Reconstruction of the Pennsylvanian-age walchian conifer Emporia cryptica sp. nov. (Emporiaceae: Voltziales)

Review of Palaeobotany and Palynology 157 (2009) 218–237

Contents lists available at ScienceDirect

Review of Palaeobotany and Palynology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / r ev p a l b o

Reconstruction of the Pennsylvanian-age walchian conifer Emporia cryptica sp. nov. (Emporiaceae: Voltziales) Genaro R. Hernandez-Castillo a,⁎, Ruth A. Stockey b, Gar W. Rothwell c, Gene Mapes c a b c

Instituto de Recursos, Universidad del Mar, Puerto Escondido, Oaxaca, 71980, Mexico Department of Biological Sciences, University of Alberta, Edmonton, Canada AB T6G 2E9 Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701, USA

a r t i c l e

i n f o

Article history: Received 22 February 2009 Received in revised form 3 May 2009 Accepted 5 May 2009 Available online 12 May 2009 Keywords: conifer Emporia Emporiaceae fossil Paleozoic Voltziales

a b s t r a c t This paper provides a whole plant concept for a new species, Emporia cryptica sp. nov. Hernandez-Castillo, Stockey, Rothwell & Mapes (Emporiaceae: Voltziales), the fourth conifer to be reconstructed from the rich fossil biota at the Late Pennsylvanian, Hamilton Quarry, Kansas. E. cryptica has an orthotropic stem, lateral plagiotropic branches with simple leaves, simple pollen cones, and compound ovulate cones. Branches have an endarch eustele with dense wood surrounding a parenchymatous pith with sclerotic nests/plates, and secondary xylem tracheids with multiseriate hexagonal bordered pits. Leaves on both penultimate and ultimate branches are simple and amphistomatic with two adaxial stomatal bands, monocyclic and dicyclic stomata, and two narrow abaxial rows of stomata with numerous trichome bases. Pollen cones are simple with helically arranged microsporophylls and adaxial pollen sacs. Prepollen is monolete, eusaccate, and monosaccate (Potonieisporites Bharadwaj). Ovulate cones are compound with bilaterally symmetrical dwarf shoots in the axils of helically arranged forked bracts. Axillary dwarf shoots bear numerous sterile scales interspersed with two megasporophylls, each bearing a single inverted terminal ovule. This plant displays morphological and cuticular characters similar to several morphogenera of Paleozoic walchian conifers but is most comparable to the fossil plant species Emporia lockardii and Hanskerpia hamiltonensis. E. cryptica is the only walchian conifer where ovules and seeds with megagametophytes, immature embryos and mature embryos have been documented, demonstrating that the most ancient conifers possessed seed dormancy and polycotyledonary embryos. This reproductive biology is similar to that of many Mesozoic and extant conifers with saccate pollen except for the presence of prepollen grains that are common among Paleozoic walchian conifers. © 2009 Elsevier B.V. All rights reserved.

1. Introduction The most ancient conifers, or walchian conifers (Mapes and Rothwell, 1984), are known from Euramerican sediments (Upper Carboniferous and Lower Permian) and traditionally have been classified in several families within the Voltziales (Florin, 1938–45; Visscher et al., 1986; Kerp et al., 1990; Mapes and Rothwell, 1991; Galtier et al., 1992; Rothwell et al., 1997; Hernandez-Castillo et al., 2001b). Walchian plants are typically represented by isolated and/or fragmentary branches, pollen cones, and ovulate cones, usually at localities where more than one species of conifers has been identified (Florin, 1938–45; Rothwell, 1982; Clement-Westerhof, 1984; Mapes and Rothwell, 1984; Clement-Westerhof, 1987; Mapes and Rothwell, 1991; Meyen, 1997; Mapes and Rothwell, 1998).

⁎ Corresponding author. Tel.: +52 1 954 107 0528; fax: +52 954 582 4992. E-mail address: [email protected] (G.R. Hernandez-Castillo). 0034-6667/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2009.05.003

The first critical systematic work on walchian conifers was compiled by Florin (1927, 1938–45, 1950, 1951). Florin's interpretations remain as some of the most influential for living and fossil conifers. Nevertheless, modern studies have called to question Florin's systematics and his interpretations of the most primitive conifers (Schweitzer, 1963; Rothwell, 1982; Clement-Westerhof, 1984; Mapes and Rothwell, 1984; Meyen, 1984; Winston, 1984; Visscher et al., 1986; Clement-Westerhof, 1987; Clement-Westerhof, 1988; Kerp et al., 1990; Mapes and Rothwell, 1991; Meyen,1997; Mapes and Rothwell,1998; Hernandez-Castillo et al., 2001a,b; Lausberg, 2002; Rothwell and Mapes, 2003; HernandezCastillo et al., 2009). The most recent interpretations result from a complete reexamination and a reevaluation of walchian conifer material, and employ new methodology and reliable criteria for circumscribing walchian conifers as species of extinct plants (Hernandez-Castillo et al., 2001b; Rothwell et al., 2005; Hernandez-Castillo, 2005; Hernandez-Castillo et al., 2009). This new methodology is based on interconnections among some organs, and a combination of morphological, cuticular, and anatomical characters that are used to

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Fig. 1. Map showing location of Hamilton Quarry, Kansas, USA. Modified from Mapes and Rothwell (1984).

Plate I. 1. Emporia cryptica sp. nov., branches. 1.

Antepenultimate shoot (arrowhead) with penultimate shoots (p) and ultimate shoots with helically arranged leaves (bracket). OUPH 17 408, scale bar = 1 cm.

219

220

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

correlate vegetative branches with pollen and ovulate cones. The approach also includes an assessment of the broad ranges of morphological and cuticular variation within a single conifer species. In the current study we employ this approach to reconstruct Emporia cryptica sp. nov. (Emporiaceae) from the Late Pennsylvanian fossil biota at Hamilton Quarry, Kansas, USA. This reconstruction is part of broader study to reinvestigate, describe and reevaluate morphological characters, and to reconstruct Paleozoic walchian conifers as complete plants, so they can be used to resolve systematic relationships among fossil and living conifers. Emporia cryptica is described and compared to other Euramerican walchians using a set of reliable diagnostic characters based on whole plant concepts (Hernandez-Castillo et al., 2001b). The excellent preservation of this new species also provides an opportunity to explore and analyze ancient conifer reproductive biology. 2. Materials and methods 2.1. Material The specimens used in this study are preserved as coalified compressions with preserved cuticles and by cellular permineralization. They occur in Upper Pennsylvanian laminated, carbonate mudstones of the Hartford Limestone, Topeka Limestone Formation, Shawnee Group,

located east of Hamilton, Kansas, USA (Fig. 1: Mapes and Rothwell, 1984; Bridge,1988; French et al.,1988; Busch et al.,1988). These beds represent channel deposits in an estuarian environment under tidal influence (French et al.,1988; Fahrer et al.,1990; Feldman et al.,1990; Fahrer, 1991; Feldman et al., 1993). The Hamilton Quarry yields an exceptionally wellpreserved and diverse biota that includes bryozoans, crinoids, fusulinids, marine microinvertebrates, non-marine bivalves, eurypterids, crustaceans, ostracods, millipedes, insects, sharks, fish, amphibians, reptiles, and a rich terrestrial flora (Mapes and Mapes, 1988; Rothwell and Mapes, 1988; Fahrer et al., 1990; Fahrer, 1991; Feldman et al., 1993; Rothwell and Mapes, 2001). Emporia cryptica is represented by 157 specimens. Thirty-three of these are plagiotropic, leafy branching systems of penultimate and ultimate shoots. Four were prepared for cuticular analysis. Seventyone are pollen cones, fourteen of which are attached to ultimate shoots. Fourteen were prepared for cuticular analysis and ten for anatomical analysis. Fifty-three are ovulate cones, eight of which are attached to penultimate shoots with leaves. Eleven were prepared for cuticular analysis, and four for anatomy. 2.2. Methods and materials Specimens were initially revealed on split surfaces of the limestones. Cuticles were macerated from the matrix with dilute (0.5–1%)

Plate II. 1–4. Emporia cryptica sp. nov., lateral branches. 1. 2. 3. 4.

Branch showing deltoid shape; penultimate shoot with leaves (arrowhead), and ultimate shoots with linear to concave leaves. OUPH 17410, scale bar = 2 cm. Irregular branching and penultimate shoot with leaves (arrowhead). OUPH 17413, scale bar = 1 cm. Branch showing deltoid shape of leaves on penultimate shoots (arrowheads) and slightly concave shape of leaves on ultimate shoots. OUPH 17414, scale bar = 1 cm. Penultimate shoot with leaves (arrowheads) and ultimate leafy shoots. OUPH 17411, scale bar = 1 cm.

