IAWAYin etJournal al. – Moroxylon 34 (2), 2013: from 169–176 China 169 FIRST RECORD Of MOROXYLON (MORACEAE) fROm THE NEOGEnE Of CHInA Ya-Fang Yin1, Xiao-Li Liu2 and Ye-Ming Cheng3,* 1Wood Anatomy and Utilization Group, Research Institute of Wood Industry, Chinese Academy of Forestry, No. 1 of Dongxiaofu, Haidian District, Beijing 100091, P.R. China 2Beijing Museum of Natural History, No. 126, Tianqiao St, Dongcheng District, Beijing 100050, P.R. China 3The Geological Museum of China, Xisi, Xicheng District, Beijing 100034, P.R. China *Corresponding author; e-mail: [email protected] abstract A new species of Moroxylon, M. xinhuaensis Yin, Liu & Cheng, with wood ana- tomical features found in modern Morus (Moraceae), is described from the Neogene of Xinhua, Yuanmou Basin, Yunnan Province, southwest China. This wood represents the first fossil wood ofMorus reported from Asia. It provides additional data for evaluating relationships between the Neogene floras of Europe and eastern Asia. Keywords: Fossil wood, Moroxylon, Morus, Neogene, Yuanmou. INTRODUCTION Morus, a genus of deciduous trees and shrubs with 16 species, is widespread across temperate areas of the northern hemisphere (U.S.A., Europe, Japan and China), and extends into tropical regions including the mountains of tropical Africa, Indonesia and South America (Zhou & Gilbert 2003). Species of Morus occur in various types of forest growing both at sea level and up to 2500 m altitude (Ter Welle et al. 1986a). In China, 11 species of Morus are widely distributed as the leaves are used to feed the commercially important silkworms and the mulberry fruit is extensively harvested for human consumption (Zhou & Gilbert 2003). Morus has a Tertiary fossil record indicating that it was once widely distributed throughout North America (U.S.A.), Europe (Czech Republic, Germany, Russia) and East Asia (China) (Collinson 1989; Liu et al. 1996). In this study, we describe a hitherto undescribed wood with similarity to Morus from the Neogene sediments of Yuanmou, Yunnan, China. MATERIALS AND METHODS The material described herein was collected from the Earth Forest near Xinhua Village, Yuanmou County, Yunnan Province, southwest China. The sediments of the Xinhua Earth Forest containing sandstone and clay belong to the lower part of the Yuanmou Formation with palaeomagnetic age about 3.4–2.5 Ma B.P. (Qian & Zhou 1991), a Late © International Association of Wood Anatomists, 2013 DOI 10.1163/22941932-00000014 Published by Koninklijke Brill NV, Leiden Downloaded from Brill.com10/04/2021 06:45:19AM via free access 170 IAWA Journal 34 (2), 2013 Pliocene equivalent of the Shagou Formation (Zhang et al. 1994). Vertebrate fossils also occur in the lower part of the Yuanmou Formation (Pan & Zong 1991). Two fossil wood species, Cedreloxylon cristalliferum (Cheng et al. 2006) and Lagerstroemioxylon yuanmouensis (Cheng et al. 2007), have been described from the Xinhua Earth Forest previously. The material was sectioned following the procedures for permineralised material outlined in Hass & Rowe (1999). Slides are deposited in the Geological Museum of China, Beijing. The thin sections were studied using a microscopic image analyzer (Olympus BX60 with DP72 digital collector). The wood was compared to slides of extant wood species housed in the Wood Collection of the Research Institute of Wood Industry, Chinese Academy of Forestry. Anatomical terms used in this paper follow the recommendations of the IAWA List of microscopic features for hardwood identification (IAWA Committee 1989). SYSTEMATIC DESCRIPTION Family: MORACEAE Genus: Moroxylon Selmeier 1993 Species: Moroxylon xinhuaensis Yin, Liu & Cheng, sp. nov. (Fig. 1) Specific diagnosis: Growth ring boundaries distinct. Wood ring porous to slightly semi-ring porous. Vessels in earlywood solitary and in radial or oblique multiples of 2 to 3, latewood vessels in clusters and in radial or oblique multiples of 2–5. Perfora- tion plates simple. Helical thickenings only in narrow vessels, along their entire length. Thin-walled tyloses common. Intervessel pits crowded, alternate, polygonal in outline. Vessel-ray and vessel-parenchyma pits similar to intervessel pits or large and elongate to oval with narrow borders. Parenchyma vasicentric, partly confluent, and marginal. Rays 1–10 cells wide, composed of procumbent body cells and 1–3 (mostly 1) marginal rows of square and/or upright cells. Holotype: P2323, specimen 18 cm long, 5 cm in width. Type locality: Xinhua Village, Yuanmou County, Yunnan Province, China. Lithostratigraphic horizon: Lower part of the Yuanmou Formation. Age: Pliocene. Etymology: The specific epithet is after the fossil locality. Repository: the Geological Museum of China, Beijing, China. Description Wood ring porous to occasionally slightly semi-ring porous. Growth rings distinct, marked by a change in vessel diameter and distribution from the latewood to the early- wood of subsequent rings, and marginal parenchyma. Narrow growth rings with one row of earlywood pores, wide growth ring with