AmericanJournal
ofBotany80(5): 500-516. 1993.
ANATOMICALLY PRESERVED GLOSSOPTERIS STEMS
WITH ATTACHED LEAVES FROM THE CENTRAL
TRANSANTARCTIC MOUNTAINS, ANTARCTICA'
KATHLEEN
B.
PIGG2,4
AND THOMAS
N.
TAYLOR3
2Department
ofBotany,ArizonaStateUniversity,
Tempe,Arizona85287-1601;and
3Department
ofPlantBiologyand ByrdPolarResearchCenter,The Ohio StateUniversity,
1735Neil Avenue,Columbus,Ohio 43210
StemsandbudsofGlossopteris
skaarensis
PiggandbudsofG. schopfii
PiggfromthePermianSkaarRidgelocalityin the
centralTransantarctic
Mountains,
Antarctica
demonstrate
thefirst
anatomically
preserved
knownwithstem/
glossopterids
leafattachment.
StemsofG. skaarensis
are 1-12 mmin diameter
(X = 3.1 mm)witha broadpith,poorlydefined
primary
xylem,
anda zoneofsecondary
xylemup to6 mmthick.Pycnoxylic
woodconforming
toAraucarioxylon
Krausis composed
oftracheids
withuni-to biseriateoval to hexagonalborderedpitson radialwalls,uniseriate
raysone to a fewcellshigh,
andcupressoid
totaxodioidcross-field
Stemshavea narrow
pitting.
zoneofsecondary
phloem,aerenchymatous
cortexwith
scattered
sclereids,
and sometimes
a narrowperiderm.
Two wedge-shaped
leaftraceseachbifurcate
to formfourstrandsin
thebase of each petiole.Smallaxillarybranchesare vascularized
by doublebranchtracesthatfuseat themarginof the
mainaxis.BudsofG. skaarensis
haveleaveswithnarrow
laterallaminaeanda thickened
midribcontaining
a widelacuna,
delicatevascularstrands,
and a prominent
In contrast,
hypodermis.
budsof G. schopfii
have uniformly
thickleaveswith
prominent,
circular
vascularbundlesheaths.
Theseanatomical
detailsareusedtoreconstruct
individual
typesofglossopterid
plants,providing
newinformation
towardunderstanding
theecologyandevolution
ofthisimportant
groupofPermianseed
plants.
Throughoutthe Permian, Gondwana was dominated
by gymnospermousplantsthatbore theentire,reticulateveined leaves of the genus GlossopterisBrongniart.Such
leaves representthe dominantelementin Permian compression-impressionflorasof Gondwana (e.g., Chandra
and Surange, 1979; Anderson and Anderson, 1985; McLoughlin, 1990b). Anatomically preservedglossopterid
leaves are also knownin rarelyoccurringpermineralized
chertsin Antarctica(Schopf,1970; Pigg,1988, 1990; Pigg
and Taylor, 1990; Taylorand Taylor, 1990) and Australia
(Gould and Delevoryas, 1977; McLoughlin, 1990a; Pigg
and McLoughlin, 1992). The low diversityGondwana
florasalso containwood ofAraucarioxylonKraus, rooting
structuresof the genus VertebrariaRoyle, pollen organs
assignable to ArberiellaPant and Nautiyal, striatebisaccate pollen of the Protohaploxypinustype,and a variety
organs(e.g.,Schopf,
ofseeds and ovule-and pollen-bearing
1973, 1976; Lacey, van Dijk, and Gordon-Gray, 1975;
Gould and Delevoryas,1977; Retallackand Dilcher, 1988;
Taylor and Taylor, 1990). The repeatedco-occurrenceof
these assemblages at numerous localities has suggested
that these disarticulatedorgans representa single group
of plants,the glossopterids.
Most reconstructions
ofthe Glossopteris
planthave been
based on disarticulatedorgans (e.g., Plumstead, 1958;
Gould and Delevoryas, 1977; Pant, 1977; Retallack and
Dilcher, 1988). Unfortunately,
however,reportsof connectionsbetweenorgansare relativelyrare.Glossopterid
leaves preservedas compression/impression
fossilshave
been occasionally reportedin attachmentto compressed
vegetativeaxes (Table 1). CompressedGlossopterisleaves
have also been foundattachedto a varietyofreproductive
structures
(e.g., Thomas, 1958; Holmes, 1974, 1990; Lacey,van Dijk, and Gordon-Gray,1975; Surangeand Chandra, 1975; Schopf,1976; Rigby,1978a; White,1978; Anderson and Anderson, 1983, 1985; Pant and Nautiyal,
1984b; McLoughlin, 1990b). Occurrencesthat demonstratethe connectionof a given reproductivestructureto
particularleaf and wood typesare valuable in providing
a criticalbasis forsortingout thetaxonomyand evolution
ofthegroup.In a fewexamples ofcompressedstemswith
attached leaves, the stems are anatomically preserved
(Etheridge, 1895, 1899; Pant and Singh, 1974; White,
22 July1992;revision
accepted14January 1978; Pant and Nautiyal, 1984a), but these specimens
'Receivedforpublication
1993.
have not yet provided detailed informationabout leaf/
Unit6des Scienceet
Meyer-Berthaud,
The authorsthankBrigitte
wood relationships.Isolated petrifiedstemsand wood are
OhioUniduLanguedoc,
Montpellier,
MaryLouiseTrivett,
Techniques
knownfromnumerousGondwana localities(e.g.,Seward,
EdithL. Taylor,TheOhioStateUniversity,
Columbus,
Athens,
versity,
1914; Kriiusel,Maithy,and Maheshwari, 1961; Kriusel,
disofTexas,Austin,forhelpful
and TheodoreDelevoryas,
University
Lee Wilcox, 1962; Maheshwari, 1972; Prasad, 1982, 1986; Mussa,
cussionand readingofan earlierdraftofthemanuscript;
1986; Mussa and Coimbra, 1987; Taylor and Taylor,
and RobertW. Roberson,ArizonaState
The Ohio StateUniversity
reconstruc- 1990; Giraud, 1991). They very fromsmall stems (e.g.,
Tempe,forassistancewiththree-dimensional
University,
tions;RobertJones,The AustralianMuseum,Sydney,foraccess to
Mussa, 1986) to large forestscontainingtreeswith subGlossopteris
linearis,and
talbragarense,
specimensof Blechnoxylon
stantialtrunks(e.g., Francis et al., 1991; Taylor, Taylor,
and
walkomii;and KristieL. Butlerforphotographic
Gangamopteris
inpartbyFacultyGrant- and Cuneo, 1992). Althoughthese reportsindicate that
wasfunded
Thisresearch
assistance.
technical
andNSF grantsBSR-9006625 at least some glossopteridswere large woody trees,they
in-AidB-600,ArizonaStateUniversity
provide littleinformationabout the systematicsor evoto KBP and DPP-8815976to TNT.
4 Author
forcorrespondence
(FAX: 602-965-6899).
lution withinthe group.
500
May
1993]
PIGG AND TAYLOR-GLOSSOPTERIS
MATERIALS AND METHODS
Permineralized peat in the central Transantarctic
Mountains, Antarcticacontains anatomicallypreserved
woodystemsand smallerbuds withtheleaves Glossopteris
skaarensis Pigg and buds of G. schopfiiPigg (Pigg, 1988,
1990). Specimens were recovered froma site on Skaar
Ridge (Global Positioning System 84049'1 18"S
163?20'370"E) (Schopf, 1970; Taylor, Taylor, and Collinson, 1989; Taylor and Taylor, 1990) and are regarded
as Late Permian(Farabee, Taylor,and Taylor, 1991). The
materialwas studiedwithserialpeels usinga modification
of the cellulose acetate peel technique (Joy,Willis, and
Lacey, 1956), etchingthe silicate matrixwith 40% hydrofluoricacid forseveral minutes(Basinger and Rothwell, 1977) and neutralizingwitha saturatedsolution of
sodium bicarbonate.Specimens were cut frompeels and
mountedon standardmicroscopeslides in xylene-soluble
Coverbond. Axes were mapped and measured with the
IBM PC-Based Three-Dimensional ReconstructionSystem (HVEM-3D), Version 1.2 (Royer, 1988). All preparations are deposited in the Paleobotanical Collections,
The Ohio StateUniversity,and bear acquisitionnumbers
14092, 14094, 14102, 14103, 14128-14214, 1425714372, 14396-14403, 18070, 18072, 18106-18206,
18208-18223, 18233-18241, 18256.
