Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004

Iamandei, Stanila, Iamandei, Eugenia & Stoia, Tiberiu, 2020, Fossil Woods From Bozovici (Sw Romania), Acta Palaeontologica Romaniae 16 (1), pp. 3-17 : 5-9

Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004

Fig. 4 , a-i. Fig. 5 , a-i.

Macroscopic description

The studied material is represented by four samples of petrified wood: three centimetric-sized samples and one of them as a big slice cut from a silicified trunk ( Fig. 3 ). All of them indicate a partially coalified wood and then silicified, showing dark color, fibrous texture and quasiregular growth rings visible with the naked eye, suggesting a conifer structure. Standard oriented thin sections were made and microscopic study was done on four samples. The studied material is deposited in the Collection of the National Geological Museum ( NGM Col. Bucharest) under the indicative numbers: 27,618; 27,619; 27,620 and 27,621 (in Fig. 3 ).

Microscopic description

The growth rings in cross section seen are distinct, broad, but rather unequal in width.

The transition from earlywood to latewood is gradual. The boundaries of the annual rings are distinct, marked by 3-15 tangential rows of thick-walled to very thick-walled and smaller cells of the latewood. There are no normal axial resin ducts and the ring boundaries are often wavy, probably due to the buttressed form of trunk.

The tracheids are polygonal in cross section, with slightly rounded corners in the earlywood and with radial/tangential diameters of 25-75/30-55 μm, smaller in the latewood, of 25-30/17-25 μm. The tracheidal wall has 5- 10 μm in the early wood, growing to 12-17 μm the double wall, in the latewood. There are 2-11 radial regular rows between two successive rays. On the tangential walls there are few, uniseriate, spaced or slightly irregular abietineous small bordered pits, of 6-8-10 μm in diameter, with small circular apertures, or vertical elliptic. The radial pits is opposite, typical abietineous, of 12-16 μm in diameter and smaller in the latewood, in 1-4 vertical rows, spaced or contiguous, sometimes presenting small irregularities in their arrangement. Crassulae are occasionally present. No helical thickenings were seen on the tracheids.

The axial parenchyma is few, dispersed, less visible in cross-section, since not always has dark content and it appear similar to tracheids. In vertical view it appears as rectangular thin-walled cells (1-3 μm the simple wall), with thin terminal (horizontal) walls smooth, slightly rugose or nodular, with 1-3 nodules. Inside, it has large dark resinous balls, or plugs with rounded endings, sometimes with convex empty spaces, or as small remains.

The rays are usually uniseriate, sometimes with local short biseriations or even biseriate, having 2-15-36 or more cells in height. Sometimes, they seem to be heterogeneous in tangential view, with often unequally sized cells, either higher, or wider (as wide as two cells when occur in biseriate rays), and have lateral intercellular spaces. Ray density is 4-8 rays per horizontal tangential mm and up to 40 rays per square mm. In radial view, the procumbent ray cells have thin and smooth horizontal walls of 2-3 μm, height of 12-17 μm or more, the marginals are slightly taller (of 20-35 μm) and have wavy outer wall. Ray-tracheids are not present. The tangential walls are slightly nodular, and indentures were not observed. The earlywood cross-fields have 3-4 glyptostroboid, sometimes taxodioid pits, but with much reduced borders, like cupressoid type, of 8-10 μm, arranged in horizontal rows, or in slightly diagonal pairs, or single in the late-wood cross-fields. In the marginal cross-fields, up to 8 pits in 1-2 horizontal rows were observed. The pit apertures are nearly round or elliptical oblique.

Affinities and discussions

The synthetic description of these specimens provided xylotomical details typical for the cupressaceous woods, especially of „taxodiaceous“ type, by the absence of the resin ducts, the shape of the tracheids, their size and wall thickness, the ray aspect in longitudinal sections, especially the presence of radial opposite pitting on 1-4 vertical rows, with crassulae on tracheids, and the cross-fields with typical glyptostroboid pitting, tending sometimes to taxodioid or even cupressoid aspect. These observed details have been compared with extant and fossil published structures of Cupressaceae of taxodiaceous type ( Greguss, 1955; Visscher & Jagels, 2003; Dolezych & Van der Burgh, 2004; InsideWood, 2004 – onwards).

The family Cupressaceae s.l., beside the classical cupressaceous members (Callitroideae and Cupressoideae), comprises now all the members of the former „taxodiaceous“ genera, with both extant and fossil forms ( Gadek et al., 2000; Farjon, 2005, 2017), included in the next subfamilies:

• Taxodioideae Endl. ex K.Koch, with Taxodium Rich. , Glyptostrobus Endl. , and Cryptomeria D.Don ;

• Sequoioideae (Luerss.) Quinn, with Sequoia Endl. , Sequoiadendron J.Buchholz and Metasequoia Hu & W.C.Cheng ;

• Athrotaxidoideae Quinn, with Athrotaxis D.Don ;

• Cunninghamhioideae (Sieb. and Zucc.) Quinn, with Cunninghamia R.Br. ;

• Taiwanioideae L. C.Li, with Taiwania Hayata.

