Rickwoodopteris hirsuta gen. et sp. nov.

Review of Palaeobotany and Palynology 132 (2004) 103 – 114 www.elsevier.com/locate/revpalbo

Cretaceous tree ferns of western North America: Rickwoodopteris hirsuta gen. et sp. nov. (Cyatheaceae s.l.) Ruth A. Stockey a,*, Gar W. Rothwell b a

Department of Biological Sciences, Faculty of Science, University of Alberta, CW 405 Biological Sciences Building, Edmonton, Alberta, Canada AB T6G 2E9 b Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701, USA Received 31 October 2003; received in revised form 28 May 2004; accepted 28 May 2004

Abstract A distinctive new permineralized stem from marine deposits of western North America provides additional evidence for the diversity of Upper Cretaceous tree ferns. The fossil occurs in a calcareous concretion from the Late Campanian Spray Formation at Shelter Point, Vancouver Island, British Columbia, Canada. It measures 20 cm long and 7 cm in maximum diameter, with adventitious roots diverging between persistent, helically arranged fronds. Frond traces are derived from an amphiphloic dictyostele, and the stem produces no medullary or cortical bundles. The pith has a sclerenchymatous center and a parenchymatous outer zone. Sclerenchyma sheaths accompany both cauline and foliar vasculature. Frond traces diverge as six to ten bundles, most often eight. At the stem periphery, the cortex produces a homogeneous sclerenchymatous hypodermis, and is clothed by a dense ramentum of both uniseriate and large multiseriate trichomes. This novel combination of characters reveals the presence of a new genus and species of tree ferns, Rickwoodopteris hirsuta gen. et. sp. nov. Cladistic analysis of stem characters infers that R. hirsuta conforms to the dicksoniaceous grade of Cyatheaceae s.l., and further clarifies our understanding of evolutionary diversification among Mesozoic filicalean tree ferns. D 2004 Elsevier B.V. All rights reserved. Keywords: Cretaceous; Cyatheaceae; Dicksoniaceae; tree fern

1. Introduction Anatomically preserved plant fossils are known from marine calcareous permineralizations in Mesozoic and Cenozoic deposits worldwide (e.g., Dawson, 1873; Stopes and Fujii, 1910; Stopes, 1918; Ogura, 1930; Stockey, 1980; Banks et al., 1981; Miller, 1990; Falder et al., 1998; Lantz et al., 1999), but until * Corresponding author. Tel.: +1-780-492-5518; fax: +1-780492-9234. E-mail address: [email protected] (R.A. Stockey). 0034-6667/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2004.05.002

recently, these were thought to be relatively isolated occurrences. However, extensive collecting in northern Japan (Nishida, 1991) and along the western coast of North America has yielded concretions at several localities that contain a wealth of plant material (Little et al., 2001; Smith and Stockey, 2001; Rothwell and Stockey, 2002; Elliott et al., 2003; Smith et al., 2003a,b; Stockey and Rothwell, 2003a,b). As a result, it is becoming increasingly clear that there is tremendous potential for these fossils to dramatically improve our understanding of Mesozoic and Tertiary plant evolution.

104

R.A. Stockey, G.W. Rothwell / Review of Palaeobotany and Palynology 132 (2004) 103–114

Many of the marine nodules contain only a single, well-preserved plant organ (e.g., Stopes, 1918; Ohana and Kimura, 1995; Lantz et al., 1999; Smith and Stockey, 2001, 2002; Stockey and Rothwell, 2003a,c), but others rival the famous Paleozoic coal balls of Euramerica and China in both systematic diversity and quality of plant preservation (e.g., Stockey and Nishida, 1986; Nishida, 1991; Little et al., 2001; Ratzel et al., 2001; Stockey and Rothwell, 2003b). Whereas, Paleozoic coal balls often preserve in situ remains, the Mesozoic and Cenozoic concretions typically contain allochthonous assemblages. Nevertheless, some of the fossils currently under investigation at the University of Alberta are extremely delicate and seldom-preserved remains, including indusiate fern sori with intact sporangia and spores (Trivett et al., 2002; Smith et al., 2003a,b; Stockey and Rothwell, 2003b), club moss shoots (Rothwell and Stockey, 2003), seeds with endosperm and embryos (Little et al., 2001, 2002), moss gametophytes (Stockey and Rothwell, 2003b), and even fungal fruiting bodies (Smith et al., 2003a,b,c). Permineralized filicalean tree ferns are abundantly represented in the calcareous marine nodules at several Cretaceous and Paleogene localities along the Pacific coast of North America (e.g., Lantz et al., 1999; Smith et al., 2003b,c). These fossils consist of stem segments and frond parts, as well as the oldest permineralized sori of both Cyatheaceae Kaulfuss and Dicksoniaceae Bower (Smith et al., 2003c). Included in the collections is a new well-preserved stem recently discovered in Upper Cretaceous (Campanian) sediments at Shelter Point, south of Cambell River on Vancouver Island, British Columbia, Canada. The specimen displays a distinctive suite of tree-fern characters that reveal a previously unknown species similar to currently known genera in the dicksoniaceous grade of the Cyatheaceae s.l. (Lantz et al., 1999). The purpose of this paper is to expand our knowledge of Mesozoic tree fern diversity by describing Rickwoodopteris hirsuta gen. et sp. nov. Morphological characters of R. hirsuta have been added to a recently compiled character matrix for fossil and living tree fern stems, and analyzed in a parsimony analysis to further extend our understanding of the evolution and phylogenetic radiation of Cyatheaceae s.l.

