植物研究雑誌1. Jpn. Bot 68: 289-299 (1993)

00 Some Petrified Plaots from the Cretaceous of Choshi， Chiba Prefecture VIII

Makoto NISHIDAa， Harufumi NISHIDAb and Yuzuru SUZUKIc

aResearch Institute of Evolutionary Biology， 2-4・28Kamiyoga， Setagaya-ku， Tokyo 158，

blntemationa1 Budo University， 841 Shinkan， Katsuura， Chiba Prefecture 299-52，

CToshiba FA System Engineering Co. 2-24-1 Harumi-cho， Fuchu， Tokyo 183

銚子産白亜系材化石 (8)

西田誠 a，西田治文b，鈴木譲 c

a財)進化生物学研究所 158 東京都世田谷区上用賀 2-4-28

b国際武道大学体育学部 292-52 勝浦市新官 841

c東芝FAシステム・エンジニアリング 183 府中市晴見町2-24-1

(Received on January 15， 1993)

Five species of permineralized woods are described. Three are new species: Xenoxylon tsuruokae，

Araucario刀lonbiseriatum， andBucklandia tylosissima. One is new locality， Cupressinoxylon cryptomerioides

Stopes and another is a twig of Bucklandia choshiensis Nishida described from the same locality.

(Continued from Nishida and Nishida， Bot. Mag. Tokyo 96: 93-101， 1983).

This paper describes the results of examinations of

more than 50 specimens of plant permineralizations

collected by Mr. Shigeru Tsuruoka， Choshi Labora-

tory， Institute ofMarine Ecosystem， Chiba U niversity

from 1976 to 1986. All holotypes described in this

paper訂 ehoused in the Laboratory of Phylogenetic

Botany， Faculty of Science， Chiba University.

34. Xenoxylon tsuruokae sp. nov. (Fig. 1)

Mαterials. Specimen no. 900108 (holotype) is a

small fragment of coniferous secondary wood， 4.7 cm

long and 2.6 cm and 1.1 cm in the wide and narrow

diameters， respectively. Specimen no. 900119 is 1.8

cm x 1.2 cm x 3.5 cm in size. Specimen no. 900126 is

a piece of secondary wood， 2.5 cm x 1.5 cm x 4.4 cm

in size. They all are well-preserved in histology.

Description. Coniferous wood consisting of

tracheids， rays and abundant wood parenchyma， lack-

ing resin canal. Growth rings faintly visible. Abrupt

transition from early to late wood consisting of only

3-4 layers of cells. Tracheids arranged regularly in

radial rows， polygonal or elongated rectangular in

outline in cross section， 30-64μm in radial and 22-60

μm in tangential dimensions in early wood; tangen-

tially elongated rectangul訂， 20-42μmin radial and

20-52μm in tangential dimensions in late wood.

Bordered pits on radial walls in early wood elliptical，

more or less horizontally compressed， 10-22μm in

horizontal and 17-24μm in vertical dimensions，

一一289一ー

290 植物研究雑誌第 68巻第5号 平成 5年 10月

Fig. 1. Xenoxylon tsuruokae sp. nov. A: Cross section showing secondary xylem with abundant wood

parenchyma. B， C: Tangential sections. Contiguous bordered pits on tangential walls oftracheids in B.

Tyloses in tracheids faintly visible in C. D， E: Radial sections. Wood p紅 enchyma(p) and uniseriate

contiguous bordered pits visible in D. Large window-like pit in cross field visible in E. p: wood

parenchyma， t: tracheids with tyloses. A: x35， B: x85， C: x85， D: x170， E: x170.

October 1993 Joumal of Japanese Botany Vol. 68 No. 5 291

arranged contiguously and exclusively in single row

and rarely in two rows. Pits on tangential walls smaller

than those on radial walls and also arranged

contiguously but in a single row. Tyloses abundant in

tracheids. Rays run at intervals of 1-13， average 4.5，

rows of tracheids， or 1-5， average 2.2， per 1 mm，

uniseriate， rarely biseriate in part and 1ー16，generally

1-8， cells or 10-266μm in height. Ray cells vertically

elnngated ovoid or rectangular in tangential section，

6-23μm in horizontal and 11-23μm in vertical

dimensions， and pitted only on radial walls. Large

window-like or single large ovoid pit in cross field.

