Philippe Et Al 2013

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Research paper

Systematics of a palaeoecologically signicant boreal Mesozoic fossil wood genus,Xenoxylon Gothan

Marc Philippe a,, Frdric Thvenard a, Natalya Nosova b, Kyungsik Kim c, Serge Naugolnykh d

a UMR 5276 of the CNRS and Universit Lyon 1, 7 rue Dubois, F69622 Villeurbanne, Franceb Komarov Botanical Institute of the Russian Academy of Sciences, ul. Prof. Popova, 2, St. Petersburg, 197376, Russiac Division of Biological Sciences, Chonbuk National University, Jeonju, 561-756, South Koread Geological Institute of Russian Academy of Sciences, 119017, Moscow, Pyzhevsky per. 7, Russia

a b s t r a c ta r t i c l e i n f o

Article history:Received 19 October 2012Received in revised form 23 January 2013Accepted 29 January 2013Available online 20 February 2013

Keywords:fossil woodXenoxylonLaurasiaMesozoicpalaeobiogeography

The genus Xenoxylon was established for gymnosperm-like fossil wood with xenoxylean radial pitting andlarge oopores in its cross-elds. It is restricted to the Mesozoic and to the Northern Hemisphere, where itis commonly found. As an indicator of cool-wet boreal climates, as suggested by its distribution, Xenoxylonis of special interest to palaeoclimatology. Its systematics, however, is poorly known with several speciesneeding re-evaluation. Xenoxylon nomenclature is also still unresolved, with various synonyms used for thesame taxa even in recent literature. Having reviewed several types and a large number of specimens weperformed a taxonomical and nomenclatural reappraisal of all species known to date. The results of thisreview are presented here, together with a taxonomical key. For most taxa stratigraphical and geographicaldistributions have also been re-evaluated.

2013 Elsevier B.V. All rights reserved.

1. Introduction

When, in 1905, Gothan coined the name Xenoxylon for a fossil woodfrom Svalbard which puzzled him, he probably did not imagine that thisname had a prolic future. At this time Xenoxylon was known only bysome poorly dated specimens from the Arctic. At present this genus isknown to occur from the late Triassic through to the latest Cretaceous,throughout the Northern Hemisphere (Laurasia), with the noticeableexception of most of North America (Philippe et al., 2009). No less than31 Xenoxylon species have been proposed (Table 1), and the genus is ofpalaeobiogeographical and palaeoecological interest (Philippe andThvenard, 1996; Ding et al., 2000; Philippe et al., 2009). Indeed its dis-tribution is restricted to Laurasia, mostly at high palaeolatitudes, and ex-panded southwards during cool intervals only, suggesting thatXenoxylonfavoured cooler/wetter climates. Reliable indicators of terrestrial cli-mates are greatly required for the understanding of Mesozoic climaticevolution. Mineralogical, sedimentological and geochemical evidenceconrm that Xenoxylon was restricted to cool-wet temperate climates(Tchoumatchenco et al., 2008; Amiot et al., 2011; Selmeier and Grosser,2011).

The taxonomy, systematics and nomenclature of the genus are,however, largely unsorted. From a taxonomic view point, some of theanatomical features of the genus that were originally considered to be

of little signicance have been re-evaluated (Philippe et al., 2009). Asfor the systematics, unexpected synonymies were recently discovered(Philippe and Hayes, 2010), whereas some names published by Chinesecolleagues have been overlooked. Few types have been reviewed. Finallythe nomenclature of Xenoxylon needs reappraisal as a putative earliersynonym (Sciadopityoxylon Schmalhausen; Philippe and Bamford,2008) and several species names are still controversial (e.g. Xenoxylonbarberi Seward).

Herewe present a reviewof the genus, with full systematic treatment,taxonomical key and distribution data.

2. Material and methods

The material for Xenoxylonwas studied at several institutional repos-itories listed with their respective abbreviations below and between pa-rentheses the number of Xenoxylon samples studied there:

BIN Komarov Botanical Institute of the Russian Academy ofSciences (RAS), St. Petersburg, Russia (30)

BMNH Natural History Museum, London, UK (17)BUPM Berkeley University Palaeontological Museum, USA (1)CNU Chonbuk National University, South Korea (70)CU Chuo University, Tokyo, Japan (2)HMB Humboldt Museum, Berlin, Germany (9)LPUL Laboratoire de Palobotanique de l'Universit de Lyon,

France (30)MNHN Musum national d'Histoire naturelle, Paris, France (2)NHMD Natural History Museum of Denmark (38)

Review of Palaeobotany and Palynology 193 (2013) 128140

Corresponding author.E-mail addresses: [email protected] (M. Philippe), [email protected]

(F. Thvenard), [email protected] (N. Nosova), [email protected] (K. Kim),[email protected] (S. Naugolnykh).

0034-6667/$ see front matter 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.revpalbo.2013.01.013

Contents lists available at SciVerse ScienceDirect

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SMNH Swedish Museum of Natural History, Stockholm, Sweden (29)TUMS Tohoku University Museum in Sendai, Japan (32)UTM University of Tokyo Museum (15).

Other abbreviations used:

ISBT Institut fr spezielle Botanik der Universitt Tbingen,Germany

NIGPAS Nanjing Institute of Geology and Palaeontology, AcademiaSinica, China

SIGMR Shenyang Institute of Geology andMineral Resources, Liaoning,China.

More than 285 samples of Xenoxylon were studied microscopically,either with scanning electronic microscopy, or light microscopy, usingthin-sections or Collodion casts (Philippe et al., 2006). For all the taxamentioned here protologues were accessed. An extensive bibliographi-cal surveywas performed,which to the best of our knowledge covers allpublished data for Xenoxylon.

3. Results

3.1. Circumscription of Xenoxylon

Since the seminal work by Gothan (1905) the circumscription ofXenoxylon has been little questioned. This genus is based on theoccurrence of at least partially xenoxylean radial pitting in thetracheids (strongly attened contiguous areolated pits; Mller-Stoll,1951; Fig. 1) and a large fenestriform oopore in the early wood cross-elds (characteristically two when a ray cell terminal wall divides thecross-eld; Fig. 2). Krusel (1949) included in Xenoxylon, woods witha mixed type of radial pitting and with 24 rounded oopores percross-eld. As clearly demonstrated by Vogellehner (1967, 1968),such woods belong to distinct genera such as Protocircoporoxylon

Vogellehner or Protopolyporoxylon Vogellehner. The term xenoxyleanapplies to a type of tracheid radial pittingwhere pits are contiguous andappear much attened. In order to quantify this attening from slideS1765 at the SMNH (holotype for Xenoxylon latiporosum; Philippe andCantrill, 2007) we measured the longitudinal diameter/radial diameterratio for 34 radial pits. The maximumwas 0.69 and the minimum 0.45,whilst the mean-value was 0.57 and the standard-deviation 0.05. Thisratio, also known as the height/width ratio, is rarely lower than 0.6in the wood of most extant species with araucarian radial pitting(sensu IAWA, 2004). The 0.6 value is thus a limit below which a radialpit can be characterised as xenoxylean (see illustration in Figs. 1 and 3).

Table 1The thirty-one species names proposed within the genus Xenoxylon; those of which type was studied are underlined.