SYSTEMATICS
Genus: Glossopteris
Brongniart
Species: G. skaarensis Pigg sp. amplif.Pigg & Taylor
Pigg,K. B. 1990. Rev. Palaeobot. Palynol. 66: 105-127.
Amplifieddiagnosis: Vegetativeleaffeaturesas delimited in Pigg,1990. Stems 1-12 mm in diam (X= 3.1 mm)
withbroad pithup to 1.1 mm across. Primaryxylemwith
helical to scalariformwall thickenings.Secondaryxylem
up to 6 mm thick;pycnoxylic;assignable to Araucarioxylon Kraus; tracheidswithuni- to biseriate,oval to hexagonal borderedpits on radial walls; uniseriaterays one
to a few cells high; cross-fieldpittingcupressoid-taxodioid. Secondaryphloemca. fiveto eightcellsthick;cortex
aerenchymatous-parenchymatous, occasionally with
clustersof sclereids;peridermup to eightcells thick;leaf
in thepetiole;axillarybranchtraces
tracestwo,bifurcating
two, fusingat base of branch.
Holotype: Specimen on 465 C3 Side and C4 Side, Pigg,
4, Plates
1990: Figs. 5, 6 and Plate VI, 1; Plates VII, 1, 3,_
VIII, 1-4. Slides 14098-14101; 14230-14248 in-thePaleobotanical Collections,The Ohio State University.
Paratypes: Specimen G2. 1, 463 E Bot Fragment,Fig.
4a and Plate V, 1 of Pigg, 1990; Specimen G2.4, 452
Fragment,Fig. 4c and Plate V, 4 of Pigg, 1990; Specimen
G2.5, 452 Fragment,Plate V, 4, of Pigg, 1990; Specimen
a in 484 C Bot no. lg, Plate VI, 5 of Pigg, 1990. Slide
14097 in the Paleobotanical Collections,The Ohio State
University.
Collectinglocality: Skaar Ridge, Beardmore Glacier,
central Transantarctic Mountains, 84?47'S, 16301 5'E,
BuckleyIsland Quadrangle(Barrettand Elliot,1973) (GPS
84049'118"S 163020'370"E).
Stratigraphicoccurrence: Upper Buckley Formation,
Late Permian.
STEMS
501
DESCRIPTION
Stems and buds of Glossopterisskaarensis-The descriptionis based on thestudyof 152 specimensofwoody
stems,of which 12 were studiedin detail (Figs. 1-14, 2224), and fiveleafybuds (Figs. 15-17, 25-30). Some ofthe
largerstemshave partiallypreservedextraxylary
tissues,
leaf bases, and axillarybranches(Figs. 1-5). These specimens are assigned to G. skaarensis on the basis of leaf
trace and corticalanatomythatis identicalto thatof the
vascular tissue and mesophyllof mature,isolated leaves
of G. skaarensis (Pigg, 1990). The smalleraxes are buds
that produced numerousleaves with G. skaarensis anatomy.Woody stemsof G. skaarensisare 1-12 mm in diam
(X = 3.1 mm, 152 stemsmeasured) and typicallypossess
a broad pith up to 1.1 mm across (Figs. 1-5). Tissue
comprisingthe pith is variable: the pith may be hollow,
septate.When tissolidlyparenchymatous,or irregularly
sue of the pith is preserved the parenchymatouscells
generallycontain dark contents.The marginof the pith
is usually scalloped or disruptedwith cavities occurring
presumablyin thepositionof theprimary
intermittently,
vascular bundles,and sometimesin association withleaf
tracedivergence(Figs. 3-5). Primaryvascular strandsare
difficult
to distinguishin transversesection. However, a
markedchange in tracheidsize and the patternof pitting
can be recognizedin longitudinalsection frominner to
outerstelarmargin.This reflectsthepositionofa primary
xylemzone (Fig. 12). Primaryxylemtracheidsare up to
8.8 Am in diam and have helical or scalariformpitting
patterns.
Outside the primaryxylemthe secondaryxylem may
be up to 6 mm thickon the largestspecimens.The wood
may appear as a continuous cylinder(Figs. 1, 2) or, at
other levels, be dissected radially by the divergenceof
several leaf traces (Figs. 3, 5, 22-24). When leaf traces
are present,the cylinderis generallydissectedby at least
fivetraces ratherthan by only one or two. Preservation
of the wood is variable, with numerous small areas of
well-preservedcells scatteredamonglargerareas ofpoorly
preservedtissue. Because of this,several featuresof the
wood are obscured,includingdetailsoftheprimaryxylem
bundles. It is also difficult
to determinewhethergrowth
rings occur in this wood. There is some suggestionof
periodicchangesin tracheiddiameterin some ofthebetter
specimens (e.g., Fig. 1, lower right).
Secondary xylem is similar to AraucarioxylonKraus
(Lepekhina and Yatsenko-Khmelevsky,1966; Maheshwari, 1972; Pant and Singh, 1987). Tracheids are 10-15
Amin diam and possess uni-to biseriate,oval to hexagonal
borderedpits (5 x 5,m) only on theirradial walls (Figs.
12-14). On some tracheids,widelyseparatedoval-shaped
pits are presentin combinationsof uniseriateto biseriate
arrangement(Figs. 12, 13). On otherstheyare crowded,
biseriate,alternate,and more hexagonal in outline (Fig.
13). The wood contains numerousuniseriate,parenchymatous rays,each one to a fewcells high(Fig. 14). Crossfieldpittingis of the cupressoid to taxodioid type(Figs.
10-11).
To the outside of the secondaryxylem the secondary
phloem occurs as a zone fiveto eightcells thickof poorly
preserved,radiallyaligned cells. The vascular cambium
is not preserved.The primarycortexis up to 5 mm thick
502
[Vol. 80
AMERICAN JOURNAL OF BOTANY
TABLE 1.
Occurrencesof glossopteridleaves attachedto stemsa
Taxon
Preservation
Age
Locality
Gl brownianabc*
Impression
Filicitesd
Impression
S. poljphyllae
Impression
S. (?) longifuliae
Impression
Permian
Australia
Permian
India
Permian
India
Permian
India
Be. voodtmazson)il
Permian
Impression
Glossopteris19"
Impression,petrifiedaxis
VertebrariaG.browniana5
Impression
Vertebraria/GI.
communisi
Impression
BL. talbragarens ek**
Impression,petrifiedaxis
Glossopteris.
Impression
V"australSmn'
Impression
G. browniana-"n
Impression
Terminal budg0
Impression
S. Iongicaulisp
Impression
cf. GI. angusttfblia.