W ood parenchyma fairy abundant and scattered

throughout increment.

Affinity.百lespecimens exhibit characteristics of

Xenoxylon in having bordered pits arranged

contiguously in a single row， abundant tyloses in

tracheids and a single 1訂 gepit or window-like pit in

the cross field. Generally， species of Xeno砂 lonlack

woodp訂enchyma，but our specimens訂eunique in

the genus in having fairly abundant wood paren-

chyma. About 15 species of Xeno砂lonhave been

described worldwide (Vogellhener 1965， 1968;

Selmeier 1968; Medlyn and Tidwe1l197 5; Yamazaki

and Tsunada 1981， 1982; Yamazaki et al. 1984;

Nishida and Nishida 1986). Of these， only three

species have wood parenchyma; X. hopeiense Chang

(1929) from the Upper Jurassic of China，X. jurassicum

(Gothan) Krauserl (1949) from the Lower Jurassic of

Germany (Franken) and X. morrisonense Medlyn et

Tidwell (1975) from the Upper Jurassic of Utah，

U.S.A. Our specimens closely resembleX. hopeiense

in having bordered pits on tangential walls of tracheids

and similar ray height， but are distinguishable in

having contiguously arranged bordered pits

(latiporosum type; Vogellhener 1965) on radial walls

instead of the often separately a町angedpits (barberi

type; Vogellhener 1965) of X. hopeiense. Xenoxylon

jurassicum differs from our specimens in having

barberi-type pitting on radial walls， with chiefly 2，

but sometimes 1 or 3-4 pits in the cross field， and in

lacking bordred pits on tangential walls (Table 1).

Xeno砂 lonmorrisonense shows some similarity to

our specimens in the pit a町angementon radial walls

of tracheids， but differs in having entirely biseriate

rays， rarely up to 35 cells high instead of lower rays.

X. morrisonense also has simple indented pits on

horizontal and tangential walls of ray cells， and exhib-

its podocarpoid pitting in the cross field (exceptional

inXeno砂 lon)instead ofthe large window-like pits. It

also lacks bordered pits on tangential walls of tracheids

(Table 1). Therefore， our specimens are designated as

Table 1. Comparison of Xenoxylon species with wood parenchyma.

Characters Ray B. p. on tangential B. p. on radial Cross field Species Width Height walls of tracheids walls pIts

X. hopeiense umsenate 1-29* + barberi type large (Chang 1929) 1-2

X. jurassicum umsenate 1-20 (30) barberi type 1-4 (Krausel 1949) mainly 2-6 (88%) mainly 2

x. morrisonense umsenate 2-35 latiporosum podocarpoid (Medlyn & Tidwe1l1975) type 1-2

X. tsuruokae umsenate 1-16 + latiporosum large (in this paper) type 1(2)

(window-like)

* According to Li et al. (1970)， up to 65 cells high.

292 植物研究雑誌第 68巻第5号 平成 5年 10月

a new species of Xeno.砂 lon.The specific epithet is

dedicated to Mr. Shigeru Tsuruoka who provided the

speclmens.

35. Araucarioxylon biseriatum sp. nov. (Fig. 2).

Material. Specimen no. 900136 (holotype) is a

fragment of secondary wood， 0.9 cm x 2.0 cm x 1.1

cm in size with well preserved histology.

Description. Coniferous wood consisting of

tracheids and rays， lacking wood parenchyma and

resin canals. Growth rings not visible. Tracheids

arranged regularly in radial rows， rectangular in cross

section， 32-64μm in radial and 30-58μmintangen-

tial dimensions. Bordered pits only on radial walls，

more or less horizontally elongated circular， 10-15

μm in diameter，出Tangedcontiguously in 1-3 rows，

and altemate when arranged in two or three rows.

Bordered pits absenton tangential walls. Septum-like

structures common in tracheids. Rays uniseriate or

sometimes entirely biseriate， and 6-42 cells or 132-

1156μm in height， 2-10， average 5.5， per 1 mm，

running at intervals of 1-10， average 4.0， rows of

tracheids. Ray cells elliptical in tangential section，

14-43μm， usually 22-32μm in vertical and 8-26μm

in horizontal widths， and pitted only on radial walls.