Species name Authority Reference Notes

arcticum Shilkina Shilkina and Yatsenko-Khmelevsky (1980) Nomen nudumbarberi Seward (as Cupressinoxylon) Krusel (1949) p.p. a synonym of X. huttonianumcanoasense Rau (as Cedroxylon) Krusel (1949) Not a Xenoxylonconchylianum Fliche Fliche (1910) Type lostellipticum Mller-Stoll Vogellehner (1968) A synonym of X. huttonianumfuxinense Ding Ding et al. (2000)hopeiense Chang Chang (1929)huolinhense Ding Ding et al. (2000)huttonianum Witham (as Peuce) Philippe and Hayes (2010)jakutiense Shilkina Shilkina (1986) A nomen nudum in Shilkina & Yatsenko-Khmelevsky, 1980japonicum Vogellehner (not validly published in 1968) Suzuki and Terada (1992) A synonym of X. meisterijurassicum Eckhold (as Protopodocarpoxylon) Krusel (1949) Not a Xenoxylon; topotypes seen[kurumaense] Tsunada Unpublished thesis (1980) Not a validly published namelatiporosum Cramer Gothan (1905)[liaoningense] Duan & Wang Duan et al. (1995) Not a validly published namemeisteri Palibin & Jarmolenko Palibin and Jarmolenko (1932)moorei Tidwell Tidwell et al. (1998) Not a Xenoxylonmorrisonii Medlyn & Tidwell Medlyn and Tidwell (1975) Not a Xenoxylonnariwaense Yamazaki, Tsunada & Koike Yamazaki et al. (1980) Type lostparvipunctatum Vogellehner Vogellehner (1965)peideensis Zheng & Zhang Zheng and Zhang (1982) As peidensephyllocladoides Gothan Gothan (1906) Type lost, topotypes seenpseudoellipticum Yamazaki & Tsunada Yamazaki and Tsunada (1981) Type lostsaadawii Youssef Youssef (2002) Not a Xenoxylonshimakurai Yamazaki & Tsunada Yamazaki and Tsunada in Yamazaki et al. (1984) = X. meisteri; type lostsuljuctense Shilkina & Khudayberdyev Shilkina and Khudaiberdyev (1971) Type losttomiense Larichev Larishchev (1948) Probably not a Xenoxylon; type losttsuruokai Nishida, Nishida, & Suzuki Nishida et al. (1993) Not a Xenoxylonwattarianum Nishida & Nishida Nishida and Nishida (1986)yatsenkoi Yunusov Yunusov in Gomolitzky et al. (1981) Not a Xenoxylonyixianense Zhang & Shang Zhang and Shang (1996)

Fig. 1. Xenoxylon latiporosum (Cramer) Gothan; sample 1991/38 at the HMB, Jurassic,Poland; typical xenoxylean radial pitting on tracheids; note that on the narrow radialface of a tracheid, pits are locally round and distant (a very rare feature for thisspecies and the latiporosum group).

129M. Philippe et al. / Review of Palaeobotany and Palynology 193 (2013) 128140


3.2. Validity of previously published material

Among the 31 binomials proposed to date within Xenoxylon, someare based on material which we consider dubious, are misplaced, orare nomenclaturally invalid. Xenoxylon arcticum, described in 1980by Shilkina and Yatsenko-Khmelevsky, is considered to be a nomennudum. Nothing in this publication identies a particular specimenin Shilkina's collection, housed at the BIN (St.-Petersburg), and wedid notnd any record of that namewhilst checking Shilkina's collection.Xenoxylon (?) tomiense Larishchev has not been considered as it wasassigned with doubt to the genus Xenoxylon (Larishchev, 1948, 1957;Mller-Stoll and Schultze-Motel, 1988). As they have several pits pereld,Xenoxylon canoasense (Rau)Krusel,Xenoxylon jurassicum (Eckhold)Krusel, Xenoxylon moorei Tidwell, Xenoxylon morrisonense Medlyn etTidwell and Xenoxylon yatsenkoi Yunusov in Gomolitzky et al. do not be-long to Xenoxylon (Philippe and Thvenard, 1996 and references therein).Moreover Xenoxylon saadawii Youssef from the late Jurassicearly Creta-ceous of Gebel Kamil, Egypt, does not have xenoxylean radial pitting(Youssef, 2002), and its cross-elds are typical for Metapodocarpoxylon

libanoticum. Yamazaki and Tsunada (in Yamazaki et al., 1984) describedXenoxylon shimakurai, a taxon in which the diagnosis includes pith fea-tures. If only the secondary xylem is considered, then X. shimakurai is an-atomically similar to Xenoxylon meisteri because of its radial pitting anddense tangential pitting. Xenoxylon yatsenkoi Yunusov in Gomolitzkyet al. (1981) has pointed oopores in the early-wood cross-elds (pl. 30g. 4 of the protologue) and although areolated pits in its tracheids areat-elliptic they are not xenoxylean (Gomolitzky et al., 1981, pl. 28g. 4, pl. 30 g. 2). With kind permission of Prof. Harufumi Nishida thetype specimen of Xenoxylon tsuruokai Nishida, Nishida et al. (1993) wasreviewed (although published as tsuruokae, this must be spelled astsuruokai as this is dedicated to Mr. Shigeru Tsuruoka); we observedonly araucarian radial pitting, and although cross-elds sometimes dis-play a large pale window (presumably poorly preserved cell wall) wellpreserved cross-elds with only one small bordered oculipore were alsoobserved in the early wood. This wood also has much axial parenchyma,whereas such parenchyma is generally exceptional in Xenoxylon.

3.3. Sub-generic morphogroups

Two informal groups are usually recognised within Xenoxylon: thelatiporosum-group and the phyllocladoides-group. These groupscan be separated on the type of pitting on the radial walls of earlywood tracheids (Figs. 3 and 4; Table 2). In the latiporosum-groupthe radial pitting is strictly xenoxylean, with only few exceptions. Inthe phyllocladoides-group pits are locally xenoxylean, but otherwisespaced and rounded. Recent discoveries in north-eastern China ledDing et al. (2000) to the proposal of a third group of species, theliaoningense-group. Since [Xenoxylon liaoningense] is not a validlypublished name and as this informal X. liaoningense group hasbeen mentioned only by Ding et al., we prefer to use here the nameof meisteri-group, which reects the name of the rst describedand validly published species of this group. These three informalgroups have no legitimate nomenclatural status.

Radial pitting in the meisteri-group usually appears latiporosum-like at rst glance, but close observation reveals biseriate pitting and/orpit clusters. In addition to these characteristic pit arrangements sometracheid portions appear unpitted (Fig. 5). Pit clusters and unpittedtracheid portions (but not biseriate pits) are also observed in thelatiporosum-group, even in the holotype, but are always extremelyrare and local. The meisteri-group is also characterised by frequent

Fig. 2. Xenoxylon phyllocladoides Gothan, sample 117 in Gothan, slide S00192-02 at theSMNH; cross-elds at the late wood/early wood transition; note that in the late woodpits are bordered, and a eld with two pits.

Fig. 3. Interpretative diagram of typical tracheid radial pitting of the latiporosumgroup.

Fig. 4. Interpretative diagram of typical tracheid radial pitting of the phyllocladoidesgroup.

130 M. Philippe et al. / Review of Palaeobotany and Palynology 193 (2013) 128140


abundant tangential pitting. Although in the latiporosum-group tan-gential pits occasionally occur, these are always uniseriate, round anddistant. In the meisteri-group the tangential pitting, when present, iscommonly bi-tri-seriate with crowded alternate pits. For woods of themeisteri-group, however, even within a single specimen both radialand tangential pittings are usually variable.

Within each of the three morphogroups described in Table 2,species are distinguished mainly on the basis of features usuallyregarded as of little signicance ray height, pit size, occurrence ofaxial parenchyma or of tangential pitting. Diameter of tracheid radialpits was once considered to be a feature with systematic value(Vogellehner, 1965), but it is now clear that it varies considerablywith both the tracheid width and the nature of fossilisation. The pitdiameter/tracheid width ratio might be a more reliable feature, butagain it is variable, even within a single specimen. Here we adopt aconservative approach andmerge taxa only if they are found to be an-atomically completely similar. Several morphospecies differ only inone character state. Although it would have been more rigorous to beable to distinguish species on two or three specic character states, ifsuch policy is applied to the set of the estimated 350 Xenoxylon speci-mens we considered (rsthand experience plus literature), only threespecies would be recognised. The data set yet available (350 specimensfor the whole Northern Hemisphere and a ca. 155 My time interval) istoo limited to convincingly support such merging.