Impression
India
Permian
Australia
Permian
S. Africa
Permian
India
Permian
Australia
Permian
Australia
Permian
Australia
Permian
S. Africa
Permian
Australia
Triassic
S. Africa
Triassic
S. Africa
--
3 x 1.1
Sessile
-
1.2 x 0.2
Permian
9.3 x 1.8
Permian
-
GZ.
recMurvaY
Impression
G. c 'lopteroides
Impression
6
1.0-4.3
x 0.1-0.3
Smooth, some leaf scars
Transversenodes
6.0 x 0.8
Transversenodes
4.5-6 x 2.5-4.5
-
8.5 x 1.8
G. indicas
Permian
Transversearticulations
15.2 x 1.8
Oval leaf scars
3.7-5.2 x 0.7
Transverseridges
1.5 x 1
Transverseridges
Petiolate
1.8-2.5 x ?
1.5 x 1-2
Sessile
7 x 1.5
Petiolate
10-12 x 2
Petiolate
Sessile
9 x 1.5
-
S. Africa
Permian
Australia
Triassic
S. Africa
Permian
India
Permian
India
Permian
India
Permian
India
Permian
India
20
Subopposite
7
0.7-2.1 x 0.5-1
Petiolate
11 x 2.5
Helical?
I
Cluster
16
Cluster
7
Cluster
Up to 7 x 0.4
Longitudinalstriations
? x 0.5
Longitudinalstriations
6.4 x ?
Longitudinalstriations
Longitudinalstriations
Longitudinalstriations
14 x ?
-
4
Whorl or tighthelix
2-8 per node
Whorl
6
Apparentwhorls
Apparentwhorls
4 per node
Apparentwhorls
2
3
-
9.5 x 2.2
Longitudinalstriations
35.2 x ?
India
8.5 x 1.7
Sessile
12.8x ?
-
-2
-
Permian-
India
3-8
"Verticel"
4
10 x 0.70.9
-
7 x 3.5
Petiolate
9.8 x 3.8
Petiolate
14 x 4
Petiolate
15.4 x 6.8
Petiolate
8.7 x 3.2
Sessile
Helical in tufts
5.8 x 0.3-0.4
Longitudinalstriations
40 x 6
-
-
Helical, close whorl
8
Singly
1 per node
Close tuft
7
Whorl or tighthelix
4
Overlapping,tighthelix
10-15
Verticelor tighthelix
4 per node
"Whorls'
5-7 per node
India
Permian
India
Permian
7
-
7 x 1.1
Sessile
2.5 x 0.8
Petiolate
17.3 x 3.1
Sessile
Brazil
Permian
S. Africa
S. Africa
7.5 x 0.6
Longitudinalstriations
0.7 x 0.25
-
-
Permian
Impression
G. obovata var. attenuataS
Impression
G. walkomiPt
Impression
Go. verticillatal
Impression
Gl searsolensisv
Compression/Cuticle
Gl. maculatav
Compression/Cuticle
Gl. sastriiv
Compression/Cuticle
Gl. oldhamiiv
Compression/Cuticle
GI. panduratav
Impression
Gl. taenioides
Impression
GI. agustifoliav
Impression
Attachmentof specimen
Leaftoial or leaves/node
-
Vertebrariaf
Impression,cast of axis
Gl. angustifolias
Impression
Stem:
Length x width(cm)
Surfae
Leaf:
lngth x width(cm)
Petiolate or sessile?
I
May 1993]
TABLE 1.
PIGG AND TAYLOR-GLOSSOPTERIS
503
STEMS
Continued
Taxon
Preservation
G. cyclopteroides
var.
cordiferav
Impression
ArberialeeukuilensisImpression
LidgettonialidgettonioidesImpression
Gl. skaarensis'
Petrifiedstem and leaves
Age
Locality
Permian
India
Permian
S. Africa
Permian
S. Africa
Permian
Antarctic
Leaf:
Length x width(cm)
Petiolate or sessile?
--
10 x 4
14 x 1.8
(3.5) x 2.7
Stem:
Length x width(cm)
Surface
-
4
_
8
-
-
-
8
-
a
Informationobtained fromsources indicated. Abbreviationsforgenericnames: Be
GI = Glossopteris;Go = Gontriglossa;S = Sagenopteris;V = Vertebraria.
bDana, 1849*.
c Rigby,Maheshwari and Schopf, 1980.
d
Bunbury,1861.
e Feistmantel,1881.
I Etheridge,1895.
gWhite, 1978.
h Zeiller, 1896.
Oldham, 1897.
Etheridge,1899.
k Pant and Nautiyal, 1984a.
Etheridge,1904.
- Seward, 1910.
n Walton and Wilson, 1932.
OWalkom, 1928.
P DuToit, 1927.
q Thomas, 1952.
r Dolianiti, 1954.
s Plumstead, 1958.
t Rigby, 1967.
u Anderson and Anderson, 1983.
v Pant and Singh, 1974.
Anderson and Anderson, 1985.
x This paper.
* Not accepted; ** Anatomicallypreserved.
to aeren(Figs. 1, 2, 4) and rangesfromparenchymatous
parenchywithan innerzone oflarger-celled
chymatous,
more
ofsmaller,
bya hypodermis
matouscellssurrounded
compactcells(Figs. 1, 2). Occasionallysmallclustersof
A periderm
sclereidsare embeddedin theparenchyma.
up to eightcellsthickoccursin someaxes. Preservation
poor.
tissuesis generally
ofextraxylary
leaftracesdivergefromthe stele
Two wedge-shaped
to formfour
and enterthepetiolewheretheybifurcate
strands(Figs. 2, 3, 5, 22-24). It is unclearwhetherthe
of the same symtracesoriginatefromthe bifurcation
fromtwoadjacentcaulinebundles.
podiumor separately
Distalto itslevelofattachment
to thestempetiolebases
in
are 1.5 x 0.58 mm in diam and oval to triangular
outline(Figs. 2, 24). At thislevel the vascularbundles
ringsoftangentially
aresurrounded
byseveralconcentric
cellsthatcomprisea bundlesheath.
elongateparenchyma
parenchyma
Thegroundtissueis composedoflarge-celled
at
hypodermis
in the centralareas and a smaller-celled
theperiphery
(Fig. 2).
xylemthebranchtraces
Atthemarginofthesecondary
appearas paired,elongateareasaccompaniedby a large
amountofsecondary
xylem(Fig.9). Theybecomeovoid
intransverse
sectionandca. 7 10,tmindiamatthemargin
fuseinto
oftheparentaxis (Figs.7, 8). Theyeventually
a singleradialstrandca. 1.8 x 0.6 mmindiamthatenters
Attachmentof specimen
Leaf total or leaves/node
=
Belemnopteris;Bi
=
Blechnoxylon;G
=
Gangamopteris;
theaxillary
branch(Figs.4, 6). Axillary
branches
areabout
one-fifth
thesize ofthemajorstemaxis (Fig. 5).
In additionto maturewoodyaxes thatbear axillary
branches,small,leafybudsofG. skaarensisalso occurin
thechert.The mostextensive
budis sectionedat thelevel
of thestemaxis and bearsat least24 helicallyarranged
leaveswiththeanatomycharacteristic
ofmatureG.skaarensisleaves (Pigg,1990; Figs. 15-17, 25-30). This bud
containsan axis 1.2mmindiameter
atthemostproximal
level witha steleca. 54 ,umin diameterconsisting
of a
broad,hollowpithsurrounded
bya ringofpoorlydefined
vascularbundles.The steleis surrounded
by a partially
preserved,
parenchymatous
cortexthatextendsintolobelike leafbases (Fig. 17). The relativepositionsof individual diverging
leaves suggeststhatthephyllotaxy
approachestwo-fifths
(Figs.25-30). The steleis too poorly
preservedto providedetailsabouttheprimary
vascular
architecture,
butatmostlevelsfivetoninepoorlydefined,
individualbundlesappearto be present.