2. Materials and methods Rickwoodopteris hirsuta is represented by a trunk segment preserved within a calcareous nodule. The specimen was recovered from Shelter Point, south of Campbell River, Vancouver Island, British Columbia, Canada (Fig. 1). The stratigraphic section at Shelter Point consists of six units, two of which yield plant remains that are anatomically preserved within calcareous concretions (Richards, 1975). The locality exposes sediments of the Upper Cretaceous Spray Formation, Nanaimo Group, and invertebrate fossils place this formation within the latest Campanian Stage of the Late Cretaceous (Richards, 1975). Despite the fact that the specimen was found in an isolated nodule, all of the nodule bearing layers in this area have been dated as Late Cretaceous based on invertebrates. Upon discovery, one side of the fossiliferous concretion was broken away revealing the fossil (Plate I, 1). The specimen was photographed and measured, and then cut transversely into five segments. Serial peels were prepared by the well-known cellulose acetate technique (Joy et al., 1956) to produce transverse sections at eight different levels. The distal-most segment was also peeled longitudinally to reveal features in this view. Slides were prepared using Eukitt mounting medium (O. Kindler, Freiberg, Germany), and images were captured digitally in transmitted light, using a Leaf Systems MicroLumina scanning camera and a PhotoPhase scanning camera (Phase One, Copenhagen, Denmark). The specimen, peels, and microscope slides are housed in the Courtenay and District Museum and Archives, Courtenay, BC, Canada. Cladistic relationships were evaluated by adding characters for Rickwoodopteris hirsuta to the 31 character matrix of Lantz et al. (1999). Phylogeny was reconstructed using equal weighted maximum parsimony (PAUP, version 4.0B10; Swofford, 2002) installed on a Power Macintosh 7100 computer to generate the most parsimonious trees (heuristic search, one tree held at each step, TBR branch swapping, steepest descent, MULPARS). To minimize a priori assumptions about the relative value of characters, all characters were unweighted, unpolarized, and multistate characters were unordered. Equally parsimonious trees were summarized using strict


105

Fig. 1. Locality map. Shelter Point is indicated by star.

consensus. As is characteristic for analyses of filicalean tree ferns (e.g., Lantz et al., 1999), the cladistic tree was rooted through Plagiogyria japonica Nakai.

3. Results 3.1. Systematics Order Filicales Family Cyatheaceae Kaulfuss, s.l. Rickwoodopteris Stockey et Rothwell gen. nov. Generic diagnosis: Stem upright, enclosed by homogeneous hypodermis, covered by persistent rachis bases, adventitious roots, and dense indument of both uniseriate trichomes and enlarged multiseriate, thickwalled trichomes. Cauline vasculature an amphiphloic dicytostele, meristeles producing ca. six- to ten-parted frond trace; medullary and cortical bundles absent

from stem; medullary and cortical cauline bundles absent. Leaf gap oval with no constrictions, length/ width ratio 2.5 –3.0:1. Stem and leaf-trace vasculature accompanied by sclerenchymatous sheaths; monarch to diarch adventitious roots diverge from cauline meristeles between diverging frond bases. Type species: Rickwoodopteris hirsuta Stockey et Rothwell sp. nov. Rickwoodopteris hirsuta Stockey et Rothwell sp. nov. Plates I,1 – 4;II,1 –6; III,1 –8. Specific diagnosis: Trunk up to 7 cm in diameter; frond bases helically arranged, oval, 1.2 – 1.5 cm wide, 1.5 – 2.5 cm high. Pith sclerenchymatous at center and parenchymatous at periphery; sclerotic nests, mucilage canals and cuboidal cells absent from ground tissues. Cauline xylem 1.8 – 2.5 mm thick; frond trace xylem ca. 0.2 mm thick. Rachis with sclerotic hypodermis; T-shaped sclerenchyma attached to hypodermis adaxially.