Finally, several Asian specimens related toXenoxylondisplay abundantsepta-like structures. They have been variously interpreted as attenedtylose-like structures, septae, cracks or fungal hyphae (Boureau, 1950;Arnold, 1953; Watari, 1960). Although thin (ca. 1 or 2 m in thickness),they obstruct the whole tracheid, as evidencedwhen fossilisation slightlyturned them (Fig. 6). As yet we have been unable to interpret them andfeel that they do not carry any taxonomical interest.

3.4. A taxonomical key for Xenoxylon species

Ding Qiu-Hong (in Ding et al., 2000) published a key to Xenoxylon inChinese that included information from some previously publishedkeys (e.g. Krusel, 1949; Nishida and Nishida, 1986). Ding et al., howev-er, did not have the opportunity to study the type of material outside ofChina, and relied for most taxa on original publication (protologue)only.

Table 2Three groups recognised within Xenoxylon Gothan; these groups have no legitimate nomenclatural status.

Tracheid pitting Latiporosum group Meisteri group Phyllocladoides group

Normal radial tracheid pitting Strictly xenoxylean, in longuninterrupted uniseriate rows

Generally xenoxylean, uniseriate rowslocally interrupted, clusters

Locally xenoxylean, otherwise mixed type,mostly uniseriate

Biseriate radial pitting Absent In some cases, alternate or opposite, spaced orcontiguous

Tangential Rare, uniseriate, spaced Occasional to common, up to triseriate, alternate,generally contiguous

Rare, uniseriate, spaced

Fig. 5. Interpretative diagram of typical tracheid radial pitting of the meisteri group.

Fig. 6. Xenoxylon meisteri Palibin et Jarmolenko, material studied by Suzuki and Terada(1992), at the TUMS; A sample 53907, septae, hyphae and/or thylosis?; B sample53903, tilted septa (arrow) showing its bidimensional nature.



Here we provide a translation of Ding Qiu-Hong's key withseveral updates and modications, since some species were notincluded by Ding et al. (2000). We also took into account otherprevious reappraisals (Vogellehner, 1965; Serra, 1966; Shilkina andKhudaiberdyev, 1971). Although we have not been able to studyrecently described Chinese species, we reviewed most of the availableXenoxylon type material (Table 1).

Features described in the revised key presented below should onlybe used for non-traumatic areas where tracheids are opposite betweentwo adjacent rows, because when tracheids alternate they developnarrow radial faces which can bear atypical pitting (Fig. 1).

1 Early wood bordered pits on radial tracheid walls: small, typically1016 mhigh1221 mwide; pits: uniseriate in long uninterruptedrows, not much attened; biseriate radial pits: alternate andcrowded; tangential tracheid pitting: completely lacking Xenoxylonparvipunctatum Vogellehner

1 Early wood bordered pits on radial tracheid walls: large, typically1538 m high2040 mwide 2, 2, and 2

2 Early wood bordered pits on radial tracheid walls: alwaysuniseriate, contiguous and compressed (xenoxylean radial pitting),very rarely spaced (only in the narrowest tracheids); tangential tracheidwalls: rarely pitted, when present: uniseriate, round and distant Xenoxylon latiporosum group (Fig. 3) 3 and 3

3 Early wood bordered pits: generally covering only half of tracheidradial wall width Xenoxylon peideensis Zheng & Zhang

3 Early wood bordered pits: generally covering the whole widthof tracheid radial walls 4 and 4

4 Some rays with traumatic resin canals/pockets Xenoxylonyixianense Zhang & Shang

4 All rays uniseriate 5, 5, and 5 (similar species)5 Rays (1) 26 (10) cells high Xenoxylon watarianum Nishida &

Nishida5 Rays mostly 510 cells high, at most 16 cells Xenoxylon

conchylianum Fliche5 Rays mostly 1020 cells high, rarely up to 25 cells Xenoxylon

latiporosum (Cramer) Gothan

2 Early wood bordered pits on radial tracheid walls: contiguous orspaced, round or elliptic, only locally xenoxylean; tracheid tangentialwalls: rarely pitted, when present these tangential pits are uniseriateand spaced Xenoxylon phyllocladoides group (Fig. 4) 6 and 6

6 Rims of Sanio: present 7 and 77 Axial parenchyma: present; radial tracheid pitting: uni-biseriate

Xenoxylon hopeiense Chang7 Axial parenchyma: absent; radial tracheid pitting: always

uniseriate Xenoxylon jakutiense Shilkina6 Rims of Sanio: absent 8 and 88 Early wood cross-eld pits usually 12 (3) times as wide than

high Xenoxylon phyllocladoides Gothan8 At least some early wood cross-eld pits: 45 times as wide as

high Xenoxylon huttonianum (Witham) Philippe & Hayes

2 Early wood bordered pits on radial tracheid walls: clearly inter-mediate; xenoxylean type frequent, intermingled with clusters of 39radial pits (those at tips being smaller andmore rounded) and/or signif-icant proportion of bi-triseriate pit rows and/or area of unpitted tra-cheid wall; tangential tracheid wall: often pitted, usually with someuni-triseriate contiguous alternate pits Xenoxylon meisteri group(Fig. 5) 9 and 9

9 Bordered pits on radial tracheid walls: always uniseriate (exceptfor traumatic areas) 10 and 10

10 Short clusters of 35 pits frequent Xenoxylon huolinhenseDing in Ding, Zheng & Zhang

10 Clusters: usually much longer; radial pitting: appearinglatiporosum-like at rst glance 11 and 11

11" Rays: (1) 38 (18) cells high Xenoxylon meisteri Palibin &Jarmolenko

11 Rays: up to 4050 cells high Xenoxylon japonicumVogellehner ex Suzuki & Terada

9 Bordered pits on radial tracheid walls of untraumatised wood:sometimes biseriate or even triseriate 12, 12, and 12

12 Uniseriate radial pit areolae: mostly round or elliptical, andspaced; biseriate pits: mostly opposite 13 and 13

13 Rays: (5) 3040 (50) cells high [Xenoxylon liaoningense]Duan & Wang

13 Rays: (1) 26 (12) cells high Xenoxylon nariwaenseYamazaki, Tsunada & Koike

12 Uniseriate radial pit areolae: generally compressed; biseriatepits: generally alternate Xenoxylon fuxinense Ding in Ding, Zheng& Zhang

12 Uniseriate radial pit areolae: very compressed; bi-triseriate pits:always alternate Xenoxylon suljuctense Shilkina & Chudajberdiev

4. Systematic classication

The systematic classication presented here relies as much as pos-sible on the reappraisal of types and published specimens. In the fewcases for which it has not been possible to study the material we havehad to rely on the protologue. Names between square brackets arenot validly published.

For distribution data we used only well documented data (eitherfrom published or unpublished sources), which was not entirely sat-isfactory since many publications do not provide information on all ofthe points mentioned in the key.

