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Gleichenia appianensis sp. nov. (Gleicheniaceae): A Permineralized Rhizome and Associated
Vegetative Remains from the Eocene of Vancouver Island, British Columbia
Author(s): Randal A. Mindell, Ruth A. Stockey, Gar W. Rothwell, and Graham Beard
Source:
International Journal of Plant Sciences,
Vol. 167, No. 3 (May 2006), pp. 639-647
Published by: The University of Chicago Press
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GLEICHENIA APPIANENSIS SP. NOV. (GLEICHENIACEAE): A PERMINERALIZED
RHIZOME AND ASSOCIATED VEGETATIVE REMAINS FROM THE EOCENE
OF VANCOUVER ISLAND, BRITISH COLUMBIA
Randal A. Mindell,* Ruth A. Stockey,
1
,
* Gar W. Rothwell,
y
and Graham Beard
z
*Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada;
y
Department of
Environmental and Plant Biology, Ohio University, Athens, Ohio 45701, U.S.A.; and
z
Vancouver Island
Paleontology Museum, Qualicum Beach, British Columbia V9K 1K7, Canada
A permineralized gleicheniaceous rhizome with an attached stipe base has been identified from the Appian
Way locality on Vancouver Island, British Columbia, Canada. The specimens are preserved in Middle Eocene
marine calcareous concretions that are studied using the cellulose acetate peel technique. The marginally
mesarch rhizome has a vitalized protostele, protoxylem elements with helical wall thickenings, and scalariform
metaxylem tracheids that occur in clusters. A continuous band of phloem and pericycle surrounds the xylem.
The inner cortex consists of a layer of small-diameter sclerenchyma fibers, and the outer cortex is composed of
larger parenchyma cells. A nodal island of sclerenchyma is present between the leaf trace and protostele at the
level of frond-trace divergence. Long metaxylem tracheids in the frond trace show septa in longitudinal section
that likely represent tyloses. Roots diverge from all sides of the rhizome with traces that run obliquely through
the cortex. Numerous associated but isolated frond segments are found in the Appian Way nodules that show a
pinched and inrolled C-shaped vascular trace and pseudodichotomous bifurcation. The frond traces have
numerous protoxylem strands, and the general anatomy is comparable to that of gleicheniaceous stipes. The
rhizome is described as a new species of Gleichenia, Gleichenia appianensis Mindell, Stockey, Rothwell, et
Beard sp. nov., and represents the first record of Gleicheniaceae in the Tertiary of North America.
Keywords: Eocene, fern, Gleicheniaceae, Hymenophyllaceae, Lygodium, Schizaeaceae.
Introduction
Gleicheniaceae is a tropical to subtropical family of three
to five living genera (Tryon and Tryon 1982; Kramer 1990)
that have long been considered to be basal leptosporangiate
ferns, based on morphological and anatomical characters
(Bower 1926; Copeland 1947). Most notable of these charac-
ters are the protostelic rhizomes, exindusiate sori with simul-
taneous maturation, and large sporangia (Bower 1926).
Phylogenetic relationships of the Gleicheniaceae have been
clarified by recent cladistic analyses using morphological and
molecular characters (Hasebe et al. 1995; Pryer et al. 1995;
Stevenson and Loconte 1996; Rothwell 1999).
Probable gleicheniaceous fossil remains are known as early
as the Permian (Yao and Taylor 1988). Mesozoic records of
the family are more common, including fronds, rhizomes with
attached stipes, and isolated fertile material (Tidwell and Ash
1994; Collinson 1996; Skog 2001). By the mid-Cretaceous,
gleicheniaceous fossils are abundant, with a large number of
specimens being assigned to Gleichenia (Berry 1922; Andrews
and Pearsall 1941). Despite this relatively rich Mesozoic his-
tory, there are no Tertiary records of the family in the New
World (Tidwell and Ash 1994; Collinson 2001). The Eocene
Appian Way flora of Vancouver Island is dominated by angio-
sperm fruits and seeds (Little et al. 2001), but several kinds of
taxodiaceous conifers are present (Hernandez-Castillo et al.
