Taxodioxylon gypsaceum (GÖPP.) KRÄUSEL, 1949

Akkemik, Ünal & Bayam, Nevriye Neslihan Acarca, 2019, The First Glyptostroboxylon And Taxodioxylon Descriptions From The Late Miocene Of Turkey And Palaeoclimatological Evaluation, Fossil Imprint 75 (2), pp. 268-280 : 272-273

Taxodioxylon gypsaceum (GÖPP.) KRÄUSEL, 1949

S t u d i e d m a t e r i a l. SAK12 and SAK15 (Repository: Fossil collection of the Department of Forest Botany, Faculty of Forestry, Istanbul University, Istanbul, Turkey).

H o r i z o n. Hüyükköy Formation.

A g e. Late Miocene (Tortonian).

L o c a l i t y. Çankırı: The village of Sakarcaören near to the town of Orta (latitude and longitude are 40°36′42.46″ N and 33°9′16.14″ E) .

D e s c r i p t i o n. The sizes of the studied specimens are: height 13.5–15.5 cm, width 6.5–14 cm, and length 2.5– 4.5 cm in SAK12 and SAK15, respectively. Microscopic description of the woods is given below.

Transverse Section (TS): Growth rings 0.5–3.0 mm in width, with distinct boundaries marked by 2–13 rows of thickwalled latewood tracheids. Latewood distinctive, earlywood/ latewood transition gradual or abrupt. No resin canals were observed. Tangential and radial diameters of tracheids are 35 (19–53) μm and 37 (18–58) μm in earlywood and 26 (15–34) μm and 10 (4–22) μm respectively, in latewood. Double wall thickness is 6 (2–10) μm in earlywood and 8 (3–12) μm in latewood, respectively ( Tab. 1). The number of tracheids between two rays is 2–14. Axial parenchyma abundant, diffuse, and seen in the latewood zone or in the transition to latewood area (Pl. 2, Figs 1, 2).

Tangential Longitudinal Section (TLS): Rays are uniseriate. Ray width is 12 (7–17) μm and height is 2–32 (mostly 5–14) cells, and 124 (20–507) μm ( Tab. 1; Pl. 2, Fig. 3). Transverse walls of axial parenchyma cells are smooth and slightly nodular (Pl. 2, Figs 4, 5).

Radial Longitudinal Section (RLS): Tracheidal pitting is 1–2(–3) seriate on the radial surface of tracheids (Pl. 2, Figs 7, 9). Crassulae slightly visible (Pl. 2, Fig. 7). Horizontal and end walls of rays are smooth (Pl. 2, Fig. 6). Cross-field pits are taxodioid and 1–6 pits in one horizontal row per cross-field (Pl. 2, Fig. 8).

C o m p a r i s o n. The studied woods show a clear latewood zone, gradual to abrupt transition from earlywood to latewood, smooth transverse walls of axial parenchyma cells and 1–3 rows of tracheid pits. We consider them as taxodioid wood. Anatomical features of the specimens are rather similar to Sequoioxylon from Turkey ( Özgüven-Ertan 1983, Akkemik et al. 2005, 2009, 2017, 2019, Akkemik and Sakınç 2013), and Taxodioxylon from Turkey ( Akkemik et al. 2009).

Regarding fossil species of Sequoioxylon and Taxodioxylon , many studies were carried out on these species (e.g. Greguss 1967, Özgüven-Ertan 1971, 1983, Yang and Zheng 2003, Erdei et al. 2009, Blokhina et al. 2010, Dolezych 2011, Iamandei et al. 2013, Koutecký and Sakala 2015, Tian et al. 2018) ( Text-fig. 5 ).

Blokhina et al. (2010) stated that the classification of these types of fossil woods is open to discussion. Some authors use “ Taxodioxylon ” and others “ Sequoioxylon ”. The name Taxodioxylon was used first by Hartig (1848) and was proposed for all woods of the tribe Sequoieae ( Sequoia ENDL. , Sequoiadendron J.BUCHHOLZ and Metasequoia HU et W.C.CHENG ), Taxodieae ( Taxodium RICH. ), and Cunninghamieae ( Athrotaxis D.DON. ). Subsequently, some authors used generic names (e.g. Biondi and Brugiapaglia 1991, Süss and Velitzelos 1997, Erdei et al. 2009). Alternatively, other authors (e.g. Greguss 1967, Basinger 1981, Özgüven-Ertan 1983, Blokhina 1986, 1997, Blokhina and Nassichuk 2000, Akkemik et al. 2005, 2009, Blokhina et al. 2010, Akkemik and Sakınç 2013) used the name Sequoioxylon only for the fossil wood showing affinity to the members of Sequoieae ( Sequoia , Sequoiadendron and Metasequoia ). Recently, Tian et al. (2018) again discussed taxodioid wood and suggested that the genus Sequoioxylon had been used for fossil woods showing wood anatomical characters of the modern representatives of Sequoioideae with traumatic resin canals, and Taxodioxylon for fossil woods without traumatic resin canals. In the light of this discussion, and the combination of the features given for these two fossil genera, we can consider our woods as Taxodioxylon .

The most common fossil species of Taxodioxylon is T. gypsaceum . In this fossil species, growth rings are generally variable, tracheids angular in cross-section, wide in earlywood, narrow in latewood, bordered pits 1–3 seriate, 15–20 µm in diameter, crassulae present, axial parenchyma abundant, horizontal walls of axial parenchyma smooth, rays uniseriate, up to 35 cells in height, cross-field pits predominantly taxodioid ( Van der Burgh and Meijer 1996, Koutecký and Sakala 2015). In contrast, T. taxodii GOTHAN has typical nodular thickening in the axial parenchyma transverse walls. Yang and Zheng (2003) stated that T. szei YANG et ZHENG had ray tracheids, nodular transverse walls in the axial parenchyma, and higher rays. Blokhina et al. (2010) commented on the absence of vertical traumatic resin canals, and presence of taxodioid type only, and larger number of cross-field pits, and 1–3 seriate tracheidal pitting in T. sizimanicum BLOKHINA. Blokhiana et al. (2010) summarized the features of Sequoioxylon laramense R.E.TORR. , S. montanense R.E.TORR. , S. dakotense R.E.TORR. and S. burgessii (PENH.) R.E.TORR. They have ray tracheids, nodular transverse walls in the axial parenchyma, very high rays with continuous biseriate ranges. Erdei et al. (2009) identified T. germanicum (GREGUSS) BURGH having 1–3 seriate vertical pits on the tracheid radial wall, the presence of crassulae, pits also recorded on tangential walls of tracheids, many cupressoid pits in cross-fields, uniseriate and occasionally biseriate rays.

The wood characters determined in this study are very similar to the characters of Taxodioxylon gypsaceum . Based on this findings, we considered our woods as T. gypsaceum . Van der Burgh and Meijer (1996) first discussed its possible botanical affinities as Athrotaxis (Sequoia) couttsiae (HEER) GARDNER , and later, Teodoridis and Sakala (2008) associated T. gypsaceum with Quasisequoia couttsiae HEER. It is generally associated with recent Sequoia sempervirens ENDL. (e.g. Dolezych 2011) as its nearest living relative ( Text-fig. 5 ).

Figures

Text-fig. 5. Distribution of Taxodioxylon gypsaceum in the Miocene (solid circles) and distribution (open circles) of its nearest representatives at present (Sequoia sempervirens, Sequoiadendron giganteum and Metasequoia glyptostroboides) (Eckenwalder 2009, Farjon 2010).