FOSSIL WOODS from the PALAEOGENE of NORTHERN KYUSHU, JAPAN Rashmi Srivastava1 & Mitsuo Suzuki2 This Paper Describes

Home , Fossil wood, Fukuoka Prefecture, Northern Kyushu, Rhus coriaria

IAWA Journal, Vol. 22 (1), 2001: 85–105

MORE FOSSIL WOODS FROM THE PALAEOGENE OF

NORTHERN KYUSHU, JAPAN by Rashmi Srivastava1 & Mitsuo Suzuki2

SUMMARY

This paper describes five species of dicotyledonous fossil wood from the lower Oligocene Tsuyazaki Formation in Tsuyazaki, Fukuoka Pre- fecture, northern Kyushu: Rhus palaeojavanica (Anacardiaceae), Alnus scalariforme (Betulaceae), Hamamelis prejaponica (Hamamelidaceae), Magnoliaceoxylon palaeogenica (Magnoliaceae) and Sonneratia kyushuensis (Sonneratiaceae). This brings the number of species described from the Tsuyazaki locality to 19. Among these 19 species modern equivalents of all species, except for Sonneratia, occur in temperate to subtropical forests. Sonneratia is found today in mangrove vegetation of tropical to subtropical regions. The presence of Sonneratia may suggest a warmer climate in Kyushu during the early Oligocene. Key words: Rhus, Alnus, Hamamelis, Sonneratia, Magnoliaceae, Palaeo- gene, Oligocene, fossil wood, Japan.

INTRODUCTION

Palaeogene strata with fossil woods are widely distributed in northern Kyushu, Ja- pan. The abundant occurrence of large fossil trunks has attracted public and scien- tific attention, and these fossil woods have been studied since 1932. To date two taxodiaceous and 17 dicotyledonous woods have been described from six localities (Table 1). The Tsuyazaki locality is especially rich in fossil woods. At a bluff on the foreshore in Tsuyazaki, Fukuoka Prefecture (Fig. 1), numerous fossil woods are found in volcanic sediments of the lower Oligocene Tsuyazaki Formation. Many pebbles of fossil wood are found in the gravel foreshore in front of the bluff. As there are no other sediments that bear fossil woods in the Tsuyazaki area (Okada & Obata 1964), it is believed that all specimens are derived from the Tsuyazaki Formation. Woods reported from Tsuyazaki include one taxodiaceous conifer (Watari 1966) and 13 dicotyledons representing 10 families (Table 1) (Suzuki 1975, 1976, 1982, 1984; Terada & Suzuki 1998). All have distinct growth-ring boundaries; some (Cas- tanea protoantiqua, Fraxinus oligocenica, Hovenia paleodulcis and Wataria oligocenica) are ring-porous. Modern equivalents of these fossil species are distributed in

1) Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226 007, India. 2) Botanical Garden, Faculty of Science, Tohoku University, Kawauchi, Aoba, Sendai 980- 0862; Photodynamics Research Center, The Institute of Physical and Chemical Research (PDC-RIKEN), Aoba, Sendai 980-0868, Japan.

Downloaded from Brill.com10/05/2021 05:26:07PM via free access 86 IAWA Journal, Vol. 22 (1), 2001 Srivastava & Suzuki — Palaeogene woods from Japan 87 References 1966 Watari 1966 Watari Suzuki 1982 Suzuki 1982 1943 Watari Ogura 1932b; Mädel 1962 & Kuroda 1949 Watari Suzuki 1976 Suzuki & Ohba 1991 Ogura 1932a Suzuki & Ohba 1991 Suzuki 1976 Suzuki 1975 Suzuki 1982 Suzuki 1976 Suzuki 1982 Suzuki 1984 Suzuki 1984 Suzuki 1984 Suzuki 1984 Suzuki 1976 & Suzuki 1998 Terada

Geological age Palaeogene Palaeogene Lower Oligocene Lower Oligocene Palaeogene Palaeogene Palaeogene Lower Oligocene Eocene Palaeogene Palaeogene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene Lower Oligocene

Loc.* 1 2 2 2 3, 4 5 2 6 3 2 2 2 2 2 2 2 2 2 2

Familiy Taxodiaceae Taxodiaceae Aceracae Cornaceae Euphorbiaceae Euphorbiaceae Fagaceae Fagaceae Fagaceae Fagaceae Fagaceae Magnoliaceae Nyssaceae Oleaceae Platanaceae Rhamnaceae Rosaceae Rosaceae Rosaceae Rosaceae Sterculiaceae Sterculiaceae

Ohba

Suzuki

Suzuki et H.

(Ogura) Mädel Ohba

Table 1. Fossil woods from the Palaeogene of northern Kyushu, Japan. Table Ogura (Ogura) M.

Suzuki et H.

Suzuki

M. Suzuki Suzuki) K. Terada et M. Terada Suzuki) K.

Suzuki Suzuki M.

Suzuki

Suzuki Ogura Gothan M.

Suzuki Suzuki Suzuki (M.