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

HCl, rinsed in distilled water, bleached in Lysol toilet bowl cleaner (Reckitt Benckiser, Toronto, Canada), allowed to air dry on microscope slides, and mounted under a cover slip with Eukitt (O. Kindler GmbH Co., Freiburg, Germany). For scanning electron microscopy, cuticles were air dried on specimen stubs and coated with (100 Å) gold, and examined on a JEOL (Japan Electron Optics Ltd.) 6301 FXV and a Phillips XL30 ESEM (FEI Co., Tokyo, Japan) scanning electron microscopes. Some anatomically preserved specimens were prepared by the cellulose acetate peel technique (Joy et al., 1956), and others were cut into wafers and ground thin enough to transmit light. Compressed specimens with some anatomical preservation were etched with 1–5% HCl, flooded with acetone, and a cellulose acetate peel was placed on the split surface. These surface pulls were removed while the acetate was still plastic enough to be pressed relatively flat under a heavy weight. Light microscopy was conducted using Zeiss Ultraphot IIIB and WL microscopes, and images captured with a MicroLumina digital scanning camera (Leaf Systems Inc., Bedford, MA) or a PhotoPhase digital scanning camera (Phase One A/S, Frederiksberg, Denmark). Images were processed using Adobe Photoshop. All specimens are housed in the Ohio University Paleobotanical Herbarium, Athens, Ohio, USA as OUPH numbers 17408–17995. 3. Results

221

3.1.1. Description 3.1.1.1. Branching systems. The specimens consist of three orders of branching with an orthotropic antepenultimate shoot that bears several lateral plagiotropic branches (Plate I, 1). Lateral branches are composed of a leafy penultimate shoot with attached ultimate leafy shoots (Plates I, 1 and II, 1–4). Some branches may show slightly irregular branching. Branch shape ranges from deltoid (Plates I, 1 and II, 1) to narrowly oblong (Plate II, 4). The largest plagiotropic branch measures 15 cm long and 7.9 cm wide (Plate II, 1). Penultimate axes range 0.1–4.0 mm in diameter. The longest ultimate axes (ca 4.2 cm long) occur near the base and mid-region of large branches, while the shortest (1.9 cm long) occur on small narrowly oblong branches (Plate II, 4). Most lateral branches are broken at the very base or the apex (Plates I,1 and II, 2–4) indicating that some plagiotropic shoots were larger than the specimens shown here. Leaves on penultimate shoots are simple, helically arranged, 2.4– 7.1 mm long and 0.6–2.0 mm wide (Plate II, 1–4). They are slightly Sshaped and spreading (extending nearly to the horizontal) in side view (Plate II, 1–4). They diverge at almost 135° and then curve towards the apex at an angle of 45° to the branch. Leaves on ultimate shoots are slightly concave to slightly S-shaped and spreading in side view (Plate II, 1–4), and narrow sub-triangular to linear in face view (Table 1). They are 1.2–2.7 mm long and 0.3–1.2 mm wide, and extend from the shoot at 26–63° at the base and 28–69° at the apex of the shoot.

3.1. Systematics Class — Coniferopsida Order — Voltziales Family — EMPORIACEAE Mapes et Rothwell Genus — Emporia Mapes and Rothwell (2003). Species — Emporia cryptica Hernandez-Castillo, Stockey, Rothwell et Mapes, sp. nov. (Plates I–XIII). Holotype: Penultimate shoot with attached ovulate cone. Specimen OUPH 17657–17724 (Plates XII, 1, 2, 4 and XIII, 3–8). Paratypes: Branches showing leaf morphology on penultimate and ultimate shoots OUPH 17408, 17410, 17411, 17413, 17414 (Plates I, 1 and II, 1–4). Anatomy of penultimate shoots and leaves 1748–17776, 17658–17724 (Plate III, 1–8). Cuticles on leaves of penultimate shoots and ultimate shoots 17747–17776, 17460–17467 (Plates IV, 1–7 and V, 1–7). Pollen cones 17484, 17485, 17487, 17497 (Plate VI, 1–4). Anatomically preserved pollen cones 17499–17511, 17592–17609 (Plate VII, 1–7). Pollen cone macerations 17639–17642 (Plate VIII, 1– 6). Ovulate cones 17653, 17655, 17954 (Plate IX, 1–3). Ovulate cone macerations 17822, 17825–17837 (Plate X, 1–3). Cuticles of ovulate cones 17697–17706, 17725–17735, 17748–17776, 17825–17837, 17893–17910 (Plate XI, 1–6). Anatomy of ovulate cones 17657– 17724, 17911–17949, 17779–17804 (Plate XII, 1–5; Plate XIII, 1–8). Collecting locality: Hamilton Quarry; NW quarter, sec. 5 and 8, T24S, R12E, Virgil seven and a half foot quadrangle, Greenwood County, Kansas, U.S.A. Fig. 1. Stratigraphic occurrence and age: Hartford Limestone, Topeka Limestone Formation, Shawnee Group, Late Pennsylvanian. Etymology: The specific epithet cryptica refers to the cryptic nature of individual characters of the plant organs when organ by organ comparison is done without a complete plant approach. Diagnosis: Leaves simple, heterophylly absent; Stomata mono- to dicylic. Pith with secretory cells in nests/plates. Tracheids multiseriate with hexagonal bordered pits; vascular rays uniseriate–biseriate, 1–3 cells high. Pollen cones 1.4–4.7 cm long, 0.8–2.9 cm wide; microsporophylls 0.5–4.5 mm long, 1.9–2.7 mm wide; pollen sacs 4–8. Prepollen of Potonieisporites type, subcircular to ellipsoidal in polar view, 100–112 μm wide, 70–80 μm long. Ovulate cones 3.0–8.6 cm long, 1.2–1.9 cm wide; axillary ovuliferous dwarf shoots fused at base; sterile scales up to 37 (typically 20–25), 1.5–3.2 mm long, 0.7–3.2 mm wide; sporophylls narrow, two per dwarf shoot.

3.1.1.2. Penultimate and ultimate shoot internal anatomy. Stems have a parenchymatous pith with nests or plates of cells with dark contents that either represent thick-walled sclereids and/or parenchyma cells that contain dark secretory substances (Plate III, 1). Pith parenchyma cells are more-or-less rectangular, longitudinally aligned, and axially elongated (Plate III, 1–2). Primary xylem tracheids have helical or scalariform secondary wall thickenings (Plate III, 1, 3). Secondary xylem that consists of files of tracheids and rays is commonly preserved (Plate III, 4, 5). Tracheids of the secondary xylem have multiseriate hexagonal bordered pits on the radial walls (Plate III, 5). Wood rays are uniseriate, one to three cells high (Plate III, 4). The outer cortex is usually poorly preserved and no clear vascular cambium, phloem or periderm can be accurately identified. However, rectangular to polygonal, thin-walled cells with dark contents similar to those found in the pith are preserved in the outer cortex. Epidermal cells are rectangular in longitudinal section and are covered by a thick cuticle. 3.1.1.3. Vegetative leaf internal anatomy. Leaves are simple, narrowly triangular with a broad base in face view and with numerous marginal trichomes (Plate IV, 1–4; Table 1). They range from rhomboidal to widely rhomboidal in cross sections (Plate III, 6). Leaves on ultimate branches are characterized by a thick cuticle on both surfaces that covers a single layer of epidermal cells (Plate III, 6–8). The epidermis is composed of thin-walled rectangular cells that are 10–14 μm long and 8–9 μm wide in cross section (Plate III, 7–8). Below the epidermis there is a one to two-layered hypodermis (Plate III, 8). In cross section, hypodermal cells are thick walled, and oblong to circular, and 9–15 μm long and 9–29 μm wide. The mesophyll of the leaf is composed of incompletely preserved thin-walled parenchyma cells (Plate III, 6–8). In cross section, mesophyll cells are 17–41 μm long and 15–61 μm wide. A bundle sheath surrounds the single vascular bundle of the leaf (Plate III, 8). The bundle sheath is not well preserved but it seems to be composed of large thick-walled, polyhedral cells (18–41 μm long and 17–38 μm) with dark contents. 3.1.1.4. Cuticles on leaves of penultimate shoots. Cuticular macerations yield dark-colored preparations in which stomatal bands are often difficult to see (Plate IV, 1). Closer examinations of these leaf macerations reveal two adaxial bands of stomata (Plate IV, 3–4) and numerous dicyclic stomata (dark spots) on the leaf surface (Plate IV, 3–5; Table 1). Stomata are ellipsoidal, 28–42 μm wide,