2005) as well as a polypore fungus (Smith et al. 2004) and
many types of filicalean ferns. The ferns of Appian Way have
only recently begun to be investigated in detail. Sori of a schiz-
aeaceous fern have been described (Trivett et al. 2002; Trivett
2006), and a general description of fern diversity is underway.
In this article we describe Gleichenia appianensis sp. nov., a
new species of gleicheniaceous ferns based on a permineralized
rhizome with an attached stipe. This rhizome and several asso-
ciated stipes represent the first record of Gleicheniaceae in the
Tertiary of North America.
Material and Methods
Specimens were collected from the Appian Way fossil lo-
cality south of Campbell River on the east coast of Vancou-
ver Island, British Columbia, Canada (lat. 49°549420N, long.
125°109400W; UTM 10U CA 5531083N, 343646E). Plant
remains occur in marine calcareous concretions in a sandy-
siltstone matrix. These shallow marine sediments have been
dated as Eocene based on fossil molluscs, decapods, and shark
teeth (Haggart et al. 1997), and stratigraphic studies are cur-
rently being conducted at the site (J. W. Haggart, personal
communication, 2004).
The fossiliferous concretions were cut into slabs, and peels
were made using the cellulose acetate peel technique (Joy
et al. 1956). Slides were mounted using xylene-soluble Eukitt
1
Author for correspondence; email ruth.stockey@ualberta.ca.
Manuscript received November 2004; revised manuscript received May 2005.
639
Int. J. Plant Sci. 167(3):639–647. 2006.
Ó 2006 by The University of Chicago. All rights reserved.
1058-5893/2006/16703-0025$15.00
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(O. Kindler, Freiburg, Germany) mounting medium. Images
were captured using a PowerPhase digital scanning camera
(Phase One, Copenhagen, Denmark) and processed using
Adobe Photoshop 7.0.
Systematics
Order—Filicales
Family—Gleicheniaceae
Genus—Gleichenia
Species—Gleichenia appianensis Mindell, Stockey,
Rothwell, et Beard sp. nov. (Figs. 1, 2a–2f )
Specific diagnosis. Rhizome small, at least 3.4 mm in di-
ameter. Protostele mixed, ca. 1.4 mm in diameter; tracheids
in chains or groups. Parenchyma cells between tracheids, thin
walled, 10–20 mm in diameter. Protoxylem strands 5–6; stele
marginally mesarch; protoxylem tracheids ca. 10 mm in di-
ameter, thickenings helical. Metaxylem tracheids scalariform,
25–63 mm in diameter. Cortex two-zoned, at least 1 mm
thick; outer parenchymatous, up to 950 mm thick, cells 25–
63 mm in diameter; inner sclerenchymatous, 125–188 mm
wide, fibers 13–38 mm in diameter. Roots diarch, numerous,
arising on all sides of rhizome. Frond trace C-shaped, origi-
nating as an arc, forming nodal island of sclerenchyma fibers
on divergence; metaxylem trach eids scalariform, up to 200 mm
in diameter, some with numerous regularly spaced horizontal
to slightly oblique septations.
Holotype. Rhizome with diverging stipe; specimen AW
258 C
2
bot and D
2
top, University of Alberta Paleobotanical
Collections (UAPC-ALTA).
Stratigraphic position and age. Oyster Bay Formation,
Middle Eocene.
Description. The rhizome of G. appianensis is 7.5 mm
long and 3.0 mm in diameter (fig. 1a,1b), but the specimen
has been abraded and was probably at least 3.4 mm in diam-
eter in life. No epidermis is preserved on the specimen.
Therefore, the presence of possible scales or trichomes can-
not be determined. The cortex is at least 1.1 mm thick and
shows two distinct zones (fig. 1a). The outer cortex is up to
950 mm in thickness and up to 25 cells wide in the most
completely preserved area. Cells in this zone are thick-walled
parenchyma, 25–63 mm in diameter. The inner cortex mea-
sures 125–188 mm in thickness and is composed of thick-
walled sclerenchyma fibers, 13–38 mm in diameter.
