Fossil Woods From Williams Point Beds, Livingston Island, Antarctica: A Late Cretaceous Southern...

F O S S I L W O O D S F R O M W I L L I A M S P O I N T B E D S ,

L I V I N G S T O N I S L A N D , A N T A R C T I C A : A L A T E

C R E T A C E O U S S O U T H E R N H I G H L A T I T U D E F L O R A

by I M O G E N P O O L E and D A V I D C A N T R I L L

ABSTRACT. The wood ¯ora from Williams Point, Livingston Island, contains 12 wood types of gymnosperm andangiosperm origin. Recent collections of material have increased the biodiversity of a postulated species-richvegetation. The gymnosperm wood can be readily assigned to four form-genera: Araucarioxylon Kraus, Araucar-iopitys Jeffrey, Podocarpoxylon Gothan and Sahnioxylon Bose and Sah. This indicates a diversity of coniferousaraucarian and podocarp trees alongside woods of uncertain af®nity (Sahnioxylon; ?Bennettitales). Two angiospermmorphotypes are assigned to the organ genera Hedycaryoxylon SuÈss (Monimiaceae) and Weinmannioxylon Petriella(Cunoniaceae). The remaining four taxa of angiosperm wood cannot be con®dently placed in extant families as theyexhibit features that suggest relationships with the Magnoliidae, Hamamelidae and Rosidae. This paper presents the®rst comprehensive taxonomic revision of the wood ¯ora from Livingston Island and discusses the palaeoecology thatprevailed at a latitude of about 60 degrees south during the Late Cretaceous. Newly described taxa are Araucarioxylonchapmanae sp. nov., Araucariopitys antarcticus sp. nov., Podocarpoxylon chapmanae sp. nov., P. verticalis sp. nov.,P. communis sp. nov., Weinmannioxylon ackamoides sp. nov., Antarctoxylon livingstonensis gen. et sp. nov., A.multiseriatum gen. et sp. nov., A. heteroporosum gen. et sp. nov. and A. uniperforatum gen et sp. nov.

KEY WORDS: Late Cretaceous, wood, angiosperm, gymnosperm, Antarctica.

F R A G M E N T A T I O N of Gondwana, during the mid-Cretaceous, coincided with the radiation and rise toecological dominance of the angiosperms. The interplay between these two events played a major role inestablishing the strongly disjunct distribution patterns of various plant groups across the SouthernHemisphere. Antarctica was a key landmass at this time as it provided terrestrial connections betweenwhat are now widely separated continents. During the break up of Gondwana, the Antarctic Peninsularegion is seen as a major connection between West (South America/Africa) and East (greater Antarctica/Australia/New Caledonia/New Zealand) Gondwana for ¯oral exchange (Hill and Scriven 1993). Despitethe postulated importance of this region we still know relatively little about its Cretaceous ¯oristics yetCretaceous strata are widespread and contain abundant macro¯oras (e.g. Aptian: Cantrill 1999; Albian:Jefferson 1983; Cantrill 1995, 1996, 1997; Coniacian: Hayes 2000) and micro¯oras (e.g. Dettmann andThomson 1987). Establishing the composition of these ¯oras is important for understanding the nature andtiming of angiosperm radiation into the Antarctic and the implications for vegetation structure and ecologyin the southern high latitudes.

Among Cretaceous ¯oras of the Antarctic Peninsula, those found at Williams Point on Livingston Island(South Shetland Islands) have attracted considerable interest largely as a result of controversial agedeterminations. The Williams Point Beds are a succession of conglomerates, sandstones and mudstoneswith interbedded tuffaceous horizons that accumulated in a dominantly ¯uvial environment (Chapman andSmellie 1992). This succession is intruded by several hydroclastic vents and a thick (c. 50 m) dolerite sill(Rees and Smellie 1989). The sedimentary strata are preserved either as isolated outcrops on top of the sill,in squeeze-up structures between pods of intrusive sill material, or as ¯at-lying strata beneath the sill. Afragmentary and poorly preserved mega¯ora was initially described and assigned a Triassic age byOrlando (1967, 1968), an age assignment supported by later workers (Lacey and Lucas 1981; Banerji andLemoigne 1987; Banerji et al. 1987; Lemoigne 1987; Barale et al. 1995). However, the Triassic age posed

[Palaeontology, Vol. 44, Part 6, 2001, pp. 1081±1112, 10 pls] q The Palaeontological Association

serious problems in interpreting the geological evolution of an essentially Jurassic±early Tertiary volcanicarc. Recent collections from a number of localities at Williams Point, including all but one of the allegedTriassic sites, revealed the presence of angiosperm leaves (Rees and Smellie 1989), wood (Torres andLemoigne 1989; Chapman and Smellie 1992) and pollen (Chapman and Smellie 1992) such that all thelocalities, except for one at the northern end of Williams Point (Text-®g. 1), can conclusively be regardedas Upper Cretaceous. The ®eld relations, lithological and sedimentological similarity, indicate that thewhole sedimentary succession at Williams Point is best regarded as Upper Cretaceous (Rees and Smellie1989; Chapman and Smellie 1992). The sill that intrudes the succession is dated as 81 Ma (Campanian)and provides an upper age limit, which is to some degree supported by preliminary palynologicalinvestigations (Chapman and Smellie 1992). Nothofagidites, which is widespread in Campanian sequencesthroughout the Antarctic Peninsula (e.g. Dettmann and Thomson 1987; Askin 1988; Dutra and Batten2000), is absent from the Williams Point Beds (Chapman and Smellie 1992). The absence ofNothofagidites, therefore, suggests that the Williams Point Beds are probably no younger than Campanian.Floras elsewhere in the Antarctic Peninisula region, such as those from the upper Albian of Alexander

1082 P A L A E O N T O L O G Y , V O L U M E 4 4

TEXT-FIG. 1. Geological sketch map of Williams Point showing the position of the fossil wood locality examined inthis study.

Island (Jefferson 1982, 1983; Falcon-Lang and Cantrill 2000) lack angiosperm wood. In contrast, theConiacian±Tertiary wood ¯oras of the Larsen Basin contain a diverse angiosperm component (e.g. Pooleand Francis 1999, 2000; Poole et al. 2000a±c; Poole and Gottwald 2001). In light of the abundance ofunequivocal angiosperm remains it is suggested that the Williams Point Beds must post-date the lateAlbian and that they are, for the moment, best considered to be Cenomanian±early Campanian (Chapmanand Smellie 1992).

To date much of our knowledge concerning the ¯ora in the Williams Point Beds is described in terms ofTriassic taxa. Thus the ¯ora, particularly the leaves, is in need of signi®cant taxonomic revision. Equallythe wood ¯ora has been partially described, but for many taxa the descriptions are invalid (Torres andLemoigne 1988, 1989), or have been placed in a non-Linnean taxonomic system (Chapman and Smellie1992). This paper represents the ®rst part of a study aimed at re-evaluating the ¯ora, in light of newcollections, in order to establish the taxonomic diversity, and forms part of a larger project examining thepattern of ¯oristic change in the Antarctic Peninsula region through the Cretaceous.

M A T E R I A L A N D M E T H O D S

Existing wood collections from Williams Point, Livingston Island, were examined and supplemented withnew material collected during the austral summer of 1998±1999. The details for repository, (type) locality,age and lithostratigraphic horizon are applicable to all of the wood material described below and have not,therefore, been repeated throughout the text. The material is derived from the Williams Point Beds,Williams Point, Antarctica, and is housed in the palaeontological collection of the British AntarcticSurvey, UK. The type locality is an ash-rich horizon outcropping between two large hydroclastic ventson Williams Point, Livingston Island, Antarctica, 62828´50S, 6088´20W. The age of the deposits isCretaceous, and an age-range of Cenomanian±early Campanian is suggested based on pollen, woodand leaf ¯oras.

Transverse, radial and tangentially-orientated thin sections of all the silici®ed wood material wereprepared using the usual techniques employed for petri®ed fossil material (e.g. Hass and Rowe 1999).

Coniferous woods possess a conservative morphology with relatively few characters such thatqualitative descriptions of wood taxa are generally unsatisfactory in separating one taxon from another(Savidge 1996; Wheeler and Baas 1998), a problem further compounded by the fact that the anatomicalstructure of wood may vary considerably throughout a single tree (Chapman 1994). This has led to aproliferation of different wood species without any clear indications of the precise characters that delimitthem. For example, Schultze-Motel (1966) noted that up to the time of his writing, some 45 species ofAraucarioxylon had been described. It is almost impossible to distinguish between woods produced bymodern araucarian conifers, except by means of a detailed quantitative approach (e.g. Ilic 1995). Thereforemany of the taxa dealt with by Schultze-Motel (1966) probably cannot be separated from each other onqualitative anatomical grounds and merely represent taxa de®ned by spatial and temporal boundaries. Inorder to classify fossil conifer woods in a way that is repeatable and clearly delimits the boundaries of thetaxon described, it is essential that anatomical features are quanti®ed (cf. Chapman and Smellie 1992). Aquantitative approach allows truly distinct taxa within an isolated ®eld of anatomical characteristics to bedistinguished from taxa that simply represent the opposing end-members of a continuum (e.g. thecontinuum which exists between wood derived from the roots, trunks and branches of a single tree).Therefore, the anatomical characteristics of the conifer wood from Williams Point were quanti®ed. Intangential longitudinal section (TLS), the mean height of 100 rays was measured (in terms of number ofcells high). In radial longitudinal section (RLS), the nature of the bordered pitting on 100 tracheid wallswas examined across the width of an annual growth ring. Three tracheid pit characteristics were quanti®ed:(1) percentage of uniseriate, biseriate and triseriate pitted tracheids; (2) the percentage of alternately tooppositely arranged multiseriate pits; and (3) the contiguity of tracheid pitting expressed as row length (i.e.the length of pit rows de®ned by touching pits or pits being separated by less than a pit diameter).Specimens were then classi®ed to generic level using KrauÈsel's (1949) scheme and, based on themorphological separation of populations, taxa were recognized.