222

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

62–78 (–104) μm long and have 5–6 subsidiary cells with overarching papillae (Plate IV, 6). Individual stomata are close to each other and sometimes share adjacent subsidiary cells (Plate IV, 6). Bands are separated by a stomatal free zone of polygonal to rectangular epidermal cells. Most regular epidermal cells in marginal and stomatal free zones have small erect papillae. Dicyclic stomata are 42–73 μm wide, 57–88 μm long, with unipapillate subsidiary cells, scattered on the entire adaxial surface (Plate IV, 3–5). The abaxial surface is completely covered by surficial trichome bases and has two narrow bands of stomata (Plate IV, 7; Table 1). These bands are 2–3 stomata wide with 6–7 subsidiary cells, and each subsidiary cell has a single overarching papilla. The leaf margin has both short and long trichomes (Plate IV,1–4). 3.1.1.5. Cuticles of leaves on ultimate shoots. Leaves on ultimate shoots are amphistomatic, with two long bands of adaxial stomata separated by a stomatal free zone (Plate V, 1–2; Table 1). Leaf margins and stomatal free zones have rectangular, longitudinally elongate epidermal cells with abundant papillae and trichome bases (Plate V, 2). Marginal trichomes are often short or broken (Plate V, 1–2). Stomatal complexes are in contact with each other and usually share subsidiary cells (Plate V, 2, 5). Stomata are monocyclic, ellipsoidal to semicircular, 53 × 44 μm, and have 5–8 subsidiary cells with overarching papillae (Plate V, 2, 5; Table 1). Dicyclic stomata are found on large leaves, and both inner and outer cycles have unipapillate subsidiary cells (Plate V, 3–4). The abaxial surface shows two narrow bands of stomata (Plate V, 6–7) that have five to six unipapillate subsidiary cells (Plate V, 7). The entire abaxial surface is covered by trichome bases that are circular at the base and surrounded by elongate epidermal cells (Plate V, 6–7). 3.1.1.6. Morphology of pollen cones. Pollen cones are simple, terminal on ultimate branches, ellipsoidal, and 1.4–4.7 cm long, 0.8–2.9 cm wide (Plate VI, 1–4). Cones bear helically arranged microsporophylls, 0.5–4.5 mm long, 1.9–2.7 mm wide (Plate VI, 1–4). Microsporophylls have a narrowly triangular distal lamina, broad base, and are attached to the cone axis by a terete shank (Plate VI, 4). Some pollen cones are in organic connection with ultimate shoots that bear leaves (Plate VI, 1, 3), but most are isolated or broken (Plate VI, 2, 4). Leaves on the

attached ultimate shoots are simple (Plate VI, 1, 3) and similar to those of vegetative ultimate shoots (Table 1). 3.1.1.7. Anatomy of pollen cones. Pollen cones have a cone axis bearing helically arranged microsporophylls with pollen sacs (Plate VII,1–5). The cone axis has a pith and cortex consisting of relatively short parenchyma cells. Most parenchyma cells contain dark or black contents (Plate VII, 1, 5). Cauline bundles of the cone axis are relatively inconspicuous and terete. The sporophyll shank has a thick epidermis with rectangular cells and parenchyma cells with dark contents surrounding the vascular bundle (Plate VII, 2–4). Internal anatomy of the microsporophyll distal lamina resembles that of vegetative leaves. Distal laminae have a thick cuticle that covers an epidermis composed of rectangular cells with dark contents, a two to four-layered mesophyll and a single vascular bundle that has helical or scalariform secondary wall thickenings on the tracheids (Plate VII, 4–5). Each microsporophyll bears four to eight, adaxial, ellipsoidal, pollen sacs that are attached to a single area on the shank (Plate VII, 1–4). Many pollen sacs are empty but some are full of monosaccate prepollen grains that conform to the sporae dispersae genus Potonieisporites Bharadwaj (1964) (Plate VII, 6–7). Grains are subcircular to ellipsoidal with a large saccus that surrounds a central body (Plate VII, 6–7). The central body has a proximal, bent, monolete suture and parallel fold that is often broken. Grains are 70–80 μm long in polar view and 110–112 μm wide. 3.1.1.8. Cuticles of pollen cones. The microsporophyll lamina has two bands of stomata separated by a stomatal free zone on the adaxial surface (Plate VIII, 1). Stomatal complexes are monocyclic with unipapillate subsidiary cells (Plate VIII, 1–2). Laminar margins and stomatal free zones have rectangular epidermal cells, abundant papillae and trichome bases (Plate VIII, 2) similar to vegetative leaves. Macerations of microsporophylls yield cuticles showing two broad bands of adaxial stomata, surficial trichome bases, papillae, and marginal trichomes (Plate VIII, 3; Table 1). Bands are separated by a stomatal free zone with numerous unipapillate epidermal cells (Plate VIII, 3). Stomata are ellipsoidal to semicircular, 25–45 μm wide× 35–54 μm long, with 5–7 unipapillate subsidiary cells (Plate VIII, 4). Papillae on subsidiary cells are

Plate III. 1–8. Emporia cryptica sp. nov., penultimate shoot and leaf anatomy. 1. 2. 3. 4. 5. 6. 7. 8.

Longitudinal section of shoot showing secondary xylem (2×), primary xylem (1×) flanking pith with parenchyma cells and sclerotic nests/plates (arrowheads). OUPH 17672, scale bar = 500 μm. Longitudinal section showing elongated sclerotic cells in nests/plates (arrowheads). OUPH 17672, scale bar = 80 μm. Longitudinal section showing spiral thickenings of primary xylem tracheids. OUPH 17672, scale bar = 30 μm. Tangential section showing uniseriate rays one to two cells high. OUPH 17672, scale bar = 30 μm. Radial section of secondary xylem showing groups of polygonal circular bordered pits on radial walls of tracheids. OUPH 17672, scale bar = 80 μm. Cross section of shoot showing ultimate leaves. OUPH 17501, scale bar = 2 mm. Cross section of ultimate leaf showing epidermis, mesophyll and endodermis. Vascular bundle is not preserved. OUPH 17502, scale bar = 1 mm. Cross section of ultimate leaf showing cuticle, epidermis, few mesophyll cells and few bundle sheath cells (arrowhead). OUPH 17501, scale bar = 0.9 mm.

Plate IV. 1–7. Emporia cryptica sp. nov., cuticular macerations of leaves on penultimate shoots. Specimens macerated from OUPH 17747. All images from adaxial surfaces unless otherwise indicated. (see on page 224) 1. 2. 3. 4. 5. 6. 7.

Leaf showing narrowly triangular shape with broad base and marginal trichomes. Scale bar = 800 μm. Marginal trichomes of Fig. 1. Scale bar = 400 μm. Leaf showing marginal trichomes and numerous dicyclic stomata (dark dots). Scale bar = 600 μm. Marginal trichomes and stomatal band (s). Scale bar = 300 μm. Dicyclic stomata with papillate outer subsidiary cells (arrowheads). Scale bar = 15 μm. Stomata (s) showing five subsidiary cells with large overarching papillae. Scale bar = 15 μm. Abaxial narrow band of stomata (s) showing subsidiary cells with overarching papillae and trichome bases (t). Scale bar = 15 μm.

Plate V. 1–7. Emporia cryptica sp. nov., cuticular macerations of leaves on ultimate shoots. Specimens macerated from M 1279 (OUPH 17460–17466). (see on page 225) 1. 2. 3. 4. 5. 6. 7.

Adaxial surface showing subtriangular shape, and two broad bands of stomata (s) separated by stomatal free zone. Scale bar = 300 μm. Adaxial surface with marginal trichomes (at left), papillate epidermal cells, trichome bases (t), and stomatal band (s). Scale bar = 800 μm. Adaxial surface showing dicyclic stomata (dark areas). Scale = 370 μm. Dicyclic stomata. Scale bar = 25 μm. Adaxial stomata showing subsidiary cells with broad overarching papillae. Scale bar = 300 μm. Abaxial surface with narrow stomatal bands (s). Scale bar = 500 μm. Abaxial trichome bases (t) and narrow stomatal band with two stomatal complexes (s). Scale bar = 25 μm.

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate III.

223

224

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

often erect (Plate VIII, 4). The abaxial surface is completely covered by surficial trichome bases that are often broken (Plate VIII, 5–6). 3.1.1.9. Morphology of ovulate cones. Seed cones are ellipsoidal, 3.0– 8.6 cm long, 1.2–1.85 cm wide and bear several helically-arranged

bracts and axillary ovuliferous dwarf shoots (Plate IX, 1–3). These cones can be differentiated from other Emporia-like cones at the locality by their long slender overall appearance (Plate IX, 1–2), and by the presence of axillary dwarf shoots that are as long as the subtending bracts (Plate IX, 3). Bracts are forked with a broad base.

Plate IV (caption on page 222).

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate V (caption on page 222).

225

226

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate VI. 1–4. Emporia cryptica sp. nov. pollen cones. 1. 2. 3. 4.

Mature ellipsoidal cone attached to ultimate shoot. OUPH 17484, scale bar = 5 mm. Detached ellipsoidal mature cone. OUPH 17485, scale = 5 mm. Immature cone with attached ultimate shoot. OUPH 17487, scale bar = 5 mm. Broken cone showing central cone axis and departing microsporophylls. OUPH 17497, scale bar = 5 mm.

Axillary dwarf shoots diverge from the cone axis at angles of 45–90° and have 20–25 sterile scales (Plate IX, 3). Sterile scales are narrowly subtriangular, triangular to ovate with a mucronate apex (Table 1). They are 1.5–3.2 mm long and 0.7–1.2 mm wide. Sporophylls are often difficult to identify unless the cone is macerated or sectioned. Sporophylls are narrow, 1.1–1.9 mm long, 0.6–0.8 mm wide with a subapical seed scar (Plate X, 1–2). They have marginal trichomes and are completely covered by trichome bases (Plate X, 1–2). Ovules/seeds are bilateral, flattened, with a rounded to subcordate base, a narrow wing, and covered with short uniseriate trichomes that are often broken (Plate X, 3). Many ovulate cones are in organic connection with

penultimate shoots that also bear simple leaves that are comparable to those found on penultimate vegetative shoots (Table 1). 3.1.1.10. Cuticles of ovulate cone bracts. Bracts are forked and have a broad base with numerous marginal trichomes (Plate XI, 1-2). They have numerous adaxial dicyclic stomata (Plate XI, 1, 3) like leaves on vegetative shoots (Table 1). The adaxial surfaces have two bands of stomata, one per forked tip (Plate XI, 1). Stomata are ellipsoidal to semicircular and have 6-8 papillate subsidiary cells with overarching papillae (Plate XI, 4). Dicyclic stomata are scattered on the entire adaxial surface and have unipapillate subsidiary cells (Plate XI, 3-5).