The rhizome has a mixed protostele up to 1.4 mm in diam-
eter (fig. 1a–1c,1g). In cross sections, metaxylem tracheids,
25–63 mm wide, appear to be arranged in chains up to five
cells long (fig. 1a–1d). Thin-walled parench yma cells 10–20 mm
in diameter occur between groups of metaxylem tra-
cheids (fig. 1d). Five to six marginally mesarch protoxylem
strands correspond to subtle lobes of the stele (fig. 1a,1b,
1f). Helically thickened protoxylem elements 10 mm in diam-
eter (fig. 1e, right) occur in clusters among scalariform meta-
xylem tracheids near the periphery of the xylem (fig. 1e,1f).
Encircling the xylem is a poorly preserved layer of putative
phloem and pericycle up to five cells wide and 60 mm across
(fig. 2f, arrow).
Diarch root traces occur on all sides of the rhizome (fig.
1a,1b, arrows) except in the area of leaf-trace divergence
(fig. 1g). Root traces are surrounded by thick-walled paren-
chyma, and their course of growth through the cortex is
oblique. No isolated roots have been identified in the matrix.
Leaf-trace divergence is initiated by the formation of an
arc of xylem at the periphery of the stele (fig. 2a, top). In
slightly more distal transverse sections, a subcircular nodal
island of sclerenchyma forms in the space between the xylem
of the leaf trace and that of the stele (fig. 2b). Continuing dis-
tally, the leaf trace and sclerotic bundle grow larger, as does
the cortex surrounding them (fig. 2c,2d). The trace itself has
endarch xylem maturation with metaxylem tracheids that
measure up to 200 mm wide; these tracheids having scalari-
form secondary-wall thickenings and regular septa (fig. 1g;
fig. 2e,2f). Spacing between these planar septa increases with
tracheid width.
Associated foliage. Two branching specimens and at least
15 isolated frond segments with gleicheniaceous characters
have been found associated with the rhizome (fig. 2g,2h; fig.
3). Frond segments show significant variation in size, ranging
from 2.5 mm to 8.0 mm in width. All have C-shaped traces
with well-developed, infolded adaxial hooks (fig. 2g). Proto-
xylem strands vary (five or more) and show endarch matura-
tion (fig. 2h). Xylem at the lateral edges of the trace is
constricted, giving the trace an angular shape (fig. 2g,ar-
rows). The vascular tissue is surrounded by a narrow sheath
of sclerenchymatous tissue (fig. 2g). To the outside of this
sheath the remaining extraxylary ground tissues are usually
thick walled toward the periphery and relatively thin walled
near the vascular trace (fig. 2g).
At levels of frond branching, the stipe and abaxial arc
both widen, and the vascular trace divides to form three sep-
arate traces before the frond divides. The changes in xylem
configuration that lead to formation of the three traces are
similar in each specimen. Proceeding distally through a series
of transverse sections in the branching region, both adaxial
hooks close to form rings that each enclose ground tissue
(fig. 3a) and then separate abaxially to form two rings of vas-
cular tissue (fig. 3b). Distally, the rings begin to open up on
Fig. 1 Gleichenia appianensis Mindell, Stockey, Rothwell et Beard sp. nov. Holotype. a, Transverse section of rhizome, showing lobed stele,
root traces (arrows), and thick, two-zoned cortex. Note that position of protoxylem strands correlate with subtle lobes of stele (numbered 1–5).
AW258 C bot 16,
328. b, Transverse section of rhizome, showing root traces (arrows) and two-zoned cortex. AW 258 C
3
side 5, 344. c, Transverse
section of stele, showing tracheary elements in chains surrounded by parenchyma cells. AW 258 C
3
side 5, 369. d, Detail of mixed protostele,
showing parenchyma between large metaxylem tracheids. AW 258 C
3
side 5, 3224. e, Longitudinal section near stele margin, showing spirally
thickened protoxylem (px) and scalariform metaxylem tracheids (mx). AW 258 C
3
side 9, 3360. f, Transverse section, showing stele periphery
with marginally mesarch protoxylem strand (px) and zone of putative phloem and pericyle (arrow). AW 258 C
3
side 5, 3128. g, Oblique
transverse section though rhizome, showing diverging leaf trace and internodal island of sclerenchyma. AW 258 D
2
top 2, 320.