Leaveson thebudsareup to 540 ,umlong.Theyappear
first
as lobed leafbases extending
fromthestemmargin
and becomeoval-triangular
in transverse
sectiondistal
to theirpointofattachment
(Figs.15, 17,27-30). Leaves
are characterized
by a thickenedmidribup to 300 ,um
acrossthatcontainsa prominent
lacuna,andconsiderably
thinner
laterallaminae(Figs. 15-17,25, 26). Mesophyll
504
AMERICAN JOURNAL OF BOTANY
[Vol. 80
is poorlypreservedbut appearssimpleand parenchy- thatthenodalanatomyofG. skaarensiswouldbe ofthe
matous,lackingpalisadeandspongy
layers.Evenonthese unilacunar,one- or two-trace
type.The petiolebecame
Although
smallleavesthecuticleis thick(Fig. 17).
oval-shaped,distalto thelevelofattachment.
it is not knownwhetherG. skaarensisleaves had long
Buds of Glossopterisschopfii-Five small buds withG.
sessile.Isolated
werenotentirely
petioles,theyapparently
laminarwings,
slight
leavesarepreserved
distalto thelevelofthestele proximalsectionsofleaves,showing
schopfii
(Figs. 18-21,31, 32). The innermost,
smallestleavesare are comparablein size and anatomyto petiolebases at250 x 31 ymandhavea prominent,
keeledcentralregion tachedto thestems(compareP1.IV, 4 ofPigg,1990with
butonlyslightly
developedlaterallaminae(Fig.19).Leaves Fig. 2, thismanuscript).
Branchtracesin G. skaarensis
to the outsideof thesehave a uniformthickness,
are originateas double vascularstrandsthatfusepriorto
is likethatin some
comparableto matureleavesin width,and have prom- entering
theaxillarybud.Thispattern
inentlacunaeinthepositionofthevascularbundles(Figs. cordaites(Mesoxylon
Traverse,1950).Stems
thompsonii,
18, 31). Leaves tendto overlapone another,enclosing producedaxillarybranchesfairlyfrequently.
up
plantwereoblanceolate,
theaxis.Tissuesoftheleaflaminaearenotwellpreserved.
LeavesoftheG. skaarensis
to 2.8 cm wide,and probablynot over 10 cm in length
midriband a coarsepolygonal-meshed
witha prominent
DISCUSSION
venationpattern(Pigg,1990). Theyhad a thickhypovasradiallysymmetrical
Glossopterisskaarensis stems with attached leavesdermisand delicatemesophyll,
midribareas,and thinlamina.
Glossopteris
skaarensisstemswithattachedleaves are cularbundles,thickened
relatively
small,branching
woodyaxes.Whenthesestems A thickcuticlecoveredepidermalcellswithsinuousanare mappedin thematrix,
sunkenstomataontheabaxial
mostofthembelongto one of ticlinalwallsandscattered,
beakcellswithprominent
fourlargeclusterscontaining
fiveto 12 axes each.Based surface.
Five to sixsubsidiary
on three-dimensional
thestoma(Pigg,1990).
reconstructions,
some oftheindi- likepapillaesurrounded
beencomparedmost
vidual sectionsprovedto be froma singleaxis thatwas
has previously
Leafmorphology
leaf impressionswith
twistedin thematrixso thatit was sectionedmorethan closelywith otherfragmentary
once. The flexibility
oftheaxes thatenablesthemto be coarse-meshed
venation,includingG. conspicua,G. retwistedin the matrix,alongwiththe relatively
and severalspeciesof Belemnopteris
simple tifera,G. shirleyi,
extraxylary
tissues,and smallamountofperiderm,
1977;Banerjee,1978;
sup- (Schopf,1976;PantandChoudhury,
thattheseaxeswereslenderstems Rigby,1978b,1983;Lacey,van Dijk,and Gordon-Gray,
portstheinterpretation
or branches.The lack of both adventitiousrootsand 1975; Pigg,1990). Anatomicaldetailshave previously
asymmetrical
withleavesfromtheBowenBasin,
xylarytissuessuggeststhattheymaynot beencomparedbriefly
havebeenrhizomes,
vines,orlianas.Whether
theseleaf- Queensland(Gould and Delevoryas,1977; Pigg,1990),
bearingaxes weremainstemsor,morelikely,thelateral but recentstudysuggestsleaves fromthetwo localities
1992).
branchesofa largertree,is notknown.
notequivalent(PiggandMcLoughlin,
areprobably
Based on theanatomydescribedabove,it is believed
skaarensisleaves can also now be comGlossopteris
Pigg.1-3,5. Serialsectionsfroma singleaxis,withFig. 1 beingthemostdistal.Bars= 1 mm.1. Transverse
skaarensis
Figs.1-5. Glossopteris
cortex(C). 451 D botr No.
ofsecondary
xylem(X), andaerenchymatous
pith(P), solidcylinder
ofwoodystemshowing
internode
sectionthrough
54, x 27. 2. Moreproximalsectionof same stemwithpetiole(at lowerright)attachedat a stillmoreproximallevelin Fig. 3. At thislevelthe
same
sectionthrough
see Fig.25. 451 D botr No. 31, x 27. See barin Fig. 1. 3. Transverse
vascularsupplyofthepetioleconsistsoffourstrands,
appearance
Thepetiolehasthecharacteristic
(arrows).
bytwostrands
petiole(PT) is vascularized
level.Heretheattached
atmoreproximal
specimen
see Fig. 24. 451 D bot r No. 4, x 27. See barin Fig. 1. 4. Obliquesectionofstemwithaxillarybranch(AX)
ofisolatedleavesof G. skaarensis,
stemat levelofnodewithseveralleaf
451 D botr No. 54, x 12.5. Mostproximalsectionofstemin Figs.1-3 showing
and petiole(PT) (at right).
tracesoccurring
at margin(arrows)and severalattachedpetioles(PT), see Fig.23. 451 D boti No. 3, x 20.
Tracesariseas doubletracesin thestem(Figs.
skaarensisPigg.6-9. Seriesshowingaxillarybranchtracederivation.
Figs.6-14. Glossopteris
proximalto axillarybranch.451 D botl No.
7-9) and fusein thecortex(Fig.6). Bar = 0.5 mm.6. Fusedbranchtraceat levelofthestemcortex,
tracesofthesamebranchtracepriorto fusion.451 D bott No. 6,
4, x 33. 7. Moreproximallevelofmainstem,showingthetwocontributing
x 33. See bar in Fig. 6. 8. Pairedbranchtracesat themarginofsecondary
xylem(arrows).451 D bott No. 18, x 33. See bar in Fig. 6. 9. More
xylem.451 D botl No. 27, x 33. See barin Fig.6. Figs.
pairedbranchtraces(arrows)inthesecondary
proximalsectionofsamespecimenshowing
10. 451 D botl No. 54,
cross-field
pitting.
taxodioidto cupressoid
10-14.Wood anatomy.Bars= 0.05 mm.Figs.10, 11. Radial sectionshowing
xylem
fromprimary
(left)to secondary
x 450. 11. 451 D bott No. 97, x 450. See barin Fig. 10. 12. Radial sectionofwood showingtransition
pitson radialwallsoftracheids
ofuni-and biseriate
distribution
451 D bottNo. 97, x 450. See barin Fig. 10. 13. Radialsectionshowing
(right).
wallsand uniseriate
rays.Notepits
lackingpitson tangential
sectionwithtracheids
and ray(at bottom).451 E topNo. 74, x 404. 14. Tangential
section(arrow).451 E topNo. 14, x 404. See barin Fig. 13.
in transverse
sectionofsmallaxis
15. Mid-longitudinal
Bars= 0.5 mm. 15-17.G. skaarensis.
and G. schopfii.