106



Etymology: The generic name Rickwoodopteris (Rickwood + pteris = Rickwood’s fern) honors Taylor Rickwood-Samson, who collected the specimen. The specific epithet hirsuta refers to the dense, heterogeneous trichomes that clothe the stem. Holotype: Specimen 2002.9.1, housed in the Courtenay and District Museum and Archives, Courtenay, BC, is here designated the holotype. Collecting Locality: On the beach at Shelter Point, south of Campbell River, Vancouver Island, British C o l u m b i a , C a n a d a ( l a t / l o n g : 4 9 j5 6 V3 9 UN , 125j11V10U W; UTM = 10U CA 434345). Stratigraphy and Age: Spray Formation, Nanaimo Group; Late Cretaceous (latest Campanian). Description: The trunk segment of Rickwoodopteris hirsuta is roughly conical, 20 cm long, rounded distally, and tapering to an abraded proximal end (Plate I,1). Cross sections reveal that the stem is somewhat crushed at the distal end, only slightly deformed in the mid-region (Plate I,2), and undistorted proximally (Plate I,3). The specimen is 7 cm in diameter at the widest point. Frond bases are helically arranged (Plate I,2) and diverge at a relatively steep angle, as is indicated by the two frond traces on the same radius as seen at the same level of section (Plate I,3, at upper right corner). Individual frond bases are oval at the periphery of the stem, 1.5 –1.8 cm wide, 2.3– 2.8 cm high, with traces that consist of about eight bundles. There appear to be 11 orthostichies (Plate I,2), suggesting that the preserved stem segment may have been in transition from 3/8 to 5/13 phyllotaxis. The stem displays a solid pith surrounded by an amphiphloic dictyostele (Plate I,3,4), and there are numerous frond traces in various stages of divergence in the cortex (Plates I,1; II,1 – 6). No pith or cortical vascular bundles are present. The cortex is largely parenchymatous, except for sclerenchyma that accom-

107

panies the diverging frond and root traces (Plates I,3,4; II,1 – 6) and a prominent, homogeneous sclerenchymatous hypodermis at the stem periphery (Plates I,3; II,6; III,1). Adventitious roots originate from the stele between rachis bases (Plate I,4), and are surrounded by a dense ramentum of trichomes as they diverge from the stem (Plate III,1). The large pith is up to 2.4 cm at the widest point (Plate I,3,4), consisting of sclerenchymatous ground tissue except near the periphery, where there is a zone parenchyma cells 2.0– 2.5 mm wide (Plates I,4; III,5). Mucilaginous cells and sclerotic nests have not been identified in either the pith or cortex. Pith sclerenchyma cells are rounded to angular in cross section, ranging 32 – 102 Am in diameter, with dark prominent walls and clear lumens (Plate III,5). The pith parenchyma cells display the same size range, but have much thinner walls (Plate III,5). In some areas, the pith parenchyma is disrupted by large galleries filled with plant debris representing fecal material (Plate III,7). Sclerenchymatous sheaths that surround both cauline and foliar vascular tissues are about 0.5 mm thick, expanding to as much as 1.5 mm to the exterior of the cauline meristeles (Plates I,4; II,1 –7; III,3 – 7). Sclerenchyma surrounding the vascular tissues consists of a combination of cells like those in the pith, and cells that have much thicker walls and very small lumens (Plate III,5,6). The mesarch amphiphloic dictyostele displays a zone of angular metaxylem tracheids 1 – 1.5 mm thick (Plate III,5,6) that is dissected by several leaf gaps (Plate I,3,4). Cauline xylem is much thicker than the leaf-trace bundles that diverge from the margins of the leaf gaps (Plate I,3,4). Metaxylem tracheids have a maximum diameter of 128 192 Am. A small number of mesarch protoxylem strands (Plate III,6, at arrow) occur within the cauline metaxylem. Phloem consists

Plate I. Rickwoodopteris hirsuta gen et sp. nov. Holotype specimen CDMA 2002.9.1 1. 2. 3. 4.

Trunk segment showing exposed outer surface in longitudinal view. Note diverging frond bases (fb) and abraded proximal end. 0.75. Scale = 10 cm. Tangential section near surface of trunk showing two diverging frond bases. A side #14 2. Scale = 3 cm. Cross section of trunk in mid-region showing solid pith (p), dictyostele with diverging frond traces, cortex (c), and a diverging frond base (fb). A bot #14 2. Scale = 6 cm. Cross section of stem near base of specimen, showing anatomical features. Note root traces diverging between leaf gaps (lg). E top #11 3.5. Scale = 1 cm.