Suzuki

Suzuki M. M. Watari Suzuki

M. Suzuki M. M. M.

M. M. M. Watari et Kuroda Watari M.

Paraphyllanthoxylon pseudohobashiraishi Lithocarpoxylon hobashiraishi oligocenica Wataria = = = Localities: 1: Four localities in Fukuoka Prefecture and one locality in Nagasaki Prefecture — 2: Munakata Tsuyazaki, Fukuoka County, Prefecture — 3: Najima, Fukuoka Fukuoka Fukuoka Prefecture Prefecture City, City, — — 5: 4: Tobata Koinoura, Nagasaki Nishisonogi Prefecture County, — Fukuoka Prefecture. 6: Isozakihana, Shingu, Kasuya County, Botanic name matsuiwa Taxodioxylon sequoianum Taxodioxylon Acer palmatoxylum Cornus tsuyazakiensis Phyllanthinium pseudohobashiraishi Castanea antiqua Castanea protoantiqua Lithocarpoxylon radiporosum hobashiraishi Quercinium Michelia oleifera Camptotheca kyushuensis Fraxinus oligocenica Platanus tsuyazakiensis Hovenia paleodulcis Prunus ascendentiporulosa Prunus paleozippeliana Prunus polyporulosa Prunus uviporulosa Reevesia oligocenica *)

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temperate to subtropical areas. In order to obtain a better understand- ing of the palaeoclimate and phyto- geography of the northern Kyushu region, additional silicified fossil woods from Tsuyazaki have been collected and studied. This paper describes five new fossil woods that resemble woods of extant Rhus, Alnus, Hamamelis, Magnolia or Michelia, and Son- neratia.

Fig. 1. Fossil wood locality of Tsuya- zaki and other two localities around Fukuoka City, northern Kyushu.

MATERIALS AND METHODS

The fossil locality is on the foreshore of a small peninsula, Tsuyazaki, Munakata County, Fukuoka Prefecture (130° 26' E, 33° 48' N). The silicified woods were em- bedded in tuffaceous sediments of the lower Oligocene Tsuyazaki Formation (Sakai 1994) that form the bluff on the peninsula (Okada & Obata 1964). Materials were collected from both the bluff sediments and from among pebbles of the gravel foreshore in front of the bluff. Transverse, tangential and radial sections were cut by a diamond saw and ground with polishing powder (Carborundum #150 and #400 on iron disk; aluminum #800 and #2000 on glass disk) to obtain thin sections. For a few fossils cellulose acetate peels (Bioden R.F.A., 0.034 mm in thickness) were made after etching the surfaces of fossil woods for 2–4 minutes with c. 1N-hydrofluoric acid followed by thorough washing. Slides of all specimens, including the type specimens, have been deposited in the Botanical Garden, Tohoku University, Sendai, Ja- pan (TUSw). For identification, the fossil woods were compared with slides in a col- lection of c. 1600 extant species of c. 120 dicotyledon families deposited in TUSw (mainly Japan, East Asia and the Northern Hemisphere), with the microscopic photo- graph library of TUS, and descriptions in literature (for example, Kanehira. 1926; Pearson & Brown 1932; Metcalfe & Chalk 1950; Panshin & De Zeeuw 1980; Chang et al. 1992).

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SYSTEMATIC DESCRIPTIONS Anacardiaceae Rhus palaeojavanica sp. nov. — Fig. 2 Material — No. 71152 (holotype) and 71195. Two small pebbles of silicified wood, both twigs with pith and primary xylem. The radius of the holotype (from pith to periphery) is 27 mm. Description — Growth rings distinct, 1.8–3.1 mm wide. Wood semi-ring-porous (Fig. 2a, b). In the earlywood, vessels are arranged in 4 or 5 layers or more; mostly solitary, sometimes in radial multiples of 2 or 3; solitary vessels circular to oval in cross section with thick (c. 3.3 μm) walls; widest solitary vessels are located at the beginning of the growth rings, average tangential diameter 150 μm, average radial diameter 200 μm. Latewood vessels narrow, minimum 20 μm in tangential diameter; solitary and in radial multiples of 2 or 3; walls c. 3 μm thick. Vessel elements short, 200–350 (average 270) μm long with horizontal to oblique end walls; perforation plates mostly simple (Fig. 2c), rarely scalariform with 1–6 bars in smaller latewood vessels (Fig. 2c–f). Intervessel pits alternate, hexagonal, with linear apertures, 8–10 μm in diameter (Fig. 2i); spiral thickening not observed. Tyloses abundant. Non-septate fibres polygonal in cross section, 15–20 μm in diameter; walls c. 3–4 μm thick; interfibre pits not observed. Axial parenchyma sparse, vasicentric usually as a uniseriate layer; terminal, 1 or 2 cells wide (Fig. 2a, b); cells polygonal to rectangular in cross section, 20–25 μm in diameter, 50–80 μm long; vessel-parenchyma pits not observed, crystals not observed. Rays narrow, 1–3- (mostly 2–3-)seriate (Fig. 2g), heterocellular (Fig. 2h); 3–70 cells (60–1300 μm) tall; 6–9 (average 8) rays per mm; uniseriate rays composed of upright cells only or both upright and procumbent cells; upright cells 25–60 μm in height and 20–30 μm in radial length (RLS); procumbent cells 15–20 μm in height and 35–75 μm in radial length (on RLS); vessel-ray pits simple, horizontally elongated, elliptical to circular and 8–20 μm in diameter; numerous; a few ray cells with small crystals. Pith flecks are present as small to large patches (c. 100–500 μm in tangential diameter) of irregularly shaped parenchymatous cells especially in the latewood zone (Fig. 2a, b). Affinity — The combination of semi-ring-porous wood, narrow to medium-sized thick-walled vessels with mostly simple perforation plates, simple vessel-ray parenchyma pits, non-septate fibres, and 1–3-seriate heterocellular rays in our fossil wood