skaarensis
Figs. 15-21. Budsof Glossopteris
sectionof smallaxis showingdetailof leaves.Note
(A) showingattachedleaves(arrows).451 D top a No. 6, x 31. 16. Obliquelongitudinal
sectionofsmallaxis withattachedleafbases,
midribarea (MR) and narrowlaterallaminae.533 B topH No. 2, x 42. 17. Transverse
prominent
sectionofbud
18. Transverse
in Figs.25-30. 451 D bot0 No. 32, x 50. Figs.18-21.G. schopfii.
and poorlydefinedstele.Thisspecimenis figured
positionsof vascularbundles,and
lacunaein leaves(arrows)thatrepresent
leaves.Note prominent
above thelevelof thestemwithencircling
youngleavesin
sectionofbud showing
in Fig. 32. 484 B I bota No. 4, x 32. 19. Transverse
laterallaminae.Thisspecimenis figured
overlapping
in Fig. 33. 484 B bot6 No.
leaves.Thisspecimenis figured
overlapping
sectionofbud showing
section.484 B botc No. 1, x 36. 20. Transverse
leaves.484 A bota No. 15, x 18.
sectionofbudwithoverlapping
1, x 42. 21. Obliquetransverse
May 1993]
PIGG AND TAYLOR-GLOSSOPTERIS
ew
V
505
STEMS
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AMERICANJOURNALOF BOTANY
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[Vol. 80
May 1993]
PIGG AND TAYLOR-GLOSSOPTERIS
STEMS
507
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508
AMERICAN JOURNAL OF BOTANY
[Vol. 80
detailstoothercoarseparedinmorphology
andcuticular
meshedleaves attachedto axes. Theyare similarto G.
including
sastriiand G. maculatain a numberoffe-atures
leafand meshshape,presenceofa petiole,sizeofabaxial
positionand irregular
epidermalcells,and hypostomatic
of stomata(Pantand Singh,1974; Tables 2,
orientation
3). In particular,
G. skaarensisand G. maculatasharea
similarmeshsize,whilemeshesof G. sastriiare larger.
Glossopteris
skaarensisand G. sastriibothhavea ringof
orbeakedpapillaesurroundsubsidiary
cellswitharching,
ing each stoma.Of the threetaxa, G. skaarensisis the
smallestleaf(estimated
to be ca. 10 cm longand 2.7 cm
wide),withbothG. maculata(9.8 x 3.8 cm)and G.sastrii
(14 x 4 cm) somewhatlarger.Midribwidthand size of
withlaminasize,while
meshesare positively
correlated
veindensitydecreases.
ofthesemediumIt is interesting
thatseveralfeatures
inleavesare positively
correlated,
sized,broad-meshed
cludinglanceolateshape,thickcuticles,and sunkenstostudmata,withsubsidiary,
beaklikepapillae.In general,
leavesindicate
iesofcuticular
structure
amongglossopterid
a widerangeoftypes(Pigg,1988).To datetherehasbeen
littlecorrelation
betweencuticleand variousmorphologhave
ical features.Instead,subtlecuticulardifferences
been used to establishadditionalspeciesof Glossopteris
becomebetter
(e.g.,Pantand Singh,1974).As affinities
betweencuticlesofanatomunderstood,
thecorrelation
whether
icallypreservedleaves may help to determine
therearetrendsin cuticleanatomywithinthesubgroups
ofglossopterids
as those
ofcomparabletaxonomicutility
of,say,theconifers.
Wood of G. skaarensisconformsto the formgenus
is
ofAraucarioxylon
Kraus.The history
Araucarioxylon
tothewoodgenusDadoxylon
complexandtiedintimately
whichalso servesas a formtaxonforPaleozoic
Endlicher,
and Mesozoic pycnoxylic
wood witharaucariancrossfieldpitting(Pant and Singh,1987; Giraud,1991). Althoughsome authors(e.g., Kriusel, Maithy,and Mathat
1964) have suggested
heshwari,1961; Vogellehner,
ofDashouldbe regarded
as a synonym
Araucarioxylon
Dadoxylonas havingwelldoxylon,otherscharacterize
bundlesand a nonseptate
definedendarchprimary
pith
and Araucarioxylon
and severalothergeneraforwood
of theprimaryxylem
characters
thatlacksthedefining
andMaheshwari,
bundlesandpith(Kriiusel,
1961;
Maithy,
1966; MaheshLepekhinaand Yatsenko-Khmelevsky,
wari, 1972; Pant and Singh,1987). Additionalcriteria
thesetwogenerainclude
thathavebeenusedtodistinguish
and paleogeographic
distribution,
typeof
stratigraphic
and raystructure.
tracheidpitting
and cross-field
pitting,
theimportance
(1972) stressed
Forexample,Maheshwari
in G. skaarensis. ofraystructure
Figs.22-24. Seriesshowingleaftracedivergence
that
the
name
and
concluded
Dadoxylon
xylemstriped,and
by solid areas,secondary
Leaf tracesrepresented
shouldbe used forwood withmultiseriate
rays,while
outercorticalandleafbasesbyclearareas.Arrowsshowpositionsofa
topartly
biseriate
woodswithuniseriate
xylemraysshould
x 20. Bar = 1 mm.
pairedleaftraceas itentersthepetiole.All figures
However,Prasad(1982)
xylem,severalleaf be assignedto Araucarioxylon.
22. Basalmostsectionshowingdissectedsecondary
Redrawnfrom451
leafbases.Matureleafat right.
tracesandtriangular
can be variablethroughout
cautionedthatraystructure
D bot r, No. 3 (see Fig. 5). 23. More distalsectionwithseveralleaf
a woodystemand cannotbe used as a majormeansof
tracesin cortex.Redrawnfrom451 D bot r, No. 4 (see Fig. 3). 24.
Pant and Singh(1987) have progenericdelimitation.
two
xylemcylinder,
Distalmostsectionshowingcompletesecondary
ofthetaxonomic
vided
further
among
problems
summary
petioles(lowerrightand upperleft).Redrawnfrom451 D bot r, No.
a newclassification
LowerGondwanawoodsand offered
31 (see Fig.2).
forthem.
woodoftheDadoxylon
We nowknowthatpycnoxylic
and/orAraucarioxylon
typesoccursin at leastthefollow-
May 1993]
PIGG AND TAYLOR-GLOSSOPTERIS
STEMS
509
10~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fig. 30 is the most proximal level, Fig. 25 the most distal. Leaves are
Figs. 25-30. Series showingleaf arrangementin bud of G. skaarensis.
phyllotaxy,exceptforperhapsleaf no. 7. Specimen
numberedin orde'rof theirpresumedproduction.This numberedsequence followsa two-fifths
becomes crushedat Fig. 27 and more distally.All figuresx 44. Bar = 0.5 mm. 25. Redrawn from451 D bot 0, No. 41. 26. Redrawn from451 D
bot 0, No. 40. 27. Redrawn from451 D bot 0, No. 39. 28. Redrawn from451 D bot 0, No. 37. 29. Redrawnfrom451 D bot 0, No. 36. 30. Redrawn
from451 D bot 0, No. 32.
510
AMERICAN JOURNAL OF BOTANY
[Vol. 80
7~~~~~~~~~~~~~~~
12
Figs. 31, 32. Leaf arrangementin buds of G. schopfii.Bars = 0.5 mm. 31. Redrawn from484 B bot f No. 4. x 42. 32. Redrawn from484 BL
bot No. 1. x77.
ing groups: cordaites, conifers,Paleozoic and Mesozoic
seed ferns,includingglossopterids.The potentialconfusion resultingfromthissituationis illustratedin a recently
published table where the genus Dadoxylon is indicated
as belongingto the Glossopteridales,while Araucarioxylon remains listed as wood of the Coniferales(Prasad,
1986; see Giraud, 1991).