108



of axially elongated sieve cells adjacent to the xylem and tangentially elongated sieve cells toward the sclerenchymatous sheath (Plate III,5,6). Frond bases are oval in both longitudinal (Plate I, 2) and transverse (Plates I,3; II,6) views. At the level of divergence, each frond base has several narrow bundles embedded in parenchymatous ground tissue (Plates I,2,3; II,6). There are two adaxial, hypocampiform bundles (Plates I,2; II,6, at bottom; Plate II,7), two lateral bundles that are broadly C-shaped (Plate II,4, at right), and two to six (usually four) abaxial bundles that are narrowly C-shaped or U-shaped (Plates I,2; II,6; III,4). Frond bases display a sclerotic hypodermis and central T-shaped sclerenchyma that has a fluted abaxial face (Plate II,6). As with the cauline bundles, foliar meristeles are amphiphloic (Plate III,3,4). Protoxylem strands occur at the abaxial side of the bundles. A few protoxylem strands display protoxylem cavity parenchyma (Plate II,3, at arrow), but most do not. Frond trace divergence is first recognized by a thinning of the xylem (Plate II,1). Progressing distally, the area of thinner xylem bulges outward (Plate II,2) until a leaf gap opens (Plate II,3). At progressively more distal levels, frond-trace bundles separate from the margins of the leaf gap until six to nine strands are produced (Plates I,2, 3; II, 4 –6). Most commonly, there are eight bundles. The first bundles to separate from the stele extend to the abaxial side of the rachis, with progressively more adaxial bundles separating at successively more distal levels (Plate II, 4 –6). The leaf gap often closes below the level where the last foliar bundles diverge from the stele (Plate II,5). Reconstructions of the leaf gap from series of transverse sections reveal that it forms a simple ellipse that lacks constrictions, and that it has a length/width ratio of 3.0– 3.5:1. As the frond traces diverge, pith sclerenchyma first extends radially (Plate II,3) and then separates at the

109

center of the developing rachis (Plate II,4 – 6). Progressing distally, the central sclerenchyma expands laterally at the adaxial side, becoming Y-shaped (Plate II,5), then T-shaped (Plate II,7) with a fluted adaxial surface (Plates I,2; II,6). A zone of hypodermal sclerenchyma like that of the stem extends progressively from the adaxial to the abaxial surface as the rachis diverges, finally closing (Plate I,2) and becoming continuous with the central sclerenchyma (Plate II,6) as the frond separates from the stem. Trichomes at the stem surface are of two distinctly different types. Many trichomes are narrow and uniseriate, consisting of thin-walled cells (Plate III,1,2). Such trichomes are 38– 64 Am in diameter, and at least several millimeters long. Other trichomes are much broader, uni- to multiseriate, and have thicker cell walls (Plate II,1,2). These occur intermixed with the narrow trichomes, and range up to five cells in cross sections and 300 Am in maximum diameter. In some places, the ramentum of trichomes is replaced by galleries that contain a mixture of compacted fecal material and oval coprolites (Plate III,8). Adventitious root traces separate from the outer surface of cauline bundles (Plate III,6, at upper left) between the positions where frond traces are developing (Plates I,3,4; II,5) and appear in slightly oblique cross section within the stem cortex (Plates I,4; II,2,5). Roots are 0.8 – 2.2 mm in diameter, and display monarch or diarch steles (Plates II,2,5; III,1). Root cortex is sclerenchymatous, particularly after divergence from the stem (Plate III,1).

4. Discussion A large stem with amphiphloic dictyostele and gaps in the stele that result from frond trace divergence

Plate II. Rickwoodopteris hirsuta gen et sp. nov. Holotype specimen CDMA 2002.9.1. Series of cross sections showing frond trace production 1. 2. 3. 4. 5. 6.

Proximal-most level showing thinning of xylem on radius of incipient frond trace. E top #9 10. Scale = 1 mm. Somewhat more distal section showing radial extension of frond trace xylem. D top #12 10. Scale = 1 mm. Level showing opening of leaf gap, and extension of pith sclerenchyma into incipient frond base. D top #12 10. Scale = 1 mm. Level at which ‘‘U’’-shaped adaxial frond trace bundles have separated. B top #15 7. Scale = 1 mm. Level at which leaf gap has closed, but adaxial frond bundles have not yet separated from stem stele. Note ‘‘Y’’-shaped sclerenchyma. C bot #13 9. Scale = 1 mm. Fully formed frond base immediately below level of rachis divergence. Note nearly complete sclerenchyma sheath enclosing rachis base, and attachment of central sclerenchyma. B top #15 7. Scale = 1 mm.