641
MINDELL ET AL.—EOCENE GLEICHENIACEAE
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Fig. 2 a–f, Gleichenia appianensis Mindell, Stockey, Rothwell, Beard sp. nov. Holotype. g, h, Associated frond segments. a, Oblique transverse
section of stele at base of stipe divergence. AW 258 D
2
top 50, 333. b, Oblique transverse section of rhizome distal to that in a, showing
sclerenchymatous internodal island (arrow) developing between arc of xylem and stele. AW 258 D
2
top 39, 320. c, Section distal to b, showing
well-developed arc of xylem, cortical expansion, and larger internodal island. AW 258 D
2
top 12, 316. d, Transverse section through rhizome at
level of leaf-trace departure. AW 258 D
2
top 2, 316. e, Longitudinal section through departing leaf trace, showing elongate metaxylem tracheids
with regular septa. AW 258 D
2
top 4, 340. f, Longitudinal section of metaxylem tracheids in stipe base, showing planar septa and scalariform
secondary-wall thickenings. AW 258 D
2
top 4, 3360. g, Isolated frond segment in transverse section showing angular, C-shaped trace with lateral
constrictions (arrows) and adaxial hooks. AW 103 D bot 0,
323. h, Transverse section through isolated frond segment showing lateral constriction
and endarch primary-xylem maturation. AW 4 C top 4, 365.
642
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Fig. 3 Transverse sections showing branching of gleicheniaceous fronds. a, Base of frond segment, showing single trace with adaxial rings of
vascular tissue forming at hooks of C-shaped trace. AW 503 C2 top 7, 330. b, Frond segment distal to a with two free adaxial rings (r) and abaxial
arc with adaxial hooks. AW 503 C top 171,
333. c, Adaxial rings of vascular tissue open on abaxial side, coincident with indentations of abaxial
arc. AW 503 C top 42, 321. d, Section distal to c, showing fusion of three-lobed abaxial arc with tissue of flattened remnants of adaxial rings and
proximal to the level shown in fig. 2h. AW 503 C top 2, 18. e, Transverse section through frond at point above bifurcation, showing two separate
axes both with angular C-shaped trace. AW 503 B bot 0, 324.
643
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their abaxial side, coincident with the development of two
constrictions on the abaxial arc (fig. 3c). At the level of con-
striction, the xylem of the abaxial arc unites with the abaxial
side of the xylem of the remnant rings (fig. 3d). Distal to this
level, the trace divides to produce three separate bundles (fig.
3d). In both branching specimens, only two of the resulting
pinnae persist (fig. 3e). In each specimen, the central segment
truncates and terminates as incompletely preserved tissue.
Discussion
Rhizomes with vitalized protosteles occur in several fern
families, most notably in the basal leptosporangiate ferns
(Bower 1926; Ogura 1972). Anatomical studies of Gleiche-
niaceae (Boodle 1901b), Schizaeaceae (Boodle 1901a), Hy-
menophyllaceae (Boodle 1900), and Cheiropleuriaceae (Bower
1915) have revealed protosteles that differ from family to
family. Lygodium Sw., the only protostelic genus in Schizaea-
ceae, shows a round cylinder of xylem with exarch matura-
tion and indistinct protoxylem strands (table 1). By contrast,
the Appian Way rhizome shows distinct marginally mesarch
protoxylem strands. The leaf trace in Lygodium diverges as
a solid cylinder (Boodle 1901a) as opposed to the arc of
xylem-enclosing sclerenchyma that characterizes the frond
trace in the Appian Way rhizome.
The Hymenophyllaceae has several protostelic genera that
were formerly grouped in the genus Trichomanes L. (Ogura
1972; Dubuisson 1997). Like those of Lygodium, the rhi-
zomes of these taxa are characterized by exarch primary-
xylem maturation, but the leaf trace diverges as a hollow
cylinder of xylem that encloses sclerenchyma (table 1; Boodle
1900). In the Appian Way fern, the leaf trace appears as an
arc of xylem with a nodal island that opens up into the char-
acteristic C-shaped trace as it diverges from the stele (table
1). Like the Appian Way rhizome, Cheiropleuria Nakai has
mesarch primary-xylem maturation, but the protoxylem
strands are indistinct, and the leaf trace diverges as a solid
cylinder that rapidly dichotomizes as it leaves the stele
(Bower 1915).