Fig. 2. Rhus palaeojavanica sp. nov. (holotype no. 71152) – a: TS, semi-ring-porous wood with a pith fleck (arrow). – b: TS, same section magnified showing vessel distribution and pith fleck (arrow). – c: RLS, simple perforation plate and scalariform perforation plate with one bar. – d: RLS, scalariform perforation plate with one bar. – e: RLS, scalariform perforation plate with five bars. – f: RLS, scalariform perforation plate with six bars. – g: TLS, heterocellular rays and paratracheal parenchyma strands (arrow). – h: RLS, heterocellular rays and circular vessel-ray pits (arrow). – i: TLS, alternate, hexagonal intervessel pits with horizontally long apertures . — Scale bar in a; for a = 250 μm; for b & g = 100 μm; for c, d, e, f & i = 25 μm; for h = 50 μm.

Downloaded from Brill.com10/05/2021 05:26:07PM via free access 90 IAWA Journal, Vol. 22 (1), 2001 Srivastava & Suzuki — Palaeogene woods from Japan 91 indicates its affinities with the genusRhus L. of the Anacardiaceae. Subgenus Toxico- dendron of Rhus is excluded because it has septate fibres. The Kyushu fossil woods have some scalariform perforation plates with few bars in narrow vessels. This character is very rare among extant Rhus. Terrazas (1994) noticed the rare occurrence of four-barred perforation plates in Rhus coriaria L. during her observation on 26 Rhus species. We found a very rare occurrence of one-barred plates in very narrow vessels of R. javanica L. deposited in TUSw. Although scalariform perforation plates are more frequent and their bar number is more in the Oligocene fossil wood than in the extant species, other characters agree with the extant Rhus. Examination of wood of the extant species Rhus ambigua Lavallée ex Dippel, R. chinensis Mill., R. integrifolia Benth. & Hook. f ex S.Wats., R. javanica L., R. potanini Maxim., R. punjabensis J.L. Stew. ex Brand. var. sinica (Diels) Rehd. & Wils., R. tri- chocarpa Miq., Toxicodendron succedaneum (L.) O. Kuntze (=Rhus succedanea L.), and T. sylvestre (Sieb. & Zucc.) O. Kuntze (= Rhus sylvestris Sieb. & Zucc.) (Kanehira 1926; Metcalfe & Chalk 1950; Chang et al. 1992) shows that the fossil wood has closest anatomical similarity to R. javanica, except for the frequency and bar number of scalariform perforation plates. Four fossil woods suggested to have affinities withRhus are known. Three species of the genus Rhoidium Unger, namely, R. juglandifolia Wall. ex Don, R. ungeri Marclin, and R. philippense Orie were reported with very brief descriptions and without illus- trations (Unger 1850). Therefore it is not possible to compare our samples with them or to ascertain whether they have any affinity with Rhus. Wheeler et al. (1978) described an Eocene wood, Rhus crystallifera, from Yellowstone National Park, USA, which has closest anatomical affinities with subgenus Toxicodendron. This species can be distinguished from our fossil wood in having exclusively simple perforation plates, septate fibres and 1- or 2-seriate rays with large crystalliferous cells. Because of this there is no fossil Rhus wood similar to the Kyushu wood, and, consequently, we describe it as Rhus palaeojavanica sp. nov., the specific epithet indicating its similarity to R. javanica. The genus Rhus L. consists of about 150 species distributed in temperate and tropical regions of the world, with five species found in Japan. Rhus javanica is a small deciduous tree commonly found in the lowlands, hills and mountains of Japan, Korea, from China to Malaysia, and in the Himalayas (Ohwi 1965).

Betulaceae Alnus scalariforme sp. nov. — Fig. 3 Material — No. 71104 (holotype) is a slender silicified trunk with pith (c. 15 cm in diameter). Description — Growth rings distinct, wide (1.9–5.9 mm), undulating and demarcated by 2- or 3-seriate bands of tangentially flattened parenchymatous cells and fibres (Fig. 3a, b). Wood diffuse-porous (Fig. 3a). Vessels numerous, 110–180 (average 160) per square mm; evenly distributed; solitary and in multiples of 2–6 (Fig. 3b); small,

Fig. 3. Alnus scalariforme sp. nov. (holotype no. 71104) – a: TS, diffuse-porous wood with undulating growth ring boundary. – b: TS, same section magnified, showing vessel multiples, fibres and diffuse-in-aggregate axial parenchyma (arrows). – c: TLS, alternate to opposite

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intervessel pitting. – d: TLS, scalariform intervessel pitting. – e: TLS, uniseriate and aggregate rays. – f: RLS, homocellular rays of procumbent cells. – g: RLS, scalariform perforation plates. — Scale bar in a; for a & e = 250 μm; b & f = 100 μm; for c, d, & g = 25 μm.