110



clearly place Rickwoodopteris hirsuta among filicalean tree ferns that traditionally were classified in the Cyatheaceae, Dicksoniaceae, and related genera (Smith, 1995). Although these ferns have been placed in as many as five families (i.e., Cyatheaceae, Dicksoniaceae, Loxomataceae C. Presl., Metaxyaceae Pichi Sermolli, and Plagiogyriaceae Bower (Kramer, 1990a,b,c,d,e), cladistic treatments indicate that they comprise a clade in which the dicksoniaceous genera plus Loxoma R. Brown, Metaxya C.B. Presl., and Plagiogyria Mettenius most often form a paraphyletic grade with respect to the Cyatheaceae s.s. (Conant et al., 1995, 1996; Pryer et al., 1995; Stevenson and Loconte, 1996; Lantz et al., 1999). For the purposes of this discussion, we refer to this tree fern clade as the Cyatheaceae s.l., and to the more restricted traditional circumscription of the cyatheaceous genera (e.g., Conant and Stein, 2001) as Cyatheaceae s.s. Rickwoodopteris hirsuta can be distinguished from all living species and previously described fossil morphospecies of filicalean tree fern trunks by a distinctive suite of several characters. These include six to ten vascular bundles in the stipe base, presence of a sclerenchyma sheath accompanying the cauline and frond trace bundles, absence of accessory bundles in the pith and cortex, homogeneous hypodermal sclerenchyma, and heterogeneous epidermal trichomes. Rickwoodopteris is the only tree fern genus to display six to ten vascular bundles in the stipe base. All other filicalean tree ferns have one, three, or

111

numerous rachial bundles at this level (Ogura, 1972; Lantz et al., 1999). Whereas the living Cyatheaceae (s.s.) are characterized by several forms of scales (Kramer, 1990a), Rickwoodopteris, living species of the dicksoniaceous grade (sensu Lantz et al., 1999), and all other extinct morphospecies of filicalean tree fern trunks except Cyathodendron texanum Arnold (Lantz et al., 1999) display a ramentum of epidermal trichomes. The combination of uniseriate trichomes and multiseriate trichomes with thick-walled cells is distinctive of Rickwoodopteris hirsuta. The absence of accessory bundles from the pith also distinguishes R. hirsuta from living and most fossil Cyatheaceae s.s. (Lantz et al., 1999) as well as from Thyrsopteris Kunze (Ogura, 1972), and from the dicksoniancous grade fossil morphospecies C. texanum (Arnold, 1945) and Oguracaulis banksii Tidwell, Nishida et Webster (1989). 4.1. Systematic relationships of Rickwoodopteris hirsuta Features of Rickwoodopteris hirsuta were added to the 31 character matrix of morphological trunk characters prepared by Lantz et al. (1999). The added characters were scored as follows: 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 3, 3, 0, 0, 0, 1, 1, 2, 0, 1, 0, 0, 0, 1, 0, 0, 1. The addition of R. hirsuta produces a matrix with more taxa (i.e., 32) than characters (i.e., 31). Therefore, even in the absence of homoplasy where one

Plate III. Rickwoodopteris hirsuta gen et sp. nov. Holotype specimen CDMA 2002.9.1 1. 2. 3. 4. 5.

6. 7. 8.

Cross section of stem periphery showing sclerenchymatous hypodermis (h), dense ramentum of heterogeneous trichomes, and diverging adventitious roots in cross section. A side #14 18. Scale = 1 mm. Stem margin in cross section, showing thin uniseriate trichomes and thicker multiseriate trichomes in attachment to the epidermis. B bot #12 31. Scale = 1 mm. Cross section of stem cortex showing abaxial frond trace bundle in cross section. Note sclerenchymatous shearth, amphiphloic meristele, and protoxylem cavity parenchyma (at arrow). B top #14 15. Scale = 1 mm. Frond trace bundles in cortex of stem, showing hypocampiform adaxial bundle (at bottom), ‘‘C’’-shaped lateral bundle with hooked margin (at center), and ‘‘U’’-shaped abaxial bundle (at top). C bot #13 10. Scale = 2 mm. Cross section of stem showing histology of (sp = sclerenchymatous pith; pp = parenchylmatous pith) pith, cauline bundle (x = xylem; p = phloem) with sclerenchyma sheath (s), and inner margin of cortical parenchyma (p). Note tangential cells in phloem (at arrow). D top #12 23. Scale = 1 mm. Cauline vascular tissue in cross section, showing position of protoxylem (black arrow) metaxylem tracheids, phloem with tangential cells, and divergence of root trace (white arrow). C bot #13 35. Scale = 1 mm. Cross section of stem showing gallery (g) filled with compacted fecal material in the parenchymatous pith, located immediately to the inside of a leaf gap. B bot #12 7. Scale = 2 mm. Cross section at margin of stem, showing gallery filled with compacted fecal material and small fecal pellots within the ramentum of trichomes. Sclerenchymatous cortical hypodermis is at bottom of photograph. A side #14 22. Scale = 0.5 mm.