The Appian Way rhizome is most similar to species of Glei-
cheniaceae. This family is composed exclusively of protostelic
forms except for one solenostelic species, Dicranopteris pecti-
nata (Willd.) Underw. (Boodle and Hiley 1909; Ogura 1972).
All other described gleicheniaceous species also have charac-
ters in common with the Appian fern. In the subfamily Stro-
matopteroideae, Stromatopteris monofilaformis Mett. (the
sole representative of the genus) is similar in stelar construc-
tion to the Appian Way fern except that tracheid chains are
significantly longer (5), and in this species there are no obvi-
ous protoxylem strands (table 1; Bierhorst 1969, 1971).
The remaining four gleicheniaceous genera, Diplopterygium
Nakai, Sticherus C. Presl, Gleichenia J.E. Smith, and Dicra-
nopteris Bernhardi (subfamily Gleichenioideae), have been
subject to substantial taxonomic revision (Holttum 1957; Tryon
and Tryon 1982; Kramer 1990), with most authors recog-
nizing Diplopterygium and Sticherus as subgenera within
Gleichenia. Rhizomes of these protostelic taxa have an inner
cortex of thick-walled cells and relatively thin-walled cells in
the outer cortex. Like those of Gleichenia appianensis,steles
of these species are small, with obvious protoxylem strands,
marginally mesarch xylem maturation, and protoxylem strands
varying in number from 5 to 15 (table 1; Ogura 1972).
Dicranopteris has similar stelar construction to G. appia-
nensis, but the frond trace diverges as a hollow cylinder
rather than an arc (table 1; Boodle 1901b; Ogura 1972).
There has been some confusion about this, because Dicra-
nopteris dichotoma (Thunb. ex Murray) Willd. is a synonym
of Dicranopteris pedata (Houtt.) Nakaike, which Boodle
originally figured as Gleichenia dichotoma Willd. and Ogura
figured as D. dichotoma.InDiplopterygium the stele is un-
lobed, and Ogura (1972) shows 11 protoxylem strands, a
number far greater than the five to six observed in G. appia-
nensis (table 1). In Sticherus flabellatus (R. Br.) H. St. John
(figured by Boodle as Gleichenia flabellata Br.; table 1), the
frond trace diverges as an arc of xylem enclosing a nodal is-
land, as in G. appianensis (Boodle 1901b; Bierhorst 1971).
However, the stele is unlobed, and Boodle (1901b) shows 14
protoxylem strands.
Table 1
Comparison of Appian Rhizome Stelar Anatomy and Leaf-Trace Divergence to
Extant Fern Genera with Ectophloic, Protostelic Rhizomes
Family and genus
Primary-xylem
maturation
Protoxylem
groups
Stele
lobed Leaf-trace divergence
Schizaeaceae:
Lygodium Exarch Indistinct No Solid cylinder of xylem
Hymenophyllaceae:
Trichomanes s.l. Exarch Indistinct No Hollow cylinder of xylem
Dipteridaceae:
Cheiropleuria Mesarch Indistinct No Dichotomizing solid cylinder of xylem
Gleicheniaceae:
Stromatopteris Marginally mesarch Indistinct Yes Solid cylinder of xylem
Dicranopteris Marginally mesarch Distinct (5–15) Yes Hollow cylinder of xylem
Diplopterygium Marginally mesarch Distinct (11) No Arc of xylem enclosing sclerenchyma
Sticherus Marginally mesarch Distinct (14) No Arc of xylem enclosing sclerenchyma
Gleichenia Marginally mesarch Distinct (5–15) Yes Arc of xylem enclosing parenchyma
Appian Rhizome Marginally mesarch Distinct (5–6) Yes Arc of xylem enclosing sclerenchyma
Sources. Data from Boodle (1900, 1901a, 1901b); Bower (1915); Chrysler (1943); Bierhorst (1969, 1971); Ogura (1972).