several rows of earlywood pores. → Figure 1. Moroxylon xinhuaensis Yin, Liu & Cheng, sp. nov. (Moraceae) (P 2323). – A: TS, distinct growth rings, ring porous to semi-ring porous wood, vessels predominantly solitary in earlywood and mostly in radial multiples and clusters in latewood. – B: TS, vessel clusters in latewood, vasicentric parenchyma (upper arrows) and marginal parenchyma (lower arrows). – Downloaded from Brill.com10/04/2021 06:45:19AM via free access Yin et al. – Moroxylon from China 171 C: TLS, alternate intervessel pits with lens-shaped apertures and coalesced pit apertures (ar- row). – D: RLS, helical thickenings in vessel elements. – E: RLS, heterocellular rays, abundant tyloses (arrow) in vessel members. – F: RLS, vessel-parenchyma pits. – G: TLS, multiseriate rays. — Scale bars: 500 μm in A; 200 μm in B, F, G; 20 μm in C, D, E. Downloaded from Brill.com10/04/2021 06:45:19AM via free access 172 IAWA Journal 34 (2), 2013 Vessels in earlywood either solitary or in radial to oblique multiples of 2 to 3, circular to oval in cross section; mean tangential diameter of solitary vessels 235 µm (range 180–296 µm), mean radial diameter of solitary vessels 299 µm (range 210–400 µm). Latewood vessels in radial or oblique multiples of 2–5, or clusters. Vessel frequency in the latewood 8–17/mm2. Perforation plates simple. Intervessel pits alternate, round to polygonal, 8–13 µm in diameter, pit apertures lens-shaped, sometimes coalescing. Helical thickenings present along the whole length of the narrow vessel elements. Mean vessel element length 243 µm (range 155–305 µm). Vessel-ray and vessel-parenchyma pits either similar to intervessel pits or large and elongate to oval with narrow borders. Thin-walled tyloses common. Axial parenchyma vasicentric, partly confluent, and marginal. Rays 2–4/mm, 1–10-seriate, mostly 6–10-seriate, uni- and biseriate rays few. Multiseriate rays 272–1382 µm (mean 678 µm) high and 30–127 µm (mean 75) wide; composed of procumbent body cells with 1–3 (mostly 1) marginal rows of square or upright cells. DISCUSSION Comparison with extant woods The diagnostic characters of this fossil, namely ring porous to slightly semi-ring porous wood, vessels solitary and in radial or oblique multiples or clusters, simple per- foration plates, alternate intervessel pits, helical thickenings in narrow vessels, vessel- ray pits similar to intervessel pits with narrow borders or simple, abundant thin-walled tyloses, vasicentric to partly confluent parenchyma, and heterocellular rays, indicate its affinities are with Moraceae (Tippo 1938; Metcalfe & Chalk 1950; Ter Welleet al. 1986a, b; Cheng et al. 1992; Wheeler 2011; InsideWood 2004-onwards). The present-day ring porous Moraceae woods compared to the fossil include species of Maclura Nutt., Broussonetia Orteg. and Morus L. (Tippo 1938; Koek-Noorman et al. 1984a, b, c; Ter Welle et al. 1986a, b). The difference between Maclura and the fossil lies in the presence of some homocellular rays and long crystalliferous parenchyma strands in Maclura (Fig. 2A–D), which are absent from the fossil (Fig. 1A–H). Brous- sonetia and Morus differ in ray pattern and parenchyma. Ring porous species of Broussonetia have rays with 1–4 marginal cells, scanty paratracheal parenchyma, occasionally aliform with short wings, and in initial bands up to 20 cells wide (Fig. 2E–H), and multiseriate rays measure up to 410–510 µm high and 3–5(–7) cells wide (Fig. 2F, G). Rays in Morus have exclusively one row of upright or square marginal cells, but are similar to the fossil in being mostly 4–6 cells wide and measuring up to 425–1100 µm high (Ter Welle et al. 1986a). Parenchyma is both paratracheal, vary- ing from vasicentric to aliform-confluent and in confluent wavy bands, and apotracheal parenchyma arranged in marginal bands (Ter Welle et al. 1986a; Cheng et al. 1992). Comparison with fossil woods To date (Gregory et al. 2009; Franco 2010), six genera for fossil woods of the Mora- ceae have been erected: Myrianthoxylon Koeniguer, Ficoxylon Kräusel, Cudranioxy- lon Dupéron-Laudoueneix, Artocarpoxylon Mehrotra, Prakash & Bande, Moroxylon Downloaded from Brill.com10/04/2021 06:45:19AM via free access Yin et al. – Moroxylon from China 173 Selmeier, and Soroceaxylon Franco. One Miocene Mexican fossil wood was placed in the modern genus Maclura (Martinez-Cabrera & Cevallos-Ferriz 2006). Except for Maclura martinezii (Martinez-Cabrera & Cevallos-Ferriz 2006) and Moroxylon Figure 2. Wood of modern Maclura and Broussonetia. – A, B: Maclura tricuspidata Carrière (CAFw 8299); C, D: Maclura pubescens (Trécul) Zhou et Gilbert (CAFw 17124, Guangdong, China); E, F, G, H: Broussonetia papyrifera (L.) L’Hér. ex Vent. (CAFw 6656, Jiangsu, China). – A, C, E: TS, showing distinct growth rings, ring porous wood, vessel arrangement, and paren- chyma. – B: TLS, long crystalliferous parenchyma strands. – D: RLS, homocellular rays. – F, G: TLS, multiseriate rays. – H: RLS, showing heterocellular rays. — Scale bars: 500 μm in A, C, E; 200 μm in F; 100 μm in D, G, H; 50 μm in B.