Consideringthe numerousAraucariox.lon stems that
reportedlylack details of the primaryxylem,the poorly
definedprimaryxylembundles of G. skaarensis may be
a real characterof this plant and not merelythe resultof
limitedpreservation.Ifso, thenat leastsome glossopterids
may have been similarto some Paleozoic gymnosperms
that lack well-developed primarybodies such as Heterangium kentuckhvensis
(Pigg,Taylor, and Stockey, 1987)
and Mesox-vlonpriapi (Trivettand Rothwell, 1985).
In comparison withthe various species of Araucarioxylonand othergeneraofGondwana Permianwoods, wood
of G. sk-aarensisis extremelysimple. For example, the
raystructureconsistingof uni-biseriaterays,one to a few
cells high,is one ofthe simplestpossible structuresof this
wood type.This wood has a less complex structurethan,
forinstance,thattypicalof the V1ertebraria
axes foundin
the same matrix.The wood is also unlikewood ofAntarcticoxylon,described by Seward (1914) and recentlyreevaluated (Meyer-Berthaudand Taylor, 1991) in known
charactersincludingsize and ray structure.Glossopteris
compressionswithattachedleaves showa similartracheid
anatomy (Pant and Singh, 1974).
Some have suggestedthat typeof cross-fieldpittingis
taxonomically significantamong many gymnosperms,
theconifers(Phillips,1948; Jane,1970). Wood
particularly
of G. skaarensis shows cross-fieldpits that appear to be
eitherof the cupressoid or taxodioid type(Figs. 10, 11).
These two types of bordered pits resemble one another
superficially,but in the taxodioid type the apertureis
May 1993]
PIGG AND TAYLOR-GLOSSOPTERIS
511
STEMS
TABLE2. Leaf morphology
ofglossopterid
leaveswithcuticlethatarefoundin attachment
tostems
Taxon
Gl. skaarensisa
Gl.
maculatab
Gl.sastriib
Gl. searsolensisb
Gl. oldhamiib
a
b
Morphology:
Shape
Apex
Midrib width
(mm)
Oblanceolate
Retuse
1.1
Broadlypolygonal
Lanceolate
Up to 2
Broadly polygonal
Up to 3
Polygonal
Up to 4
-
3.5
Long polygonal
Obtuse
Lanceolate
Rounded
Lanceolate
Spatulate
Obtuse, pointed
TABLE
58
40
12-40, X = 25
17-50, X = 31
61-94, X= 71
Veryacute
25-42
30-70
70-88
Vein concentration:
Center(cm2)
Lateral (cm2)
13.7
19
5-13, X = 9
13-20, X= 17
4-9, X= 6
10-20,X= 15
12-20
16-24
10
23
resemble the poorly preserved secondary xylem of our
stems. The assignmentof Araguainorachisas a gymnosperm, and possibly a glossopteridstem, ratherthan a
seed fernrachis,seems more likely.
Other stems from the Skaar Ridge matrix and from
Australiansilicifiedpeats currently
understudyresemble
specimens described by Mussa (1986) fromthe Permian
of Brazil as Paulistoxyloninflatum,Piracicaboxylon
agrestinum,
and Austroscleromedulloxylon
geraldinii.
Previousstudiesofglossopteridstem/leafattachmentAlthoughspecimens of Glossopteris
are most commonly
found as detached leaves, attachmentof leaves to stems
has been reportedin numerousinstances(Table 1). One
of the earliestreports(Dana, 1849) has been regardedas
based on poorly preservedmaterialthat cannot be evaluated (Rigby,Maheshwari,and Schopf,1980). In general,
glossopteridleaves have been reportedattachedto three
different
types of axis: 1) Vertebraria-like
axes; 2) axes
withrhomboidalleafscars;and 3) axes witheithersmooth
stems or shallow, longitudinalstriationsof wrinkleson
the surfaces.Other specimens show clustersof leaves at-
3. Cuticular
featuresofglossopterid
leavesfoundin attachment
tostemsv
Taxon
Epidermal cells
(lower) (I x w Mm)
Epidermal cells:
Intercostalshape
Shape over veins
Gl. skaarensisb
24 x 45
Irregular,sinuous margin
Elongate
GI. maculatac
88 x 38
Irregular,sinuous margin
Gl. sastriie
85 x 23
Irregular,sinuous margin
Elongate,straightmargin
105 x 38
Polygonal,sinuous margin
Narrow,rectanguloid
Gl. searsolensisc
Gl. oldhamiic
-
Irregular,straightmargin
Informationobtained fromsources indicated. Generic abbreviationGI
Pigg, 1990 and this paper.
c Pant and Singh, 1974.
b
2.9 x 0.06
2.9 x 0.06
2.5 x 1.5
1.6 x 0.6
5.2 x 1.85
5.8 x 0.9
4.4 x 0.65
5.6 x 0.6
7 x 1
5 x 0.5
Vein angle ():
With midrib
With margin
GI = Glossopteris.
Pigg, 1990 and this paper.
Pant and Singh, 1974.
largerthantheborderand theborderwalls slope outward,
ratherthaninward,as in thecupressoidtype(Jane,1970).
Cupressoid cross-fieldpits have been considered characteristicof modem araucarian wood, and of the fossil
(Prasad, 1982). Whetherthe trangenus Araucarioxylon
sitional morphologyseen in the cross-fieldpits of G.
skaarensisis significantis unclear,but the classification
systembased on cross-fieldpittingdeveloped by Phillips
(1948) was establishedon data fromextantconifers.Like
stomatal and cuticularstructures,wood charactersmay
eventuallyturnout to be less definitiveamong the seed
ferns.
The G. skaarensisstems also resemble specimens described fromthe Permian of Brazil as Araguainorachis
simplissima(Mussa and Coimbra, 1987). The resemblance is based on the lack of pronounced primaryvascular bundles,a broad pithregionwithsimilarlyvariable
anatomy,and generalpatternsofpreservationofthewood.
are considerablylargerthan our
Axes ofAraguainorachis
material,on the orderof 6 cm in diam. Mussa and Coimbra (1987) interpretedthis fossil as part of a seed fern
frondrachis.The tissuestheyinterpretas corticalremains
a
Mesh size (cm):
Near midrib
Near margin
Mesh shape
Stomata:
Distribution
Orientation
Density (mm2)
Hypostomatic
Irregular
90.6
Hypostomatic
Irregular
36
Hypostomatic
Irregular
63
Hypostomatic
Irregular
157
Irregular
Frequent
Glossopteris.
Subsidiarycells:
Number/Stoma
Morphology
Width (Jm):
Guard cells
Stoma
5-6
Papillate
34 x 9
9
Ordinary
-
43 x 18
24 x 5
6-7
Papillate
21 x 7
-
39 x 21
Papillate
52.5 x 25
-
512
AMERICAN JOURNAL OF BOTANY
[Vol. 80
tachedto shortaxis segmentsthatlack distinguishing 1978). White(1978) suggestedthatall threeaxes bore
structures.