Plate VII. 1–7. Emporia cryptica sp. nov., pollen cone radial and cross sections and in situ Potonieisporites prepollen grains. 1. 2. 3. 4. 5. 6. 7.

Cone attached to ultimate leafy shoot. OUPH 17503, scale bar = 2 mm. Microsporophylls with adaxial pollen sacs (arrowhead). OUPH 17511, scale bar = 500 μm. Stalk showing attached pollen sacs (arrowheads). OUPH 17503, scale bar = 500 μm. Microsporophylls showing distal lamina with upturned tip (bracket), and adaxial pollen sacs (arrowheads). OUPH 17511, scale bar = 340 μm. Cross section showing cone axis, shank and distal lamina. Note shape and tissues of outer microsporophylls. OUPH 17602, scale bar = 1 mm. Distal view of grain. OUPH 17511, scale bar = 20 μm. Distal view of grain showing saccus, central body and parallel folds. OUPH 17511, scale bar = 25 μm.

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

227

228

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate VIII. 1–6. Emporia cryptica sp. nov., leaves from ultimate shoots with attached pollen cones (1–3) and SEM of microsporophylls (4–6). 1. 2. 3. 4. 5. 6.

Adaxial surface showing two bands of stomata (s) and dicyclic stomata (dark dots). OUPH 17500, scale bar = 800 μm. Adaxial surface showing trichome bases (t), papillate epidermal cells, and stomata (s) with subsidiary cells and overarching papillae. OUPH 17500, scale bar = 500 μm. Microsporophyll showing adaxial surface with triangular shape, stomatal bands (s) and marginal trichomes. OUPH 17639, scale bar = 500 μm. Stomatal complex showing five subsidiary cells with erect to slightly overarching papillae. OUPH 17639, scale bar = 10 μm. Microsporophyll showing abaxial surface and marginal uniseriate trichomes. OUPH 17639, Scale bar = 500 μm. Abaxial trichome bases showing circular to ellipsoidal shape. OUPH 17639, scale bar = 40 μm.

Leaf margins and stomatal free zones have rectangular epidermal cells with numerous papillae and trichome bases. The abaxial surface has two narrow bands of stomata and is entirely covered by trichome bases (Plate XI, 6). 3.1.1.11. Cuticles of ovulate cone sterile scales. Sterile scales are amphistomatic with narrow bands of stomata (Table 1). The adaxial surface has two stomatal bands, while the abaxial surface may have up to three narrow bands. Stomatal complexes have 7-8 papillate subsidiary cells. Leaf margins and stomatal free zones have rectangular epidermal cells with numerous papillae and trichome bases (Table 1). 3.1.1.12. Anatomy of ovulate cones. Ovulate cones have a woody axis bearing bracts that subtend axillary dwarf shoots with inverted seeds (Plate XII, 1-5). Cone axes have a similar anatomy to that of vegetative shoots with a central parenchymatous pith composed of isodiametric parenchyma cells and scattered groups of sclerotic

cells (Plate III, 1; Plate XII, 2, 4). The cone axis is endarch with a eustele of primary tracheids with helical wall thickenings and a well-developed zone of secondary xylem. Secondary xylem is composed of tracheids with multiseriate hexagonal bordered pits and uniseriate rays one to two cells high. Most cone axes show a few layers of bark, where cells are difficult to differentiate due to their dark contents. Vascular traces to bracts and axillary dwarf shoots can be seen departing from the main axis (Plate XII, 2, 4). However, most cells are dark and it is difficult to see how much primary and secondary xylem is present. The bract and dwarf shoot arise as a single unit, but they separate almost immediately after diverging from the cone axis (Plate XII, 2). In cross section, bracts are rhomboid to triangular in cross sections. They are 0.8-1.2 mm long and 0.1-0.3 mm in wide. Bract anatomy is similar to that of vegetative leaves with a well-differentiated epidermis, hypodermis and mesophyll (Plate XII, 3-5). The bract has one vascular bundle that extends up to 2/3 of the total length (Plate XII, 4).

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

229

Plate IX. 1–3. Emporia cryptica sp. nov., ovulate cones. 1. 2. 3.

Mature narrow, elliptical cone with attached penultimate shoot. Note cone axis (c) with bracts (arrowheads) subtending axillary dwarf shoots. OUPH 17653, scale bar = 1 cm. Cone showing attached penultimate shoot with leaves at base (arrowhead). OUPH 17655, scale bar = 1 cm. Cone base showing leaf on penultimate shoot (white arrowhead), cone axis (c), and subtending bract (black arrowhead) with axillary dwarf shoot. OUPH 17954, scale bar = 1 cm.

Ovuliferous axillary dwarf shoots have sterile scales on all surfaces but they are concentrated on the abaxial surface toward the shoot apex (Plate XII, 1, 3, 5). Dwarf shoots extend from the axis at 45°-90°. The number of scales may be up to 37; however, most dwarf shoots have 20-25 (Plate XII, 2-5). Dwarf shoots display pith, primary and secondary xylem (Plate XII, 2, 4). Dwarf shoots have a narrow zone of secondary xylem (Plate XII, 4), and produce a series of vascular bundles that are often seen as dark cells. A single vascular bundle enters the base of each sterile scale. Ovules and seeds are bilaterally symmetrical, ovoid to ellipsoidal, 2.4-7.0 mm long, 1.4-1.8 mm wide and inverted so that the micropyle faces the cone axis (Plate XII, 1, 2, 4). Each seed has two narrow wings (Plate XIII, 1-2). The sarcotesta is single-layered, while the sclerotesta

is composed of several layers of thick-walled cells (Plate XIII, 1-3). The endotesta is typically single-layered but up to three layers of cells have been observed in some sections. No integumentary vascular tissue has been identified. The nucellus comprises a single layer of cells that is free from the integument except at the chalaza, and it shows a nucellar beak at the tip of the pollen chamber (Plate XIII, 3, 4-6). The pollen chamber sometimes contains monosaccate prepollen grains that are assignable Potoniesporites and are surrounded by a translucent substance that changes the optical properties of the slides (Plate XIII, 3-5). Mature cones have seeds in which the integument, nucellus, megaspore membrane, megagametophyte, and embryos are preserved (Plate XII, 1; Plate XIII, 6-8). The embryo is polycotyledonary, and is

230

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate X. 1–3. Emporia cryptica sp. nov., SEM of sporophylls and seed. 1. 2. 3.

Adaxial surface showing sporophyll and sub-apical seed scar. OUPH 17827, scale bar = 250 μm. Abaxial surface showing sporophyll trichome bases and marginal trichomes. OUPH 17827, scale bar = 200 μm. Seed showing trichome bases (bottom left). OUPH 17822, scale bar = 500 μm.

separated from the megagametophyte by a narrow corrosion cavity (Plate XIII, 8). 4. Discussion and conclusions 4.1. Systematic relationships of Emporia cryptica Comparisons of Emporia cryptica to Euramerican Voltziales at the whole plant level are more meaningful for assessing the taxonomy of extinct conifer plant species than comparisons of individual organs to previously described morphotaxa. This is because there are overlapping ranges of variation in morphological and cuticular characters of individual organs (particularly vegetative organs) for many walchian conifers (Tables 2–4; Hernandez-Castillo et al., 2001b; Rothwell et al., 2005; Hernandez-Castillo, 2005). Even though morphological and cuticular characters of leaves on dispersed penultimate and ultimate shoots were traditionally used to typify walchian conifer species (i.e., Florin 1927, 1938–45; Clement-Westerhof, 1984; Visscher et al., 1986), leaves have some of the most overlapping characters among species of walchian conifer organs (Hernandez-Castillo et al., 2001b; Hernandez-Castillo, 2005; Rothwell et al., 2005). The practice of relying primarily on leaf characters to identify isolated and/or fragmentary walchian conifer remains is most useful for identifying morphotaxa. However, most morphotaxa are extremely difficult to correlate to any previously described species of conifer plants, and can not be used to infer developmental series or phylogenetic relationships because a complete plant is not known (HernandezCastillo et al., 2001b; Hernandez-Castillo, 2005). Similarly, ovulate cones are often used to differentiate walchian conifers and have played an important role in their systematics (i.e., Florin, 1938–45, 1950, 1951; Clement-Westerhof, 1987, 1988; Kerp and Clement-Westerhof, 1991; Mapes and Rothwell, 1991, 2003). However, good preservation and attached cones are required to accurately assign cones to vegetative branches (Hernandez-Castillo et al., 2001b). Emporia cryptica conforms to the general architecture recently determined for the earliest walchian conifers (Lausberg, 2002; Hernandez-Castillo et al., 2003). These were small trees with orthotropic stems from which plagiotropic lateral branches of determinate growth arise in pseudowhorls. Lateral branches bear terminal pollen cones on ultimate branches and terminal seed cones on penultimate branches.