Two or three fairly large half-bordered pits， broad

ovoid in outline and 15-20μm in long diameter， in

cross field.

Affinity. The specimen apparently belongs to

Araucario.砂 lon，because it has arucarian type pitting

on tracheids and lacks wood parenchyma. More than

200 species of Araucario.砂lonhave been described

worldwide (Schultz-MotelI962). However， our speci-

men exhibits unique biseriate rays. The same feature

also occurs inA. hujinαmiense Ogura from the Lower

Cretaceous of Wakayama (Ogura 1956) and Choshi

where our specimen was collected (Nishida 1971) and

inA. ohzuanum Nishida et al. (1992) from the Upper

Cretaceous of Chilean Patagonia. Our specimen also

resembles A. hujinamiense in having rays exceeding

40 cells in height. However， our specimen differs

from A. hujinamiense in lacking tylosis in tracheids，

which is abundant in the latter (Table 2). Our speci-

men is also different from A. ohzuanum in lacking

tyloses and wood parenchyma (Table 2).百lespecific

epithet of the new species originates from the entirel y

bisseriate rays which are r訂 ein Araucario.刀lon.

36. Cupressinoxylon cryptomerioides Stopes，

Catalog. Mesoz. Pl. Brit. Mus. (Nat. Hist.) Cret. Flora

Pt. 2， Lower Greensand (Aptian) Plants of Britain.

186 (1915). Seward， Fossil plants IV， 193 (1919).

NishidaandNishida，Bot.Mag. Toky099: 196(1986)

(Fig. 4， A & B).

Materials. Specimens Nos. 900105 and 900134

紅 epieces of secondary wood. 1.2 cm x 0.8 cm x 3.2

cm and 1.0 cm x 1.0 cm and 3.7 cm in dimensions，

respectively， and well preserved in histology.

Briefnote. The specimens exhibit diagnostic char-

acters similar to those of Cupressinoxylon

cηptomerioides Stopes from the Lower Cretaceous

ofEngland (Stopes 1915) and from the Upper Creta-

ceous of Saghalien (Nishida and Nishida 1986). They

are characterized by abundant wood parenchyma， low

rays， 1-5 cells high， and a single half-bordered pit in

the cross field. This species could represent twigs of

C. vectense Barber (see Nishida and Nishida 1986).

Distribution. England (Aptian) and Saghalien (Late

Turonian-Santonian). New to Honshu， Jap如.

37. Bucklandia tylosissima sp. nov. (Fig. 3).

Materials. Specimen no. 900146 (holotype) is

1.8 cm x 0.8 cm x 2.5 cm， and specimen no. 900158

is 1.8 cm x 1.7 cm x 2.6 cm in size. Both訂'epieces

ofsecondaη， wood with fairly well-preserved histol-

ogy.

Description. Cycadeoidealean wood consisting of

tracheids， rays and wood p訂 enchyma，and lacking

mucilage canals or ducts. Growth rings visible. Gradual

transition from early to late wood， consisting of 4-5

October 1993 Joumal of Japanese Botany Vol. 68 No. 5

Fig. 2. Araucarioxylon biseriatum sp. nov. A & B: Cross sections. W ood parenchyma not discemible. C，

D: Tangential sections showing uni-and biseriate rays. E， F: Radial sections. Araucarian-type pitting on

tracheids visible in center ofE. Large ovoid 1 or 2 pits visible in F. A: x35， B: x170， C: x35， D: x85， E:

x170， F: x170.

293

294 植物研究雑誌第68巻第5号 平成 5年 10月

Table 2. Comparison of Araucarioid species with tyloses or wood parenchyma.