For each entry at specic level we use the following format:

Species name

Basionym and full bibliographical reference to the protologueSynonymyNote(s)Type: repository; reappraised or not; later typication(s) if anyDistribution: 1) source for the type; 2)rst appearance datum(FAD) lastappearance datum (LAD); and 3) palaeogeographical range

4.1. Generic level

FOSSIL-GYMNOSPERMAEPINOPHYTA?Morphogenus Xenoxylon Gothan, Abh. Knigl. Preuss. Geol.Landesanst. ser. 2. 44: 38. 1905.Type: Xenoxylon latiporosum (Cramer) Gothan, Abh. Knigl. Preuss.Geol. Landesanst. ser. 2, 44: 108. 1905. (Pinites latiporosus Cramer) note that the combination is made by Gothan only in the Register(a plant name index) of his thesis (1905).Diagnosis: Tracheidoxyls without axial resin channels; axialparenchyma: occasional and then sparse; radial tracheid pitting: at leastlocally xenoxylean, i.e. with contiguous pits much wider than high;ray-cell walls: thin, smooth, unpitted except for cross-elds where thereis one (rarely two) window-like unbordered oopores that occupy thewhole eld in the early-wood, sometimes more restricted and narrowlybordered in both the late-wood and the reaction wood (slightly modi-ed from Vogellehner, 1968).Synonymy: The oldest description of a fossil wood with a Xenoxylonanatomy is that of Peuce huttoniana in 1833 by Witham of Lartington(Philippe and Hayes, 2010). The name Peuce Lindley et Hutton is apoorly dened generic name (unused for more than a century) with di-vergent Mesozoic and Palaeozoic syntypes, neotypied by Palaeozoicmaterial (Andrews, 1955), which should not be used for Mesozoic



tracheidoxyls (Philippe and Bamford, 2008). The wood P. huttonianawas subsequently assigned to genera Pinites Lindley et Hutton,Elatoxylon Hartig and Cedroxylon Kraus in Schimper, but none of thesenames should be used for fossil wood as their diagnoses, their circum-scriptions, and their syntypes (several are polytypic) are unclear(Bamford and Philippe, 2001; Philippe and Bamford, 2008; Philippeand Hayes, 2010). Corresponding nomenclatural and taxonomicalsynonymies are too uncertain to question the largely automaticlectotypication of these generic names by Andrews (1955), despitethe fact that they potentially have priority over Xenoxylon.

In 1877 Schmalhausen briey described a wood collected by Gbelin the Jurassic of the Mangyshlak Peninsula (Caspian Sea, westernKazakhstan) as Sciadopityoxylon vetusta. Given the date, this genericname is validly published (ICBN, art. 38.1; McNeill et al., 2012) andshould be considered for synonymy. Schmalhausen's description isstrongly reminiscent of Xenoxylon. In 1879 Schmalhausen gave amore complete description of the features of extant Sciadopityswood (and hence those features he considered to be diagnostic forhis Sciadopityoxylon): The Sciadopitys-wood is very similar to that ofcommon pine, but it does not have the resin canals of the latter, and inthe upper and lower rows of ray-cells the irregular tooth-like thickeningsof pinewood are lacking. By Sciadopitys the tracheids have pits on theirradial walls, which are uniseriate, rarely biseriate in very lax woods,sometimes so densely distributed that they are contiguous, sometimesmore or less irregularly distant from one another. The ray-cells haveon their lateral side, like in pinewood, large pores which are oval-transversal in spring wood, almost oblique and slit-like in the autumnwood, and single on the width of the tracheid. In tangential view therays are always uniseriate, (Schmalhausen, 1879: 40; our transla-tion). A Jurassic wood tting this description is likely to belong toXenoxylon. Moreover this genus was later documented in the Jurassicof Mangyshlak (Philippe and Thvenard, 1996), and Schmalhausen(1879) reported other samples with similar anatomy from the Juras-sic of Murayevnya (Ryazan oblast', Russia). Unfortunately, Gbel'swood specimen has not been illustrated and is apparently lost. At theBIN the only specimenwe located fromMangyshlak, a typicalXenoxylonlatiporosum, was collected in 1956 by R.I. Vyalova. It is therefore impos-sible, at present, to consider priority of Sciadopityoxylon over Xenoxylon.A neotype should, however, be designated for Sciadopityoxylon.

The recently described Protosciadopityoxylon Zhang, Zheng et Ding(Zhang et al., 1999; Zheng et al., 2008) is similar toXenoxylon. It displaysxenoxylean radial pitting and fenestriform oopores, but the latter arenarrowly bordered or even sub-taxodioid (sic). Several authors haveassigned samples to Xenoxylon that sometimes exhibit bordered ooporesin the cross-elds, for example Gothan and his material from Knig KarlLand (Fig. 7), and Dorofeyuk and Filin (1969) and their Siberianmaterial.In Protosciadopityoxylon even early-wood oopores in non-compressionwood are bordered. This justies the separation of Protosciadopityoxylonfrom Xenoxylon (Zhang Wu & Zheng Shaolin, in litt., 2010).

Range: Xenoxylon has been recorded from the Carnian (LateTriassic; Fliche, 1910; Vogellehner, 1965; Yamazaki and Tsunada,1981, 1982) to the Maastrichtian (Late Cretaceous; Spicer andParrish, 1990; Terada et al., 2011). Palaeobiogeographically it hasbeen found through all Eurasia (including southern plates such asGeorgia, Northern Iran, South China and Indosinia, but has not yetbeen recorded from Sibumasu, India, Arabian Peninsula), Greenland,Alaska and Canada (Alberta).

4.2. Species

Xenoxylon conchylianum FlicheXenoxylon conchylianum Fliche, Flore fossile du Trias en Lorraine etFranche-Comt: 234, pl. 23 gs. 45. 1910.

Note: In his protologue Fliche emphasises the presence of radiallyelongated cross-elds and low rays. Age is also used by Fliche as an

argument to distinguish this species, since Xenoxylon had then onlybeen recorded from the Jurassic. The original illustration is crude andof little diagnostic value, the original description is limited, and type re-vision has long been recommended (Krusel, 1919). Vogellehner statedthat this species is in nahe Verwandschaft (closely related) to hisXenoxylon parvipunctatum (Vogellehner, 1965: 46), but although bothtaxa have some rounded pits intermingled among usual xenoxyleanpits, in Xenoxylon conchylianum all pits are said to be contiguous.Type:We searched for the specimen described by Fliche inNancy (whereFliche spent most of his professional life, and where part of hispalaeobotanical collection is now housed) and in other FrenchMuseumswhere the Fliche's fossil wood collection could have been housed. Thissearch was unsuccessful. To the best of our knowledge this collectionhas never been reviewed. The protologue is so restricted in termsof char-acteristic features that it is not possible to design a neotype.

Distribution: 1) type Carnian (not Muschelkalk) of Vaubexy, Vosges,France; 2) FAD/LAD Schilfsandstein, Early Carnian, Lorraine, France;this taxon was also reported from the Middle Jurassic of Hebei,China (Wang, 1995) but with a poor illustration; in his unpublishedthesis, Khudaiberdyev mentioned (Table 1, p. 19) the occurrenceof this taxon in the Jurassic of Middle Asia but later omitted thisdata (Shilkina and Khudaiberdyev, 1971; Khudaiberdyev, 1993);unpublished material from Baikal area at the BIN is labelled Xenoxyloncf. conchylianum, but the preservation is poor; 3) geographical rangeWestern Europe.

Xenoxylon fuxinense Ding in Ding, Zheng et Zhang

Xenoxylon fuxinense Ding in Ding, Zheng et Zhang, ActaPalaeontologica sinica, 39: 245, pl. 1 gs. 16. 2000.

1933 Xenoxylon latiporosum (Cramer) Gothan in Gothan et Sze1980 [Xenoxylon kurumaense] Tsunada, unpublished MSc Thesis,Waseda University1981 Xenoxylon cf. suljuctense Shilkina et Khudaiberdyev in Yamazakiet Tsunada

Note: This species appears similar to Xenoxylon suljuctense, differingonly in details of the tracheid pitting pattern (occurrence of some

Fig. 7. Xenoxylon phyllocladoides Gothan, slide S1827/03 at the SMNH; material seen byGothan, with locally bordered oopores (arrow).



opposite to sub-opposite pit pairs); sample S4846 seen at the SMNH,from Fengtien, Hsi-Hsien and determined by Gothan and Sze (1933)as Xenoxylon latiporosum, has inated tips bearing both alternate andopposite biseriate pits in untraumatised wood.

Type: Not seen by us but studied by Ding et al. (2000), sample Fx-3,stored at the SIGMR.

Distribution: 1) type Haizhou Coal Mine, Fuxin, Liaoning, Fuxin Fm.,AptianAlbian, Early Cretaceous; 2) FAD Liassic, Negoya Fm., KurumuaGroup, Toyama Prefecture, Japan, LAD-type; and 3) geographical rangeJapan and Liaoning, north-eastern China.