Quantitative data for the dicotyledonous angiosperm wood material follow the recommendations of the

P O O L E A N D C A N T R I L L : C R E T A C E O U S W O O D S 1083

IAWA (International Association of Wood Anatomists) Committee (1989), except in the case of vesselelement length where the measurements were taken from thin sections, as macerations are not possiblewith fossil material. Mean values given are the range shown by the individual specimens assigned to thatspecies followed by the total range, in parentheses, for that character depicted by all specimens. If thematerial is stated as having undergone compression then the quantitative data given should be used as aguide only. Af®nities were drawn by consulting reference literature (e.g. Metcalfe and Chalk 1950, 1989;Greguss 1955; Metcalfe 1987; Cutler and Gregory 1998) and wood anatomical atlases (e.g. Greguss 1972;Schweingruber 1978, 1990; Ilic 1991). The material was compared with slides of extant genera incollections at the Royal Botanic Gardens, Kew; Utrecht and Leiden branches of the National Herbarium ofThe Netherlands; and the Federal Institute of Wood Biology and Wood Protection, Hamburg. Computer-ized wood databases (e.g. Wheeler et al. 1986; Ilic 1987; LaPasha and Wheeler 1987; Richter andTrockenbrodt 1995) were searched although the results were not informative. The results of thesecomparative studies are discussed for each fossil species; the taxa listed as having anatomical similarityshould not be considered exhaustive and similarities may only lie within limited parts of the respectivefamilies. Although comparisons are made with the anatomy of extant taxa it is important to note that thesefossil woods were found unassociated with other organs and, therefore, it cannot be assumed that theparent plant was similar in all characters to any extant taxon mentioned. However the comparisons serve asan introduction to those families with the characteristic combinations of anatomical characters seen in thefossil material, which will be of use to future studies of mid±Late Cretaceous fossilized woods.

Torres and Lemoigne (1989) erected the organ genus `Dicotyloxylon' for woods from Antarctica.However, this taxon lacks a generic diagnosis and a type species, and is thus invalidly published. As wewere unable to consult the original material described by Torres and Lemoigne (1989), and thus were notable to validate `Dicotyloxylon', we have erected a new fossil genus, Antarctoxylon, for all dicotyledonouswood with equivocal af®nity from the Cretaceous and Tertiary of Antarctica. Woods described by Torresand Lemoigne (1989) have been assigned, where possible, to Antarctoxylon. Material originally describedby Chapman and Smellie (1992) has been redescribed in light of additional specimens assignable to theirmorphotypes.

S Y S T E M A T I C P A L A E O N T O L O G Y

Order CONIFERALES

Family ARAUCARIACEAE Henkel and W. Hochst, 1865

Genus ARAUCARIOXYLON Kraus, in Schimper, 1870

Type species. Araucarioxylon carbonaceeum (Witham) Kraus, in Schimper 1870 (p. 381), designated by Andrews(1970) as the type species.

Araucarioxylon chapmanae sp. nov.

Plate 1, ®gures 1, 3, 5, 7, 9

vp.1992 Coniferwood-Cretaceous-clusteredpits Chapman and Smellie, pp. 176±180.

Derivation of name. After Dr J. L. Chapman who worked on the Williams Point wood ¯ora.

Type specimens. P. 3055.213 (Pl. 1, ®gs 1, 3, 5, 7, 9), holotype; P. 1806.14, paratype.

Diagnosis. Secondary wood with predominantly biseriate, alternate, close-packed pits. Cross-®eldscharacterized by 2±11 pits (mode 3; mean 4´6). Rays short, 1±11 cells high, ray cells often with resinspools.

Description. This description is based on two specimens, one (P. 1806.14) originally assigned to Coniferwood-Cretaceous-clusteredpits by Chapman and Smellie (1992), the other from recently collected material (P. 3055.213).


P. 1806.14 is estimated to be 17 cm in diameter whereas P. 3055.213 has an estimated diameter of 30 cm and is thusthought to represent mature trunk wood. The wood is largely composed of tracheids that form distinct growth ringswith a narrow latewood zone that ranges from 1±3 cells wide (Pl. 1, ®g. 9). Tracheids are generally square torectangular in cross section and axial parenchyma is absent.

In radial section bordered pits in tracheid walls are predominantly biseriate (74 per cent), sometimes uniseriate (21per cent), rarely triseriate (5 per cent) (Pl. 1, ®g. 1). Pits are crowded, alternate, close-packed and range from circular tohexagonal or polygonal in outline and measure 11±20 mm in diameter (Pl. 1, ®g. 3). Pit apertures are round and 3±6 mmin diameter. Ray cells measure 112±245 mm long with square to rounded, rarely oblique end walls. Cross-®eld regionsare characterized by 2±11 pits (mode 6; mean 5´5) (Pl. 1, ®g. 5). Cross-®eld pits are simple, 6±10 mm diameter withlarge pit apertures measuring 4±8 mm in diameter.

In tangential section rays are 1±25 (mode 3, mean 4´6) cells high (Pl. 1, ®g. 7). Ray cells 22±48 mm wide, 19±47 mmtall and often with dark contents. Resin spools (cf. Stopes 1914) can be present in ray cells and tracheids adjacent torays.

Af®nity. Alternate, close-packed, polygonal pits, on the radial walls of the tracheids, in conjunctionwith a large number of cross-®eld pits, characterize extant araucarian conifers. On this basis thematerial is assigned to the Araucariaceae. Wood anatomy within the Araucariaceae is conservative withrelatively few characters available to separate taxa at the speci®c level. Quanti®cation of features suchas cross-®eld pit number, cross-®eld pit diameter, tracheid pit diameter and ray height have proved tobe of some use in separating species (Ilic 1995). Fossil wood with this pitting-type is assigned toAraucarioxylon after the scheme of KrauÈsel (1949), which has at least 50 described species (Schultze-Motel 1966; Cantrill 1990). However, as mentioned above, the anatomical boundaries between speciesis generally poorly circumscribed. For this reason we have con®ned our comparison to material alreadydescribed from the Antarctic. Araucarioxylon wood is widely reported from Cretaceous (Torres et al.1982; Torres and Lemoigne 1989; Chapman and Smellie 1992; Torres 1993; Falcon-Lang and Cantrill2000, 2001) and Tertiary (Gothan 1908; Lacey and Lucas 1981; Torres and Lemoigne 1988) stratawithin the Antarctic Peninsula. Araucarioid wood described by Chapman and Smellie (1992) withalternate araucarioid pitting (Coniferwood-Cretaceous-clusteredpits) contains two different types.Amongst the three specimens examined one is best assigned to Araucarioxylon as the pits arepredominantly biseriate close-packed and polygonal. The other two specimens (P. 1806.9, 13) are bestplaced in Araucariopitys as they typically have uniseriate rows of pits (73 per cent) and only towardsthe end walls of cells, or adjacent to the rays, do the pits become bi- or rarely triseriate (27 per cent)(see below). The single specimen (P. 1806.14) of Araucarioxylon is consistent with the other specimendescribed here. Both specimens differ from Araucarioxylon ¯oresii described from Williams Point(Torres and Lemoigne 1989) by having a greater number of cross-®eld pits and higher percentage ofbiseriate pitting.

Araucarioxylon wood has also been reported and described from the Aptian of Byers Peninsula (Torreset al. 1982; Falcon-Lang and Cantrill 2001) and the Albian of Alexander Island (Falcon-Lang and Cantrill2000). The material from Alexander Island differs from these Araucarioxylon chapmanae in the lowernumber of cross-®eld pits (1±4) and slightly shorter rays (mean 4´6 cells) (Falcon-Lang and Cantrill 2000).In addition, Araucarioxylon sp. 1, from the Aptian of Byers Peninsula, and Araucarioxylon sp. 2, from theAlbian of Alexander Island, both have a greater abundance of uniseriate pitting than that seen inAraucarioxylon chapmanae. Furthermore, Araucarioxylon sp. 1 has fewer cross-®eld pits and tallerrays than the Williams Point material described here. Torres (1993) reported Araucarioxylon wood fromCape Shirreff (Livingston Island) but this wood is too poorly preserved to warrant further consideration.One species of Agathoxylon, Agathoxylon sp. A, has been described by Ottone and Medina (1998) from theAlbian of Brandy Bay (James Ross Island) but Agathoxylon differs from Araucarioxylon chapmanae byhaving fewer cross-®eld pits (1±4).

Genus ARAUCARIOPITYS Jeffrey, 1907

Type species. Araucariopitys americana Jeffrey, 1907 (p. 435) from the Cretaceous of North America.


Araucariopitys antarcticus sp. nov.

Plate 1, ®gures 2, 4, 6, 8, 10

vp.1992 Coniferwood-Cretaceous-clusteredpits Chapman and Smellie, pp. 176±180, pl. 4, ®gs 22±26; pl. 5,®gs 27±31; pl. 6, ®gs 32±35.

Derivation of name. After the Antarctic where this material is found.

Type specimens. P. 1806.9 (Pl. 1, ®gs 2, 4, 6, 8, 10), holotype; P. 1806.13, paratype.

Diagnosis. Secondary wood with predominantly uniseriate pitting. Biseriate pitting, alternate, close-packed, pits circular to hexagonal and con®ned to the ends of tracheids. Cross-®elds characterized by 2±9pits (mode 6, mean 5´8). Rays short, uniseriate, 1±14 (mode 4; mean 4´65) cells tall.

Description. This description is based on two specimens composed only of secondary xylem. P. 1806.9 and P. 1806.13are derived from branch wood estimated to be c. 11 and 9 cm in diameter respectively (Chapman and Smellie 1992). Thegrowth rings are distinct and characterized by a narrow zone of late wood ranging from 1±5 cells in width (Pl. 1, ®g. 10).