Characters Tyloses Wood Species parenchyma

Araucarioxylon + huiinamiense

(Ogura 1960)

A. pseudohujinamiense + (Nishida and Oishi 1982)

A.ohzuanum + + (Nishida et al. 1992)

A. biseriatum

(in this paper)

Xenoxylon tsuruokae + + (in this paper)

*Cells high.

layers of cells. Tracheids a町angedregular匂inradial

rows， polygonal or elongated rectangular in shape in

cross section， 28-60μm in radial and 24-56μmin

tangential widths in the early wood， and 10-40μmin

radial and 20-56μm in tangential widths in the late

wood. Bordered pits on radial walls araucarian type，

hexagonal in out1ine， 12-17μm in diameter， arranged

contiguously and altemately in two or three rows.

Scalariform pits often visible， 7-10μm and 27-29μm

in size. Bordered pits sometimes on tangential walls，

arranged contiguously in single row. Tyloses abun-

dant in tracheids. Rays chiefly uniseriate， rarely

biseriate in part， 1-24 cells or 64-804μm in height，

running at intervals of 1-11， average 5.1， rows of

tracheids， and 1-7， average 5.1， per 1 mm. Ray cells

vertically elongated ovoid or circular in tangential

section， 30-45μm in vertical and 18-40μm in hori-

zontal widths， and pitted on all walls. Simple pits

sp町田lyarranged in single row on horizontal walls.

Single large ovoid pit or rarely 2-3 smaller circular

pits in cross field. W ood parenchyma scattered

throughout increment.

Affinity. As described above， the specimens are

Ray Cross field Width Height plts

often biseriate 1--49* large ovoid

umsenate 2-29 large ovoid

chiefly biseriate 1-11 podocarpoid mainly 2-7 1 or 2--4

often biseriate 6--42 large ovoid 1 or 2-8

umsenate 1-16 window-like

characterized by the presence of both araucarian and

scalariform pits on tracheids， abundant tyloses in

tracheids， low uniseriate rays (1-24 cells high)， and a

single circular or 2-3 ovoid pits in the cross field. Our

specimens resemble P horo砂lonjaponicum (Nishida)

Suzuki et al. (1991) from the same locality and hori-

zon in general structure except for the cross field

p社tingand pitting on tracheids. P horo砂 lonjaponicum

chiefly has 4-12 scalariform or horizontally elon-

gated cross field pits instead of the single， or 2-3，

circular or ovoid pits found in our specimens. In

addition， P. japonicum exhibits exclusively scalari-

form pitting on tracheids instead of the dominant

araucarian type of pitting in our specimens. P.

japonicum was described originally by Nishida (1960)

as Tetracentronites， which belongs to the homoxylous

dicotyledonous woods. It was reidentified by Suzuki

et al. (1991) as a bennettitalean wood and assigned to

Phoro砂lonwhich was described originally from the

Cretaceous of Northem Manchuria (Sze 1954). The

type species P. scalariforme Sze also exhibits domi-

nant scalariform pitting on tracheids and 1-6 circular，

non-scalariform pits in the cross field. Sahnio砂lon

October 1993 Joumal of Japanese Botany Vol. 68 No. 5

Fig.3. Bucklandiαηlosissima sp. nov. A， B: Cross sections. Scattered wood parenchyma visible in A.

Arrow in B shows abietinean pits on horizontal walls ofray cells. C， D: Tangential sections. Bubble-like initiation oftylosis visible in C. Abietinean pits on tangential walls ofray cells visible in D. E， F: Radial sections showing single pit in cross field and araucarian-type bordered pits (in E) and scalariform pitting

(in F) on tracheids. A: x35， B: x170， C: x85， D: x340， E: x170， F: x170.

295

296 植物研究雑誌第 68巻第5号 平成 5年 10月

Bose and Sah (1954)， which includes 10 or more

species (Bose and Sah 1954; Boureau 1954， 1955;

Jarmolenko 1936; Salard 1968; Lemoigne and

Torres 1968)， was first described as a vesselless

dicotyledonous wood by Sahni (1932) but was later

recognized as a bennettitalean thin trunk by Bose and

Sah (1954). Some species of Sahnio砂 lonresemble

B. tylosissima in gross mo叩hology，especially in

having scalariform tracheids. However， they differ

fromB.り/losissimain lacking tyloses in tracheids and

in having more or less bi-or multiseriate rays and 6-

10 or more ray-tracheid pits. Our specimens very

closely resemble Bucklandiαchoshiensis Nishida

(1969) and B. tsuruokae H. Nishida et Nishida (1983)

from the same locality and horizon in having uniseriate

rays， araucarian-type pitting on tracheids， and 1-2 or

more pits in the cross field. However， these two

species show exclusively araucarian-type pitting on

tracheids and lack tyloses which is abundant in our

specimens as well as in P horo砂lon.Our specimens

also differ from B. indica Seward (1913)， B. sahnii

Bose (1953)， B. guptai Sharma (1967) and B.