Xenoxylon hopeiense Chang

Xenoxylon hopeiense Chang, Bull. Geol. Soc. China, 7: 250, pl. 1 gs.14, text gs. 17. 1929.

1936 Phyllocladoxylon heizoense Shimakura1967 Xenoxylon barberi (Seward) Krusel in Shilkina (p.p., sample674 at the BIN)2011 Dacrydioxylon sp. in Selmeier et Grosser

Note 1: According to Chang (1929) similar to Xenoxylonphyllocladoides, but featuring Rims of Sanio; assigned toX. phyllocladoidesby Gothan and Sze (1933); good illustration provided by Ding et al.(2000, pl. 4 gs. 15); X. phyllocladoides topotypes from Poland neverhave Rims of Sanio and thus it is worth separating this species.

Note 2: The material described as Xenoxylon phyllocladoides byJiang et al. (2008) from the Lanqi Formation, Liaoning, might belongto Xenoxylon hopeiense as it displays Rims of Sanio.

Note 3: The wood from North Korea (Botandai of Heizyo)described as Phyllocladoxylon heizoense Shimakura (Shimakura, 1936)is also similar to Xenoxylon hopeiense (syntypes seen at the TUMS). Itis illustrated in Kim et al. (2005, pl. 19).

Note 4: The wood described as Dacrydioxylon sp. by Selmeier andGrosser (2011) belongs to Xenoxylon hopeiense; it has axial parenchy-ma and Rims of Sanio (Selmeier and Grosser, 2011, pl. 6 g. 2).Type: Not seen; Professor C.Y. Chang (Beijing University) described thetype specimen, recorded as block n 188 from the Geological Survey;this large block, over 3 tons in weight, had been on exhibition (Hsiao,1935) but was since lost, probably during the Sino-Japanese war;recent researches in this town failed to locate this type specimen(Jiang Zikun, in litt.). Among the syntypes of Phyllocladoxylonheizoense Shimakura, sample 6874 at the TUMS is designated hereas the lectotype for that name, and as the neotype of Xenoxylonhopeiense Chang.

Distribution: 1) type Late Jurassic, Hopei, North-Eastern China (Chang,1929); 2) FAD Beipiao Fm., Early Jurassic, Liaoning (Wang et al.,2006), LAD Aptian, Shahai Fm., Yixian, Western Liaoning (Zhangand Shang, 1996), and Lipovtsy Fm., Southern Primorye, Russian FarEast (Afonin, 2008); and 3) geographical range North-eastern China(Beijing, Heilongjiang, Liaoning, Xinjiang), Eastern Siberia and Arctic(Alexandra I., Franz-Josef Land, Canadian Arctic Archipelago).

Xenoxylon huolinhense Ding in Ding, Zheng et Zhang

Xenoxylon huolinhense Ding in Ding, Zheng et Zhang, ActaPalaeontologica sinica, 39: 246, pl. 2 gs. 16. 2000.

Note 1: From the original illustration (pl. 2 g. 4) it seems that theclustering of radial pits is an artefact due to wavy wood grain (an un-dulating tracheid wall renders some pits out of focus); the smallersize and different shapes of the pits at the tips of the pit row showsit is no artefact; it is observed that pit clusters usually occur on the

widest tracheid portions, and that pit rows are often interruptedwhere tracheids are narrow.

Note 2: This wood is similar to Xenoxylon nariwaense, except forthe occurrence in the latter of some opposite biseriate pit pairs,which might be a local feature only.

Type: Not seen by us but studied by Ding et al. (2000), sample H14,stored at the SIGMR.

Distribution: 1) type Huolinhe Coal Mine, Inner Mongolia AutonomousRegion, Early Cretaceous, Huolinhe Fm.; 2) FAD/LAD this taxon isknown only from its type specimen; and 3) geographical range InnerMongolia Autonomous region, China.

Xenoxylon huttonianum (Witham) Philippe et Hayes

Peuce huttonianum Witham of Lartington, Internal Structure of FossilVegetables, 70, pl. 14 g. 9, pl. 15 gs. 4 et 5 (huttoniana et hutonii).1833.

1833 Peuce huttoniana (p. 70)"huttonii" (p. 63) Witham1848 Elatoxylon huttoniana Hartig1849 Peuce huttonii Brongniart1849 Pinites huttonianus Gppert in Bronn1870 Cedroxylon huttonianum Kraus in Schimper1904 Cupressinoxylon barberi Seward1949 Xenoxylon barberi (Seward) Krusel1968 Xenoxylon ellipticum Schultze-Motel ex Vogellehner2010 Xenoxylon huttonianum (Witham) Philippe et Hayes

Note: Wang's datum for Xenoxylon ellipticum from theHongweikeng Formation, Carnian, Northern Guangdong (Wang,1991) exhibits some biseriate radial pitting and therefore belongsto the meisteri-group.

Type: Seen; slide 51498 at the MNH London, Nicol's collection, chosen asthe neotype for Peuce huttonianum (Philippe and Hayes, 2010); in Berlin,at the HMB, a fossil wood labelled Araucarioxylon wrttembergicus be-longs to Xenoxylon huttonianum, but this is probably not the type ofPinites wuerttembergicus Goeppert (indicated as kept in Mnchen bySchuster, 1909).

Distribution: 1) type Whitby, Yorkshire, UK; 2) FAD EarlyPliensbachian (Davoei Zone) of Lincolnshire, UK (unpublished data,sample V25987 at BMNH), LAD Humphresianum zone, Bajocian,Osnabruck, Germany (unpublished data, leg. F. Wittler); and 3) geo-graphical range endemic in Western Europe.

Xenoxylon jakutiense Shilkina

Xenoxylon jakutiense Shilkina in Takthajan, A.L. (Ed.), Problemypaleobotaniki, 154, pl. 4 gs. 14.1986.

Note: This name was quoted as jakutense in Shilkina andYatsenko-Khmelevsky (1980: 115) but was only validly pub-lished in 1986; Ding et al. (2000) assigned this wood to theirliaoningense-group (here meisteri-group) on the basis of someround tracheid radial pits appearing somewhat spaced out along thetracheid; however, this arrangement is the result of crassulae, andXenoxylon jakutiense is therefore more similar to Xenoxylon hopeiense.Its radial pitting is strictly uniseriate, but Shilkina's protologue (1986)emphasises that the specimen tracheids are narrow.

Type: Seen, Coll. 691, spec. 1/335 in wood slides collection of BIN,three slides.



Distribution: 1) type AptianAlbian of Olenek River Basin, Siberia;2) FAD/LAD other materials have not yet been reported to ourknowledge; and 3) geographical range Eastern Siberia.

Xenoxylon japonicum Vogellehner ex Suzuki et Terada

[Xenoxylon japonicum] Vogellehner, Palaeontographica, Abteilung B,124: 145. 1968.Xenoxylon japonicum Vogellehner ex Suzuki et Terada, J. Phytogeogra-phy Taxonomy 40: 96. 1992.

1934 Xenoxylon latiporosum (Cramer) Gothan in Shimakura, deSuzuki et Terada, 1992: 961936 Xenoxylon latiporosum (Cramer) Gothan in Shimakura pro parte

Note 1: Distinguished from Xenoxylon latiporosum by Vogellehner onthe basis of frequent tangential pitting and high rays (in this order);Vogellehner did not typify his new taxon (his name is thus not validlypublished according to ICBN, art. 37.1), but referred to all the specimensdescribed collectively by Shimakura (1936) as X. latiporosum. Thesesyntypes were reviewed by Suzuki and Terada (1992: 96) who selecteda lectotype (sample n 6870 in Shimakura, 1936) on the basis of preserva-tion and of ray height. This lectotype does not display tangential pittingand exhibits the typicalmeisteri-type of radial pitting. Suzuki and Terada(1992) noted that some of the Shimakura's samples have much lowerrays. For one of them e.g., n 57601 from Northeast China, housed at theTUMS, we observed: ray height 211 cells, mean 4.22, standard deviation1.9; 27 counted. Using the above key n 57601 keys out here as Xenoxylonmeisteri, Xenoxylon japonicum and X. meisteri often co-occur in the samelocalities, and thus might originate from the same plant species.