1881;Plumstead,
1958;Pant,1967), reproductive
features
(Feistmantel,
whilestillothersare reportedas clustersof leaves that
Observation
ofthesespecimens
byoneofus (KBP) fails
lack a preservedstem(e.g.,Plumstead,1958; Anderson toverify
White'sinterpretation
oftheleaftransition
series
and Anderson,1985).
and fertile
natureofthesespecimens.Although
a variety
thought
to be attachedto ofleafmorphologies,
Glossopteris
leaveswerefirst
including
smallscales,arefoundin
thatshowed thesurrounding
Vertebraria
axesonthebasisoftwospecimens
matrixand in otherspecimensfromthe
ridge,pre- Mudgeelocality,detailsofthecentralregionofthespeca leafwithitspetioleadjacentto a transverse
axis (Zeiller,1896). imenareobscureand theattachment
sumablya node, on a Vertebraria
ofleaveswiththese
AdditionalspecimensweredescribedbyOldham(1897), variedmorphologies
to theG. linearisaxis are notclear
Arber(1902), and Dolianiti(1954) as attachedto Ver- (Fig. 33 ofWhite,1978). The "terminalbud" originally
longitu- describedbyWalkom(1928) is certainly
tebrariaon thebasis of shallow,discontinuous
moreplausible
dinalwrinkles
and deepergroovesthatanastomoseat the as a shootapex bearingscalelikeleaves(Walkom,1928;
areas,ortrans- White,1978),butagain,no clearevidencehas beenprenodeto formnarrowelongaterectangular
ofGlos- sentedthatthisaxisbearsfertile
theseputativeattachments
versesepta.Generally
leaves.Squamellaampla
axes have beendiscounted White,thelargewoodyaxis withlenticular
sopterisleavesto Vertebraria
scars,is conby most authors(Waltonand Wilson, 1932; Thomas, siderablylargerthanboththeG. linearis(Mudgee)axis
anatomicalstud- and Walkom's(1928) axis,and bearslargerleafscarslike
1952;PantandSingh,1974).Moreover,
therootingnatureofthese thoseof G. linearisthatare foundproximalto attached
ies of Vertebraria
underscore
axes(WaltonandWilson,1932;SurangeandMaheshwari, vegetativeleaves (Fig. 33 of White,1978, at bottom).
1962;Schopf,1965;Pantand Singh,1968;Gould,1975). Consequently,
thereis no basis forinterpreting
thisaxis
StemswithrhomboidalleafscarsincludetwoAustra- as a cone. Thereis, likewise,no reasonto assumethe
leavesde- Mudgeespecimenrepresents
lian plants.One is a stembearingGlossopteris
a "wholeplant"as asserted
scribedby Etheridge
(1895), fromMudgee,New South byEtheridge
(1895) andWhite(1978),as itcouldas likely
linearisby be a branchofa largerwoodyplant.
Wales,thatwas laterassignedto Glossopteris
White(1978). The secondis a smallplant,Blechnoxylon A secondAustraliangenus,Blechnoxylon
talbragarfromtheTalbragarDistrictofNew South ense,is based on impressions
of a small,delicateplate
talbragarense,
Wales (Etheridge,1899), thathas been redescribedas withsomedetailsofinternal
anatomy(Etheridge,
1899).
byPantand Nautiyal(1984a). Althoughoriginally
Glossopteris
talbragarense
describedas a fern,Blechnoxylon
is
Bothoftheseplantshave anatomically
stems. clearlya seed plantwithsecondaryxylem,nodes and
preserved
witha petrified internodes,
The Mudgeespecimen,an impression
ofnarrowdichotomously
and clusters
veined
leavesattached leaveswithdenselydistributed
trichomes
(Seward,1910).
axis,showsa crownofeightGlossopteris
toa stoutaxis 15.2cmlongx 1.8cmwide.On thesurface As withG. linearis,
resectioning
and studyofxylemanatare crowdedrhomboidalleafbase scars.The stemanat- omyofBlechnoxylon
mayadd to a clearerunderstanding
butlikeG. skaarensisstemsit ofitsrelationships.
Pantand Nautiyal(1984a) suggested
omyis poorlypreserved,
has a broadpith,indistinct
primary
bundles,and a wide itas a speciesofGlossopteris
(G. talbragarense).
Although
withtheglossopterids
zoneofdensesecondary
xylem(White,1978).In contrast morphological
similarities
certainly
to theG. skaarensisstems,thepithin theMudgeespec- exist,observationsof the materialby one of us (KBP)
somecellswith failedto confirmthe reticulatenatureof the venation
imenappearsheterogeneous,
containing
Detailsofthesecondary describedby Pantand Nautiyal(1984a), althougha few
dark,possiblyresinouscontents.
information
aboutwood mesophyll
cellsare preserved
thatcouldhave beenmisxylemarenotknown,butfurther
further
thatthe
structure
prep- takenforvenation.Etheridge
(1899) suggested
might
possiblybe obtainedthrough
smallpyriform
bodiesborneby some oftheaxes might
aration.
natureofthe represent
reproductive
structures,
buttheycouldas likely
Etheridge
(1895) assertedtheglossopterid
mor- be scaleleavesofsmallvegetative
itlackedtheVertebraria
leaves.Further
invesalthough
Mudgeespecimen,
at thetimeto characterize
Glossopteris tigationof thistaxon,and the discoveryof additional
phologythought
itsrelationship
to theglossopterids.
stems.This specimenwas laterstudiedbyWhite(1978) material,
mayclarify
it as G. linearisMcCoybased on itssim- At present,however,the lack of a reticulatevenation
who identified
leaves of thatspecies. pattern
andlackofknowledge
about
ilaritieswithdetachedvegetative
typicalofGlossopteris
ofvarying its reproductive
On thebasisoffurther
associatedleaffragments
structures
taxonomic
precludesfurther
series assignment.
Whitereconstructed
a transitional
morphologies,
wereborneon theMudgeeaxis
The moretypicaloccurrence
ofglossopterid
leavesatofleavesthatshethought
extendedfrom tachedtosmoothstemsorstemswithdelicatelongitudinal
(Fig. 35 of White,1978). The transition
vegetativeG. linearisleaves through"gangamopterid" striationsor wrinkleshas been reportedby numerous
re- authors(Bunbury,1861; Feistmantel,
leaves to "scale fronds"to fertilemicrosporophylls
1881;Pant,1967;
toSquamellaWhite,a genusshecreatedforisolated Rigby,1967; Pant and Singh,1974; Andersonand Anferred
instemmorphology
microsporophylls
(White,1978). White(1978) also as- derson,1983,1985).Differences
may
and/orpositionon
signeda secondaxisfromMudgeebearingscalelikeleaves be explainedin thecontextofgrowth
to thegenusSquamella (Fig. 20 of White,1978). This theplant,ratherthanas evidenceofdifferent
stemtypes,
describedbyWalkom(1928) as or even species.For example,specimenswithlenticular
specimenwas originally
ofa larger scars,liketheaxisfromMudgee,shownarrowinternodes,
a "terminal
bud."A thirdspecimen,
consisting
scarswas whilein otherspecimens(e.g.,Dolianiti,1954) the inlenticular
woodyaxisbearinghelicallyarranged
assignedto Squamella ampla White(Fig. 31 of White, dividualleavesare morewidelyspaced.Variationin in-
May 1993]
PIGG AND TAYLOR-GLOSSOPTERIS
ofshortand
a combination
ternodallengthcouldreflect
longshoots,as suggestedby some authors(e.g.,Plumstead,1958; Pantand Singh,1974),or merelyvariation
one wouldexpectalonga branchin a treewithproleptic
branching.
Reconstructionsof Glossopteris-Previous
reconstruc-
have been suggestedby
tionsof the plant Glossopteris
Edwards(1935),Seward(1941),Plumstead(1958),Rigby
(1967, 1969),Pant(1977),Pantand Singh(1974),Gould
and Delevoryas(1977),and Retallackand Dilcher(1988,
Etheridge(1895) ofsporiferum").
as "Dictyopteridium
as a small
of Glossopteris
feredthe firstreconstruction
woody plant,based on the Mudgee specimenthathe
the entireplant.White(1978) has
thoughtrepresented
on thisspecimen.Edwards
also based a reconstruction
on Oldham's(1897)
(1935),whobasedhisreconstruction
and
Glossopteris
and Seward(1941),describing
material,
plantas a
theglossopterid
reconstructed
Gangamopteris,
thatGlossopteris
smallshrub.Plumstead(1958) suggested
was a largewoodytreewithdeciduousleaves bornein
on branchesoflarge
whorlson shortshootsthatoccurred
Dadoxylontrunks.Rigby(1967) consideredGangamopofa singlelargetree,
teriswalkomiito be smallfragments
borne
to oppositely
bearingshortshootsand alternately
theGlossopterisl
leaveson longshoots.He reconstructed
plantas a tall treewithwhorledsmall
Gangamopteris
in tufts(Rigby,1969),and as a smallunleavesgrowing
branchedtreewitha crownof largeleaves at the top,
similarto some moderncycads.A plantwithlongand
by Pant and Singh
shortshootswas also hypothesized
(1974).