In radial section tracheids are characterized by circular to polygonal bordered pits predominantly in uniseriate rows(73 per cent) and less commonly in biseriate rows (27 per cent) (Pl. 1, ®gs 2, 4). Biseriate pit rows tend to beconcentrated towards the end walls of the tracheids. Such pits are crowded, alternate, close-packed and range fromcircular to hexagonal in outline. Tracheid end walls often appear swollen. Uniseriate pit rows tend to have contiguouspits that are often longitudinally ¯attened (P1. 1, ®g. 4). Pits measure 7±15 mm in diameter with round pit apertureswhich measure 4±8´5 mm wide and generally occupy 50 per cent of the total pit diameter. Ray cells measure121±216 mm in length with end walls oblique to rounded. Cross-®eld regions are characterized by 2±9 pits (mode 6,mean 5´8) (Pl. 1, ®g. 6) with pit diameters measuring 6±12 mm. Pit apertures are commonly obliquely-orientated ovalto slit-like, rarely circular, and measure 2±5 mm in diameter.

In tangential section rays are uniseriate, 1±14 (mode 4, mean 4´65) cells tall (Pl. 1, ®g. 8). Ray cells measure13±33 mm (mean 26´8 mm) in height and 11±28 mm (mean 25´1mm) in width.

Af®nity. Two specimens, referred to Coniferwood-Cretaceous-clusteredpits by Chapman and Smellie(1992), are best placed in Araucariopitys antarcticus as the bordered pits on the radial walls arepredominantly uniseriate and only become bi- or triseriate either towards the end walls of the tracheidsor adjacent to where the tracheids meet ray cells. This is consistent with Araucariopitys as circumscribedby Jeffrey (1907). Araucariopitys has also been described from the Albian of Alexander Island (Falcon-Lang and Cantrill 2000) and the Aptian Cerro Negro Formation on Byers Peninsula, Livingston Island(Falcon-Lang and Cantrill 2001). These woods are almost identical to each other (Falcon-Lang andCantrill 2001), differing only in a slightly greater number of pits per cross-®eld in the Alexander Islandspecimens. Moreover, the Cerro Negro Formation taxon compares well with Araucariopitys antarcticusdescribed here but differs in having slightly shorter rays (1±10 cells high) that often have biseriateportions, a smaller number of cross-®eld pits per ®eld (1±6, rarely 9), and less frequent (i.e. only 2 percent) biseriate pits on the radial tracheid walls.


E X P L A N A T I O N O F P L A T E 1

Figs 1, 3, 5, 7, 9. Light micrographs of Araucarioxylon chapmanae sp. nov., P. 3055´213. 1, radial longitudinal section(RLS) showing the contiguous alternate biseriate pitting; ´ 60. 3, RLS, biseriate to triseriate pitted tracheidsillustrating the hexagonal shape of the bordered pits; ´ 125. 5, RLS of the cross-®eld region with 2±11 pits per cross-®eld; ´ 125. 7, tangential longitudinal section (TLS) illustrating the short barrel shaped rays; ´ 60. 9, transversesection (TS) growth ring with narrow late wood band; ´ 60.

Figs 2, 4, 6, 8, 10. Light micrographs of Araucariopitys antarcticus sp. nov., P. 1806´9. 2, RLS, illustrating thepredominantly uniseriate nature of the bordered pitting; ´ 60. 4, RLS, uniseriate rows of pits with horizontally¯attened margins where touching the adjacent pit; ´ 125. 6, RLS of ray cells showing the cross-®eld regions with2±9 pits per ®eld; ´ 125. 8, TLS illustrating the narrower rays of this taxon compared with Araucarioxylon chapmanae;´ 60. 10, TS through growth increment with narrow late wood zone and abrupt transition to early wood; ´ 60.

P L A T E 1

POOLE and CANTRILL, Araucariopitys, Araucarioxylon

Family PODOCARPACEAE Endlicher, 1847

Genus PODOCARPOXYLON Gothan, 1904

Type species. Podocarpoxylon juniperoides Gothan, in Gagel, 1904 (p. 272) from Russia.

Remarks. Fifteen wood specimens from the Williams Point Beds can be assigned to the organ genusPodocarpoxylon. On closer examination these specimens could be separated into three groups based onquantitative anatomical characters (Text-®g. 2). A plot of pit contiguity versus the percentage of uniseriatepit rows generates three discrete groups of specimens (Text-®g. 2). These three groups are supported by afurther suite of characters, such as the presence of tangential pitting, bordered pit clustering and cross-®eldpit arrangement. The addition of ten new Podocarpoxylon specimens in this study, along with the ®veexamined by Chapman and Smellie (1992), served only to blur the boundaries between taxa recognized byChapman and Smellie (1992), which had been de®ned by features such as ray height and cross-®eld pitnumber. Auxillary characters include the presence and abundance of axial parenchyma. However, inpoorly preserved material, the degree of cell wall degradation prior to silici®cation makes it dif®cult todistinguish. Despite this, axial parenchyma can be recognized and used to separate groups within thematerial examined.

Podocarpoxylon chapmanae sp. nov.

Plate 2, ®gures 1±4

vp. 1992 Coniferwood-Cretaceous-spacedpits Chapman and Smellie, pp. 173±176.


TEXT-FIG. 2. Plot of pit contiguity versus the percentage of uniseriate pitting for Podocarpoxylon specimens illustratingthe three anatomically distinct ®elds used to group the wood into taxa.


Figs 1±4. Light micrographs of Podocarpoxylon chapmanae sp. nov., P. 3055.258. 1, transverse section (TS) throughgrowth increment illustrating a narrow late wood zone, ´ 60. 2, radial longitudinal section (RLS) highlighting thescattered bordered pits and cross-®eld regions with 1±4 pits per ®eld; where two pits are present they are eitheropposite or oblique in arrangement; ´ 125. 3, tangential longitudinal section (TLS) of wood with short narrow raysthat can be up to 19 cells tall; ´ 60. 4, TLS of tracheids with pitting on the tangential walls; ´ 125.

Figs 5±6. Light micrographs of Podocarpoxylon verticalis sp. nov., P. 3055.273. 5, TS through growth increment; notethe lack of late wood and only minor change in cell size; ´ 60. 6, RLS illustrating the contiguous pitting thatcharacterizes this taxon; ´ 125.

P L A T E 2

POOLE and CANTRILL, Podocarpoxylon

Derivation of name. After Dr J. L. Chapman who worked on the Williams Point wood ¯ora.

Type specimens. P. 3055.258 (Pl. 2, ®gs 1±4), holotype; P. 1806.12, paratype.

Diagnosis. Compact wood largely composed of tracheids with rare to absent axial parenchyma. Tracheidseither with uniseriate or biseriate rows of podocarpoid pits on the radial walls. Pit contiguity 3´8±4´4.Cross-®elds occupied by 1±4 pits; where two pits are present they are either opposite or oblique inarrangement. Tangential walls with small circular bordered pits that occur either isolated or in short rowsup to four pits tall.

Description. The description is based on two specimens, P. 3055.258 and P. 1806.12. P. 3055.258 has at least 35 ringincrements that show little curvature, suggesting that it is derived from a trunk with an estimated diameter of c. 35 cm.P. 1806.12 is also derived from trunk wood (c. 30 cm in diameter) that is in excess of 30 years old (Chapman andSmellie 1992). Ring boundaries are demarcated by a narrow late wood zone 3±6 cells wide. False rings also occurtowards the middle of the growth cycle and are demarcated by a decrease in cell size and an increase in wall thicknessfor 2±4 cells.

In radial section the tracheids are marked by circular podocarpoid bordered pits. Pits are arranged in uniseriate(48±61 per cent), biseriate (39±51 per cent) or rarely triseriate (0´5 per cent) rows. Where biseriate, the pits are usuallyopposite (38±49 per cent) or less frequently alternate (0´7±2´6 per cent). Bi- or triseriate pits usually only persist for ashort section of the pit row (up to seven pits high). Pits are 15±23 mm in diameter with round, occasionally elliptical,apertures measuring 4±11 mm wide and generally occupying between 50 and 61 per cent of the total pit diameter. Pitcontiguity is 3´8±4´4. Ray cells have rounded end walls and the cross-®eld regions are characterized by 1±4 (mode 1,mean 1´44) pits. Cross-®eld pits are 7±12´5 mm in diameter with circular to obliquely elliptical pit apertures measuring4±7 mm wide.

In tangential section, rays are uniseriate, 1±42 (mode 1, 2, mean 5´8) cells tall. Ray cells measure 13±27 mm (mean15´7 mm) in height, and 8±18 mm (mean 13´4 mm) in width. Tangential walls are pitted with small, circular, borderedpits which measure 10±14 mm in diameter and occur either isolated or in short rows up to four pits in length.

Af®nity. Podocarpoxylon chapmanae can be distinguished from the other two Podocarpoxylon taxa, P.verticalis and P. communis described below, by the frequent occurrence of pitting on the tangential walls,values intermediate between P. verticalis and P. communis for pit contiguity, and the percentage ofuniseriate pitting. Torres and Lemoigne (1989) described Podocarpoxylon sp. 1 from the Williams PointBeds. Their taxon lacks pitting on the tangential walls and appears to have more contiguous pitting (Torresand Lemoigne 1989, pl. 2, ®gs 3±6) than that seen in P. chapmanae. Therefore, on this basis it is notconsidered to be the same. Among the material identi®ed by Chapman and Smellie (1992) only P. 1806.12has a similar abundance of tangential pitting and is assigned to P. chapmanae.

Elsewhere in the Antarctic Peninsula, Podocarpoxylon has been recorded from Aptian strata on ByersPeninsula (Livingston Island) where two species were recognized (Falcon-Lang and Cantrill 2000). Albiansequences on Alexander Island also contain two species. All four taxa differ from the material describedhere in having fewer cross-®eld pits and higher amounts of uniseriate pitting.



