Alnus tschemrylica BLOKHINA et SNEZHKOVA

Koutecký, Vít & Sakala, Jakub, 2015, New Fossil Woods From The Paleogene Of Doupovské Hory And České Středohoří Mts. (Bohemian Massif, Czech Republic), Acta Musei Nationalis Pragae Series B 71 (3 - 4), pp. 377-398 : 383-384

Alnus tschemrylica BLOKHINA et SNEZHKOVA

Pl. 3, Fig. 5–8, Text-fig. 10

1999 Alnus tschemrylica BLOKHINA et SNEZHKOVA , p. 468, fig. 1a–o.

M a t e r i a l: Vrbice 91/04, 92/04, 93/04, 97/04.

D e s c r i p t i o n. Wood is diffuse-porous ( Text-Fig. 10 ); growth rings are distinct and 1–4.8 mm wide.

Vessels: Occasionally solitary (20–25%), mostly in radial multiples of 2–7 and clusters, rarely in tangential multiples of 2; solitary pores oval to angular, radially elongated. Tangential diameter 14–45–77 µm, radial diameter 28–119 µm; pore density ranges from 110 to 160 per square mm. Perforation plates scalariform, with 18–24–29 bars; intervessel pits alternate and opposite.

Rays: Homocellular, two types: 1) mostly uniseriate occasionally biseriate, composed exclusively of procumbent cells, and 2) large aggregate.

Axial parenchyma: Not observed.

Fibres: Not observed.

D i s c u s s i o n. All features (diffuse porous wood, very small vessels, scalariform perforation plates with many bars, very thin rays as well as large aggregate rays) indicate that our wood belongs to the subfamily Betuloideae of Betulaceae ( Hall 1952) .

In the subfamily Betuloideae , there are two anatomically similar genera: Betula and Alnus . The difference between these genera cannot be generalized, but the presence of predominantly uniseriate rays together with aggregate rays is rather typical of Alnus ( Hall 1952) . Moreover, our wood shows small tangential diameter of vessels, and alternate arrangement of intervessel pits. All the above-mentioned features point to the genus Alnus .

There are only a few fossil woods attributed to Alnus or Alnoxylon so far: Alnus latissima WHEELER et al. , A. scalariforme SRIVASTAVA et SUZUKI , A. tschemrylica BLOKHINA et SNEZHKOVA and Alnoxylon vasculosum FELIX emend. MÜLLER-STOLL et MÄDEL.

A. latissima ( Wheeler et al. 1977) and A. scalariforme ( Srivastava and Suzuki 2001) have fewer bars in their perforation plates, and only uniseriate rays. Alnoxylon vasculosum is according to Srivastava and Suzuki (2001) similar to A. scalariforme , but it has no scalariform perforation plates. Our wood shows the greatest similarity with Alnus tschemrylica ( Blokhina and Snezhkova 1999) . This fossil species has occasionally biseriate rays and scalariform perforation plates with up to 30 bars. We designate our wood type 5 as Alnus tschemrylica .

Fossil leaves and fruits of Alnus are described from the Tertiary of north-western Bohemia as A. gaudinii (HEER) E. KNOBLOCH et KVAČEK , A. kefersteinii (GÖPPERT) UNGER and A. rostaniana SAPORTA from the České středohoří Mts. (e.g., Kvaček and Walther 2004, Akhmetiev et al. 2009). The first author of this contribution found several fossil leaves directly at Vrbice, which were later identified by Z. Kvaček (pers. comm. 2014) as Alnus sp.

Figures

Text-fig. 10. Schema of transversal section of A. tschemrylica (sample 97/04). v – vessel, r – ray, ar – aggregate ray, grb – growth-ring boundary.