Downloaded from Brill.com10/05/2021 05:26:07PM via free access 92 IAWA Journal, Vol. 22 (1), 2001 Srivastava & Suzuki — Palaeogene woods from Japan 93 tangential diameter 25–75 (average 50) μm, radial diameter 25–90 (average 59) μm. Vessel elements 480–890 (average 605) μm long; end walls oblique; perforation plates exclusively scalariform with 15–26 (average 20) bars (Fig. 3g). Intervessel pits mostly alternate, hexagonal, bordered with linear apertures (Fig. 3c), sometimes opposite and rarely scalariform (Fig. 3d). Non-septate fibres polygonal or tangentially flattened in cross section, 15–30 μm in diameter; walls 3–4 μm thick, small pits sparsely arranged on radial walls. Axial parenchyma sparse, diffuse and diffuse-in-aggregate (Fig. 3b); cells tangentially flattened in cross section, 15–20 μm in diameter and 60–90 μm long. Rays uniseriate and aggregate (Fig. 3e). Uniseriate rays 11–18 (average 15) per mm; homocellular, composed wholly of procumbent cells (Fig. 3f); 2–24 cells or 50–600 μm high; ray cells 15–25 μm in height and 50–100 μm in radial length (RLS). Aggregate rays 50– 425 μm wide and up to 4 mm high; ray-vessel pits not observed. Affinity — The combination of diffuse-porous wood, presence of undulating growth rings, numerous narrow and evenly distributed vessels, exclusively scalariform perforation plates, alternate to opposite intervessel pitting, homocellular uniseriate and aggregate rays indicates affinities with section Gymnothyrsus of the genus Alnus of the Betulaceae. However, our sample sometimes has scalariform intervessel pitting, a feature which has not been reported previously in any extant Alnus species or in fossil records of the genus. So far six fossil woods with similarity to Alnus are reported from Tertiary deposits of the world. These are Alnus sp. Slijper (1932) from the Pliocene of Europe, Alnoxy- lon sp. Hofmann (1944) from the Lower Oligocene of Europe, Alnoxylon vasculosum Felix emend. Müller-Stoll & Mädel (1959) from the Pliocene of Germany and Aus- tria, Alnoxylon sp. Petrescu & Nutu (1969) from the Upper Miocene of Romania, Alnus latissima Wheeler et al. (1977) from the Eocene of USA and Alnoxylon sp. Gottwald (1981) from the Pliocene of Europe. Alnus sp. (Slijper 1932) has diagonal and radial vessel multiples, alternate intervessel pitting, and exclusively uniseriate rays with no aggregate rays. Alnoxylon sp. (Hofmann 1944) has aggregate rays, but the vessel size and other details are not given. Alnoxylon vasculosum (Müller-Stoll & Mädel 1959) is similar to our fossil wood in vessel size, frequency, number of bars per plate, rays, but differs by lacking scalariform intervessel pitting. Alnoxylon sp. (Petrescu & Nutu 1969) differs in having wider vessels (mean tangential diameter 100–200 μm), exclusively alternate intervessel pitting, and uniseriate rays. Alnus latissima (Wheeler et al. 1977) also resembles our fossil wood but lacks scalariform intervessel pitting; the axial parenchyma was not described. Alnoxylon sp. (Gottwald 1981) has opposite intervessel pitting, diffuse-in-aggregate parenchyma and in bands of 3 cells wide, and exclusively uniseriate rays. Because the Kyushu fossil wood differs from all previously described fossils, it is named as Alnus scalariforme sp. nov., the specific epithet originating from its characteristic scalariform intervessel pitting.

Fig. 4. Hamamelis prejaponicum sp. nov. (holotype no. 71517) – a: TS, diffuse-porous wood. – b: TS, same section magnified showing vessels and fibres. – c: TLS, showing uniseriate rays. – d: TLS, showing uniseriate rays and rays partly biseriate (arrow). – e: RLS, heterocellular rays with large crystals in ray cells. – f: RLS, scalariform perforation plate with thin bars. –

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g: TLS, opposite and transitional intervessel pitting. – Scale bar in a; for a & c = 250 μm; for b & d = 100 μm; for e = 50 μm; for f & g = 25 μm.