Among primitive conifers, E. cryptica has a novel combination of characters that includes: 1) three orders of branching, 2) lack of heterophylly, 3) simple, needle-like, amphistomatic vegetative leaves, 4) monocyclic and dicyclic stomata on all leaves and leaf-like organs, 5) parenchymatous pith with sclerotic nests/plates, 6) multiseriate, hexagonal, circular bordered pits on secondary xylem tracheids, 7) simple pollen cones with 4–8 adaxial pollen sacs per microsporophyll, and 8) ovulate cones bearing dwarf shoots separate from the bracts with often 20–25 abaxially-oriented sterile scales, interspersed with two sporophylls, and 9) one inverted seed per sporophyll with two narrow wings, and polycotyledonary embryos. Comparisons between E. cryptica and the most completely known Euramerican walchian Voltziales are summarized in Tables 3 and 4. Among those taxa Walchia garnettensis sensu Winston, Otovicia hypnoides (Florin) Kerp, Swinkels, & Verwer and Emporia lockardii (Mapes & Rothwell) Mapes & Rothwell emend. Hernandez-Castillo, Stockey, Rothwell & Mapes have relatively similar suites of characters for vegetative lateral branches, leaves, pollen and ovulate cones (Tables 3 and 4). However, they all differ from E. cryptica in at least four specific characters of growth architecture and vegetative lateral branches (e.g., penultimate leaf types, heterophylly, adaxial and abaxial stomatal patterns), and at least five pollen and ovulate cone characters (e.g., pollen sac number, bract/dwarf shoot separation, bract length, sterile scale number, and sporophyll number). Walchia garnettensis sensu Winston (1984) differs from E. cryptica in at least eleven systematically informative characters (Tables 3 and 4). Some of these characters are not known for W. garnettensis yet (i.e., leaf abaxial stomatal distribution, type, number and position of pollen sacs, bract and dwarf shoot and sporophyll organization, etc.) Therefore, a comprehensive reexamination of W. garnettensis would be helpful for more thoroughly evaluating its relationships with E. cryptica and other Paleozoic conifers. Otovicia hypnoides differs from E. cryptica by having 1) forked penultimate leaves (position-dependent heterophylly), 2) primarily adaxial stomata with scattered abaxial stomata on leaves and microsporophylls, 3) bracts and dwarf shoots separate throughout their entire length, 4) sterile scales apparently all around the dwarf shoots, and 5) winged seeds with a forked micropylar region (Tables 3 and 4; Kerp et al., 1990). Even though the appearance of O. hypnoides generally resembles that of E. cryptica, diagnostic characters such as position-dependent heterophylly, cuticles of vegetative leaves,

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate XI. 1–6. Emporia cryptica sp. nov., bracts from ovulate cones. 1. 2. 3. 4. 5. 6.

Adaxial surface showing forked tip, broad base and bands of stomata (s) on forked tips. OUPH 17899, scale bar = 1.5 mm. Adaxial surface of bract base showing surface trichomes. OUPH 17697, scale bar = 1.2 mm. Forked tip showing adaxial dicyclic stomata (arrowheads). OUPH 17698, scale bar = 500 μm. Adaxial dicyclic stomata (bracket) and narrow band of stomata (s). OUPH 17706, scale bar = 180 μm. Adaxial non-functional dicyclic stoma and papillate epidermal cells. OUPH 17706, scale bar = 80 μm. Abaxial papillate epidermal cells (left), scattered stomata (s) and trichome bases (right). OUPH 17698, scale bar = 150 μm.

231

232

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

microsporophylls, and leaves on branches attached to cones suggest different growth architecture, leaf development, and ovulate cone organization from that of E. cryptica (Tables 3 and 4). Emporia lockardii differs from E. cryptica by having 1) positiondependent heterophylly, 2) monocyclic stomata only, 3) 8–14 adaxial pollen sacs, 4) bract and dwarf shoots separate throughout their entire length, 5) sterile scales all around the dwarf shoot, and 6) 1–3 sporophylls per ovuliferous dwarf shoot (Tables 3 and 4). Despite these differences, vegetative branches, and pollen and ovulate cones of E. cryptica are extremely difficult to differentiate from those of E. lockardii at the Hamilton Quarry (Hernandez-Castillo, 2005; Hernandez-Castillo et al., 2009) without particularly thorough study of the respective specimens. A similar situation occurs with pollen and ovulate cones from the Hamilton Quarry, where incomplete specimens of E. lockardii and E. cryptica easily can be confused with each other because of the overlapping ranges of variation displayed by different developmental stages of each plant (Hernandez-Castillo, 2005). Therefore, among all the Euramerican voltzialean conifers, E. cryptica is most similar to E. lockardii, which supports its assignment as a new species within the genus Emporia. 4.2. Reproductive biology of Emporia cryptica Due to the exceptional preservation of many Hamilton Quarry fossils, numerous ovules and seeds have been recognized at different developmental stages. As demonstrated by Mapes and Rothwell (1984), these developmental stages can be compared to those of living conifers when anatomical sections are available. The integument in young ovules of E. cryptica shows three layers (sarcotesta, sclerotesta, and endotesta) that are similar in tissue composition to those found in E. lockardii and Hanskerpia hamiltonensis (Mapes and Rothwell, 1984; Rothwell et al., 2005; Hernandez-Castillo et al., 2009). The sarcotesta in E. cryptica forms a very small wing that is more obvious in immature ovules but is reduced in mature seeds. The wing is covered by numerous trichomes and a thick cuticle, similar to those of some extant conifers (Chowdhury, 1961; Mapes and Rothwell, 1984; Rothwell et al., 2005). The sclerotesta is composed of several layers of cells that are full of dark contents suggesting that these seeds may have produced some sort of secretory substance. The nucellus in immature ovules has up to three layers of cells, but is often represented by a single layer in mature ovules, and it forms a nucellar beak like that in living conifers (Chamberlain, 1935; Gifford and Foster, 1989). Pollen chambers of E. cryptica ovules and seeds contain a few prepollen grains that are surrounded by a substance that has a

different refractive index than that of the rest of the ovule. Mapes and Rothwell (1984) hypothesized that the ratio between the open micropyles and diameter of prepollen grains in E. lockardii serve as indirect evidence of a pollination drop mechanism. A similar correlation has been found in E. cryptica, where prepollen grains are rather large and it would be difficult for them to find their way into the micropyle by wind currents alone. Immature, abortive, and mature ovules have been described for E. lockardii but no megagametophytes or embryos have been found for that species (Mapes and Rothwell, 1984; Rothwell et al., 2005). The only embryos previously reported for Paleozoic conifers are represented by Moyliostrobus texanus Miller & Brown (Miller and Brown, 1973; Mapes, 1987) and cones (Mapes et al., 1989) that are now assigned to E. cryptica. These seeds of E. cryptica contain polycotyledonary embryos, providing the first evidence for seed dormancy in Paleozoic conifers (Mapes et al., 1989). Cellular megagametophytes of E. cryptica described here are the first known in Paleozoic conifers and the oldest in the conifer lineage. Thus, E. cryptica not only had seed dormancy as previously proposed by Mapes et al. (1989), but probably had a similar pollination drop mechanism to that seen in other fossil conifers with prepollen grains (E. lockardii and O. hypnoides), and in living conifers with saccate pollen grains (Owens and Blake, 1983; Mapes and Rothwell, 1984; Owens et al., 1987; Kerp et al., 1990; Owens and Morris, 1998; Runions et al., 1999; Tomlinson and Takaso, 2002). Two types of pollination associated with saccate pollen grains are known among living conifers (Runions and Owens, 1996; Runions et al., 1999; Tomlinson and Takaso, 2002). One involves inverted ovules and a pollination drop, while the other does not. Instead the pollen reaches a micropyle by floating in rainwater. The first type would be equivalent to the proposed pollination mechanism for E. cryptica and other walchians (Mapes and Rothwell, 1984; Kerp et al., 1990), where an inverted ovule produces a pollination drop that facilitates prepollen grains reaching the pollen chamber during early stages of reproduction. 5. Conclusions Emporia cryptica was a conifer tree of small stature with lateral plagiotropic branches and terminal pollen and ovulate cones, and is one of only a few species of fossil conifers for which morphological, anatomical and cuticular ranges of variation for vegetative and fertile organs are well known. Emporia cryptica stresses the value of whole plant reconstructions for Paleozoic conifers and reinforces the growing understanding that isolated and/or fragmentary conifer organs can be best used as morphotaxa. Although morphotaxa do not reflect complete

Plate XII. 1–5. Emporia cryptica sp. nov., ovulate cone anatomy. 1. 2. 3. 4. 5.

