Glyptostrobus europaeus (BRONGN.) UNGER

Uhl, Dieter, Krüger, Pia S. & Wuttke, Michael, 2018, Epidermal Anatomy of Glyptostrobus Europaeus (Brongn.) Unger from The Late Oligocene of The Westerwald (Rhinelandpalatinate, W-Germany), Fossil Imprint (Poland) 74 (3 - 4), pp. 334-340 : 336-338

Glyptostrobus europaeus (BRONGN.) UNGER

Text-figs 2–3

S e l e c t e d s y n o n y m y. Only references which are important for nomenclature and refer to occurrences in the Westerwald or its direct vicinity; for more comprehensive lists of synonymies see LePage (2007) and Winterscheid et al. (2018).

1833 Taxodium europaeum BRONGN. , pp. 168–176.

1850 Glyptostrobus europaeus (BRONGN.) UNGER , pp. 434–435.

1851 Cupressites brongniartii GÖPP. ; Weber, p. 161.

1937 Glyptostrobus europaeus HEER ; Weyland, p. 74.

1997 Glyptostrobus sp. ; Müller, p. 46.

2011 Glyptostrobus europaeus (BRONGN.) UNGER ; Uhl et al., p. 121, fig. 4.

2006 Glyptostrobus europaeus (BRONGN.) UNGER ; Winterscheid, p. 74; pl. 18, fig. 1, pl. 22, fig. 8, pl. 23, fig. 9, pl. 24, figs 1– 2.

2014 Glyptostrobus europaeus (BRONGN.) UNGER ; Winterscheid and Kvaček, pp. 7– 8, pl. 1, figs 3–5, pl. 8, fig. 26, pl. 9, fig. 1.

2016b Glyptostrobus europaeus (BRONGN.) UNGER ; Winterscheid and Kvaček, pp. 117–118, pl. 1, fig. 7, pl. 4, fig. 2.

2017 Glyptostrobus europaeus (BRONGN.) UNGER ; Krüger et al., p. 68, pl. 1A–B.

2018 Glyptostrobus europaeus (BRONGN.) UNGER ; Winterscheid et al., pp. 124–125, pl. 4, figs 9–11.

M a t e r i a l. 38 twig remains of which 15 bear one or more cones at the end of the twigs (marked in bold): MMM- 2012-009, -018, -021, -022, -046, -049, -050, -053, -054, -057, -059 (SEM samples were taken from this specimen), -062, -063, -064, -065, -067, -076, -077, -080, -081, -082, -084, -085, -086, -088, -090, -093, -105, -107, -110, -113, -116, -121, -150, -156, -189, -196, -197.

D e s c r i p t i o n. Long slender twig fragments, with cupressoid needles, up to 3 mm long and up to 1 mm wide. 15 specimens bear one or more elliptical to obovate cones at the end of the twigs ( Text-fig. 2a–b ). Seed-scales elongated, flabellate, thinning-out towards the base and with semicircular (abraded?) apex ( Text-fig. 2b ).

Only abaxial cuticles could be analysed. Normal epidermal cells in stomata free zones ( Text-fig. 3a–b ) are usually elongated, orientated more or less parallel to the axes of the needles, 22–72 μm (average 39.8 μm) long and 9–24 μm (average 16.0 μm) wide. The length to width ratio of these cells is 1.3–5.2 (average 2.6). Stomatal complexes are elliptical, with (4–)5 subsidiary cells ( Text-fig. 2d–e ). The long-axis of the stomata are usually orientated oblique or parallel to the long axis of the needles ( Text-fig. 2c ). Outer walls of guard cells forming prominent lateral lamellae ( Text-fig. 2d–e ).

R e m a r k s. The taxon can be identified by the characteristic form and arrangement of the needles, together with the occurrence of typical cones attached to twigs (cf. Uhl et al. 2011, Krüger et al. 2017), however the finer details of the seed-scales could not be observed in this material (cf. Text-fig. 2b ). The form and arrangement of epidermal cells, as well as the stomatal complexes, clearly correspond to the published data for this taxon from other sites, as well as the only modern species G. pensilis (Tab. 1). Only small areas of the needle surfaces however could be analysed by means of SEM, due to incomplete splitting of the needles. Over all there is considerable variability in certain morphological features (e.g. size of epidermal cells), between cuticles from different fossil localities,

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ranging from Eocene up to Late Miocene, as well as in any comparison with modern G. pensilis (Tab. 1). However, as a number of cuticular features (such as cell size and orientation of stomatal complexes) varies considerably in modern G. pensilis , depending on needle type (linear, linear-subulate and scale-line [cuppressoid]), and even position within a needle (adaxial vs. abaxial) ( Ma et al. 2004) it is difficult to interpret the variability of fossil cuticles as most come from only a few (or even single) needles. Thus it is not clear whether the observed variability in the fossil taxon may reflect ecological, climatic or even evolutionary differences between different populations of G. europaeus .

Attempts to isolate cuticles of a number of plants species from the fossiliferous sediments of Norken using standard preparation techniques have so far been unsuccessful as the cuticles fragmented into rather small and taxonomically meaningless pieces during preparation ( Krüger et al. 2017). When looking at the in situ cuticles of Glyptostrobus from Norken it becomes obvious that this is due to the fact that the cuticles had already fragmented within the sediment ( Text-fig. 2c–d ). It is not clear whether this is due to long term diagenetic processes which affected the cuticles after deposition and before the material was mined or whether this is simply an effect of drying out and maybe oxidation after the material had been dumped on the spoil tips or even after it had been collected.

Figures

Text-fig. 2. Glyptostrobus europaeus from Norken. a) Overview of slab with twigs and two cones attached to twigs (MMM-2012-059). b) Cone exhibiting flabellate seed-scales (MMM-2012-022). c) SEM-image of the cuticle near the base of a needle (MMM-2012-059). d) Detail of c) showing stomata and fragmented cuticle. e) Detail of d) showing the cuticle around a single stomatal apparatus.

Text-fig. 3. SEM-images of Glyptostrobus europaeus from Norken. a) Detail of a split short shoot (MMM-2012-059). b) Detail of a), showing the apical part of a needle with stomatal-free zone and only a few stomata towards the base of the needle.