644
INTERNATIONAL JOURNAL OF PLANT SCIENCES
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As in G. appianensis, living species of Gleichenia s.s. have
a lobed stele with 5 to 15 protoxylem strands and a frond
trace that diverges as an arc of xylem enclosing a nodal is-
land (table 1; Boodle 1901b; Ogura 1972). Our specimen is
most similar to Gleichenia dicarpa R. Br. (¼Gleichenia cir-
cinnata Sw.) as illustrated by Boodle (1901b) and Ogura
(1972). This species has five protoxylem strands, a lobed
stele, and a similar mode of leaf-trace divergence (Ogura
1972). The nodal island formed in G. dicarpa is parenchyma-
tous (Ogura 1972), while that of the Appian Way rhizome is
sclerenchymatous.
The presence of planar septa in the long metaxylem tra-
cheids of the frond trace of G. appianensis is a feature un-
known in extant Gleichenia. However, such septa probably
represent tyloses, which have been observed in the stipes of
numerous fern families (Ogura 1972) and specifically in the
protoxylem of Gleichenia (Chrysler 1943).
The fossil record of Gleicheniaceae has been reviewed by
several authors (Tidwell and Ash 1994; Collinson 1996,
2001, 2002; Skog 2001). Remains are predominantly com-
pression/impressions and are described from as far back as
the Permian (Yao and Taylor 1988). The fossil record of
North American Gleicheniaceae begins in the Triassic, with
spores from eastern North America (Cornet and Traverse
1975), fertile frond compressions and spores from New Mex-
ico (Ash 1969), and fronds from Virginia (Cornet and Olsen
1990). While Cretaceous compression records are abundant
(Andrews and Pearsall 1941; Rushforth 1971; Crabtree 1988;
Wing et al. 1993; Skog and Dilcher 1994), Tertiary remains
of any sort are scarce worldwide (Tidwell and Ash 1994;
Collinson 2001).
Anatomically preserved rhizomes of Gleicheniaceae are
rare in the fossil record. Antarctipteris sclericaulis Millay and
Taylor (1990), a rhizome from the Triassic of Antarctica,
was suggested to have gleicheniaceous affinities based on its
mixed protostele, simple frond trace, and scalariform tra-
cheids. Unlike G. appianensis, the Antarctic specimens lack
any clear protoxylem strands in the stele (Millay and Taylor
1990). Antarctipteris sclericaulis also has axially elongate
sclerenchyma strands surrounding the stele and bar-shaped
leaf traces (Millay and Taylor 1990) that do not occur in G.
appianensis.
Gandolfo et al. (1997) described the charcoalified remains
assignable to Gleicheniaceae from the Turonian (Late Creta-
ceous) of New Jersey. Rhizomes with attached frond bases of
Boodlepteris turoniana Gandolfo have a dorsiventral proto-
stele without distinguishable protoxylem strands (Gandolfo
et al. 1997), while the protoxylem strands in G. appianensis
are distinct and there is no evidence of dorsiventrality.
Thus, we have placed the Appian rhizome in a new species,
G. appianensis Mindell, Stockey, Rothwell et Beard sp. nov.
Of those extant species of Gleichenia studied anatomically, G.
appianensis is most similar to G. dicarpa. It should be noted
that while a few species of all gleicheniaceous genera have
been studied in anatomical detail, there are a large number of
species that have not been sectioned. Nevertheless, with the
current body of literature, the anatomical distinctions between
the gleicheniaceous genera seem to be clear (table 1).
The numerous associated frond segments known from the
Appian Way could be those of G. appianensis; however, they
have not been found in attachment. The infolded, angular
C-shaped traces with characteristic constrictions are indica-
tive of the Gleicheniaceae, as is the pseudodichotomous branch-
ing (Chrysler 1943, 1944; Ogura 1972). The latter clearly
represent fronds that follow the same branching sequence as
that described for Sticherus intermedius (Bak.) Chrysler
(Chrysler 1943, 1944). While the bifurcating frond in Glei-
cheniaceae appears superficially to be an even dichtomomy, a
central terminal or dormant bud occurs between the lateral
axes. Histological studies through this region show that the
lateral traces diverge from the margins of the central trace,
the latter persisting in the form of a bud and, thus, the pseu-
dodichotomy (Chrysler 1943).