Longitudinal section showing cone axis (C), bracts (B) subtending axillary dwarf shoots (D) with sterile scales (Ss) and seeds (Se). HOLOTYPE, OUPH 17657, scale bar = 5 mm. Longitudinal section showing cone axis (C), bracts (B), and axillary dwarf shoots (D) with sterile scales (Ss) and seeds (Se). Note seed micropyles at arrowheads. HOLOTYPE, OUPH 17680, scale bar = 5 mm. Cross section showing cone axis (C), bracts (B), axillary dwarf shoots (D), and sterile scales (Ss). Note axillary dwarf shoot axis and abaxial location of most sterile scales. OUPH 17787, scale bar = 5 mm. Longitudinal section showing cone axis (C), bract (B), and axillary dwarf shoots (D) with sterile scales (Ss). Note wood of vascular traces at dwarf shoot base, and vascular traces of bract and sterile scales as files of cells with dark contents (at arrowheads). HOLOTYPE, OUPH 17718, scale bar = 5 mm. Cross section showing cone axis (C) and axillary dwarf shoot bearing sterile scales. Note vascular traces into sterile scales as dark content cells (black arrowheads) and vascular bundle of sterile scale (white arrowhead). OUPH 17787, scale bar = 5 mm.

Plate XIII. 1–8. Emporia cryptica sp. nov., anatomy of ovule and seeds. (see on page 234) 1. 2. 3. 4. 5. 6. 7. 8.

Cross section of axillary dwarf shoot showing sterile scales (Ss) and two seeds. OUPH 17927, scale bar = 300 μm. Winged seed showing integuments (In) and nucellus (N). OUPH 17921, scale bar = 200 μm. Transverse section of seed at micropylar end showing integuments (In) and nucellar beak (Nb). HOLOTYPE OUPH 17672, scale bar = 150 μm. Nucellar beak with enclosed prepollen grain. HOLOTYPE OUPH 17672, scale bar = 45 μm. Monosaccate prepollen grain enlarged from Fig. 4. HOLOTYPE OUPH 17672, scale bar = 30 μm. Longitudinal section of ovule showing sarcotesta (Sa), sclerotesta (Sl), endotesta (En), nucellus (Nu) with prepollen grains, megagametophyte and young embryo (Ye). Note nucellar beak and pollen chamber above young embryo. Also note megagametophyte tissue differentiation and corrosion cavity. HOLOTYPE, OUPH 17677, scale bar= 400 μm. Seed showing integuments (In), micropyle (Mi), and embryo remains (E). HOLOTYPE, OUPH 17686, scale bar = 800 μm. Seed showing integuments (arrowhead), micropyle (Mi), megaspore membrane (Mm), cellular megagametophyte (M), and embryo (E). HOLOTYPE, OUPH 17657, scale bar=800 μm.

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate XII.

233

234

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Plate XIII (caption on page 232).

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

235

Table 1 Comparison of morphological and cuticular characters of leaves and leaf-like structures on vegetative and fertile organs of Emporia cryptica sp. nov. Species/characters

Shape Shape Length (face view) (side view) (mm)

Leaves on penultimate shoots Nt, Li

Ss, Sp

Leaves on ultimate shoots

S, Li

Sss, Sc, Sp

Leaves on branches with attached to pollen cones Microsporophylls

Nt, Li

Sc, Sss

Tr

Sc

Leaves on branches with attached to ovulate cones Bracts of ovulate cones

Nt, Li

Ss, Sp

Nt, Li, Fr

Ss, Sc

Sterile scales of ovulate cones

Ns, Tr, Ov

Ss, Sp

2.4–7.1

Width (mm)

Stomata Structure

0.6–2.0

Monocyclic, dicyclic 1.2–2.7 0.3–1.2 Monocyclic, dicyclic 2.5–3.0 0.2–0.8 Monocyclic, dicyclic 1.4–4.7 0.8–2.9 Monocyclic, dicyclic 3–7 0.6–2.0 Monocyclic, dicyclic Monocyclic, 5–8 2–3 dicyclic 1.5–3.2 0.7–1.2 Monocyclic, dicyclic

Papillae Distribution (adaxial/abaxial)

Number of stomata per band

Subsidiary Subsidiary cell cells number

Two long, broad bands/ two, narrow bands Two long, broad bands/ two, narrow bands Two long, broad bands/ two narrow bands Two long, broad bands/ few scattered or none Two long, broad bands/ two narrow bands Two long, broad bands/ two narrow bands Two long, broad bands/ two–three narrow bands

2–5

5–6

Overarching Abundant

2–12

5–8

Overarching Abundant

2–8

7–8

Overarching Abundant

2–8

5–7

Overarching Abundant

2–5

5–6

Overarching Abundant

2–5

6–8

Overarching Abundant

1–2

7–8

Overarching Abundant

Epidermal cells

Trichome bases (adx/abx) Few/ abundant Abundant/ abundant Abundant/ abundant Abundant/ abundant Abundant/ abundant Abundant/ abundant Abundant/ abundant

Leaf shape abbreviations: El = Elliptical, Fr = Forked Tip, Li = Linear, l = Lanceolate, Ns = Narrow sub-triangular, Nt = Narrowly triangular, Ob = Oblong, Ov = Ovate, Wo = Widely oblong, Sc = Slightly concave, Sp = Spreading (extending nearly to the horizontal), Sq = Squamose (= scale like), Ss = S-shaped, Sss = Slightly S-shaped, St = Sub-triangular, Tr = Triangular.

conifers and are not suitable either for comparisons to species of extinct conifer plants or to infer phylogeny, they serve as the basis for basic paleobotanical research in an array of topics such as biodiversity, paleobiogeography, paleoecology and stratigraphy among others. On the other hand, extinct species of conifer plants cannot be reconstructed unless a large number of wellpreserved specimens is available for study and organ correlations are accurate. Emporia cryptica is the first conifer with preserved megagametophytes and embryos at different developmental stages suggesting that the most ancient conifers already possessed a similar reproductive biology (seed dormancy, polycotyledonary embryos) to that of extant conifers (Mapes and Rothwell, 1984). Therefore, information derived from cones of E. cryptica and other conifers at the Hamilton Quarry is available to serve as the basis for future studies in fossil conifer reproductive biology. Up to the present, the Hamilton Quarry is the

only Paleozoic locality in the world where several conifer species have been described as extinct species of plants (Rothwell and Mapes, 2001; Hernandez-Castillo, 2005; Rothwell et al., 2005; HernandezCastillo et al., 2009), and the Emporiaceae is now the best known family of Paleozoic fossil conifers. Acknowledgements We thank Royal Mapes for his help and enthusiasm in collecting material for more than 30 years. We also thank Zhao-Hua Liu (Ohio University) for some cuticle preparations, and George Braybrook, Rakesh Bhatnagar, and Jack Scott (University of Alberta) for some SEM assistance. This work was supported in part by Consejo Nacional de Ciencia y Tecnología (Grants 050213 and 054521) to GRHC, the National Science Foundation (Grant EF-0629819) to GWR, GM, and RAS, and NSERC Grant (A-6908) to RAS.

Table 2 Emporia cryptica sp. nov. whole plant characters. Growth architecture/vegetative branches

Stem anatomy

Pollen cones

Ovulate cones

Stem: Orthotropic Branch type: Plagiotropic

Stele type: Endarch stele Pith organization: Parenchymatous pith with sclerotic nests/plates Primary xylem: Tracheids with helical to scalariform wall thickenings Wood: Picnoxylic

Cone type: Simple Cone position: Terminal

Cone type: Compound Cone position: Terminal

Order of attached branch: Ultimate shoot

Order of attached branch: Penultimate shoots

Leaf morphology: Simple

Heterophylly: Absent

Leaves on attached branch: Same as vegetative ultimate leaves Leaf distribution: Penultimate Secondary xylem: Tracheids Microsporophyll type: Simple shoots with simple leaves. multiseriate with hexagonal bordered pits Leaf distribution: Ultimate shoots Wood rays: Uniseriate, 1–3 Microsporophyll shape: Composed of a with simple leaves cells high stalk and a heeled distal lamina Stomatal complexes: Monocyclic Bark: Scarce Microsporophyll stomatal distribution: and dicyclic Two bands of adaxial stomata and few, scattered abaxial, Leaf stomatal distribution: Pollen sacs position and number: Amphistomatic, two adaxial Adaxial on stalk, four to eight bands and two abaxial narrow bands Prepollen grains: Monosaccate, Potonieisporites Bharadwaj

Leaves on attached branch: Simple and similar to leaves on penultimate shoots Bract type: Forked.