112


synapomorphy defines each resolved node, it is not possible to obtain a fully resolved tree. In such situations, bootstrap and jackknife values also are expected to be extremely low for virtually all nodes of the trees. Nevertheless, addition of R. hirsuta to the analysis provides both an additional test of overall tree fern relationships as hypothesized by Lantz et al. (Fig. 28 of Lantz et al., 1999), and gives a general idea of the systematic position of Rickwoodopteris within the tree fern clade.

The results of 1000 random addition sequence replicates of the heuristic analysis of the 32 taxon and 31 character matrix yielded 105 most parsimonious trees of 125 steps. The strict consensus of all 125 step trees (Fig. 2) has basically the same topology as the cladogram from the 31 character matrix of Lantz et al. (i.e., Analysis 1 and Fig. 28 of Lantz et al., 1999), except that (1) Rickwoodopteris hirsuta is added to the tree, and (2) there is less resolution (i.e., a larger number of polytomys) in the mid-region

Fig. 2. Cladogram of Cyatheaceae s.l., wherein Rickwoodopteris occurs within a dicksoniaceous grade that subtends a cyatheaceous clade at the apex of the tree. See text for details.


of the tree (cf. Fig. 2 and Fig. 28 of Lantz et al., 1999). In agreement with previous results of relationships among filicalean tree ferns, living and fossil species of the Cyatheaceae s.l. form a clade that is subtended by a paraphyletic grade that includes living and fossil dicksoniaceous species plus Loxoma cunninghamii R. Brown in A. Cunningh., and Metaxya rostrata (H.B.K.) C. Presl (Fig. 2). At the first node distal to the root, Plagiogyria japonica, there are is a polytomy that consists of three clades. These are: (1) L. cunninghamii+(Calochlaena dubia + Culcita macrocarpa); (2) Thyrsopteris elegans+(Oguracaulis banksii + Cyaathodendron texanum); (3) the remainder of the dicksoniaceous and cyatheaceous taxa. At the next node on the stem, there is a large polytomy that includes Cystodium sorbifolium, Cibotium barometz, M. rostrata, R. hirsuta, Nishidacaulis burgii, ‘‘Cibotium’’ tasmanense, Cibotium oregonense, Cibotium iwatense, a small clade consisting of Dicksonia antarctica+(Lophosoria quadripinnata + Conantiopteris schuchmanii), and a larger clade that contains all of the cyatheaceous taxa (Fig. 2). The apex of the tree consists of the same living and fossil species of Cyatheaceae s.l. in the same order within the tree as in the results of Lantz et al. (1999), except that the positions of Cyathocaulis yezopteroides and Cyathocaulis nihei-takagii are reversed in the results of the current analysis (Fig. 2). These results are also broadly concordant with those from tree fern analyses by several other workers who previously analyzed either living species only (Hasebe et al., 1995; Pryer et al., 1995; Stevenson and Loconte, 1996) or both living and fossil species (Lantz et al., 1999). In the results of all these studies, tree ferns form a monophyletic group in which the Cyatheaceae s.l. is monophyletic, and the dicksoniaceous species plus Metaxya and Loxoma form a paraphyletic grade at the base of the tree. The highly concordant topologies in the results of Lantz et al. (1999) and the current analysis further support the more general results by previous workers, and reveal that Rickwoodopteris represents a member of the dicksoniaceous grade. Together with a wealth of additional cyatheaceous/dicksoniaceous remains that are preserved in carbonate nodules from the west coast of North America, Rickwoodopteris reflects that an active diversification of Cyatheaceae s.l. was underway during the Cretaceous.

113

Acknowledgements We thank Taylor Rickwood-Samson and Tim Obear from Nanaimo, British Columbia for providing the specimen for study. This study was supported in part by the Natural Sciences and Engineering Research Council of Canada Grant A-6908 to RAS.