Permineralized frond segments are known from the Meso-
zoic. These are all placed in Gleicheniaceae based on the
characteristic C-shaped trace and, sometimes, the fertile
structures that are present. Phipps et al. (2000) assign Glei-
chenipteris antarcticus to the family based on sporangial
shape and arrangement and point to a close association with
rachides of Antarctipteris sclericaulis (Millay and Taylor
1990). It should be noted, however, that A. sclericaulis lacks
the characteristic C-shaped trace near the level of stipe diver-
gence from the rhizome.
Sharma and Bohra (1977) describe gleicheniaceous stipes
from the Jurassic Rajmahal Hills of India. These show the
constricted, infolded, C-shaped trace observed in many ex-
tant species of Gleichenia (Chrysler 1944). Gandolfo et al.
(1997) described charcoalified fertile frond remains that gave
enough characters to place Boodlepteris turoniana within the
Gleicheniaceae as a sister group to Stromatopteris in a cladis-
tic analysis based on morphological and anatomical charac-
ters. The trace in these fossil fronds is C-shaped with two
visible endarch protoxylem strands and is surrounded by a
cortex of thick-walled sclerenchyma. The stipe traces associ-
ated with G. appianensis are superficially similar to those of
Boodlepteris in that they have endarch xylem maturation
and scalariform metaxylem tracheids, but they differ from
the Appian Way stipes in having numerous protoxylem
strands and a cortex that is typically parenchymatous toward
the trace and sclerenchymatous toward the periphery of the
stipe. Branching of the fronds in Boodlepteris turoniana was
observed only externally and suggests that branching was ei-
ther dichotomous or pseudodichotomous (Gandolfo et al.
1997). Branching in G. appianensis fronds is preserved ana-
tomically and clearly shows a pseudodichotomous pattern, as
illustrated by Chrysler (1943) for a living gleicheniaceous
species.
Gleichenia chaloneri Herendeen et Skog (1998) has been
described from fusainized frond segments from the early Cre-
taceous (Albian) of Bedfordshire, England. These frond frag-
ments have a C-shaped trace with incurved arms and 7–8
protoxylem strands. Like the Appian Way frond remains, scle-
renchyma immediately surrounds the vascular tissue. Histol-
ogy of the branching regions is not known in the branching
specimens described by Herendeen and Skog (1998), but they
are similar in most respects to our isolated stipes and rachides.
The specimens described in this article are the only Ter-
tiary macrofossils of the Gleicheniaceae thus far described
from the New World, and they provide direct evidence for
Gleicheniaceae in the Eocene of North America. In addition
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to the vegetative remains described in this article, spores of
Gleicheniidites Ross have also been identified from the Ap-
pian Way locality by Sweet (1997). Biogeographic reviews of
the ferns (Tidwell and Ash 1994; Collinson 2001, 2002;
Skog 2001) all point to the poor worldwide record of Glei-
cheniaceae in the Tertiary. The family is well represented in
North America in the Triassic (Tidwell and Ash 1994) and
Cretaceous (Berry 1922; Andrews and Pearsall 1941; Rush-
forth 1971; Crabtree 1988; Skog and Dilcher 1994; Gandolfo
et al. 1997). However, in addition to some spore records and
ambiguous compressions known from Europe and South
America (Collinson 2001), clear Tertiary records are known
only from the Eocene of southeast England (Holttum 1957)
and the Oligocene of Australia (Blackburn and Sluiter 1994).
Today, the family’s Northern Hemisphere distribution is
restricted to tropical and subtropical latitudes (Tryon and
Tryon 1982).
The branching frond segments described here from Appian
Way represent the first anatomically preserved bifurcating
leaves of Gleicheniaceae in the fossil record, and they demon-
strate that the pseudodichotomous branching pattern of Glei-
cheniaceae was established by at least the early Tertiary. The
presence of anatomically preserved rhizomes, fronds, and
spores confirms that this long-lived family persisted at the
northwestern margin of the North American continent at
least until the Eocene.
Acknowledgments
We thank Art Sweet, Geological Survey of Canada, for ac-
cess to palynological data. This work was supported in part
by Natural Sciences and Engineering Research Council of
Canada grant A-6908 to R. A. Stockey.
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