Note 2: In his protologue Vogellehner (1968) also questioned theattribution of some samples to Xenoxylon japonicum; the material de-scribed in 1950 by Boureau (probably now in Paris, not yet located)from the Liassic? of Vietnam similarly has high rays (up to 36 cells)and some round pits, Boureau's material is probably referable toX. japonicum along with the late Early Cretaceous (AptianAlbian?)specimen from Alaska described by Arnold (1953)(a review of theslides should be undertaken).

Type: Lectotype seen, slide no. 6870 deposited at the TUMS.

Distribution: 1) type Late Triassic, the quarry of Botandai,Pyongyang, North Korea; 2) FAD/LAD to our knowledge othermaterialshave not yet been reported; and 3) geographical range Eastern Siberia.

Xenoxylon latiporosum (Cramer) Gothan

Xenoxylon latiporosum (Cramer) Gothan in Abhandl. Preuss. Geol.Landesanst. 44: 108. 1905.Pinites latiporosus Cramer in O. von Heer (Ed.), Flora Fossilis Arctica,176, pl. 40 gs. 18. 868.

1868 Pinites pauciporosus Cramer in O. von Heer, p. 1761870 Araucarioxylon latiporosum (Cramer) Kraus in Schimper, p. 3841887 Araucarioxylon koreanum Felix with doubt, vide Philippe, 19951911 Araucarites latiporosus (Cramer) Tuzson p. 31

Type: Seen, sample S1764 and the three associated slides S1765,S1766, and S1767 at the SMNH are the holotypes (Philippe and Cantrill,2007).

Distribution: 1) Holotype Brentskardhaugen Bed, ToarcianBajocian(Reolid et al., 2010), Green Harbour, Spitzberg; 2) FAD UpperKokuibelsu Subsuite, Norian, Central Pamir, Tajikistan (Khudaiberdyev,1993), but there are several other data only dated as Late Triassic,

LAD Yuliangzi Fm., EarlyMid Maastrichtian, Heilongjiang (Sun et al.,2007); and 3) geographical range probably covering the northernmostboreal hemisphere, in Asia, Europe and northernNorth America (south toAlberta), but several datamust be reappraised. In particular a reviewof allthe Japanese material found them to t within Xenoxylon meisteri.

[Xenoxylon liaoningense Duan et Wang in Li et Cui]

[Xenoxylon liaoningense Duan etWang in Duan, Cui etWang], Proc. Inter.Symp. Tree anatomy & Wood Formation, Tianjin, China (Wu Shuminged.), International Academic Publishers, Beijing, p. 168, gs. 79 p. 169(unnumbered plate), gs. 14 p. 170 (unnumbered plate). 1995.[Xenoxylon liaoningense Duan et Wang in Li et Cui], Atlas of fossil plantanatomy in China, Science Press, Beijing, p. 114115, plates only, notext. 1995.

Note 1: This name is not validly published as no type is selectedwhereas two specimens are mentioned; as there is no indication ofa repository; and as the different diagnoses in this paper are not clear-ly related to taxa (ICBN, arts. 32.1 d, 37.1, 37.7; McNeill et al., 2012).This name was published a second time during the same year (in Liand Cui, 1995), but with no protologue. It was further described andillustrated (copy of original illustration) in Zheng et al. (2008) butagain without diagnosis and type designation. As there are some dis-crepancies in the protologue and as the type details are lacking it wasjudged importunate to validate the name here.

Note 2: Anatomically similar to Xenoxylon nariwaense, which haspriority and differs only by ray height; but since we have not yetseen any of the types and as ages are different we are reluctant to es-tablish this synonymy.

Type: Not seen, stored in Beijing, at Institute of Botany, Chinese Acad-emy of Sciences (Zhang Wu & Zheng Shaolin pers. com.).

Distribution: 1) type Shahai Fm., Aptian, Yixian, Western Liaoning;2) FAD/LAD to our knowledge no othermaterials have been reported;and 3) geographical range North-eastern China.

Xenoxylon meisteri Palibin et Jarmolenko

Xenoxylon meisteri Palibin et Jarmolenko, Trudy VGRO, 51: 177,text-g. 1 (Meisterii). 1932.

1936 Xenoxylon latiporosum (Cramer) Gothan in Shimakura, pro parte1981 Xenoxylon pseudoellipticum Yamazaki et Tsunada

Note 1: The holotype for Xenoxylon pseudoellipticum, supposedlykept at Waseda University, Japan, is in fact lost (Profs. Mitsuo Suzuki& Harufumi Nishida pers. com.); it is, however, well illustrated anddescribed in its protologue; Yamazaki & Tsunada assigned it to thephyllocladoides-group but early wood radial pits are neither roundnor spaced.

Note 2: The diagnosis of Xenoxylon shimakurai includes pithfeatures (Yamazaki et al., 1984); as long as only secondary xylemis considered, it ts within Xenoxylon meisteri; unfortunatelyX. shimakurai type is lost (Profs. Mitsuo Suzuki & Harufumi Nishidapers. com.).

Note 3: The taxonomic signicance of tangential radial pitting withinthe genus Xenoxylon was questioned (Shilkina and Khudaiberdyev,1971: 131); within material from the same provenance heavily tangen-tially pitted wood and tangentially unpitted wood generally co-occur(Shimakura, 1936; our observations). Dense tangential pitting inXenoxylon latiporosum-like wood is, however, encountered only in woodfrom the Cretaceous of Asia (including the Arctic) making justiable thedistinction of a morphospecies. The correct name for this taxon isXenoxylon meisteri, a name minimally illustrated in its protologue butthe holotype of which is available at the BIN. The original diagnosis for



X. meisteri reads: Wood rings distinct, about 5 mmwide, late wood thinwith thick-walled cells, early wood cells (up to 5 times) larger,subparenchymatous; resin canals lacking; medullary ray uniseriate,composed of 311 superposed cells, with a single (very rarely two)large simple lateral pore; prosenchymatous cells thin-walled, atgrowth-ring limit somewhat thickened, divided by sub-tyloses (sic),pits only radial, uniseriate or very rarely sub-biseriate, elliptical-compressed in dense rows, 1518 m high and 3033 m wide (ourtranslation, prosenchymatous cellsmeans here tracheids).

Note 4: Specimens showing the characteristics of Xenoxylonmeisteri have usually been assigned to Xenoxylon latiporosum; a com-plete review is necessary, and all literature data for X. latiporosummust be reconsidered, especially those from Asia; most, if not all,specimens from the Tetori series (Cretaceous of Japan) belong toX. meisteri, as is, for example, the wood illustrated by Kim et al.(2005), pl. 6.

Note 5: In traumatic wood biseriate opposite pairs and axial paren-chyma can be observed (sample 44490 in Suzuki and Terada, 1992,seen at the TUMS).

Type: Seen, sample 507/N224 at the BIN, three slides; other materialslabelled as Xenoxylon meisteri at the BIN include no. 508/no. 224 (5slides) and wood no. 6 (3 slides).

Distribution: 1) type Vitichsk Nagorie, Vitim Plateau, east of BaikalLake, Eastern Siberia, Cretaceous (Palibin and Jarmolenko, 1932);2) FAD Beipiao Fm., Early Jurassic of Liaoning (Ding et al., 2000)and Kuruma Group (cf. Nagoya Fm.), Toyama Prefecture, Japan(Yamazaki et al., 1984), older material might belong here (Xenoxyloncf. japonicum, Late Triassic, southwestern Japan, Yamazaki et al.,1980), LAD Late Cretaceous of Dauria, Transbaikalia (Dorofeyukand Filin, 1969); and 3) geographical range Japan, north-easternChina, Eastern Siberia, but several Asian specimens assigned toXenoxylon latiporosum probably belong here.

