was a mixed mesoare thickened and sclerified walls, the absence of the tab- phytic forest, attitudinally storied, with remains of preular parenchyma could suggest some resemblance to our Miocene sempervirent vegetation of paratropical or subspecimen with a current Sabaloid Palms. tropical climate, suggesting a Miocene pluvial mixed The comparison with fossil taxa described until now mesophytic forest of warm-temperate climate. shows a possible resemblance to the form described by This mixed mesophytic forest with Lauraceae and Coni- Grambast (1962), but since the longitudinal sections are fers, include the following genera: Tetraclinoxylon, Thunot very revealing and due to the xylotomical similitudes joxylon, Chamaecyparixylon, Cupressinoxylon, Taxodiof our specimen with the current Sabaloid Palms, we oxylon, Sequoioxylon, Pinuxylon, Magnolioxylon, Cinname it Rhizopalmoxylon sp. aff. sabaloides. namomoxylon, Spiroplatanoxylon (not Icacinoxylon), Liquidambaroxylon, Eucaryoxylon, Rhysocaryoxyton, CONCLUSIONS Pterocaryoxylon (?), Fagoxylon, Quercoxylon, Alnoxylon, Populoxylon, Salicoxylon, Nyssoxylon, Pa- Twenty years ago we started the study of the Middle Mi- raphyllanthoxylon, Piranheoxylon, Aceroxylon, Fraxocene Petrified Forest from Zarand, Apuseni Mountains, inoxylon, and Rhizopalmoxylon, taking into account new and it still remained an important topic of further re- palaeoxylotomical identifications. searches even after many field trips in the region. Thus, In this paper we present some newly identified woods or many hundreds of petrified wood samples collected from reattributed to other taxon as new combinations from the there were prepared and studied, and much of them are Mid-Miocene Zarand Petrified Forest of Zarand that will still in various stages of study. Their identification in- complete the upward list with 15 new taxa, as it follows. crease the number of fossil trees from the Badenian forest Conifers: Cupressinoxylon sp., Thujoxylon sp., of the Tălagiu island. Chamaecyparixylon sp., Taxodioxylon taxodii Gothan, This study could support a more precise palaeoenviron- Sequoioxylon gypsaceum (Goepp.) Greguss, Sequoioxymental and palaeoclimatic reconstruction. The geological lon multiseriatum Ramanujam et Stewart, comb.nov. evolution of the Tălagiu caldera allowed the best condi- Agiosperms: Liquidambaroxylon speciosum Felix, Fagtions for silicification of the remains of the Mid-Miocene oxylon subcaucasicum Privé et Brousse, Fagoxylon crisforest occurring on the slopes of the volcano. Over 40 tallophorum van der Burgh, Quercoxylon sarmaticum Starostin & Trelea, Paraphyllanthoxylon botarii sp. nov.,