Sterile scale number: 20–25 Sterile scale organization: Interspersed among sporophylls Sterile scale location: Abaxial Sporophyll number: 2 Sporophyll organization: Free from sterile scales

Bract length: Equal to axillary dwarf shoot Seed position and type: Terminal, inverted. Bracts stomatal distribution: Seed shape and symmetry: Amphistomatic, two bands of adaxial Ellipsoidal, bilateral stomata and two abaxial narrow bands Bract attachment to dwarf shoot: Fused at Seed ornamentation: Pilose base

Dwarf shoot symmetry: Bilateral, dorsiventral

Seed anatomy: 3-layered integument, simple pollen chamber, and nucellar beak

⁎Hetero phylly

Stomatal distribution Stomatal pattern (vegetative leaves) Adx/Abx

Pollen cone

Pollen cone attached Microsporophylls (type, shape, branch/leaves stomatal distribution)

Pollen Sacs

Simple

Absent

Emporia lockardii Orthotropic? Plagiotropic Simple & forked Hanskerpia Orthotropic? Plagiotropic Forked hamiltonensis 3 Thucydia Orthotropic Plagiotropic Simple mahoningensis 4 Utrechtia Orthotropic? Plagiotropic Forked floriniformis 5 Walchia ? Plagiotropic Simple garnettensis

Simple

2

Simple

Position dependent Position dependent Absent

Two bands/two narrow bands Two bands/two short, narrow, ind. rows Parallel rows/parallel rows Two bands/absent

Simple, Terminal

1

Amphistomatic, Mono, Dicyclic Amphistomatic, Monocyclic Amphistomatic, Monocyclic Adaxial, Monocyclic

Ultimate, simple as veg. ult leaves Ultimate, simple as veg. ult leaves ?, ?

Simple, Stalked-heeled, Two narrow bands/ absent Simple, Stalked-heeled, Two to four narrow bands/ absent ?, ?, ?

Adaxial, 4–8 Adaxial, 8–14 ?,?

Position dependent Absent

Amphistomatic, Monocyclic Amphistomatic, Monocyclic

Two bands/two bands

No microsporophylls present Simple, Stalked-heeled, ?

Terminal, 3–4 Adaxial, ?

Two long bands/few scattered

Simple, Terminal

Ultimate, simple as veg. ult leaves Ultimate, simple as veg. ult leaves ?, ?

6

Plagiotropic Forked

Simple

Simple, Terminal

Simple

Irregular

Simple & forked

Primarily adaxial, Mono-inc dicyclic Amphistomatic, Mono-inc dyciclic Adaxial, Monocyclic

Two bands/scattered

Plagiotropic Simple

Position dependent Absent

Stem

Lateral branches

Emporia cryptica

Orthotropic

Plagiotropic Simple

Otovicia ? hypnoides 7 Ernestiodendron ? filiciforme 8 Barthelia furcata ?

Penultimate leaves

Forked

Simple Simple Simple

Size dependent

Simple, Terminal ?, ? Compound, Terminal Simple, Terminal

Parallel rows/parallel Simple, Terminal rows Two bands/absent Simple, Terminal

Ultimate, simple as veg. ult leaves Ultimate, simple as veg. ult leaves ?, Forked as veg. leaves

Simple, ?, One- two narrow ?, ? bands/two narrow bands forming rows later Simple, Stalked-heeled, Two Adaxial, ? long bands/few stomata groups Simple, Stalked-heeled, ? ?, ? Forked, Leafy, Two long bands w rows/ absent

Adaxial, ?

Table references: 1Mapes and Rothwell, 1984, 1991 and Hernandez-Castillo et al., 2009. 2Rothwell et al., 2005. 3Hernandez-Castillo et al., 2001b. 4Mapes and Rothwell, 1991. 5Emended by Winston (1984). 6Kerp et al., 1990. 7Florin, 1938–45. 8 Rothwell and Mapes, 2001. ⁎ Heterophylly is based on differences in the shape of leaves, where two distinctive types of leaves are known, see types in Hernandez-Castillo et al., 2001b; Hernandez-Castillo, 2005. Adx = adaxial surface, Abx = abaxial surface, SS = sterile scales. Stalked-heeled = microsporophyll composed of a stalk and a heeled distal lamina.

Table 4 Comparison of prepollen and ovulate cone characters of Emporia cryptica sp. nov. and other Paleozoic conifers. Characters that differ from those of E. cryptica are recorded in bold face type. Partially overlapping characters are recorded in italics. Taxa/characters

Emporia cryptica 1

Emporia lockardii Hanskerpia hamiltonensis 3 Thucydia mahoningensis 4 Utrechtia floriniformis 5 Walchia garnettensis 6 Otovicia hypnoides 7 Ernestiodendron filiciforme 8 Barthelia furcata 2

Prepollen

Compound ovulate organ

Attached branch to Leaves on attached shoot OC/FZ and leaves Stomata type Stomatal distribution

Bract

Potonieisporites, Monosaccate Potonieisporites, Monosaccate ?, ?

Cone, Terminal Cone, Terminal Cone/zone?

Potonieisporites, Monosaccate Potonieisporites, Monosaccate Potonieisporites, Monosaccate Potonieisporites, Monosaccate ?, ?

Fertile zone, Intercalary Cone, Terminal Cone, Terminal Cone, Terminal Cone, Terminal Fertile zone, Intercalary

Penultimate, Simple Penultimate, Forked Penultimate, Forked Penultimate, Simple Penultimate, Forked Penultimate, Simple? Penultimate, Simple? Penultimate, Simple w leaf scar Penultimate, Forked

Forked, Equal to dwarf shoot Forked, Equal to larger than dwarf shoot Forked, Much larger than dwarf shoot Simple, Larger than dwarf shoot Forked, Larger than dwarf shoot Forked, Equal to larger than dwarf shoot Forked, Larger than dwarf shoot Forked, Larger than dwarf shoot Forked, Larger than dwarf shoot

Potonieisporites, Monosaccate

Amphistomatic, mono, dicyclic Amphistomatic, Monocyclic Amphistomatic, Monocyclic Adaxial, Monocyclic Amphistomatic, Monocyclic Amphistomatic?, Monocyclic Primarily adaxial, Monocyclic Amphistomatic, Mono-inc dicyclic Adaxial, Monocyclic

Two long, broad bands/ two narrow bands Two bands/two short, narrow, ind. rows Parallel rows/parallel rows Two bands/absent Two bands/two bands Two bands?/? Two bands/few groups Parallel rows/parallel rows Two bands/absent

References as in Table 3. SS = sterile scales, OC/FZ = Ovulate cone/Fertile zone, stomatal distribution indicating adaxial/abaxial surfaces.

Bract and ovuliferous dwarf shoot

Dwarf Sterile scale shoot position/number symmetry

Sporophyll position/ number

Ovules/ Seeds Position, type

Shape, symmetry

Fused at base Separate throughout Fused at base Separate throughout Separate throughout ?

Bilateral

Terminal, Inverted Terminal, Inverted Terminal, Inverted Terminal, Inverted Terminal, Inverted ?, ?

Ellipsoidal, bilateral Ellipsoidal, bilateral Ellipsoidal, bilateral Ellipsoidal, bilateral Ellipsoidal, bilateral ?, ?

Separate throughout Separate throughout Separate throughout

Terminal, Inverted Terminal, Inverted Terminal, Inverted?

Ellipsoidal, bilateral Ellipsoidal, bilateral Ellipsoidal, bilateral

Bilateral

Abaxial, 20–37 (usually 20–25) All around, 14–30

Bilateral

All around, b15?

Bilateral

All around, 10–15

Interspersed with SS, 2 Interspersed with SS, 1–3 Interspersed with SS, 1–2 Terminal, 3–4

Bilateral

All around?, N10

Terminal, 1

Bilateral

?, b5?

?, ≥3?

Bilateral Bilateral

All around?, 12– 18 All around?, 5–10

Interspersed with SS, 2 Terminal, 1

Radial

All around, N10

Interspersed with SS, ?

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

Ultimate leaves

Taxa/characters

236

Table 3 Comparison of growth architecture, leaf, and pollen cone characters of Emporia cryptica sp. nov. and other Paleozoic conifers. Characters that differ from those of E. cryptica are recorded in bold face type. Partially overlapping characters are recorded in italics.

G.R. Hernandez-Castillo et al. / Review of Palaeobotany and Palynology 157 (2009) 218–237