Figs 1±2. Light micrographs of Podocarpoxylon verticalis sp. nov., P. 3055.273. 1, radial longitudinal section (RLS)of the cross-®eld regions. Cross-®elds are characterized by 1±5 pits; where two pits are present they are arrangedvertically; ´ 60. 2, tangential longitudinal section (TLS) showing rays and resin ®lled cells; ´ 60.

Figs 3±6. Light micrographs of Podocarpoxylon communis sp. nov., P. 3055.218. 3, transverse section showing thesubtle ring boundary that occurs in this taxon; ´ 60. 4, RLS of ray with resin ®lled cells and tracheids showinguniseriate rows of pits; ´ 60. 5, RLS illustrating the opposite nature of the cross-®eld pits; ´ 125. 6, TLS illustratingthe variation in ray cell height; ´ 60.

P L A T E 3

POOLE and CANTRILL, Podocarpoxylon

Podocarpoxylon verticalis sp. nov.

Plate 2, ®gures 5±6; Plate 3, ®gures 1±2

Derivation of name. Latin verticalis, referring to the characteristic vertical arrangement of the cross-®eld pits.

Type specimens. P. 3055.273 (Pl. 2, ®gs 5±6; Pl. 3, ®gs 1±2), holotype; P. 3055.262, paratype.

Diagnosis. Wood composed of tracheids and rare axial parenchyma (Pl. 3, ®g. 2). Tracheids commonlywith uniseriate rows of podocarpoid pits on the radial walls. Pit contiguity high, 6´3±8´2. Cross-®eldregions with 1±5 pits; where two pits are present they are vertical, only rarely oblique in arrangement.

Description. The description is based on two specimens, P. 3055.273 and P. 3055.262. P. 3055.273 has at least 27, andP. 3055.262 has 15 growth rings. The ring increments in both specimens show little curvature, suggesting that thespecimens are derived from large diameter organs, and the lack of reaction wood suggests that they probably representtrunk wood. The parallel nature of the rings indicates that the organs were substantially older than the maximumnumber of increments suggests. The rings are subtle, with a narrow late wood zone up to seven cells wide (Pl. 2, ®g. 5).There is very little change in cell size towards each ring boundary, although the change in wall thickness de®nes thering boundary.

In radial section the tracheids are marked by circular, bordered pits arranged in mainly uniseriate (90´6±94 per cent)or rarely biseriate (6±9´4 per cent) rows (Pl. 2, ®g. 6). When biseriate, the pits are usually opposite (3´4±7´3 per cent) orless frequently alternate (2±2´7 per cent), and usually only persist for a short section (i.e. up to ®ve pits) of the pit row.Pits are 15´6±25 mm in diameter with round pit apertures, measuring 3´6±5´6 mm wide, which generally occupy 22±35per cent of the total pit diameter. Where pits touch they are slightly ¯attened longitudinally. Pit contiguity is 6´3±8´2.Ray cells have rounded end walls, and cross-®eld regions are characterized by 1±5 (mode 1, 2, mean 1´98) pits (Pl. 3,®g. 1). Cross-®eld pits are 10´5±17 mm in diameter with steeply oblique and elliptical pit apertures almost as large asthe pit itself. Where there are two pits per cross-®eld they are predominantly arranged vertically.

In tangential section, rays are uniseriate and 1±36 (mode 2, 4, mean 5´88) cells high (Pl. 3, ®g. 2). Ray cells measure27´6±46 mm (mean 34´9 mm) in height and 16±31 mm (mean 22´3 mm) in width.

Af®nity. Amongst Podocarpoxylon wood from Williams Point, P. verticalis differs from other species bythe high pit contiguity (6´3±8´2), vertical arrangement of the cross-®eld pits, and relatively tall ray cells.The wood material described by Chapman and Smellie (1992) does not encompass any specimen thatappears similar. Podocarpoxylon sp. 1 (Torres and Lemoigne 1989) from Williams Point is also distinctfrom P. verticalis in that the cross-®eld pits are oppositely arranged (Torres and Lemoigne 1989, pl. 2, ®g8). Podocarpoxylon wood has been described from the Aptian of Byers Peninsula (Livingston Island)(Falcon-Lang and Cantrill 2001) and the Albian of Alexander Island (Falcon-Lang and Cantrill 2000).Wood taxa from both areas differ from P. verticalis in that the cross-®eld pits are only rarely arrangedvertically.

Podocarpoxylon communis sp. nov.


.1989 Podocarpoxylon sp. Torres and Lemoigne, pp. 16±20, pl. 2, ®gs 1±8.vp.1992 Coniferwood-Cretaceous-spacedpits Chapman and Smellie, pp. 173±176, pl. 3, ®gs 17±21.v.1992 Coniferwood-Cretaceous-lowrays Chapman et Smellie, pp. 181±183, pl. 5, ®gs 28±31; pl. 6, ®gs

36±38.v. 2001 Podocarpoxylon sp. 2 Falcon-Lang and Cantrill, pp. 287±288, ®g. 8.

Derivation of name. Latin, communis, in reference to the abundance of this taxon with respect to other coniferousmorphotypes within this ¯ora.

Type specimen. P. 3055.218 (Pl. 3, ®gs 3±6), holotype.

Material. P. 3055.191, 228, 241, 265, 283, P. 1806.15, 16, 19, 21.


Diagnosis. Secondary wood with tracheids that have predominantly uniseriate rows of podocarpoid pits onthe radial walls. Pit contiguity is low 1´6±3´4. Cross-®eld regions with 1±3, rarely four pits; where two pitsare present they are opposite or oblique and only rarely vertically arranged.

Description. The description is based on ten specimens with the largest (P. 1806.15) being derived from a trunk with anestimated diameter of 32 cm (Chapman and Smellie 1992). Ring increments are marked by a narrow late wood zone ofup to nine cells wide (Pl. 3, ®g. 3). False rings are frequent in some specimens (e.g. P. 1806.21).

In radial section the tracheids are characterized by circular bordered pits arranged in uniseriate (87±100 per cent) orbiseriate (0±13 per cent) rows (Pl. 3, ®g. 4). When biseriate the pits are usually opposite (0±13 per cent) or lessfrequently alternate (0±2 per cent). Biseriate pits usually only persist for a short section (i.e. up to four pits tall) of thepit row. Pits are 13´5±18´1 mm in diameter with round pit aperture, 4´2±10´4 mm wide, generally occupying 31±64 percent of the total pit diameter. Pit contiguity ranges from 1´6±3´4. Ray cells have rounded or square end walls and cross-®eld regions are characterized by 1±4 (mode 1, 2, mean 1´36) pits (Pl. 3, ®g. 5). Cross-®eld pits are 6´4±11´2 mm indiameter with circular to obliquely elliptical pit apertures measuring 5´1±7´6 mm across.

In tangential section, rays are uniseriate and 1±32 (mode 1, 3, mean 4´8) cells high (Pl. 3, ®g. 6). Ray cells measure14´3±27´4 mm in height and 14±18´9 mm in width. Tangential walls have rare, small, circular bordered pits.

Af®nity. Podocarpoxylon communis can be distinguished from both Podocarpoxylon chapmanae and P.verticalis by a lower pit contiguity (1´6±3´4), two pits per cross-®eld that are generally opposite orobliquely positioned, and relatively low ray cell heights. Among the material previously described fromWilliams Point this is most similar to Coniferwood-Cretaceous-spacedpits described by Chapman andSmellie (1992) based on low pit contiguity values and rare tangential pitting. The material referred toConiferwood-Cretaceous-lowrays also ®ts within this taxon based on the total variation seen in thematerial examined (Text-®g. 2). One of the distinguishing features between the taxa identi®ed byChapman and Smellie (1992) was the presence of abundant axial parenchyma in Cretaceous-lowrays(P. 1806.16, 19). In contrast, specimens P. 1806.15 and P. 1806.21 lack axial parenchyma. However, theadditional material examined in this study only served to blur the boundaries between these two taxa. Axialparenchyma is absent in some specimens (P. 3055.191, 218), rare in one (e.g. P. 3055´265) or morefrequent (e.g. P. 3055.241). Despite these differences, the low pit contiguity, the opposite or oblique cross-®eld pits, and relatively low ray cell numbers unite all of these specimens. Podocarpoxylon communis isindistinguishable from material referred to Podocarpoxylon sp. 2 from the Aptian of Byers Peninsula(Falcon-Lang and Cantrill 2001).

ANTHOPHYTA

Order ?BENNETTITALES Engler, 1892

Genus SAHNIOXYLON Bose and Sah, 1954

Sahnioxylon antarcticum Lemoigne and Torres, 1988


.1988 Sahnioxylon antarcticum Lemoigne and Torres, pp. 939±945, pl. 1, ®gs 1±10; pl. 2, ®gs 1±9.

.1989 Sahnioxylon antarcticum Lemoigne and Torres; Torres and Lemoigne, p. 21, pl. 3, ®gs 1±8.

Material. P. 3055.21, 31, 305.