dichotoma Sharma (1969) from the Jurassic of India

in having tyloses which the latter species do not

(Table 3). Our specimens exhibit features of wood

structure intermediate between Phoroxylon and

Bucklandia. Specific epithet originates from tyloses

in the tracheids， a feature first recognized in

Bucklαndia.

38. Bucklandia cf. choshiensis Nishida， Phyto-

morphology 19: 28 (1969). (Figs. 4 C & D).

Materiα1. Specimen no. 900117 is a piece of twig，

0.9 cm in diameter and 1.5 cm in length， consisting of

p訂tof the cortex， secondary and primary xylem， and

pith， with well preserved histology.

Description. Seconaary xylem manoxylic， con-

sisting of tracheids and abundant rays， and lacking

Table 3. Comparison of petrified Bucklandia species.

Characters Species

Ray Pits in cross Bordered pit Width Height field arrangement

1-3* araucarlan multiseriate

1-2 1--48料 1--6 or more scalariform， araucarian rarely 3 2--4 rows

1-2 20-30 ヲ

mostly 1

B. indica (Seward 1917)

B. sahnii (Bose 1953)

B. guptai (Sharma 1967)

B. dichotoma (Sharma 1969)

1--4 1-83 1--4 scalariform， araucarian chiefly 2 usually 40--45 1-3 rows

B. choshiensis (Nishida 1969)

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B. tsuruokae (Nishida and Nishida 1983)

B. tylosissima (in this paper)

1-16 chiefly 1-8

1-2 araucarian 1-2 rows

* 1: uniseriate， 2: biseriate， 3: triseriate. **cells high.

1-24 1-3 scalariform， araucarian 2-3 rows

October 1993 Journal of Japanese Botany Vol. 68 No. 5

Fig. 4. Cupressinoxylon cryptomerioides Stopes (A， B) andBucklandia cf. choshiensis Nishida (C， D). A:

Tangential section showing low rays， less than 5 cells high and bordered pits on tangential walls of

tracheids. B: Radial section showing separate bordered pits and single cross field pit. C， D: Cross sections

showing secondary wood and pith with mucilage canals (arrows). A: x85， B: x170， C: x7， D: x35.

297

298 植物研究雑誌第 68巻第5号 平成 5年 10月

wood parenchyma and resin ducts. Bordered pits on

radial walls somewhat vertically compressed hexago-

nal in outline， 10-18μm in diameter， arranged

contiguously and altemately in 2-4 rows. Bordered

pits on tangential walls smaller， 10-12μm in diam問

eter， sparsely紅 rangedin single row. Rays 4-12 per 1

mm， uniseriate and p訂 tiallybiseriate， 1-56 cells high

or24-2000μm in height. Ray cells pitted on all walls.

Single large ovoid pit， 10-14μm and 15-18μm in

short and long diameters， respectively， or smaller

circular 2-3 pits less than 10μm in diameter， in the

cross field. W ood p訂 enchymanot examined. Pri-

m訂yxylemend訂'Ch;tracheids chiefly with scalariform

pitting. Pith 4-5 mm in diameter， consisting of large

parenchyma cells and mucilage canals. Parenchyma

cells 50-156μm in diameter and 46-150μm long.

Mucilage canals 100-176μm in diameter， encircled

by 5-6 epithelial cells， usually occluded with brown

substance， and scattered throughout pith， 3.6 in aver-

age per 1 squ訂 emm.

Affinity. The specimen is a Cycadopsidean twig

because it has a large pith with abundant mucilage

canals. It exhibits diagnostic characters similar to

those of Bucklandia choshiensis Nishida (1969) from

the same locality and horizon except for the lack of

wood parenchyma which are fairly abundant in B.

choshiensis. This lack of wood parenchyma can be

attributed to the young age of the tissue. Our specimen

represents an ultimate twig of B. choshiensis.