Xenoxylon nariwaense Yamazaki, Tsunada et Koike

Xenoxylon nariwaense Yamazaki, Tsunada et Koike, Memoirs of theSchool for Science and Engineering of Waseda University, 44: 93, pl.1 g. 1, pl. 2 gs. 12, pl. 3 gs. 16, text-g. 2. 1980.

Note1: Xylologically similar to [Xenoxylon liaoningenseDuan etWang],which is probably an earlier taxonomical synonym; unfortunately theconfused and poorly illustrated protologue for [X. liaoningense] makes itdifcult to judge whether it is a synonym and material reappraisal isnecessary.

Note 2: Shimakura and Fujiyama (1962) studied Xenoxylon woodfrom the same provenance as the type of Xenoxylon nariwaense;they assigned it to Xenoxylon latiporosum.Type: Not seen, no. 79040303-a (holotype) and 79040303-b(paratype), at Waseda University, Japan; both lost according to Prof.Mitsuo Suzuki (pers. com.).Distribution: 1) types Hinabata Fm, Nariwa Group, Norian, LateTriassic, Hinabata, Okayama Prefecture, Japan (Yamazaki et al.,1980); 2) FAD/LAD other materials have not yet been reported;and 3) geographical range Japan.

Xenoxylon parvipunctatum Vogellehner

Xenoxylon parvipunctatum Vogellehner, Erlanger geologischenAbhandlungen 59: 43, pl. 9 g. 81, pl. 10 gs. 8691, pl. 11 g. 92. 1965.

Note: Where a cross-eld is crossed by a ray parenchyma trans-verse wall in some cases it has two oopores (Vogellehner, in a letterquoted by Selmeier, 1968); in establishing this taxon, Vogellehnerpointed out mostly the small size of radial pits; however, it is also

worth noting that radial pits are not particularly attened, sometimesbiseriate alternate, sometimes spaced (protologue, pl. 10 g. 88); theradial pitting conforms to that of the meisteri-group, whereas thetangential pitting is absent.Type: Not seen, ISBT, Mgdefrau collection, SMF 31, SMS 31ac, SMSV31ac.Distribution: 1) type Schilfsandstein, Early Carnian, Simmerhausen,southern Thuringia, Germany (Vogellehner, 1965); 2) FAD/LAD other materials have not yet been reported to our knowledge; and 3)geographical range Western Europe.

Xenoxylon peideensis Zheng et Zhang

Xenoxylon peideensis Zheng et Zhang, Bulletin Shenyang Institute ofGeology and Mineral resources 5: 332, pl. 31 gs. 112. 1982(peidense).

Note 1: This species was described in Chinese (Zheng and Zhang,1982) without clear indication of a type specimen and no diagnosisyet at this time, this was in accordance with the rules of the ICBN(art. 32.1); subsequently, it was mentioned by He Dechang (1995)as X. peideense but this is probably more a cacography than anorthographic variant as the correct form is X. peideensis (ICBN, rec.60D1); authors put emphasis on a mesh-like structure which mightbe due to alteration.

Note 2: Radial pit rows covering only half of the width of the tracheidwall are often observed inwoods of both the latiporosum-group and themeisteri-group. By Xenoxylon peideensis, however, such half-covering issupposed to be the dominant gure.Type: Not seen by us but studied by Ding et al. (2000), HP39 (Zheng andZhang, 1982: 349), stored at the SIGMR, Shenyang, China (ZhangWu &Zheng Shaolin, in litt.).Distribution: 1) typeMishan, Eastern Heilongjiang, Dongshengcun Fm,Middle Jurassic; 2) FAD Beipiao Fm., Early Jurassic, Kazuo, Liaoning(Ding et al., 2000), LAD Huolinhe Fm, Late Jurassic/Early Cretaceous,Huolinhe mine, Jarud, Inner Mongolia (He Dechang, 1995); and 3) geo-graphical range from our database Xenoxylon peideensis is endemicin North-eastern China (Liaoning, Heilongjiang).

Xenoxylon phyllocladoides Gothan

Xenoxylon phyllocladoides Gothan, Verh. Russ.-Kais. Mineral. Gesell.44: 454, g. 4. 1906.

1882 Araucarioxylon latiporosum (Cramer) Kraus, in Conwentz1940 Mesembrioxylon sp. in Sitholey1955 Mesembrioxylon sp. in Jacob et ShuklaXenoxylon barberi auctorem plurime, sed vide Xenoxylon huttonianumibidem1988 Xenoxylon jurassicum Gothan in Matyjasik et Gierlinski sednon Kraeusel

Note 1: For a long while this taxon was referred to as Xenoxylonbarberi (Seward) Krusel, a name based on Cupressinoxylon barberiSeward, the syntypes of which are all from the Toarcian of Whitby(Yorkshire, UK), and are stored at the BMNH (as 51495, 51496 and51498); these syntypes were assigned to Xenoxylon huttonianum(Philippe and Hayes, 2010), and thus the name X. barberi is not rele-vant to Xenoxylon phyllocladoides synonymy.

Note 2: Matyjasik and Gierliski (1988) use the name XenoxylonjurassicumGothan, but Gothan never erected such name; unfortunate-ly the only published Xenoxylon jurassicum is that of Krusel (1949)based on Protopodocarpoxylon jurassicum Eckhold, itself based onPodocarpoxylon sp. Gothan, which was used for a wood from theXenoxylon phyllocladoides type locality; investigations by us of thistype locality yielded numerous topotypes of Protopodocarpoxylonjurassicum, which are clearly not Xenoxyla (Philippe et al., 2006).



Type: Not seen, said to be deposited in Warsaw, at Polish GeologicalInstitute; this and other polish collections with palaeontologicalsections were contacted thanks to the help of Michal Zaton andLeszek Marynowski (Sosnowiec University), but without success.We have, however, examined topotypes (Philippe et al., 2006).

Among them we propose sample MP1571 at the LPUL as the neotypeand illustrate it here (Fig. 8) since Gothan's protologue is minimallyillustrated.Description of the neotype: tracheidoxyl; no axial parenchyma or resincanals; growth-rings marked, early- to late-wood transition abrupt,late-wood limited to 25 layers of cells; transverse section of tracheidssquare to hexagonal; rays average 7 cells high (mean 7.6, standard devia-tion 5.3, n=38); tangential pitting limited to rare round isolated andsmall areolated pits; ray cell walls thin and smooth, pitted only incross-elds; transverse ray cell walls perpendicular, ray cells 24 tra-cheids wide; cross-elds with a single unbordered oopore occupyingthe whole eld, with width three times that of the height in the widesttracheids, square to rectangular (width 0.5 times that of the height) inthe late-wood; two oopores occur in about 2% of the cross-elds, eitherin high marginal cells or in widest cross-elds when they are divided bythewall of a transverse ray cell; when tracheids alternate from one radialrow to the other, the oopore sometimes does not occupy the whole eld;

Fig. 8. Xenoxylon phyllocladoides Gothan neotype (sample MP1571 at the LPUL, Bathonian, Anna brick pit, Gnaszyn, south-central Poland) in radial section; A three alternatingtracheids on the left, radial pitting variable; B wide early wood tracheids with biseriate (on the right) and uniseriate radial pitting; C cross-elds (on tracheid casts) with largefenestriform oopores, variable in size and usually larger in marginal cells; D cross-elds (on ray cell casts), oopores not always occupying the whole eld; E late woodcross-elds, relatively round, slightly bordered (a local gure); F showing the rare condition of two-pits per cross-elds in a ray marginal cell.