Description. This description is based on three pieces of secondary xylem only. Parallel growth rings number between45 and 50, indicating that these specimens originated from large branches or trunks. The growth zones are demarcatedby a change in tracheid diameter (Pl. 4, ®g. 1). Narrow zones (i.e. 3±7 cells in width) of large-diameter tracheidsalternate with wider zones (i.e. usually >10 cells, often up to 40� cells, in width) of relatively small-diameter tracheids(Pl. 4, ®g. 1). The mean radial diameter of the large-diameter tracheid measures 79±81 mm (range 53±103 mm), with amean tangential diameter of 49±61 mm (range 25±75 mm) and mean radial tracheid wall thickness of c. 4 mm(1´5±6 mm). The mean radial diameter of the small-diameter tracheid measures 37±53 mm (range 25±58 mm) with a


https://www.researchgate.net/publication/284327253_On_Sahnioxylon_rajmahalense_a_new_name_for_Homoxylon_rajmahalense_Sahni_and_S_andrewsii_a_new_species_of_Sahnioxylon_from_Amrapara_in_the_Rajmahal_Hills_Bihar?el=1_x_8&enrichId=rgreq-da68d095-a39c-4915-ad15-9219401d06d2&enrichSource=Y292ZXJQYWdlOzIyNzUwMTI4MTtBUzo5ODkyODk1MTMwMDEwNkAxNDAwNTk3OTA4NjQw

mean tangential diameter of 41±45 mm (range 23±68 mm), and a radial tracheid wall thickness of c. 6 mm (range4±8 mm). Pitting is generally more abundant in the radial tracheid walls than in the tangential walls, especially in thezone of large-diameter tracheids. Pits in the large-diameter tracheid zone range from circular, sometimes uniseriate,but more commonly biseriate, rarely triseriate, opposite, occasionally alternate, with wide borders and diameters of13±18 mm that grade into transitional (with pit diameters of c. 25 mm) and scalariform (with pit diameters up to 70 mm)arrangements. Transitional and scalariform pitting dominate (Pl. 4, ®gs 3±6). Pits in the small-diameter tracheid zoneoccur only in the radial walls. They are uniseriate or irregularly uniseriate, closely to well spaced with narrowerborders and diameters of c. 10 mm (Pl. 4, ®g. 6). Between the tracheids and the rays, pits are large and window-like,c. 15 mm in diameter, some with much reduced borders; others are apparently simple. There are 1±3 per cross-®eld inthe large-diameter tracheids (Pl. 4, ®g. 7) but become more numerous, i.e. up to seven per cross-®eld, and morecircular±square in shape in the small-diameter tracheids (Pl. 4, ®g. 5). The rays are uniseriate, part biseriate, andbiseriate (Pl. 4, ®g. 3), very rarely triseriate and composed of procumbent cells (Pl. 4, ®g. 2) that measure 250±300 mmin radial length by c. 50 mm in both tangential and radial height. Some of the ray cells have small, globular contents,which may be a preservational feature or natural ray cell content present prior to petri®cation. Uniseriate rays range,from 100±1130 mm in height; multiseriate rays range from 220±1620 mm in height.

Af®nity. Sahnioxylon is a form genus for fossil woods whose primitive features place it betweenCycadeoideae, Gnetales and vesselless angiosperms, and thus at the base of the Anthophytes (Philippeet al. 1999). Lemoigne and Torres (1988) and Torres and Lemoigne (1989) described such vesselless fossilwood from Williams Point, Livingston Island. From the brief description of S. antarcticum given byLemoigne and Torres (1988) we can conclude that our specimens are very similar, differing from thosealready assigned to S. antarcticum only in quantitative measurements. This discrepancy could be the resultof the relative position within the plant from which the material was originally derived. Therefore, it iswithout any doubt that these specimens can be assigned to S. antarcticum, erected for such vesselless(homoxylous) fossil wood from Antarctica. Philippe et al. (1999) have undertaken a review of the woodsassigned to Sahnioxylon and concluded that the occurrence of this fossil wood type is restricted toAntarctica, India and China.

Class MAGNOLIOPSIDA Cronquist, Takhatjan and Zimmermann, 1966Family MONIMIACEAE A. L. de Jussieu, 1809

Genus HEDYCARYOXYLON SuÈss, 1960

Hedycaryoxylon tambourissoides Poole and Gottwald, 2001


vp. 2001 Hedycaryoxylon tambourissoides Poole and Gottwald, pp. 210±212, pl. 1, ®gs 1±6.

Material. P. 3055.3, 15, 28, 32.

Description. This description is based on four specimens, all probably originating from branch or trunk organs. Thesmallest minimum estimated diameter is c. 5 cm (P. 3055.3); the other specimens are larger, although estimated



Figs 1±7. Light micrographs of Sahnioxylon antarcticum, P. 3055.31. 1, transverse section showing zones of largediameter tracheids and small diameter tracheids; ´ 65. 2, radial longitudinal section (RLS) of ray showingprocumbent ray cells and the tracheids in tangential section (TLS) on right caused by compression of the specimen;´ 65. 3, RLS showing the scalariform arrangement of the tracheid pits; ´ 150. 4, RLS showing opposite, transitionaland scalariform arrangement of the tracheid pits and circular tracheid-ray pits in the zone of small diametertracheids; ´ 150. 5, TLS showing uniseriate and biseriate rays; ´ 65. 6, RLS showing biseriate arrangement oftracheid pits; ´ 150. 7, RLS showing the horizontally elongate and scalariform arrangement of the tracheid-ray pitsin the zone of large diameter tracheids; ´ 150.

P L A T E 4

POOLE and CANTRILL, Sahnioxylon

diameters cannot be determined because of the more or less parallel nature of the rays and growth ring curvature. Allspecimens have undergone a degree of compression. The wood is diffuse porous, with very indistinct growth ringsvisible only with the naked eye. Vessels are solitary, paired, in radial ®les of 3±4 (±8) pores; very occasionally vesselsoccur in groups (Pl. 5, ®g. 1). Mean tangential diameter of vessels measures 88±99 mm (range 30±150 mm) and meanradial diameter is 80±113 mm (range 40±155 mm). Mean vessel element length measures 823±843 mm [range (125)550±1070 mm]. Mean vessel abundance is 22±43 mmÿ2 (range 21±51 mmÿ2). Perforation plates are scalariform withfew (i.e. 6±12) bars (Pl. 5, ®g. 2). Intervessel pitting is opposite to horizontally elongate (diameter c. 13 mm) toscalariform; in one specimen, P. 3055.28, more alternately arranged pits can be seen in radial longitudinal section, butin tangential section the pitting is obviously scalariform. Vessel-ray pitting is relatively wide (Pl. 5, ®g. 4) and oppositeto scalariform (c. 20 mm in diameter) in arrangement. Tyloses are absent in P. 3055.32 but present in the otherspecimens (Pl. 5, ®g. 3). Axial parenchyma could not be determined. Rays are of two sizes: uni- to triseriate and up to1050 mm in height; and wide, i.e. up to 12-seriate and 3525 mm in height (Pl. 5, ®gs 2±3). The rays are heterocellularand composed of procumbent, square, trapezoid and upright cells (Pl. 5, ®g. 5). This gives rise to the variation in raycell dimensions in tangential section. More upright cells occur towards the margins of the multiseriate rays. Narrowrays tend to be composed of more square/upright cells. Dark, amorphous contents are present in some ray and ®brecells (Pl. 5, ®g. 4). There are 1±4 rays per tangential millimetre. Fibres are septate in P. 3055.15 and P. 3055.28 butseptae are not determinable in P. 3055.32 and P. 3055.3, possibly owing to the preservation of the material.

Af®nity. Fossil material with this anatomical structure has been described by Poole and Gottwald (2001),and P. 3055.15 and P. 3055.28 were named as paratypes to their species, Hedycaryoxylon tambourissoides.Two new specimens exhibiting similar anatomical structure to H. tambourissoides, P. 3055.3 andP. 3055.32, have subsequently been found at the same locality. The description given above is basedon all the Williams Point material for completeness. These fossils resemble extant taxa of several familiesbut the greatest anatomical similarity is shared with the subfamily Monimioideae within the Monimiaceaesensu lato in having the combination of both narrow and wide rays with characteristic ray cell parenchymashapes, septate ®bres, short scalariform perforation plates with relatively few bars, and opposite toscalariform pitting. Further details and discussion are given in Poole and Gottwald (2001).

Family CUNONIACEAE R. Br., in Flinders, 1814 (nom. conserv.)

Genus WEINMANNIOXYLON Petriella, 1972

Weinmannioxylon ackamoides sp. nov.


.1990 `Caldcluvioxylon propaniculata' Torres, pp. 104±106, pl. 23, ®gs 1±11.v.1992 Dicotwood-Cretaceous-heterorays Chapman and Smellie, p. 183, pl. 8, ®gs 48±49, 51±52..1994 `Caldcluvioxylon collinsense' Zhang and Wang, pp. 235±236, pl. 2, ®gs 1±5.

Derivation of name. After the anatomical similarity to extant Ackama from New Zealand.


Material. P. 3055.1, 2.



Figs 1±5. Light micrographs of Hedycaryoxylon tambourissoides. 1, TS showing vessel arrangement and a wide ray,P. 3055.15; ´ 50. 2, RLS showing scalariform perforation plates and tyloses, P. 3055.28; ´ 123. 3, TLS showing thewide multiseriate rays and narrower uni- to triseriate rays, P. 3055.15; ´ 50. 4, RLS showing the horizontallyelongate to scalariform nature of the vessel-ray pits, P. 3055.28; ´ 246. 5, RLS showing the square, upright and rareprocumbent ray cells, P. 3055.28; ´ 50.

P L A T E 5

POOLE and CANTRILL, Hedycaryoxylon

Diagnosis. Diffuse porous. Vessels solitary or occasionally in short radial chains of up to seven; vesseldiameters small. Perforation plates scalariform with up to 50 narrow bars. Intervessel pitting opposite toscalariform. Rays uniseriate and multiseriate (maximum 5-seriate), heterocellular; majority of rays>500 mm in height; multiseriates sometimes axially united by uniseriate marginal cells. Vessel-ray pittingcircular to horizontally elongate.

Description. This description is based on three well-preserved pieces of wood. P. 1806.11 has a minimum diameter ofapproximately 6 cm (excluding outer rings and bark) with the pith present in the centre. The other two specimens arefrom branch or trunk organs with unknown diameters owing to the more or less parallel nature of the rays and growthring curvatures. This description is, therefore, based on both relatively juvenile and mature material.