We wish to express our thanks to Mr. Shigeru

Tsuruoka， Choshi Laboratory， Institute of Marine

Ecosystem， Chiba University， for his courtesy in

providing all the specimens studied in this paper. This

study was supported by a Grant-in-Aid for Scientific

Research from the Ministry ofEducation， Science and

Culture No. 02640533 to M. Nishida.

References

Bose M. N. 1953. Bucklandia sahnii sp. nov. from the Jurassic

ofthe RajmahalHills， Bihar. Palaeobotanist3: 41-50， 7 pls.

一一一一 andSahS.C.D.1954.0nSahnio.砂lonrajmahalense， a new name for H omo.砂 lonrajmahalense Sahni and S.

andrewsii， a new species of Sahnio.砂lon仕omArnrapara in

the Rajmahal Hills， Bihar. Palaeobotanist 4: 1-8，2 pls.

Chang C. Y. 1929. A new Xeno砂lonfrom North China. Bull.

Geol. Soc. China 8: 243-255.

Jarmolenko A. B. 1936. On the Mesozoic woods from the

U.S.S.R. devoid of vessels. Sovietskaja Bot加 ica67: 234-

245 (in Russian with English resume).

Krausel R. 1949. Die fossilen Coniferen-Holzer (unter Aussluss

vonAraucario刀lonKrauss). (2) Kritische Untersuchungen

der Diagnostik lebender und fossiler Koniferen-Holzer. Palaeontgr. B. 89: 82-203.

Lemoigne Y. and Torres T. 1988. Paleoxylologie de l' Antarctide:

Sahnioxylon antarcticum n. sp. et interpretation de la double

Zonation des cemes des bois secundaires du ge町 ede

structure (Parataxon) Sahnioxylon. C. R. Acad. Sci. Paris T.

306， Ser. 11: 939-945.

Medlyn D. A. and Tidwell W. D. 1975. Conifer wood from the

Upper Jurassic ofUtha. 1. Xeno.砂 lonmorrisonense sp. nov.

Amer. J. Bot. 62: 203-208.

Nishida H. and Nishida M. 1983. On some petrified plants from

the Cretaceous of Choshi， Chiba Prefecture VII. Bot. Mag. Tokyo 96: 93-101.

Nishida M. 1962. On some petrified plants from the Cretaceous

ofChoshi， ChibaPrefecture. Jpn. J. Bot.18: 87-104.

一一一一ー 1969.A petrified trunk of Bucklandia choshiensis sp.

nov. from the Cretaceous of Choshi， Chiba Prefecture， Japan. Phytomorphology 19: 28-34.

一一一一一 1973.On some petrified plants from the Cretaceous of

Choshi， Chiba Prefecture VI. Bot. Mag. Tokyo 86: 189-

202.

一一一一-and Nishida H. 1986. Structure and affinities of the

petrified plants from the Cretaceous ofNorthem Japan and

Saghalien III. Petrified plants from the Upper Cretaceous of

Saghalien (1). Bot.乱1ag.Tokyo 99: 191-204.

一一一一一 andOishi T. 1982. Some petrified pl如 ts企omthe

Cretaceous ofKwanto Mountains (2). J. Jpn. Bot. 57: 343-

348.

Ogura Y. 1960. Tyloses in tracheids inAraucario砂 lon.J. Fac.

Sci.， Univ. Tokyo， sect. III， 7: 501-509.

Salard M. 1968. Contribution a la connaissance de la flora

fossile de la Nouvelle Caledonie avec uns introcuction

stratigrafique de J acques A vias. Palaeontogr. B. 124: 1-81.

Selmeier A. 1968.Xeno刀loncf.jurassicum (Eckhold) Krausel

aus dem Schilfsandstein von Ruckersdorf bei Ausbach

(Mittel仕anken).N. Jh. Geol. Palaont. Abh. 131: 243-251.

Seward A. 1917. Fossil plants III. Cambr. Univ. Press， London. 一一一一一 1919.Fossil plants IV. Cambr. Univ. Press， London.