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Hamamelidaceae Hamamelis prejaponicum sp. nov. — Fig. 4 Material — No. 71517 (holotype) is a small pebble (2 × 3 cm in diameter and 4 cm in length) which may have originated from a fairly large silicified trunk because an- nual ring boundaries are parallel. Description — Growth rings distinct, relatively narrow (1.3–2.8 mm wide), demarcated by 2 or 3 rows of tangentially flattened fibres (Fig. 4b). Wood diffuse-porous (Fig. 4a). Vessels numerous, 160–204 (average 178) per square mm; evenly distributed; quite uniform in size except the slightly narrower vessels at the ends of the growth rings; circular, oval or slightly polygonal in cross section; solitary and in short radial or tangential rows of 2–4 vessels (Fig. 4b); narrow, tangential diameter 30–55 (average 41), radial diameter 40–65 (average 54) μm; thin-walled. Vessel elements 990–1650 (average 1226) μm long; end walls oblique; perforation plates exclusively scalariform with 20–40 (average 31) thin bars (Fig. 4f). Intervessel pitting opposite, bordered with orbicular apertures, 5–6 μm in diameter (Fig. 4g). Non-septate fibres polygonal in cross section, 15–25μ m in diameter; thick-walled (c. 3–4 μm) (Fig. 4b). Axial parenchyma apotracheal diffuse; cells polygonal in cross section, 20–25 μm in diameter and 62–100 μm in length. Rays uniseriate, very occasionally partly biseriate (Fig. 4c, d), 12–16 (average 14) rays per mm; heterocellular, 3–30 cells (75–600 μm) high; procumbent cells 15–25 μm in height and 20–100 μm in radial length (RLS); upright or square cells 30–45 μm in height and 15–30 μm in radial length (RLS). Ray-vessel pits poorly observed, slightly elongated to short elliptical, opposite to alternate arrangement. Single crystals present in ray cells (Fig. 4e). Affinity — The features of this wood, i.e., diffuse-porous wood, mostly solitary oval to polygonal narrow vessels, exclusively scalariform perforation plates, apotracheal diffuse parenchyma and uniseriate heterocellular rays with crystals indicate affinities with the genus Hamamelis L., particularly with H. japonica Sieb. & Zucc. of the Hamamelidaceae. Heterocellular rays are more pronounced in H. japonica than in the Kyushu fossil wood. A number of fossil woods with affinities to Hamamelidaceae are known from Ja- pan, Europe and the USA. Among them, Hamamelidoxylon castellanense Grambast- Fessard (1969), H. rhenanum van der Burgh (1973) and H. mägdefrauii (Greguss) van der Burgh (1973) resemble the Kyushu wood. Hamamelidoxylon castellanense can be differentiated by the less abundant vessels and 1–3-seriate rays. In H. rhenanum, vessels are narrower (30–50 μm in tangential diameter), perforation plates have 20– 40 bars, axial parenchyma is paratracheal and apotracheal diffuse, and rays are 1–3- seriate. Hamamelidoxylon mägdefrauii also has narrow vessels and mostly uniseriate rays, but its scalariform perforation plates have up to 40 bars and some reticulate perforation plates are also present (Greguss 1969). Since the Kyushu wood differs from all of the aforementioned species, it is assigned to the new fossil species Hamame- lis prejaponica sp. nov. The specific epithet is derived from the closest modern species, H. japonica, which is a deciduous shrub or small tree native to Japan (Ohwi

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1965). The genus Hamamelis consists of 6 species distributed in East Asia and eastern North America (Willis 1973).

Magnoliaceae Magnoliaceoxylon palaeogenica sp. nov. — Fig. 5 Material — No. 71339 (holotype) is a pebble (3 × 4 cm in diameter and 3 cm long) which originated from a silicified trunk or branch. Description — Growth rings faintly distinct, narrow to wide (0.8–6 mm), demarcated by 2–5-seriate bands of marginal parenchyma. Wood diffuse-porous (Fig. 5a). Vessels numerous, 94–142 (average 115) per square mm; evenly distributed; mostly in multiples of 2–9, some in clusters, rarely solitary (Fig. 5a); narrow, tangential diameter 40–75 (average 54) μm, radial diameter 40–80 (average 66) μm; thin-walled. Vessel elements 380–800 (average 610) μm long with oblique end walls (Fig. 5c); perforation plates exclusively scalariform with 4–15 bars (Fig. 5d). Intervessel pits scalariform (Fig. 5e). Non-septate fibres square, polygonal or circular in cross section, 15–20 μm in diameter, pits not observed. Axial parenchyma in apotracheal bands, usually in marginal bands, 2–5 cells wide, and sometimes in bands of 1–4 cells wide in addition to the marginal ones (Fig. 5a); cells rectangular in cross section, 15–20 μm and 20–30 μm in tangential and radial diameters, respectively; 75–200 μm in length; oil cells and crystals absent. Rays 1–4- (mostly 3-)seriate (Fig. 5c), 7–11 (average 10) rays per mm; heterocellular (Fig. 5b); uniseriates very rare, 1–6 cells (25–175 μm) high, composed of upright cells only; multiseriates 4–27 cells (average 15) or 65–675 μm high, composed of procumbent cells in the centre of the ray with uniseriate margins of 1–6 rows of upright cells at one or both ends of the ray (Fig. 5c); upright cells 25–80 μm in height and 15–40 μm in radial length (RLS); procumbent cells 20–30 μm in height and 25–100 μm in radial length (RLS); vessel-ray pits oval or long elliptical (3 or 4 pits per cross field), almost simple, rarely horizontally elongated (Fig. 5b); unilaterally compound; oil cells and crystals not observed. Affinity — The combination of characters in this fossil wood, viz., numerous narrow vessels which are mostly in radial multiples, exclusively scalariform perforation plates, scalariform intervessel pitting, marginal banded parenchyma and 1–4-seriate heterocellular rays is diagnostic of the Magnoliaceae (Metcalfe & Chalk 1950; Canright 1955; Metcalfe 1987). This wood shows resemblance with the genera Magnolia L., Manglietia Blume, and Michelia L. in many quantitative characters (Metcalfe 1987). Liang et al. (1993) described the wood anatomy of many Chinese species of the family. They provided a wood anatomical key to five Chinese genera of the family. Using this key, the Kyushu fossil wood falls into the category ʻMagnolia (evergreen species)ʼ. Among the evergreen Magnolia, M. nitida W.W. Smith var. lotungensis (Chen & C.T. Tsoong) B.L. Chen & Noot. resembles our fossil wood in all anatomical features except for the presence of spiral thickenings in the vessels. Nevertheless, it is difficult to assign the fossil to a single genus because many genera of the family share wood anatomical characters.