The wood is diffuse porous (Pl. 6, ®g. 1) with indistinct growth rings. Vessels are circular to elliptical, solitary,paired and occasionally in radial groups of mainly four vessels, rarely up to seven abutting cells, occasionally up to 20or more in rows separated by some ®bres. Mean tangential vessel diameter measures 56±99 mm (range 35±135 mm)and mean radial diameter is 69±94 mm (range 50±135 mm). Mean vessel element length measures 806±973 mm (range610±1475 mm). Mean vessel abundance is 28±46 mmÿ2 (range 19±72 mmÿ2). Perforation plates are scalariform with®ne bars ranging from (3) 8±50 per plate (Pl. 6, ®gs 5±6). Intervessel pitting is opposite (rarely alternate), transitionaland scalariform (Pl. 6, ®g. 5), with pit diameters ranging from 10±55 mm. Ray parenchyma pits are simple, circular toelliptical in the procumbent cells (Pl. 6, ®g. 3). Vessel-ray pits are more scalariform in the upright cells (up to 16 mm indiameter), occasionally opposite and horizontally (sometimes diagonally) elongate (Pl. 6, ®g. 6). Tyloses are absent/rare except in those vessels associated with the traumatic parenchyma. Mean ®bre tangential diameter is 18 mm (range12´5±25 mm) and radial diameter is 17 mm (range 10±22´5 mm), and mean combined wall thickness of the ®bresmeasures 17 mm (range 10±25 mm). No pitting was observed on the ®bre walls. The only parenchyma determinablewas the traumatic parenchyma mentioned by Chapman and Smellie (1992). Rays are uniseriate and multiseriate 2±4(5) cells wide (Pl. 6, ®gs 4±5), and number between three and seven per mm. Uniseriate rays range from 175±625 mmin height. The body of the multiseriate rays ranges from 450±1425 mm high with wings extending from 1±5 (9) cells inlength, which sometimes axially unite multiseriate rays (Pl. 6, ®gs 4±5). Multiseriate rays are heterocellular andcomposed of procumbent cells forming the body of the ray and more square/upright cells forming marginal rows (Pl. 6,®gs 2±3, 6). Uniseriate rays are composed of more upright cells. Dark, amorphous deposits are occasionally present inthe ray cells.

Remarks. Tile cells were reported by Chapman and Smellie (1992) but on closer examination of P. 1806.11these appear to be square body cells in amongst the procumbent cells (see Chapman and Smellie 1992,pl. 8, ®g. 49), thus appearing like tile cells. Tile cells in modern wood are usually upright and rarely square;therefore, these square tile cells may be a primitive or elementary type of tile cell.

Af®nity. The distribution of the vessels in transverse section coupled with the presence of uniseriate andmultiseriate rays with uniseriate rows of marginal cells, scalariform perforation plates, opposite toscalariform intervessel, and circular to scalariform vessel-ray pitting, are very similar to extant taxabelonging to the Aquifoliaceae, Cunoniaceae (including Eucryphia), Ericaceae, Escalloniaceae andGomortegaceae. On closer comparison with modern taxa of these families, the fossils described here donot have the marked radial groups or lines of vessels and rays up to 15 cells wide and 5 mm high as in theAquifoliaceae. Abundant spiral thickenings and the combination of simple and scalariform perforationplates that characterize the Escalloniaceae are absent in the fossil material. The Ericaceae also have spiralthickenings and wider rays up to 10-seriate. In the Gomortegaceae the rays are biseriate only and vessel-ray pits are large and simple. Within the Cunoniaceae, Ackama does show remarkably similar anatomy tothe fossil material (compare Pl. 6 with ®gs 1±2 and 4±7 in Patel 1990). This corroborates the observation



Figs 1±6. Light micrographs of Weinmannioxylon ackamoides, P. 1806.11. 1, TS showing vessel and ray distribution;´ 50. 2, RLS showing procumbent and square-upright ray cells at margins of ray; ´ 123. 3, RLS showing the small rayparenchyma pits and horizontally elongate-scalariform vessel-ray pits; ´ 123. 4, RLS showing scalariform perforationplates and vessel-ray pits; ´ 123. 5, TLS showing heterocellular uniseriate and multiseriate rays; ´ 50. 6, TLS showingthe scalariform arrangement of intervessel pits and upright cell axially uniting two multiseriate rays; ´ 123.

P L A T E 6

POOLE and CANTRILL, Weinmannioxylon

made by Chapman and Smellie (1992). Extant Ackama and Caldcluvia have now been synonymised(Mabberley 1997).

Other cunoniaceous-like fossil wood has been described from Antarctica: (1) Weinmannioxylonnordenskjoeldii Poole, Cantrill, Hayes and Francis, from Upper Cretaceous strata on James Ross andLivingston Islands is similar to the anatomy of primitive Cunoniaceae (Poole et al. 2000a); (2)unpublished (thus invalid) `Caldcluvioxylon propaniculata' fossil wood from the Eocene±Oligocene ofKing George Island shows very close anatomical similarity to extant Caldcluvia (Torres 1990); and (3) aPalaeocene fossil also from King George Island invalidly assigned to `Caldcluvioxylon' as `Caldcluvi-oxylon collinsense' (Zhang and Wang 1994) on the basis of its similarity to both extant Caldcluvia and thespecimen described by Torres (1990).

The material assigned to Weinmannioxylon ackamoides differs from W. nordenskjoeldii in that W.nordenskjoeldii has more abundant vessels in cross section, no radial multiples of vessels, and lacks theuniseriate wings that commonly axially unite the multiseriate rays in W. ackamoides.

The two species of `Caldcluvioxylon' have been separated on vessel-ray pit characters only (Zhang andWang 1994): `C. propaniculata' has scalariform and `C. collinsense' has circular to horizontally elongatepits. Both types of pitting are present in W. ackamoides. `Caldcluvioxylon propaniculata' Torres (1990,unpublished) differs from W. ackamoides in having more abundant solitary vessels and more vessels intransverse section. `Caldcluvioxylon collinsense' differs from W. ackamoides in vessel abundance anddegree of semi-ring porosity (both of which are quantitative features known to vary with the environmentalregime; e.g. Carlquist 1980).

All the Antarctic cunoniaceous specimens mentioned here can be included within the organ genusWeinmannioxylon, erected by Petriella (1972) for fossil woods with an anatomy similar to that found inthe Cunoniaceae, with no emendment to the generic diagnosis. Anatomical differences between existingspecies of Weinmannioxylon and W. ackamoides support the erection of the new species for these woods.The quantitative variation exhibited by the species of `Caldcluvioxylon' and the specimens described herecould be the result of variation in environmental factors and is not great enough to justify separation;hence, these specimens have been assigned to W. ackamoides.

Class incertae sedis

Genus ANTARCTOXYLON gen. nov.

Generic diagnosis. Xylem of dicotyledonous angiosperm. Growth rings absent or indistinct. Wood diffuseto semi-ring porous. Vessels solitary and/or grouped. Perforation plates simple and/or scalariform. Raysheterocellular, mainly multiseriate. Parenchyma diffuse.

Type species. Antarctoxylon livingstonensis gen. et sp. nov.

Antarctoxylon livingstonensis gen. et sp. nov.


.1989 `Dicotyloxylon' sp. 3 Torres and Lemoigne, pp. 23±24, pl. 4 ®gs 3, 5, 8±9.v.1992 Dicotwood-Cretaceous-dumpirays Chapman and Smellie, pp. 186, pl. 7, ®gs 43, 47; pl. 8, ®g. 50.



Figs 1±8. Light micrographs of Antarctoxylon livingstonensis, P. 1806.17. 1, TS showing vessel arrangement; ´ 50. 2,RLS showing mainly procumbent ray cells and one row of square marginal cells; ´ 123. 3, RLS showing widescalariform vessel-ray pits; ´ 123. 4, RLS showing narrower scalariform vessel-ray pits; ´ 123. 5, TLS showing themultiseriate rays; ´ 50. 6, TLS showing the opposite-scalariform arrangement of intervessel pits and the highbordering sheath cell in the ray; ´ 123. 7, RLS showing scalariform perforation plate and opposite to transitional pitson the tails of the vessel; ´ 123. 8, TLS showing the scalariform intervessel arrangement of the pits; ´ 123.

P L A T E 7

POOLE and CANTRILL, Antarctoxylon

Derivation of name. After Livingston Island where the fossils were found.


Material. P. 3055.17, 19, 24, 25, 27.

Diagnosis. Diffuse porous. Vessels solitary, in small clusters or radial chains of up to about seven pores;vessel diameters small to medium. Perforation plates scalariform (up to 55), occasionally branched.Intervessel pits dense, mainly transitional to scalariform. Vessel-ray pitting scalariform. Rays up to 5-seriate, heterocellular with occasional `border' or sheath cells. Multiseriate rays always <1´5 mm in height.

Description. This description is based on six pieces of fossil wood with one specimen (P. 1806.17) having an estimateddiameter of approximately 44 cm. Minimum diameters for the other specimens cannot be estimated because oftheir more or less parallel rays and growth ring curvature, but probably originate from branches/trunks. The woodis diffuse porous with indistinct growth rings. Vessels are more or less circular when solitary, paired or in radialgroups of up to 7 (±10) and small clusters (Pl. 7, ®g. 1). Mean tangential vessel diameter measures 64±101 mm(range 38±138 mm) and mean radial diameter is 73±100 mm (range 43±150 mm). Mean vessel element lengthmeasures 510±1030 mm (range 310±1200 mm). Mean vessel abundance is 27±50 mmÿ2 (range 21±54 mmÿ2).Perforation plates are scalariform (Pl. 7, ®gs 6±8) with the number of bars ranging from relatively few, i.e. 4±9 (inP. 3055.17, 19, 24, 25) through intermediate, i.e. 9±30 (in P. 3055.27), to relatively numerous, i.e. 24±53 (inP. 1806.17). Intervessel pitting is opposite (rarely grading into a more alternate arrangement), transitional toscalariform with pit diameters ranging from 4±25 mm (Pl. 7, ®gs 5±6). Vessel-ray pits are circular to horizontallyelongate and scalariform with pits 4±12 mm in diameter (Pl. 7, ®gs 4±5). Tyloses are absent in P. 1806.17 and3055.19, 25 and 27 but present in P. 3055.17 and 24. Mean ®bre tangential diameter measures 24±32 mm (range12±43 mm) and radial diameter is 22±35 mm (range 15±50 mm) for P. 3055.24 and 25. Fibre dimensions wereindeterminable in the other specimens owing to poor preservation. No parenchyma was observed. Rays are rarelyuniseriate but mainly multiseriate, 2±4 (±8) cells wide (Pl. 7, ®g. 3), and number between three and nine per tangentialmillimetre. Rays are heterocellular and range from (100) 200±1320 mm in height. The body of the rays is composedpredominantly of procumbent cells with 1±3 marginal rows of more upright cells (Pl. 7, ®gs 2, 4±5). Occasionallywithin the rays of P. 1806.17, 24 and 25 there are enlarged cells (termed `border cells' by Chapman and Smellie 1992)which are larger than the rest of the ray cells (Pl. 7, ®g. 6). The `border cells' in P. 1806.17 are either upright or circular;the latter have been speculated to be an elementary type of sheath cell (Chapman and Smellie 1992). In P. 3055.17 and25 these enlarged cells conform to the accepted de®nition of sheath cells. Dark, amorphous contents are present inmany of the procumbent ray cells (Pl. 7, ®g. 2).

