Middle Eocene (Bartonian) Ficus from Monte Di Malo (Vicenza - Italy)
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IAWA Journal, Vol. 31 (3), 2010: 353–362 MIDDLE EOCENE (BARTONIAN) FICUS FROM MONTE DI MALO (VICENZA - ITALY) Mauro Bernabei1, Bernardetta Pallozzi2, Loris Ceccon3, Paolo Mietto4 and Guido Roghi5 SUMMARY The Middle Eocene (Bartonian, ~ 40 Ma) deposits of the Lessini Moun- tains in the Veneta region are well-known for their well-preserved fossil plants which have been studied since the XVII century. A fossil wood sample recently found in the Val Matta area, in the Municipality of Monte di Malo (Vicenza, Italy), is described. This piece of wood has anatomical characteristics that occur in the extant genus Ficus of the Moraceae, and it is Europe’s oldest known wood of the genus. Key words: Moraceae, Ficus sp., Ficoxylon, fossil wood, Bartonian Age, Middle Eocene, Italy. INTRODUCTION The Lessini shelf formed during the Eocene as a result of repeated volcanic activity (Bosellini 1989). It was rich in freshwater environments and vegetation, as testified by the rather common discovery of fossil leaves, fruit, seeds, branches, and wood (Mietto 1992). The earliest studies of the fossil plants of this region date back to the XVII century. The rich fossil Eocene flora in this area mainly comes from the lo- calities of Fosse di Novale (Squinabol 1901) and Muzzolon (Massalongo 1858, 1859; Meschinelli & Squinabol 1892; Fabiani 1915). Additionally, in the Pisciolone Valley near Monte di Malo, fragments of fossil lauraceous wood and a conifer cone have been found (Omboni 1892; Pedron 1991). The objectives of this paper are to 1) describe the anatomy of a fossil wood dis- covered in the Val Matta area (Fig. 1), in the Municipality of Monte di Malo (Vicenza, Italy); 2) determine the sample’s systematic affinities; 3) compare the characteristics of this fossil wood with those of other finds, such as leaves and fruit, from nearby fos- 1) CNR-IVALSA, Trees and Timber Institute, San Michele all’Adige, TN, Italy — Corresponding author [E-mail: [email protected]]. 2) Museo Civico “D. Dal Lago”, Corso Italia 63, 36078 Valdagno, VI, Italy [bernardetta.pallozzi@ alice.it]. 3) Via Cristoforo 14, 36015 Schio, VI, Italy – Centro Studi del Priaboniano, Via Chiesa, 36034 Pri- abona, Monte di Malo, VI, Italy [[email protected]]. 4) Dipartimento di Geoscienze, Università degli studi di Padova, via Giotto 1, 35137 Padova, VI, Italy [[email protected]]. 5) Istituto di Geoscienze e Georisorse – CNR, via Matteotti 55, 35137 Padova, Italy [guido.roghi@ igg.cnr.it]. Downloaded from Brill.com09/27/2021 04:23:33PM via free access 354 IAWA Journal, Vol. 31 (3), 2010 Figure 1. Location where the examined specimen was found ( ) (Vicenza, Italy). sil plant locations and 4) offer a general interpretation of the ancient landscape of this area, based on the climatic and ecological requirements of the fossil’s nearest living relatives and its anatomical characteristics. GEOLOGICAL CONTEXT The fossil wood sample that is the subject of this study was found in Middle Eocene volcanodetritic levels in the Matta Valley (Beccaro 2003) (Fig. 2). The Matta Valley succession consists of silty marls, whose upper parts are inserted between pelitic and volcanodetritic layers. On the basis of lithological analogy and stratigraphic position, this succession can be ascribed to the “Roncà horizon” (former Vulcaniti di Roncà), whose age is hypothesized as being towards the end of the Lutetian and the beginning of the Bartonian Age, some forty million years ago (Mietto 1992). MATERIALS AND METHODS The sample (catalogue number CSP 67, an abbreviation of the Priabonian Centre of Studies) is currently located at the Museum of Fossils “Munier-Chalmas and De Lap- parent” of Monte di Malo (Vicenza). It is a stem fragment that is 19.6 cm long, 8.6 cm wide and 7.9 cm thick. In some regions the sample is compressed and deformed. Ground thin sections of cross, radial and tangential sections were prepared and photographed using an Olympus C7070 digital camera and an Olympus CX41 microscope. Vessel frequency was calculated by counting elements in 15 areas, whereas other anatomical characteristics were determined by averaging 25 measurements. Measure- ment techniques and the terminology used generally follow the guidelines of an IAWA Committee (1989). “Image Tool” software was used to measure elements. The relation- Downloaded from Brill.com09/27/2021 04:23:33PM via free access Bernabei et al. — Eocene Ficus from Italy 355 Legends Hyaloclastite basalt Volcanogenis sandstone Fine-grained limestone Silty marl Black clay Mineralized wood Seed Carbon fragments Plant remains Molluscs V o l c a n i s d t e f R à g e A u t e i a n / B r o L Figure 2. Stratigraphic section of Val Matta (Monte di Malo, Vicenza, Italy) (translated from Beccaro 2003). ship of the fossil to extant plants was assessed using