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So far, twelve fossil woods with names suggesting affinities to the family Magnolia- ceae have been reported from Europe, America and Japan. Among them, Magnoli- oxylon micheloides Hofmann (1952) from the Oligocene of Austria and Canada (Roy & Stewart 1971) and Talauma multiperforata Kruse (1954) from Eden Valley, Wyo- ming, were excluded from this family because their anatomical features are not con- sistent with the family Magnoliaceae (Van der Burgh 1973; Wheeler et al. 1977). Liriodendroxylon tulipiferum Prakash, Brezinova & Buzek (1971) from the Oligocene of Bohemia and L. multiporosum Scott & Wheeler (1982) from the Eocene of Clarno Formation, USA differ from our fossil wood in having opposite intervessel pitting. Magnoliaceoxylon wetmorei Wheeler, Scott & Barghoorn (1977) from the Eocene of Yellowstone National Park, USA differs in having wider vessels (75 μm in mean tangential diameter), more bars in the perforation plates (up to 26), opposite and scalariform intervessel pitting, and higher rays. Magnoliaceoxylon panochensis (Page) Wheeler, Scott & Barghoorn (1977), from the Upper Cretaceous of California, has opposite and transitional intervessel pitting, abundant diffuse and some paratracheal parenchyma, mostly homocellular rays (Page 1970; Wheeler et al. 1977). Magnoli- oxylon parenchymatosum van der Burgh (1973) from the Netherlands has narrow vessels, perforation plates with few bars, banded axial parenchyma and spiral thickenings in the vessels. Magnolioxylon krauselii (Greguss) van der Burgh (1973) from the Tertiary of Hungary has some simple perforation plates. Magnolioxylon scandens Schönfeld (1958) also has some simple perforation plates and scalariform perforation plates with many bars (up to 33). Magnolia radiata Scott & Wheeler (1982) from the Eocene Clarno Formation, USA differs in having less frequent vessels (44–78 per square mm), opposite intervessel pitting, scalariform perforation plates and very high rays (0.2–2 mm). Magnolia angulata Scott & Wheeler (1982), also from the Clarno Formation, has a vessel size similar to the Kyushu wood but has opposite and scalariform intervessel pitting and mostly biseriate rays up to 1200 μm tall. Michelia oleifera Suzuki (1976) from the same locality of the Kyushu wood (Oligocene) differs in having opposite to scalariform intervessel pitting and abundant large barrel-shaped oil cells in axial and ray parenchyma. The genus Magnoliaceoxylon was established by Wheeler et al. (1977) for fossil woods with anatomical similarity to extant genera of Magnoliaceae. They counted two species in this genus; i.e., M. wetmorei Wheeler, Scott & Barghoorn and M. panochensis (Page) Wheeler, Scott & Barghoorn. Since the Kyushu wood differs from all of the fossil magnoliaceous woods described so far, it is placed in the new fossil species Magnoliaceoxylon palaeogenica sp. nov. erected herein.

Fig. 5. Magnoliaceoxylon palaeogenica sp. nov. (holotype no. 71339) – a: TS, diffuse-porous wood with marginal parenchyma bands (arrow) and apotracheal parenchyma bands (long arrow). – b: RLS, heterocellular rays with large oval and long elliptical vessel-ray pits. – c: TLS, 1–4-seriate rays. – d: RLS, scalariform perforation plate. – e: TLS, scalariform intervessel pitting. – Scale bar in a; for a = 250 μm; for b & e = 50 μm; for c = 100 μm; for d = 25 μm.