Remarks. It is possible that two morphotypes are included in this fossil species, distinguished by thenumber of bars per perforation plate. However, we do not believe that one character alone is suf®cient towarrant further subdivision.

Af®nity. `Dicotyloxylon' sp. 3 (Torres and Lemoigne 1989) was considered to be similar to palaeotaxonDicotwood-Cretaceous-dumpirays (Chapman and Smellie 1992) but differ in that `Dicotyloxylon' sp. 3lacks the enlarged `bordering' or elementary sheath cells (which are also absent from the paratypes listedabove) and has rays that are probably shorter (i.e. up to 600 mm, as determined from the illustrationbecause no details are given in the text) than those seen in the specimens assigned to A. livingstonensis.Nevertheless the species diagnosis for A. livingstonensis encompasses the anatomical rangeexhibited by `Dicotyloxylon' sp. 3. Therefore, we synonymize the latter with A. livingstonensis. Thecharacters exhibited by A. livingstonensis occur today in, for example, the Aextoxicaceae, Cunoniaceae,Eupteleaceae, Icacinaceae, Magnoliaceae and Monimiaceae.



Figs 1±6. Light micrographs of Antarctoxylon multiseriatum, P. 1806.10. 1, TLS showing vessel arrangement; ´ 50. 2,RLS showing predominantly procumbent- and some square ray cells; ´ 50. 3, RLS showing scalariform andtransitional vessel pitting; ´ 100. 4, TLS showing multiseriate rays; ´ 50. 5, RLS showing scalariform perforationplates and more opposite vessel pitting; ´ 123. 6, oblique RLS showing scalariform vessel-ray pits and perforationplates; ´ 123.

P L A T E 8


Antarctoxylon multiseriatum sp. nov.


.1989 `Dicotyloxylon' sp. 1 Torres and Lemoigne, p. 23, pl. 4, ®gs 1±6.

.1989 `Dicotyloxylon' sp. 4 Torres and Lemoigne, p. 25, pl. 4, ®g. 4.v.1992 Dicotwood-Cretaceous-multiserirays Chapman and Smellie, p. 185, pl. 7, ®gs 44±46.

Derivation of name. After the characteristic tall, multiseriate rays.


Material. P. 3055.26, 30.

Diagnosis. Diffuse to semi-ring porous. Vessels solitary or in radial chains of up to seven; vessel tangentialdiameter small. Perforation plates scalariform with c. 15 bars per plate. Intervessel pitting bordered, tightlypacked, alternate, opposite and scalariform. Vessel-ray pitting circular to scalariform. Rays of two sizes:uniseriate/biseriate and multiseriate, heterocellular. Multiseriate rays up to 11-seriate and majority>1´5 mm in height.

Description. This description is based on three pieces of secondary xylem from a large branch or small trunk. Two ofthe specimens (P. 1806.10, P. 3055.26) have minimum estimated diameters of 10 cm whereas the third specimen isfrom an organ of unknown, but probably greater diameter. The wood is semi-ring to diffuse porous with relativelydistinct growth rings. Vessels are circular, elliptical, solitary, paired and in radial groups of usually about four, rarelyup to seven (Pl. 8, ®g. 1). Mean tangential vessel diameter measures 73±83 mm (range 50±120 mm) and mean radialdiameter is 83±107 mm (range 50±138 mm). Mean vessel element length measures 831±896 mm (range 630±1050 mm).Mean vessel abundance is c. 37±47 mmÿ2 (range 34±60 mmÿ2). Perforation plates are scalariform with ®ne barsranging from (5) 9±22 per plate (Pl. 8, ®gs 5±6). Tyloses are rare or absent. Intervessel pitting is opposite-alternate onthe tails of the vessel element (Pl. 8, ®g. 5), becoming more tightly packed, circular, opposite-alternate to transitionaland scalariform (Pl. 8, ®g. 4) along the vessel. Pits are c. 8 mm in diameter along the length of the vessel elements.Vessel-ray pits are circular, horizontally elongate to scalariform, measuring up to c. 20 mm in diameter (Pl. 5, ®g. 6).Rays are uniseriate/biseriate, measuring 170±930 mm or 7±18 cells (average 400 mm) in height; or multiseriate (Pl. 8,®g. 3), up to 11 cells wide and 880±3500 mm (average 1970 mm) in height. There are between three and 11 rays permillimetre. The multiseriate rays are heterocellular, composed mainly of procumbent cells (Pl. 8, ®g. 2), with fewsquare and upright cells located mainly in marginal rows. The uniseriate rays have generally more square and uprightcells. Fibre measurements could not be made.

Af®nity. `Dicotyloxylon' sp. 1 and `Dicotyloxylon' sp. 4 (of Torres and Lemoigne 1989) have anatomicalcharacters that are similar to those of Antarctoxylon multiseriatum, and also originate from Williams Point,Livingston Island. `D.' sp. 1 and `D.' sp. 4 probably differ from each other by the presence of alternateintervascular pits in `D.' sp. 1 (no details are given by Torres and Lemoigne for the intervascular pitting of`D.' sp. 4 except that they are bordered) and the slight difference in number of vessels in the radial ®les.Antarctoxylon multiseriatum encompasses both of these distinctions but differs from `D.' sp. 1 and `D.' sp.4 in that the latter has no growth rings visible. This character is not considered great enough to warrant adifferentiation into separate taxa; therefore `D.' sp. 1 and `D.' sp. 4 are here synonymized withA. multiseriatum, which shows anatomical similarity with extant taxa in, for example, the Chloranthaceae,Eupteleaceae, Icacinaceae, Monimiaceae and Trimeniaceae.



Fig 1±6. Light micrographs of Antarctoxylon heteroporosum. 1, TS showing vessel arrangement, P. 3055.8; ´ 50. 2,RLS showing procumbent and square ray cells, P. 3055.14; ´ 50. 3, TLS showing multiseriate rays, P. 3055.14; ´ 50.4, TLS showing multiseriate ray with one enlarged cell and narrower uni- to quadriseriate rays, P. 3055.14; ´ 50. 5,RLS showing scalariform vessel-ray pits, P. 3055.8; ´ 123. 6, TLS showing the opposite to horizontally elongate andtransitional intervessel pit arrangement, P. 3055.14; ´ 123.

P L A T E 9


Antarctoxylon heteroporosum sp. nov.


Derivation of name. After the presence of both simple and scalariform perforation plates in the wood.

Type specimen. P. 3055.14 (Pl. 9, ®gs 3±4, 6), holotype.

Material. P. 3055.8, 12, 16.

Diagnosis. Vessels solitary, paired and in short radial groups (of up to six pores). Perforation plates simpleand scalariform. Intervessel pitting opposite, transitional and scalariform. Vessel-ray pitting scalariform.Rays 1±4 cells wide, composed of procumbent and square cells.

Description. This description is based on four specimens with a minimum estimated diameter for the smallestspecimen (P. 3055.14) being 8 cm. The remaining specimens are from larger organs, but the diameters cannot beestimated because of the parallel nature of the rays and growth ring curvature. The wood is diffuse porous withindistinct growth rings. Vessels are solitary, paired or in radial ®les of 3±4 (±6); occasionally they may be in smallgroups of 3±5 (Pl. 9, ®g. 1). Mean vessel tangential diameter measures 67±112 mm (range 45±150 mm) and meanradial diameter is 69±99 mm (range 50±130 mm). Mean vessel element length measures 705±855 mm (range450±1080 mm). Mean vessel abundance is 35±64 mmÿ2 (range 29±79 mmÿ2). Perforation plates are either simpleor scalariform, with 1±8 bars per plate (Pl. 9, ®gs 3±4). Intervessel pitting is opposite, horizontally elongate totransitional and scalariform (Pl. 9, ®g. 6). Vessel-ray pitting is scalariform (Pl. 9, ®g. 5). Tyloses are absent. Axialparenchyma could not be determined. Rays are narrow (1±2 cells wide) and multiseriate [3±8 (10) seriate] and up to3450 mm in height (Pl. 9, ®gs 3±4). The rays are heterocellular and composed of square and procumbent cells withmore square cells located towards the margins of the rays. In P. 3055.14 there are occasional enlarged, round-elongatecells (idioblasts) present within the body of the ray (Pl. 9, ®g. 4). Some ray cells have dark, amorphous contents butnone observed in the enlarged idioblasts. In P. 3055.16 the rays are super®cially reminiscent of those inHedycaryoxylon tambourissoides, but these are probably traumatic (seemingly abnormal xylem can be seen incross section) and probably do not represent the true nature of the rays.

Af®nity. Simple and scalariform perforation plates occur in a number of families but taxa withgenerally similar overall anatomy occur in, for example, the Icacinaceae, Lauraceae, Monimiaceae andMagnoliaceae.

Antarctoxylon uniperforatum sp. nov.