Comparing the anatomical structure of the studied material with fossil "taxodiaceous" genera ( Greguss, 1967) we found some similarities with Sequoioxylon Torrey, 1923 with Taxodioxylon (Hartig) Gothan, 1905 but especially with Glyptostroboxylon Conwentz, 1884 . The distinction between those three genera is problematic enough, since some paleoxylologists contest the validity of the genus Sequoioxylon Torrey , considering that the diagnosis of Taxodioxylon genus is sufficiently comprehensive and the establishment of new domains of competence can complicate the fossil wood identification ( Privé-Gill, 1977).

A more recent revision of the fossil cupressaceous morphogenera ( Dolezych & Van der Burgh, 2004) resulted in new revised diagnoses of them. Since it appears to be more similar to our material, we reproduce here only the diagnosis of the genus Glyptostroboxylon Conwentz, 1884 , as is emended by Dolezych & Van der Burgh (2004):

Coniferous wood with distinct growth rings. Tracheids in the earlywood wider than in the latewood. On the radial walls of tracheids, pits in 1–3(4) vertical rows. Wood parenchyma with thin and smooth to moderately thick and pitted terminal (horizontal) walls. Rays are homogeneous, mostly uniseriate. Cross-field pits in the earl ywood are predominantly glyptostroboid, but also some cupressoid and taxodioid pits may be present.

In our studied specimens, the pattern of tracheids within the growth-rings, their radial abietineous pitting, spaced arranged in 3-4 vertical rows on wider earlywood tracheids, in 1-2 rows on the narrower latewood tracheids, the presence of axial parenchyma with smooth to quite nodular horizontal walls, the homogeneous, mostly uniseriate rays, sometimes with biseriate storeys or even as biseriate rays, the ray-cells with tangential walls slightly rugose, sometimes nodular, and the cross-fields with 1-4 glyptostroboid (and taxodioid) pits - more numerous, on two horizontal rows, in the marginals - represent a combination of features very similar to those described by authors for Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004 and, obviously, with the species diagnosis.As it was shown by Dolezych & Van der Burgh (2004) in their revision, Glyptostroboxylon tenerum (Kraus) Conwentz, 1884 was the initial basionym for the genus (its first name was Glyptostrobus tener Kraus, 1864 ). It was taken later again in discussion by Seward (1919, p. 198) and Jurasky (1933), but only Kraüsel (1949) was the one who established the correct name, in respect of ICBN Rules, however noting the wide variability of the glyptostroboid pits, up to the cupressoid, in the cross fields.

Now, Glyptostroboxylon tenerum is interpreted as fossil wood of Cunninghamia , because Gothan (1905) and later, Rudolph (1935), Watari (1948), Süss & Velitzelos (1997) and Fairon-Demaret et al. (2003) have also observed affinities between the wood of Glyptostroboxylon tenerum and the one of the extant Cunninghamia , and Dolezych & Van der Burgh (2004), after a new investigation on the original material from Wetterau, the type-locality, have observed that the affinity of this wood is not to Glyptostrobus , but clearly to Cunninghamia . Thus, they have described a new species of Glyptostroboxylon ( G. rudolphii ), emending also the genus’ diagnosis and taking it as basyonim. The species name come from the name of a scientist who, they say, firstly discussed the affinity of the fossil to the recent wood of Cunninghamia vs. Glyptostrobus ( Rudolph, 1935) , observing that the pits in cross-fields of the fossil wood are glyptostroboid and taxodioid, in a random distribution.

The newly described species, Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004 represents, most probably, the fossil wood of Glyptostrobus europaeus (Brongniart) Unger , described on the basis of adpressions of shoots, leaves and cones, and frequently found in the European Cenozoic formations (see Greguss, 1967; Hofman, 1952; Ramanujam, 1960; Zalewska, 1953).

An interesting discussion is made by Teodoridis & Sakala (2008), who observed that there is a disproportion between abundant leaves and cones/seeds of Glyptostrobus in the Most Basin ( Czech Republic) and only one specimen of fossil wood found preserved as xylite rather difficult to identify, attributable to this genus, traditionally considered as the main coal-generating element: “association of Glyptostrobus ” sensu Kvaček & Buzek (1982) (in Kvaček, 1999; Teodoridis & Sakala, 2008, p. 307).