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Sonneratiaceae Sonneratia kyushuensis — Fig. 6 Material — No. 71259 (holotype) is a pebble about 5 × 6 cm in diameter and 6 cm long, which was originated from a silicified trunk or branch. Description — Growth rings indistinct, 1.2–2.4 mm wide, demarcated by 2 or 3 rows of tangentially flattened fibres and narrower vessels (Fig. 6a). Wood diffuse- porous (Fig. 6a). Vessels evenly distributed, 15–29 (average 22) per square mm; solitary and in radial multiples of 2 or 3 (Fig. 6a), sometimes up to 6; solitary vessels oval or circular in cross section, medium-sized, tangential diameter 90–150 (average 119) μm and radial diameter 115–210 (average 175) μm, walls thick (c. 5 μm). Vessel elements 240–520 (average 390) μm long with transverse to oblique end walls; perforation plates exclusively simple (Fig. 6f). Intervessel pits polygonal, 5–6 μm in diameter (Fig. 6e), alternate, bordered, variously shaped minute dark structures present around pit apertures. Thin-walled, septum-like tyloses sometimes present. Septate fibres thick-walled (c. 4.2 μm) (Fig. 6b); polygonal in cross section, 10– 18 μm in diameter. Axial parenchyma absent. Rays exclusively uniseriate, 14–22 (18) rays per mm; nearly homocellular, composed of procumbent cells; cells 20–40 μm in height and 30–90 μm in radial length (RLS); ray-vessel pits small, round to oval (Fig. 6d); crystals absent. Affinity — The combination of diffuse-porous wood with medium-sized vessels that are solitary and in multiples, exclusively simple perforation plates, septate fibres, absence of parenchyma and uniseriate homocellular rays suggests affinities with the genus Sonneratia L. of the family Sonneratiaceae (Pearson & Brown 1932; Metcalfe & Chalk 1950; Gamble 1972; Rao et al.1987b). The variously shaped minute dark structures around intervessel pit apertures may be decomposed vestured pits. If so, the presence of vestured pits supports the affinity of the fossil to Sonneratia. There are five extant species ofSonneratia in tropical mangrove forests in the world, and we examined wood of S. alba Smith, S. apetala Buch.-Ham., S. caeseolaria (L.) Engl. (syn. S. acida L.) and S. griffithii Kurz. The anatomical structure of all four extant species is similar. The Kyushu fossil wood differs from the extant species in absence of crystals in ray cells, wider vessels (mean tangential diameter of those extant species is 88–95 μm whilst that of the fossil is 119 μm ) and shorter vessel elements (mean element length of the extant species is 650–670 μm whilst that of the fossil is 389 μm). Rao et al. (1987a) reported the presence of a few (5–20%) scalariform, modified scalariform and reticulate perforation plates in addition to simple perforation plates in all four extant species. Only simple perforation plates have been observed in the Kyushu wood. Therefore, the fossil wood differs in several anatomical characters from the examined four extant species of Sonneratia.

Fig. 6. Sonneratia kyushuensis sp. nov. (holotype no. 71259) – a: TS, diffuse-porous wood with indistinct growth ring (arrow) (pith-side towards top). – b: TLS, uniseriate rays and septate fibres (arrow). – c: RLS, homocellular rays. – d: RLS, vessel-ray pits. – e: TLS, intervessel pits with vestured pit-like structure. – f: RLS, simple perforation plate. – Scale bar in a; for a = 250 μm; for b = 100 μm; for c & f = 50 μm; for d & e = 25 μm.

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Fossil woods similar to Sonneratia are known from many Asian countries. These include: Sonneratioxylon aubrevillei Louvet (1970) from the Middle Eocene of Libya; S. caeseolarioides Shete & Kulkarni (1982) from the Deccan Intertrappean Beds of India; S. dakshinense Ramanujam (1957) from the Mio-Pliocene of India; three species from the Deccan Intertrappean Beds of India, i.e.,S. duabangoides Shallom (Chitaley 1977), S. intertrappeum Birader & Mahabale (1975) and S. nawargaoensis Bande & Prakash (1984); S. prambachense Hofmann (1952) from the Upper Oligocene of Austria; S. preapetalum Awasthi from the Palaeogene and Neogene of India (Awasthi 1969; Lakhanpal et al. 1984; Mehrotra 1989), Java and Sumatra (Kramer 1974), and Thailand (Vozenin-Serra et al. 1989). Mehrotra (1989) synonimized all of the Indian species into S. preapetalum because the species differ only in minor anatomical characters, such as the presence or absence of septate fibres and ray height.Sonneratioxylon aubrevillei Louvet differs from our fossil wood in having narrower vessels (50–100 μm). Sonneratia prambachense Hofmann emend. Kramer has scanty paratracheal parenchyma. However, axial parenchyma is almost absent in extant Sonneratia and the Kyushu wood. The Kyushu wood is similar to Sonneratioxylon preapetalum, except that homocellular rays and thin-walled sparse tyloses are present in the fossil described here. Therefore, the Kyushu wood differs from all fossil wood species of Sonneratioxylon described to date. The genus Sonneratia L. is represented by five littoral species distributed in mangrove swamps of India, tropical East Africa, Madagascar, Hainan and the Ryukyu Islands, Micronesia, Malaysia, New Hebrides and the Solomon Islands, and North Australia (Willis 1973). Only one species, S. alba, is found in Japan. This species, S. alba, grows in the southernmost Ryukyu Islands which have a subtropical climate. There are no extant representatives of this genus in Kyushu Island.

DISCUSSION

In the present study five new species of dicotyledonous fossil woods are described from the Lower Oligocene deposits at Tsuyazaki, Fukuoka Prefecture, northern Kyushu. Four have anatomical characters very similar to those of the modern genera, Rhus, Alnus, Hamamelis and Sonneratia. The magnoliaceous wood, however, cannot be assigned to any modern taxon because the extant genera belonging to the Magnoliaceae have overlapping characters. The occurrence of scalariform perforation plates in modern Rhus is very rare. The Kyushu fossil wood, which is otherwise identical to the extant Rhus javanica, has scalariform perforation plates with 1–5 bars in some narrow vessels. Spiral thickenings, a character found in modern Rhus, are not found in the fossil woods of the genus. This may be because the climate was warmer at the time of deposition; some workers have correlated the presence of spiral thickenings with a seasonal temperate environment (Cox 1941; Sweitzer 1971), and modern Rhus javanica occurs in subtropical to warm temperate regions of East Asia. In modern Alnus, alternate and opposite intervessel pitting occurs, but in the fossil wood of Alnus we observed scalariform as well as alternate and opposite pitting. Scalariform pitting is another primitive feature recorded for the first time in fossil Alnus. In contrast,