References Arnold, C.A., 1945. Silicified plant remains from the Mesozoic and Tertiary of western North America. Mich. Acad. Sci., Arts Lett. 30, 3 – 34. Banks, H.P., Ortiz-Sotomayor, A., Hartman, C.M., 1981. Pinus escalantensis sp. nov., a new permineralized cone from the Oligocene of British Columbia. Bot. Gaz. 142, 286 – 293. Conant, D.S., Stein, D.B., 2001. Phylogenetic and geographic relationships of the tree ferns (Cyatheaceae) on Mount Kinabalu. Sabah Parks Nat. J. 4, 25 – 42. Conant, D.S., Raubeson, L.A., Attwood, D.K., Stein, D.B., 1995. The relationships of papuasian Cyatheaceae to new world tree ferns. Am. Fern J. 85, 328 – 340. Conant, D.S., Raubeson, L.A., Attwood, D.K., Perera, S., Zimmer, E.A., Sweere, J.A., Stein, D.B., 1996. Phylogenetic and evolutionary implications of combined analysis of DNA and morphology in the Cyatheaceae. In: Camus, J.M., Gibby, M., Johns, R.J. (Eds.), Pteridology and Perspective. Royal Botanic Gardens, Kew, pp. 231 – 248. Dawson, J.W., 1873. Note on the fossil plants from British Columbia, collected by Mr. James Richardson in 1872. Geol. Surv. Canada, Rept. Progress, 1872 – 1873, pp. 66 – 71. Elliott, L.L., Stockey, R.A., Beard, G., 2003. Fossil walnuts from the Late Eocene of Vancouver Island. Fifth BC Paleontology Symposium. Malaspina University College, Nanaimo, BC, p. 10. Abstracts. Falder, A.B., Rothwell, G.W., Mapes, G., Mapes, R.H., Doguzhaeva, L.A., 1998. Pityostrobus milleri sp. nov., a pinaceous cone from the Lower Cretaceous (Aptian) of southwestern Russia. Rev. Palaeobot. Palynol. 103, 253 – 261. Hasebe, M., Wolf, P.G., Pryer, K.M., Ueda, K., Ito, M., Sano, R., Gastony, G.J., Yokoyama, J., Manhart, J.R., Murakami, N., Crane, E.H., Haufler, C.H., Hauk, W.D., 1995. A global analysis of fern phylogeny based on rbcL nucleotide sequences. Am. Fern J. 85, 134 – 181. Joy, K.W., Willis, J., Lacey, W.S., 1956. A rapid cellulose peel technique in paleobotany. Ann. Bot. 20, 635 – 637. Kramer, K.U., 1990a. Cyatheaceae. In: Kramer, K.U., Green, P.S. (Eds.), The Families and Genera of Vascular Plants. Pteridophytes and Gymnosperms, vol. I. Springer-Verlag, Berlin, pp. 69 – 74. Kramer, K.U., 1990b. Dicksoniaceae. In: Kramer, K.U., Green, P.S. (Eds.), The Families and Genera of Vascular Plants. Pteridophytes and Gymnosperms, vol. I. Springer-Verlag, Berlin, pp. 94 – 99.

114


Kramer, K.U., 1990c. Loxomataceae. In: Kramer, K.U., Green, P.S. (Eds.), The Families and Genera of Vascular Plants. Pteridophytes and Gymnosperms, vol. I. Springer-Verlag, Berlin, pp. 172 – 174. Kramer, K.U., 1990d. Metaxyaceae. In: Kramer, K.U., Green, P.S. (Eds.), The Families and Genera of Vascular Plants. Pteridophytes and Gymnosperms, vol. I. Springer-Verlag, Berlin, pp. 186 – 187. Kramer, K.U., 1990e. Plagiogyriaceae. In: Kramer, K.U., Green, P.S. (Eds.), The Families and Genera of Vascular Plants. Pteridophytes and Gymnosperms, vol. I. Springer-Verlag, Berlin, pp. 201 – 203. Lantz, T.C., Rothwell, G.W., Stockey, R.A., 1999. Conantiopteris schuchmanii, gen. et sp. nov., and the role of fossils in resolving the phylogeny of Cyatheaceae s.l. J. Plant Res. 112, 361 – 381. Little, S.A., Stockey, R.A., Beard, G., 2001. Angiosperm fruits and seeds from the Eocene of Vancouver Island. Botany 2001. Plants and People, vol. 265, p. 66. Albuquerque, New Mexico, Abstracts. Little, S.A., Stockey, R.A., Beard, G., 2002. Fruits and seeds from Appian Way (Eocene) of Vancouver Island, British Columbia, Canada. 6th European Paleobotany – Palynology Conference, Athens, Greece, pp. 118 – 119. Abstracts. Miller Jr., C.N., 1990. Stems and leaves of Cunninghamiostrobus goedertii from the Oligocene of Washington. Am. J. Bot. 77, 963 – 971. Nishida, H., 1991. Diversity and significance of Late Cretaceous permineralized plant remains from Hokkaido, Japan. Bot. Mag. Tokyo 104, 253 – 273. Ogura, Y., 1930. On the structure and affinities of some Cretaceous plants from Hokkaido. J. Fac. Sci., Imp. Univ. Tokyo, Sect. 3 2, 381 – 412. Ogura, Y., 1972. Comparative Anatomy of Vegetative Organs of Pteridophytes. Gebru¨der Borntraeger, Berlin. Ohana, T., Kimura, T., 1995. Further observations of Cunninghamiostrobus yubariensis Stopes and Fujii from the Upper Yezo Group (Upper Cretaceous), Hokkaido, Japan. Trans. Proc. Palaeont. Soc. Jpn. N.S. 178, 122 – 141. Pryer, K.M., Smith, A.R., Skog, J.E., 1995. Phylogenetic relationships of extant ferns based on evidence from morphology and rbcL sequences. Am. Fern J. 85, 205 – 282. Ratzel, S.R., Rothwell, G.W., Mapes, G., Mapes, R.H., Doguzhaeva, L.A., 2001. Pityostrobus hokodzensis, a new species of pinaceous cone from the Cretaceous of Russia. J. Paleontol. 75, 895 – 900. Richards, B.C., 1975. Longusorbis cuniculosus: a new genus and species of upper Cretaceous crab; with comments on Spray Formation at Shelter Point, Vancouver Island, British Columbia. Can. J. Earth Sci. 12, 1850 – 1863. Rothwell, G.W., Stockey, R.A., 2002. Anatomically preserved Cycadeoidea (Cycadeoidaceae), with a reevaluation of the systematic characters for the seed cones of Bennettitales. Am. J. Bot. 89, 1447 – 1458. Rothwell, G.W., Stockey, R.A., 2003. Anatomically preserved vascular and non-vascular cryptogams from the lower Cretaceous