Table 3Radial pitting exhibited by the neotype of Xenoxylon phyllocladoides Gothan. Wood isconsidered normal when the tracheids of two adjacent radial rows are opposite, and al-ternate when otherwise. Pitting in the tips of the tracheid is also differentiated. Per-centages are based on counts of 120 pits.

Radial pitting Normal wood Alternate wood Tracheid tips

Uniseriate distant 78 87 0Uniseriate contiguous round 14 13 8Uniseriate xenoxylean 3 0 1Biseriate opposite 4 0 86Biseriate alternate 1 0 5



ray marginal cells usually not differentiated, locally up to twice as high asinner ray cells; radial pitting variable, from uniseriate spaced to biseriatealternate (Table 3); tracheid tips obtuse to shortly acuminate, denselypitted.Distribution: 1) typeMiddle Jurassic (Bajocian or Bathonian) of Poland(Gothan, 1906); 2)FAD Upper Kokuibelsu Subsuite, Norian, CentralPamir, Tajikistan (Khudaiberdyev, 1993)/LAD Kedrova Fm., Albian,Talovka River Basin, northwestern Kamchatka (Afonin, 2010); and 3)geographical range probably covering the whole of Europe and Asiaat mid to high palaeolatitudes, but material reappraisal is needed.

Xenoxylon suljuctense Shilkina et Chudajberdiev

Xenoxylon suljuctense Shilkina et Chudajberdiev, PalaeontologiaUzbekistana, 2: 132, pl. 80 gs. 14. 1971.

Note: Original diagnosis was written in Russian in 1971, and thusts ICBN requirements for validity (art. 32.1).Original diagnosis (our translation): Annual rings are visible. Radial pitsuniseriate or biseriate. Uniseriate pits large, connected, strongly at-tened in vertical direction, ovoid in their shape, with elongated innerapertures. Biseriate pits alternate, covering almost all the length of thetracheid wall, closely connected, of irregular pentagonal shape. Innerpit aperture round. Rays are low, from 1 to 10 rows of cells high, com-monly 56 cells. Cross eld pits are ovoid, elongated in horizontal direc-tion, one pit per cross eld. Tangential walls of tracheids bear numeroussmall round uniseriate pits, sometimes biseriate pits with oblique inneraperture. Wood parenchyma absent.Type: Not seen, indicated as sample 1, stored at the Botanical Insti-tute of Uzbekistan, Tashkent.Distribution: 1) type Middle Jurassic of Sulyukta, southernFerghana, Kyrgyzstan; 2) FAD Late Triassic, Heizyo Middle School,Pyongyang, North-Korea (sample 62067 at the TUMS, unpublished)/LAD type; and 3) geographical range Central Asia and Korea.

Xenoxylon wattarianum Nishida et Nishida

Xenoxylon wattarianum Nishida et Nishida, 1986, gs. 56. 1986.

Note: There are some discrepancies in the protologue; the descrip-tion states that rays are always uniseriate, whilst a partly biseriate rayis gured (Nishida and Nishida, 1986, g. 5B); on the same tangentialview a cluster of 12much compressed large pits is gured, completelydifferent from the other tangential pits (probably resulting from therotation of some radial pits); dense tangential pitting was not observedwhilst reviewing the holotype; this wood is similar to Xenoxylonlatiporosum, but differs in ray height (Nishida and Nishida, 1986: 200).Type: Seen, sample 11109 at Chuo University, Tokyo, Japan.Distribution: 1) type Turonian/Santonian, Nayba River, SouthernSakhaline; 2) FAD/LAD this taxon is represented only by the typespecimen; and 3) geographical range Eastern Siberia.

Xenoxylon yixianense Zhang et Shang

Xenoxylon yixianense Zhang et Shang, The Palaeobotanist 45: 46, pl.12. 1996.

Note: This wood is unique among the Xenoxyla as it features radialresin canals.

Type: Not seen but studied by Ding et al. (2000); SZ001 deposited atFuxin Mining College, Fuxin, Liaoning, China.

Distribution:1) type Baitazigou, Yixian, Liaoning, Shahai Fm, EarlyCretaceous (Zhang and Shang, 1996); 2) FAD/LAD this taxonis represented only by the type specimen; and 3) geographicalrange north-eastern China.

5. Discussion of Xenoxylon systematic position

On the basis of xylotomy it is impossible to assign Xenoxylon to aprecise group within the Lignophyta. Indeed, as reected by Gothan'schoice of the root Xeno (foreign or alien in Greek), this wood hasno equivalent among modern plants. It has never been found in con-nection with leafy or reproductive structures.

Xenoxylonwasrst thought to be thewoodof amodern conifer or per-hapsPodozamitesBraun (Nathorst, 1897), and subsequently hypothesisedto be thewood of Baiera Braun (Arnold, 1953) or Sciadopitys (Jarmolenko,1933; Bailey, 1953) or of some extinct Podocarpaceae (Shilkina andKhudaiberdyev, 1971). In 1957 Larishchev noticed that Xenoxylon fre-quently co-occurred with Sciadopitys-like foliages in Siberia. LaterBose and Manum (1990) demonstrated that these foliages werenot Sciadopitys-related but members of an extinct conifer family,the Miroviaceae (an extinct family including the genera TritaeniaMaegdefrau et Rudolf, Mirovia Reymanwna and SciadopityoidesSveshnikova). Organic geochemistry ruled out the Pinaceae fromXenoxylon relationships, and evidenced similarities with extantCupressaceae s.l. and Podocarpaceae (Marynowski et al., 2008), butbona de Miroviaceae wood has not yet been studied. Interestinglycross-elds similar to these of Xenoxylon can be observed in Miroviaeximia (Gordenko) N. Nosova (Natalia Gordenko, pers. com.) whichmay provide further light on Xenoxylon relationships.

The stratigraphic range of Miroviaceae also ts well with that ofXenoxylon, i.e. CarnianMaastrichtian. Interestingly Miroviaceae occurin the Early Jurassic of Mangyshlak (Nosova and Kiritchkova, 2008)from where Sciadopityoxylon vetustawas described, in the Mid Jurassicof Polandwhere Xenoxylon also occur (Philippe et al., 2006; Nosova andWciso-Luraniec, 2007) and in several other localities where Xenoxylonis documented (such as the Lipovtsy Fm. of Southern Primorye, RussianFar-East; Afonin, 2008).

More recently Xenoxylon was assigned to the Protopinaceae(Youssef, 2002). However, this morphotaxon has no phylogeneticallegitimacy, as it comprises a group of woods with different afnities.

6. Conclusion

This review based on consulting little known Russian, Japaneseand Chinese literature as well as fossil material provides greater clar-ity to Xenoxylon systematics. However as we note above there is still alot of work that needs to be done: most specimens need to bereappraised. The stratigraphical and geographical distributions givenhere for each species is only tentative. It is likely that hidden in an as-sumed geographically widespread genus with apparently little anatomi-cal differentiation lies an interesting biodiversity. In particular Xenoxylonhuttonianum and Xenoxylonmeisteri are here, for the rst time, evidencedas taxa of palaeobiogeographical signicance.

Acknowledgements

Prof. Harufumi Nishida is most gratefully acknowledged forallowing revision of his material and Prof. Mitsuo Suzuki for lab facil-ities and permission to access Shimakura's material as well to his ownmaterial. We thank Michal Zaton for the help in trying to locate theXenoxylon phyllocladoides type in Poland and in collecting topotypes.Eric Buffetaut, Leszek Marynowski, Platon Tchoumatchenco, JohannSchnyder, Michal Zaton, Frank Wittler, Zhang Wu and Zheng Shao-linprovidedmaterial. Jiang Hong-En kindly helped with Chinese literatureand translated Ding et al.'s key (2000), adapted here. Jiang Zikun kindlyprovided information on some Chinese types. David Cantrill and SteveMcloughlin also helped with accessing and studying the collections inStockholm. Paul Kenrick's editing is also acknowledged, as well as thatof two anonymous reviewers.



Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.revpalbo.2013.01.013.

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