As information, the monotypic extant genus Glyptostrobus pensilis (Staunton) K. Koch , named Shui Song (water pine), or Chinese deciduous cypress, or Canton water pine, is a not very tall tree, of relatively warm and wet climate, which can resist in colder climate too, having deciduous shoots. Even if it lived in Europe during the Cenozoic as an important coal-generator tree, maybe as an eco-form adapted to a wet environment, like peat-bog, the extant biogeographic areal of Glyptostrobus is very restricted, in some low, damp and riparian areas, in South-east China (Guangzhou) and Vietnam ( Greguss, 1955; Earle, 1998). It appears also in Japan and in the West part of North America, as Jim Basinger, Professor of Saskatchewan University - Canada observed, and sent us this information (written comm., 1998): “ I have seen it growing in the United States, Japan, and China. Living trees are generally found in relatively warm climates. In southern China (Guangzhou) the trees are semideciduous. Some foliage is retained all year. In cooler climates, it will be entirely deciduous. This is the case in the mid-western United States and in Japan. In the fossil record, for instance in the arctic fossil floras we have worked with, it appears that the trees were entirely deciduous. I believe that the conflicting reports on the evergreen or deciduous character of Glyptostrobus were the result of observation of trees under different climatic regimes”.

After the revision and emendation of Glyptostroboxylon genus, new specimens were described and other revised as Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004 :

- Teodoridis & Sakala (2008) studying a fragment of sideritized wood from Bílina Mine, from the Most Basin, described G. rudolphii , as having crassulae, large intercellular spaces between ray-cells and cross-field pits exclusively glyptostroboid.

- Vassio et al. (2008), described G. rudolphii from Middle Pliocene, studying in situ stumps from Stura di Lanzo right riverbank, NW Italy, based on their typical features, especially the presence of exclusively glyptostroboid cross-field pits.

- Dolezych, in Erdei et al. (2009) studying xylotomically stumps from the Miocene Fossil Forest of Bükkábrány ( Hungary), described wood structures comparable to Glyptostroboxylon Conventz emend. Dolezych and Van der Burgh , having similar cross-field pits. Such an idea is confirmed also by the presence of the organic-rich sediments underlying and embedding the stumps, which provided a high abundance of Glyptostrobus Endlicher wood remains, foliage, cones and seeds.

- Gryc & Sakala, (2010), took again in study some woods from the Miocene opencast lignite mine of Bükkábrány ( Hungary), exposed in the Visitor Centre of the Ipolytarnóc Fossils Nature Reserve, and described Glyptostroboxylon rudolphii , having cross-field pits mainly glyptostroboid.

- Havelcová et al. (2013) described G. rudolphii from the Stump Horizon in the Bílina open cast mine ( Czech Republic), having typical details.

- Koutecky & Sakala, (2015) described G. rudolphii also from Doupovske hory, Czech Republic, having glyptostroboid and taxodioid pits (1–2, occasionally up to 4) in cross-field, and rays up to 12 cells high.

Some forms of Glyptostroboxylon previously described, could be reassigned to the real equivalent of Glyptostrobus , i.e. Glyptostroboxylon rudolphii Dolezych et Van der Burgh (2004) , since they are characterized mainly by glyptostroboid cross-field pits.

- Thus, the species described by Kostyniuk (1938), as having oval or round and glyptostroboid pits in cross-fields, clearly agree with G. rudolphii , to which it could be reassigned.

- Iamandei et al. (2001), described a specimen from the Early Sarmatian from Leucuşeşti – Fălticeni, Northeastern Romania as G. tenerum wich could be reassigned too, as G. rudolphii , having also glyptostroboid cross-fields.

- Nagy et al. (2002) described G. tenerum from the late Badenian deposits of Prăvăleni (South Apuseni Mountains), which can be reassigned to G. rudolphii .

- Recently, Akkemik et al. (2017) published the first Glyptostroboxylon from central Turkey, and then Akkemik et al. (2019) identified G. rudolphii from another site of central Turkey based on the nearest features such as 2-5 pits per cross-field, predominantly glyptostroboid, but also taxodioid and apparently higher ray height.

Therefore, taking into account the entire discussion and the affinities of our studied specimens, found at Bozovici area, we think they could be attributed to the species Glyptostroboxylon rudolphii Dolezych et Van der Burgh, 2004 , probably representing fragments of trunk or thick branches, as the size of the tracheids and of the ray cells show, which is also in accord with the observations on the annual rings.

Figures

Fig. 4 a-i. (graphic scale, μm). Glyptostroboxylon rudolphii Dolezych et Van der Burgh 2004, Bozovici, Romania. a-c. Cross section – distinct growth rings, earlywood and latewood tracheids. d-f. Tangential section – uniseriate and biseriate rays, parenchyma with resin plugs and smooth or nodular terminal (horizontal) walls. g-i. (radial section) – up to 4- seriate radial pitting on tracheids, 1-4 pits cross fields (i), or 2-8 in marginal cross fields (i).

Fig. 5 a-i. (graphic scale, μm). Glyptostroboxylon rudolphii Dolezych et Van der Burgh 2004, Bozovici, Romania. a-c. (cross section) - earlywood and thick-walled latewood tracheids, wavy growth rings. d-f. (tangential section) – uni- and biseriate rays, parenchyma with resin plugs and nodular terminal (horizontal) walls. g-i. (radial section) – radial 1-3-4 seriate pitting on tracheids, 1-3-4 pits cross fields, more in marginal cross fields.

Fig. 3 Two of the studied samples (nos. 27621, 27622).