Gould and Delevoryas(1977) providedperhapsthe
to date,
reconstruction
Glossopteris
mostcomprehensive
and compressed
specimens.Furbased on bothpetrified
was suggested
of thisreconstruction
by
therrefinement
of
Retallackand Dilcher(1988) in theirreconstruction
Thisnameis invalid,however,since
"Dictyopteridium."
betweenthepetrified
similarities
theysuggested
although
GouldandDeDictyopteridium,
material
andcompressed
name the anatomicallyprelevoryasdid not formally
servedseed-bearing
megasporophylls.
in theGlossopteris
Thereare severalcommonfeatures
to date.Theseincludethefolreconstructions
presented
plantswerearlowingsuggestions:1) the Glossopteris
borescent;2) the presenceof longand shortshoots;3)
leaveswerebornein whorlsortighthelices;and 4) leaves
weredeciduous.The G. skaarensismaterialallowsus to
discussand reexaminethebases forthesevariousideas.
thematerialwe
is unclearwhether
1) Arborescence-It
theentirestemofa small,
seefromSkaarRidgerepresents
woodyplant,or thedistal,possiblydeciduous,branches
form.If theseaxes are branches,
ofa larger,arborescent
thengiventhe lack of largestemsin the silicifiedpeat
to thelargerparent
thatattachments
itis unlikely
matrix,
by detailsof
stemcan be readilyresolved.Correlation
wood anatomymaybe possibleifjuvenilewood borne
appreciablyfrommaturestem
by twigsdoes not differ
and Stockey,
wood(e.g.,Carlquist,1975;Cevallos-Ferriz
suchas tra1990). Furtheranalysisof wood characters
cheidlengthwhereavailablemayalso be helpfulin dethepositionofa givenspecimenon theplant
termining
STEMS
513
plantsfor
(e.g.,Carlquist,1975). So far,all glossopterid
is knownare at leastmarwhichanyinternalstructure
thetinystemsofrBlechnoxylon
ginallywoody,including
(Etheridge,1899). One would expectgymnospermous
bifacialvascularcambium,
stemsto have a functioning
oftheecologicalhabitoftheplant.
regardless
2) Long and shortshoots-A numberof researchers
borelongandshortshoots
thatGlossopteris
havesuggested
(e.g.,Plumstead,1958;Pantand Singh,1974;Gouldand
Delevoryas,1977;RetallackandDilcher,1988).Presumaretypably,thewhorlsofleavesin whichglossopterids
icallyfoundwould be the shortshoots,whilethe less
encountered,oppositelyor alternatelyarfrequently
ranged,individualleavesoccuron longshoots,including
Glossopteris
themainaxis(e.g.,Dolianiti,1954).Whether
boretrueshortshootslikethoseof Ginkgo,or whether
lengthand elongationmerely
thevariationin internodal
suchas one wouldfindin an extant
seasonality
reflected
hardwoodtree,is notclear.It is also unclear
temperate
boreits reproductive
like Ginkgo,Glossopteris
whether,
withvegetative
on spur shoots,intermixed
structures
leaves.
Glos3) Whorledvs. helicalleafarrangement-Both
possessanatomicalevskaarensisand G. schopfii
sopteris
in a two-fifths
idencethatleaveswerehelicallyarranged
The suggestion
bysomeofa whorledarrangephyllotaxy.
mentbased on compressedspecimensmaybe theresult
of relatively
large,broad leaves attachedalonga small
Thereis no compelling
areaon shortcrowdedinternodes.
boretheirleavesin whorled,
evidencethatglossopterids
decussate,or othermorespecializedarrangements.
4) Deciduousness-Evidencefordeciduousleaves is
based on depositionalratherthandirectanatomicalfealeaves were
thatglossopterid
tures.The firstsuggestion
byPlumstead(1958)whoobserved
deciduouswasoffered
foundindensemats
leavesweretypically
thatcompressed
of "autumnalbanks."LaterRetallack(1980) correlated
and not
in varvedstratawithfall/winter,
leafoccurrence
layers.In G. skaarensisthe petiolesatspring/summer
tachedto the stemare presentbeyondthe level where
theyare separatefromthe stem,at a level moredistal
thanthepositionofan abscissionzone.Thequestiondoes
not seem to be one of whetherleaves abscised,since
leavesalso produceabscissionlayersuponleaf
evergreen
suchas Isoetes,
fall(in contrastto a fewpteridophytes,
therewas a
thatdo not).Rather,thequestionis whether
with
thatwascorrelated
relatedto seasonality
periodicity
olderleaveswereshedindividually
leafdrop,orwhether
(Chabot
as newoneswereadded,as in manyevergreens
observationmaybe
and Hicks, 1982). One interesting
in shalescontaining
compressed
notedhere:frequently
littlevarileaves the glossopteridleaves demonstrate
ability,exceptforsize. This may suggestthattotalleaf
perhapsinresponsetoa comperiodically,
dropoccurred
frost
stresses
binationofphysiological
stress,
(e.g.,drought,
leafdropofthistypein
experience
etc.).Extantconifers
responseto variousair pollutants(F. Telewski,Buffalo
and Erie CountyBotanicalGardens,personalcommunication;1992). In some plants,suchas Ginkgo,leaves
may be lost in a totalleafdrop eventat the end of a
514
[Vol. 80
AMERICAN JOURNAL OF BOTANY
growing
season,ratherthanthemoregradualautumnal
leafloss typicalofangiosperms.
Leafsenescence,
theabscissionprocess,and theactualleafdropdo notalways
occurtogether
in angiosperms,
as senescentleavesoften
remainon temperate
treeswellintothewinter.It maybe
thatthe physiological
mechanismsassociatedwithleaf
intheglossopterids
replacement
differed
fromthosemore
typicalof angiosperms.
It is also possiblethatwhorlsof
glossopterid
leavesabscisedas entireshootsystems,
like
thosefoundin extantconiferssuchas Taxodium.This
wouldaccountforthecommonoccurrence
offossils
showinga disarticulated
branchwithleavesattached.
The presenceof glossopterid
scale leaves,oftenscatteredamongmaturevegetative
leavesthroughout
thematrix,has been well documentedby manyauthors(e.g.,
Lacey,van Dijk, and Gordon-Gray,
1975;White,1978).
Whilesome scaleshave beendemonstrated
to be fertile
microsporophylls,
othersmaybe vegetativebud scales.
The questionof leafpolymorphism
in Glossopteris
has
notyetbeenfullyaddressed.
Fromtheevidencethathas beenassembledto dateit
is clearthatthe conceptof Glossopteris
encompassesa
varietyofdifferent
typesofplants.Previousreconstructionsofthe"Glossopteris
plant"havebeenbroadlybased
on limitedinformation.
Continuedstudy,particularly
of
anatomically
preserved
specimenssuchas G. skaarensis,
willincreasetheresolution
withwhichwe can viewglossopteridsand allow us to understand
moreclearlythe
diversity
present.Greaterknowledgeof thediversity
of
thisinteresting
groupwillenableus toaddressmoreclearlythebroaderphylogenetic
andecologicalquestionsabout
theseplantsthatdominated
thePermianGondwanalandscape.
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