Downloaded from Brill.com10/05/2021 05:26:07PM via free access 100 IAWA Journal, Vol. 22 (1), 2001 Srivastava & Suzuki — Palaeogene woods from Japan 101 References Suzuki 1982 Suzuki 1982 Suzuki 1976 Suzuki 1976 Suzuki 1975 Suzuki 1982 Suzuki 1976 Suzuki 1982 Suzuki 1984 Suzuki 1984 Suzuki 1984 Suzuki 1984 Suzuki 1976 1966 Watari

Distribution Temp ST-Temp Temp Temp Temp Temp – ST-Temp Temp Temp Temp Temp – Temp – – Trop-ST – Temp

Habit D D D D D D – E D D D D – E – – E – –

Similar extant Acer palmatum Rhus javanica Alnus Cornus Castanea Hamamelis japonica Magnoliaceae Michelia Camptotheca acuminata Fraxinus Platanus Hovenia dulcis Prunus Prunus zippeliana Prunus Prunus Sonneratia alba – Sequoia or Metasequoia

Familiy Aceracae Anacardiaceae Betulaceae Cornaceae Fagaceae Hamamelidaceae Magnoliaceae Magnoliaceae Nyssaceae Oleaceae Platanaceae Rhamnaceae Rosaceae Rosaceae Rosaceae Rosaceae Sonneratiaceae Sterculiaceae Taxodiaceae Table 2. Composition of the fossil wood flora of Tsuyazaki. of 2. Composition of the fossil wood flora Table

sp. nov.

Anatomically closely similar extant taxa of the fossil species described in original references. – = unknown. Habit of the similar extant taxa; D = deciduous, E evergreen, = temperate, – unknown. Temp = subtropical, = tropical, ST Trop Distribution range of the similar extant taxa;

Fossil name Acer palmatoxylum Rhus palaeojavanica Alnus scalariforme Cornus tsuyazakiensis Castanea protoantiqua Hamamelis prejaponica Magnoliaceoxylon palaeogenica Michelia oleifera Camptotheca kyushuensis Fraxinus oligocenica Platanus tsuyazakiensis Hovenia paleodulcis Prunus ascendentiporulosa Prunus paleozippeliana Prunus polyporulosa Prunus uviporulosa Sonneratia kyushuensis oligocenica Wataria sequoianum Taxodioxylon 1) 2) 3)

Downloaded from Brill.com10/05/2021 05:26:07PM via free access 102 IAWA Journal, Vol. 22 (1), 2001 Srivastava & Suzuki — Palaeogene woods from Japan 103 occasional scalariform and reticulate perforation plates are reported in modern Sonneratia (Rao et al. 1987a, b), but we did not observe multiple perforation plates in the Kyushu fossil wood of Sonneratia. In total, one coniferous and 18 dicotyledonous species of 14 families are known at the Tsuyazaki locality. This suggests that there was a flora mostly composed of dicotyledons at the Tsuyazaki area during the Early Oligocene (Table 2). In Table 2, the extant taxa wood anatomically similar to the fossil species of Tsuyazaki are listed with their ecological habits and distribution ranges. Of these nineteen taxa, ten taxa are known to be deciduous and three are evergreen. Eleven taxa occur in temperate regions, two taxa occur in subtropical to temperate regions, one taxon in tropical to subtropical regions. Although there is no extant taxon comparable to Wataria oligocenica, the distinct ring porosity of the fossil suggests it was a deciduous tree growing in a seasonal climate. The habit of three fossil species of Prunus (P. ascendentiporulosa, P. polyporulosa and P. uviporulosa) is unknown, but most extant Prunus species occur in temperate regions. The ecological habits and distribution ranges of the taxa anatomically similar to the fossil species suggest that the Tsuyazaki flora was composed of mostly deciduous dicotyledonous trees with a mixture of evergreen dicotyledonous trees and conifers under the warm temperate climate. The presence of Sonneratia indicates either warmer climate conditions near the depositional site, because presently all modern species of Sonneratia are distributed in littoral mangrove swamps of tropics to subtropics, or a fossil species of Sonneratia with a different climatic preference than the extant species. In Japan one species, S. alba, is found in the southernmost Ryukyu Islands where a subtropical climate prevails, about 500 km from northern Kyushu. Presence of warmer conditions was previously indicated by the presence of Pal- moxylon and Paraphyllanthoxylon in the Palaeogene sediments of northern Kyushu (Watari 1966). The Palmoxylon is not yet described anatomically. Paraphyllanthoxylon resembles Bischofia javanicaof the Euphorbiaceae, which is a monotypic genus widely distributed in the tropics of southern territories of eastern Asia (Watari 1943, 1966). Two species of Lithocarpoxylon (Table 1) have radial porous wood and their affinities are suggested to be with evergreen Quercus, Lithocarpus, and Pasania, which are mainly distributed from subtropical to warm temperate regions in Asia. The occurrence of those fossils indicates a fairly warm climate during the Palaeogene in northern Kyushu.

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