.1989 `Dicotyloxylon' sp. 2 Torres and Lemoigne p. 23, pl. 4, ®gs 2±7.

Derivation of name. After the characteristic abundance of simple perforation plates.


Diagnosis. Vessels more or less circular, solitary, paired and in short radial groups, small to large indiameter. Perforation plates simple, very rarely scalariform with a maximum of three wide bars.



Figs 1±5. Light micrographs of Antarctoxylon uniperforatum, P. 3055.20. 1, TS showing vessel arrangement; ´ 50. 2,RLS showing square and more upright ray cells; ´ 123. 3, RLS showing simple perforation plate; ´ 123. 4, TLSshowing two axially united rays; ´ 123. 5, TLS showing ray distribution, relatively short vessel elements and simpleperforation plates; ´ 50.

P L A T E 1 0


Intervessel pitting mainly alternate, rarely opposite to scalariform. Vessel-ray pitting circular tohorizontally elongate. Rays 1±3 cells wide, majority < 500 mm in height, occasionally axially united.

Description. This description is based on one specimen with an unknown estimated diameter owing to the more or lessparallel nature of the rays and growth ring curvature. The wood is diffuse porous with only one indistinct growth ring.Vessels are circular, solitary, paired, occasionally in radial ®les or groups of three vessels (Pl. 10, ®g. 1). Meantangential diameter measures 92 mm (range 60±130 mm) and mean radial diameter is 104 mm (range 55±145 mm).Mean vessel element length measures 453 mm (range 270±650 mm) and mean vessel abundance is 21 mmÿ2 (range19±25 mmÿ2). Perforation plates are simple but many are `pinched' in radial view (Pl. 10, ®g. 4). Rarely are there barsin the end plates, but when present they are thick and reach a maximum of three per plate. Intervessel pitting isbordered, alternate, occasionally opposite. Vessel-ray pitting is circular to elliptical. Tyloses are absent. Rays aremainly uni- or biseriate, occasionally triseriate, and up to 520 mm in height (Pl. 10, ®gs 3, 5). Occasionally the rays areaxially united by the more upright marginal cells (Pl. 10, ®g. 4). The body of the ray is heterocellular and composed ofprocumbent and square cells (Pl. 10, ®g. 2). Some of the ray cells have dark, amorphous contents (Pl. 10, ®g. 2).

Af®nity. Torres and Lemoigne (1989) described a fossil wood with similar anatomical characters also fromWilliams Point, Livingston Island and called it `Dicotyloxylon' sp. 2. Unfortunately no height was givenfor the rays, nor were they illustrated. However, all other anatomical characters of `Dicotyloxylon' sp. 2 arein concordance with the species diagnosis of Antarctoxylon uniporosum and therefore `Dicotyloxylon' sp.2 has been synonymized with this species. These anatomical characters can be seen in taxa belonging tothe Buxaceae, Cunoniaceae, Gomortegaceae and Lauraceae.

D I S C U S S I O N

The Williams Point Beds of Livingston Island are important palaeobotanically because they contain awell-preserved, diverse ¯ora of wood (e.g. Chapman and Smellie 1992), palynomorphs and leaves(Orlando 1967, 1968; Lacey and Lucas 1981; Banerji et al. 1987; Banerji and Lemoigne 1987; Rees andSmellie 1989) which are crucial to our understanding of the diversity and ecology of high latitudeAntarctic biotas. Initially this ¯ora was assigned a Triassic age based on the leaves (e.g. Orlando 1967,1968). However, the subsequent demonstration that the ¯ora is Cretaceous means that the wholeassemblage needs signi®cant taxonomic revision. A revision of the dicotyledonous angiosperm andconifer wood ¯ora has been presented here. The conifers include Araucariaceae (two species) andPodocarpaceae (three taxa), while the angiosperms are represented by two species that have anatomicalfeatures consistent with members of extant Monimiaceae and Cunoniaceae. Four further angiosperm woodtypes have been described and assigned to Antarctoxylon, an organ genus erected herein for fossildicotyledonous angiosperm woods of equivocal taxonomic af®nity, with either scalariform or scalariformand simple perforation plates, from the Cretaceous and Tertiary of Antarctica.

The leaf ¯ora is more diverse and represents many groups of non-woody plants assigned to Triassicorgan taxa and is thus in need of taxonomic revision. Conifer foliage has a conservative architecture thatmakes the distinction of taxa dif®cult when based on leaf morphology alone. Although the angiospermcomponent of the leaf ¯ora is still poorly known, Rees and Smellie (1989) recorded from the WilliamsPoint Beds eight angiosperm leaf types, ranging from simple, entire margined microphyllous shapes topalmate forms.

The occurrence of at least two conifer leaf species (i.e. Pagiophyllum and Elatocladus; Banerji andLemoigne 1987), one angiosperm leaf species (i.e. Cinnamomum ?Lauraceae; Rees and Smellie 1989) andseven other angiosperm leaf types coupled with ®ve conifer, six angiosperm, and at least one ?bennettitewood species, described herein, suggests a highly diverse tree ¯ora for high latitude vegetation (Chapmanand Smellie 1992). A species-rich mixed-angiosperm conifer forest is suggested from both wood andpalynological evidence, although at this stage it is not possible to say which, if any, group of plantsdominated the canopy. Nevertheless it seems likely that the vegetation comprised a conifer forest with arelatively diverse angiosperm component (Chapman and Smellie 1992). Ferns, which are by far the mostabundant and diverse group, are represented by leaves and petri®ed rachides. Large tree-ferns would haveformed part of the tree ¯ora (Chapman and Smellie 1992) in association with the ?bennettite Sahnioxylon.


Understorey fern taxa, such as the Gleicheniaceae and Osmundaceae (Cantrill 1997), along withsphenopsids such as Equisetites (Lacey and Lucas 1981), probably inhabited the moist forest ¯oor andbanks of streams. Thalloid liverworts probably allied to the Marchantiales (e.g. Thallites; Lacey and Lucas1981) and epiphytic ferns would have grown on moist, shaded banks or clung tenaciously to damp rocks,trunks and branches.

The wide tracheid zones in the ?bennettite Sahnioxylon and the relative abundance of early wood tissuein the conifer woods indicate a high biomass productivity, thus suggesting favourable growing conditions.Based on the predominance of entire-margined microphyllous leaves, Rees and Smellie (1989) suggested amean annual temperature range of 13±208C. A period (probably annual) of dormancy is re¯ected in theproduction of the predominantly distinct growth rings in the wood material. The growth rings in the coniferwood are distinct but the late wood is always very narrow (2±4 cells). Similar growth ring characteristicshave been noted for other high latitudes sites in the Permian (Weaver et al. 1997) and Cretaceous (Parrishand Spicer 1988). At a palaeolatitude of 598S (Grunow et al. 1991) there would be suf®cient seasonality toinduce tree dormancy as a result of the annual decrease in light intensity and temperature. However, theangiosperm wood material from the same ¯ora exhibits only indistinct growth rings. This conifer-angiosperm growth ring phenomenon has been observed in other ¯oras (e.g. Poole 2000). Parrish andSpicer (1988) suggested that the conifer ring characteristics seen in high latitude wood are a response torapid change in photoperiod at the end of the growing season (i.e. through a biochemical switch rather thanas a result of progressive limitation of resources such as water or temperature). This may suggest differentgrowth process controls at the onset of dormancy in angiosperm wood when compared with conifer wood(Chapman and Smellie 1992). With continued studies of these fossil ¯oras greater understanding of thisunique southern, high-latitude ecosystem in terms of habit, diversity and dynamics will be obtained. These®ndings will aid our understanding of Late Cretaceous Gondwanan ¯oras and modern austral ¯oras.

Acknowledgements. We thank the British Antarctic Survey for the opportunity to undertake ®eldwork in Antarctica.Drs D. Cutler, P. Rudall, A. M. W. Mennega, Professor P. Baas and Dr H. Richter are thanked for allowing access tothe wood slide collections housed in the Jodrell Laboratory, Royal Botanic Gardens, Kew; Utrecht and Leidenbranches of the National Herbarium of The Netherlands; and the Federal Institute of Wood Biology and WoodProtection, Hamburg respectively.

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https://www.researchgate.net/publication/294698765_IAWA_List_of_microscopic_features_for_hardwood_identification?el=1_x_8&enrichId=rgreq-da68d095-a39c-4915-ad15-9219401d06d2&enrichSource=Y292ZXJQYWdlOzIyNzUwMTI4MTtBUzo5ODkyODk1MTMwMDEwNkAxNDAwNTk3OTA4NjQw

https://www.researchgate.net/publication/236247567_A_cretaceous_macroflora_from_a_freshwater_lake_deposit_President_Head_Snow_Island_Antarctica?el=1_x_8&enrichId=rgreq-da68d095-a39c-4915-ad15-9219401d06d2&enrichSource=Y292ZXJQYWdlOzIyNzUwMTI4MTtBUzo5ODkyODk1MTMwMDEwNkAxNDAwNTk3OTA4NjQw

https://www.researchgate.net/publication/236247567_A_cretaceous_macroflora_from_a_freshwater_lake_deposit_President_Head_Snow_Island_Antarctica?el=1_x_8&enrichId=rgreq-da68d095-a39c-4915-ad15-9219401d06d2&enrichSource=Y292ZXJQYWdlOzIyNzUwMTI4MTtBUzo5ODkyODk1MTMwMDEwNkAxNDAwNTk3OTA4NjQw

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IMOGEN POOLE

Wood Anatomy SectionNational Herbarium of The Netherlands

Utrecht University Branch, PO Box 801023585 CS Utrecht, The Netherlands

DAVID J. CANTRILL

British Antarctic SurveyNatural Environment Research Council

Madingley Road, High CrossCambridge CB3 0ET, UK

Typescript received 15 August 2000Revised typescript received 13 December 2000


Fossil Woods From Williams Point Beds, Livingston Island, Antarctica: A Late Cretaceous Southern...

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