Sharma B. D. 1967. Invesugations on the Jurassic flora of

Rajmahal Hills， India 4. On a new species indianBucklandi孔

B. guptai with remarks on B. sahnii of Bose. Ameghiniana

4: 35-45.

一一一一一 1969.Bucklandia dichotoma sp. nov. from the middle

Jurassic ofRajmahal Hills， India. Ameghiniana 6: 303-308.

Stopes M. C. 1915. Catalogue ofthe Cretaceous Florall. Lower

Greensand (Aptian) plants of Britain. Laugmans & Green， London.

Suzuki M.， Joshi L. and Noshiro S. 1991. Tetracentron wood

October 1993 Joumal of Japanese Botany Vol. 68 No. 5 299

合omthe Miocene ofNoto Peninsula， Central Japan， with a

shortrevision ofhomoxylic fossil woods. Bot. Mag. Tokyo

104: 37-48. Sze H. C. 1954. On the s加 ctureand relationship of P horo砂lon

scalariforme Sze. Scientic Sinica 3: 527-531，4 pls.

Torres T. and Lemoigne Y. 1989. Fossil wood findings of angiospermous and gymnospermous of the Upper Creta-

ceous at Williams Point， Livingstone Island， South Shetland Islands， Antarctica. Ser. Cient. INACH 38: 10-29.

Vogellhener D. 1965. Untersuchungen zur Anatomie und

Systematik der verkieselten Holzer aus dem frankischen

und Sudthuringischen Keuper. Erlanger Geol. Abh. 59: 3-

76.

一一一一 1968.Zur Anatomie und Phylogenie Mesozoischer

Gymnospermenholzer 7: Prodromus finer Monographie der

Protopinaceae 11. Die Protopinoiden Holzer des Jura.

Palaeontogr. B. 124: 126-162.

Yamazaki S. and Tsunada K. 1980. Some fossil woods from the UpperTriassic N ariwa Group， Southem J apan. Mem. School

Sci. & Engin. Waseda Univ. 44: 91-131.

一一一一 and一一一1982.Palaeobotanical study on Fusinites

occurring in the Lower Jurassic Kuruma Group， Southwest

Japan. Mem. School Sci. & Engin.， Waseda Univ. 46: 73-123.

一一一一一，一一一一andHagiwara 1. 1984. Comparison between the Liassic and Neocomian species of Xenoxylon Gothan occurring in the Hida Terrane， Central Japan. Mem. School

of Sci. and Engin.， Waseda Univ. 48: 93-115.

要 旨

千葉大学海洋生態系研究センターの鶴岡繁氏

が 1976-1986の約 10年間に銚子市犬吠埼附近の

下部白亜系から採集した 50点余の植物石化化石

を同定し， 3新種， 1新分布種および、既知種の小

枝の 5種を確認できた.

Xenoxylon tsuruokae sp. nov.は木部柔組織をも

っという Xenoxylonの中では特異な形質をもち，

仮道管の接続壁上にも有縁孔紋をもっという点で

Xenoxylon hopeiense Changに似るが，本種の仮道

管放射壁上の有縁孔は lαtiporosum型で，後者の

bαrberi型と異る(表1). Araucarioxylon biseriatum

sp. nov.は放射組織がしばしば 2列になることと，

木部柔組織をもっ点で、 Araucarioxylonohzuanum

Nishida et al. (パダゴニア産)に似ているが，本

種の仮道管にはチローシスがないので，たくさん

のチローシスをもっ後者と区別できる(表 2).

Bucklandiαtylosissima sp. nov.はソテツ植物と

しては稀なチローシスをもつので Bucklandiaの

他の種と区別できる(表 3).

Cupressinoxylon cryptomerioides Stopes ははじめ

はイギリスで記載されたが，サハリン，北海道の

上部白亜系からも知られ，Cupressinoxylon vecト

ense Barberの小枝と思われる. 中部日本(本州)

新産である.Bucklandia cfr. choshiensis Nishida

は径 0.9cmで， 銚子からすでに報告されている

Bucklandia choshiensis Nishidaの末端枝であると

思われる.