of western North America. Botany, p. 62. Mobile, AL. Abstracts no. 232. Smith, A.R., 1995. Non-molecular phylogenetic hypothesis for ferns. Am. Fern J. 85, 104 – 122. Smith, S.Y., Stockey, R.A., 2001. A new species of Pityostrobus from the lower Cretaceous of California and its bearing on the evolution of Pinaceae. Int. J. Plant Sci. 162, 669 – 681. Smith, S.Y., Stockey, R.A., 2002. Permineralized pine cones from the Cretaceous of Vancouver Island, British Columbia. Int. J. Plant Sci. 163, 185 – 196. Smith, S.Y., Currah, R.S., Stockey, R.A., 2003a. Cretaceous and Eocene poroid hymenophores from Vancouver Island, British Columbia. Mycologia 96, 180 – 186. Smith, S.Y., Rothwell, G.W., Stockey, R.A., 2003b. Cyathea cranhamii sp. nov., anatomically preserved tree fern sori from the Lower Cretaceous of Vancouver Island, British Columbia. Am. J. Bot. 90, 755 – 760. Smith, S.Y., Rothwell, G.W., Stockey, R.A., 2003c. Anatomically preserved tree fern sori from the lower Cretaceous of Vancouver, Island. Botany, p. 63. Mobile, AL, no. 234. Stevenson, D.W., Loconte, H., 1996. Ordinal and familial relationships of pteridophyte genera. In: Camus, J.M., Gibby, M., Johns, R.J. (Eds.), Pteridology in Perspective. Roy. Bot. Gard., Kew, pp. 435 – 487. Stockey, R.A., 1980. Jurassic araucarian cone from southern England. Palaeontol. Assoc. Lond. 23, 657 – 666. Stockey, R.A., Nishida, M., 1986. Pinus haboroensis sp. nov. and the affinities of permineralized leaves from the Upper Cretaceous of Japan. Can. J. Bot. 64, 1856 – 1866. Stockey, R.A., Rothwell, G.W., 2003a. Anatomically preserved Williamsonia (Williamsoniaceae): evidence for bennettitalean reproduction in the late Cretaceous of western North America. Int. J. Plant Sci. 164, 251 – 262. Stockey, R.A., Rothwell, G.W., 2003b. Pteridophytes and non-vascular cryptogams from the Cretaceous and Tertiary of Vancouver Island. Fifth BC Paleontology Symposium. Malaspina University College, Nanaimo, BC, p. 9. Abstracts. Stockey, R.A., Rothwell, G.W., 2003c. Cretaceous tree fern radiations: new permineralized Dicksoniaceae. Botany, p. 63. Mobile, AL, no. 237. Stopes, M.C., 1918. New bennettitean cones from the British Cretaceous. Philos. Trans. R. Soc. Lond. 208B, 389 – 440. Stopes, M.C., Fujii, K., 1910. Studies on the structure and affinities of Cretaceous plants. Philos. Trans. R. Soc. Lond., Ser. B 201, 1 – 90. Swofford, D., 2002. PAUP*: Phylogenetic Analysis Using Parsimony (*and Other Methods). Ver. 4. Sinauer Associates, Sunderland, MA. Tidwell, W.D., Nishida, H., Webster, N., 1989. Oguracaulis banksii gen. et sp. nov., a mid-Mesozoic tree fern stem from Tasmania, Australia. Pap. Proc. R. Soc. Tasman. 123, 15 – 25. Trivett, M.L., Rothwell, G.W., Stockey, R.A., 2002. A permineralized schizaeaceous fern from the Late Eocene of Vancouver Island, British Columbia, Canada. Botany, p. 63. Madison, WI, Abstracts 248.