information from Metcalfe and Chalk (1950), Ilic (1987, 1991), the Intkey programme (Dallwitz et al. 2000; Richter & Dallwitz 2002) and InsideWood (2004–onwards). RESULTS Anatomical description Growth rings absent. Wood diffuse-porous, vessels solitary, in short radial multiples, and occasional irregular clusters formed contiguous radial multiples (Fig. 3A, B); vessel frequency on average two per mm2; isolated vessels round or oval in outline, with an average tangential diameter of 165 µm (ranging from 78–261 µm) and an average radial diameter of 174 µm (ranging from 87–334 µm). Vessel element lengths average 430 Downloaded from Brill.com09/27/2021 04:23:33PM via free access 356 IAWA Journal, Vol. 31 (3), 2010 A 500 µm B 200µm C D 50 µm A 200 µm B E 200 µm F 500 µm Figure 3. – A & B: Diffuse-porous wood, vessels solitary and in short radial multiples, axial paren- chyma bands 6–8 cells wide, transverse sections. – C & D: Heterocellular rays with procumbent body cells and marginal rows of square/upright cells, radial section. – E & F: Rays commonly 3–5-seriate. Average ray height 15–30 cells. Perforation plates simple, tangential sections. µm (ranging from 281–511 µm). Perforation plates simple. Vessel pits alternate, oval to polygonal in outline with an average diameter of 12 µm (ranging from 8–15 µm). Vessel–ray pits simple or with a reduced margin. Tyloses not obvious; thin-walled if present. Fibres non-septate, with thin walls, which is probably due to wood decay prior to fossilization. Uniseriate rays rare, rays usually 3–5-seriate (Fig. 3C–E); heterocellu- lar with procumbent body cells and 1 or 2 rows of square or erect marginal ray cells (Fig. 3D). Crystals and radial latex tubes not found. Average height of the rays: 25 cells, Downloaded from Brill.com09/27/2021 04:23:33PM via free access Bernabei et al. — Eocene Ficus from Italy 357 ranging from 15 to 40, 660 (413–1020) µm; width 54 (28–86) µm. Axial parenchyma abundant, arranged in regular, tangential bands 6–8 cells wide, with about one band per mm making up 30–40% of the wood’s cross-sectional surface (Fig. 3A, B). All measurements of the anatomical elements may be affected by the severe deformation of the wood. Occasional isolated axial parenchyma cells. DISCUSSION AND CONCLUSIONS The distinctive characteristics of our sample include: low vessel density (~2/mm2), wide parenchyma bands, vessel–ray parenchyma pits with reduced borders, rare uniseriate rays and heterocellular 3–5-seriate rays. These anatomical characteristics indicate a relationship with the Moraceae family (Metcalfe & Chalk 1950; Koek-Noorman et al. 1984; Ilic 1987, 1991; InsideWood 2004). Our sample was further compared with fossil and modern Moraceae genera (Gregory et al. 2009; InsideWood 2004). Today there are some 38 genera and 1150 species of Moraceae (Mabberley 2008). Comparison with modern woods Amongst modern species, the Monte di Malo specimen strongly resembles the genus Ficus (Koek-Noorman et al. 1984; InsideWood 2004). The genus Ficus can be distinguished from other Moraceae by the presence of a few relatively large vessels, tangential parenchyma bands of 3–15 cells wide and mostly non-septate libriform fibres, with some sporadically septate ones (Koek-Noorman et al. 1984). The wide parenchyma bands, which in some samples may represent about 40% of the axial tis- sue, are rarely found in other Moraceae genera (Koek-Noorman et al. 1984; Martinez- Cabrera & Cevallos-Ferriz 2006; Martinez-Cabrera et al. 2006). Other genera within the same family that have a relatively large amount of axial parenchyma arranged in bands are Clarisia, Parartocarpus and Morus. However, parenchyma bands in Morus and Clarisia are 2–4 cells wide (ter Welle et al. 1986a, b), in Parartocarpus they are 3–4 cells wide (ter Welle et al. 1986b). Thus we suggest this Bartonian age wood is related to the genus Ficus. At present, the genus Ficus consists of 800–900 species that are found in all five con- tinents and are characterized by a great variety of growth forms, including trees, shrubs and climbers, in habitats ranging from tropical rain forests to desert-like conditions and savannahs (Koek-Noorman et al. 1984; Mabberley 2008; Abasolo et al. 2009). In spite of this diversity in growth form and wide distribution, the wood anatomy of Ficus is so homogeneous that Koek-Noorman et al. (1984) gave a single wood-anatomical description for the entire genus. Furthermore, according to the same authors, there is no relationship between the anatomical characteristics and the geographical distribu- tion of Ficus species. The wood-anatomical uniformity within the genus Ficus is one reason we are not establishing a new species for this wood. Comparisons with fossil Moraceae woods There are only a few fossil woods that have been attributed to the Moraceae, fewer than ten genera and about thirty species, most being species of Ficoxylon (Gregory et al.