References Bharadwaj, D.C., 1964. The organization in pollen grains of some early conifers. Palaeobotanist 12, 18–27. Bridge, T.E., 1988. Geology and stratigraphy of the Hamilton Quarry area. In: Mapes, G., Mapes, R.H. (Eds.), Regional Geology and Paleontology of Upper Paleozoic Hamilton Quarry Area in Southeastern Kansas: Kansas Geological Survey Guidebook, vol. 6, pp. 27–35. Kansas Geological Survey. Kansas. Busch, R.M., Bogina, M.A., Clark, M.H., 1988. Genetic stratigraphy of fossil localities. In: Mapes, G., Mapes, R.H. (Eds.), Regional Geology and Paleontology of Upper Paleozoic Hamilton Quarry Area in Southeastern Kansas: Kansas Geological Survey Guidebook, vol. 6, pp. 59–65. Kansas Geological Survey. Kansas. Chamberlain, C.J.,1935. Gymnosperms, structure and evolution. Univ. Chicago Press, Chicago. Chowdhury, C.R., 1961. The morphology and embryology of Cedrus deodara (Roxb.) Loud. Phytomorphology 11, 283–304. Clement-Westerhof, J.A., 1984. Aspects of Permian palaeobotany and palynology; IV, The conifer Ortiseia Florin from the Val Gardena Formation of the Dolomites and the Vicentinian Alps (Italy) with special reference to a revised concept of the Walchiaceae (Goeppert) Schimper. Rev. Palaeobot. Palynol. 41, 51–166. Clement-Westerhof, J.A., 1987. Aspects of Permian palaeobotany and palynology; VII, The Majonicaceae, a new family of Late Permian conifers. Rev. Palaeobot. Palynol. 52, 375–402. Clement-Westerhof, J.A., 1988. Morphology and phylogeny of Paleozoic conifers. In: Beck, C.B. (Ed.), Origin and Evolution of Gymnosperms. InColumbia University Press, New York, pp. 298–337. Fahrer, T.R., 1991. Paleoecology and sedimentology of the Late Carboniferous (Pennsylvanian) Hamilton Lagerstätte, Greenwood County, Kansas. M.S. Thesis, Ohio University, Athens, Ohio. Fahrer, T.R., Mapes, R.H., Maples, C.G., 1990. Geometry of the Late Carboniferous Hamilton Lagerstätte, Greenwood County, Kansas. Geological Society of America Abstracts and Program, Boulder, Colorado, p. 22:A6. Feldman, H.R., Franseen, E.K., Fahrer, T.R., Maples, C.G., 1990. Geology and sedimentology of the Hamilton Lagerstätte. 1990. Society of Vertebrate Paleontology Upper Paleozoic of Eastern Kansas, Excursion Guidebook, pp. 36–41. Feldman, H.R., Archer, A.W., Kvale, E.P., Cunningham, C.R., Maples, C.G., West, R.R., 1993. A tidal model of Carboniferous Konservat-Lagerstätte Formation. Palaios 8, 485–495. Florin, R., 1927. Preliminary descriptions of some Palaeozoic conifers. Arkiv für Botanik 21, 1–7. Florin, R., 1938–45. Die Koniferen des Oberkarbons und des unteren Perms. Palaeontogr., Abt. B 85, 1–729. Florin, R., 1950. Upper Carboniferous and Lower Permian conifers. Bot. Rev. 16, 258–282. Florin, R., 1951. Evolution in cordaites and conifers. Acta Horti Bergiani 15, 285–388. French, J.A., Watney, W.L., Anderson, J.E., 1988. Stratigraphic and sedimentologic considerations relating to the fossiliferous limestones (Upper Pennsylvanian?) at Hamilton Quarry, Greenwood County, Kansas. In: Mapes, G., Mapes, R.H. (Eds.), Regional geology and paleontology of Upper Paleozoic Hamilton Quarry area in southeastern Kansas. Kansas Geological Survey Guidebook, vol. 6, pp. 37–58. Kansas Geological Survey. Kansas. Galtier, J., Scott, A.C., Powell, J.H., Glover, B.W., Waters, C.N., 1992. Anatomically preserved conifer-like stems from the Upper Carboniferous of England. Proc. R. Soc. Lond., B Biol. Sci. 247, 211–214. Gifford, E.M., Foster, A.S., 1989. Morphology and evolution of vascular plants, 3rd Edition. WH Freeman and Co., New York. 626 pp. Hernandez-Castillo, G.R. 2005. Systematics of the most ancient conifers. Ph. D. Thesis, University of Alberta, Edmonton, Alberta, Canada. Hernandez-Castillo, G.R., Rothwell, G.W., Mapes, G., 2001a. Compound pollen cone in a Paleozoic conifer. Am. J. Bot. 88, 1139–1142. Hernandez-Castillo, G.R., Rothwell, G.W., Mapes, G., 2001b. Thucydiaceae fam. nov., with a review and reevaluation of Paleozoic walchian conifers. Int. J. Plant Sci. 162, 1155–1185. Hernandez-Castillo, G.R., Rothwell, G.W., Stockey, R.A., Mapes, G., 2003. Growth architecture of Thucydia mahoningensis, a model for primitive walchian conifer plants. Int. J. Plant Sci. 164, 443–452. Hernandez-Castillo, G.R., Stockey, R.A., Rothwell, G.W., Mapes, G., 2009. Reconstructing Emporia lockardii (Voltziales: Emporiaceae) and initial thoughts on Paleozoic conifer ecology. Int. J. Plant Sci. 170 (8), 1056–1074. Joy, K.W., Willis, A.J., Lacey, W.S., 1956. A rapid cellulose peel technique in palaeobotany. Ann. Bot. 20, 635–637. Kerp, H., Clement-Westerhof, J.A., 1991. Aspects of Permian palaeobotany and palynology; XII, the form-genus Walchiostrobus Florin reconsidered. N. Jb. Geol. Paläeont. Abh. 183, 257–268.

237

Kerp, J.H.F., Poort, R.J., Swinkels, H.A.J.M., Verwer, R.,1990. Aspects of Permian palaeobotany and palynology. IX. Conifer-dominated Rotliegend floras from the Saar–Nahe Basin (? Late Carboniferous–Early Permian; SW-Germany) with special reference to the reproductive biology of early conifers. Rev. Palaeobot. Palynol. 62, 205–248. Lausberg, S., 2002. Neue Kenntnisse zur saarpfälzischen Rotliegend-Flora unter besonderer Berücksichtigung der Coniferentaxonomie und des Hinterlandes. Doctoral Thesis, Westfälische Wilhelms-Universität, Münster, Germany. Mapes, G., 1987. Ovule inversion in the earliest conifers. Am. J. Bot. 74, 1205–1210. Mapes, G., Mapes, R.H., 1988. Regional Geology and Paleontology of Upper Paleozoic Hamilton Quarry Area in Southeastern Kansas: Kansas Geological Survey Guidebook, vol. 6. Kansas Geological Survey. Kansas. Mapes, G., Rothwell, G.W., 1984. Permineralized ovulate cones of Lebachia from late Palaeozoic limestones of Kansas. Palaeontology 27, 69–94. Mapes, G., Rothwell, G.W., 1991. Structure and relationships of primitive conifers. N. Jb. Geol. Paläont. Abh. 183, 269–287. Mapes, G., Rothwell, G.W., 1998. Primitive pollen cone structure in Upper Pennsylvanian (Stephanian) walchian conifers. J. Paleontol. 72, 571–576. Mapes, G., Rothwell, G.W., 2003. Validation of the names Emporiaceae, Emporia and Emporia lockardii. Taxon 52, 327–328. Mapes, G., Rothwell, G.W., Haworth, M.T., 1989. Evolution of seed dormancy. Nature 337, 645–646. Meyen, S.V., 1984. Basic features of gymnosperm systematics and phylogeny as evidenced by the fossil record. Basic features of gymnosperm systematics and phylogeny as evidenced by the fossil record. Bot. Rev. 50, 1–112. Meyen, S.V., 1997. Permian conifers of western Angaraland. Rev. Palaeobot. Palynol. 96, 351–447. Miller, C.N., Brown, J.T., 1973. A new voltzialean cone bearing seeds with embryos from the Permian of Texas. Am. J. Bot. 60, 561–569. Owens, J.N., Blake, M.D., 1983. Pollen morphology and development of the pollination mechanism in Tsuga heterophylla and T. mertensiana. Can. J. Bot. 61, 3041–3048. Owens, J.N., Morris, S.J., 1998. Factors affecting seed and cone development in Pacific silver fir (Abies amabilis). Can. J. For. Res. 28, 1146–1163. Owens, J.N., Simpson, S.J., Caron, G.E., 1987. The pollination mechanism of Engelmann spruce (Picea engelmannii). Can. J. Bot. 65, 1439–1450. Rothwell, G.W., 1982. New interpretations of the earliest conifers. Rev. Palaeobot. Palynol. 37, 7–28. Rothwell, G.W., Mapes, G., 1988. Vegetation of a Paleozoic conifer community. In: Mapes, G., Mapes, R.H. (Eds.), Regional geology and paleontology of Upper Paleozoic Hamilton Quarry area in southeastern Kansas: Kansas Geological Survey Guidebook, vol. 6, pp. 213–223. Kansas Geological Survey. Kansas. Rothwell, G.W., Mapes, G., 2001. Barthelia furcata gen. et sp. nov., with a review of Paleozoic coniferophytes and a discussion of coniferophyte systematics. Int. J. Plant Sci. 162, 637–677. Rothwell, G.W., Mapes, G., 2003. Validation of the names Utrechtiaceae, Utrechtia, and Utrechtia floriniformis. Taxon 52, 329–330. Rothwell, G.W., Mapes, G., Mapes, R.H., 1997. Late Paleozoic conifers of North America; structure, diversity and occurrences. Rev. Palaeobot. Palynol. 95, 95–113. Rothwell, G.W., Mapes, G., Hernandez-Castillo, G.R., 2005. Cladistic relationships among the most ancient conifers (Voltziales). Taxon 52, 733–750. Runions, C.J., Owens, J.N., 1996. Pollen scavenging and rain involvement in the pollination mechanism of interior spruce. Can. J. Bot. 74, 115–124. Runions, C.J., Rensing, K.H., Takaso, T., Owens, J.N., 1999. Pollination of Picea orientalis (Pinaceae): Saccus morphology governs pollen buoyancy. Am. J. Bot. 86, 190–197. Schweitzer, H., 1963. Der weibliche Zapfen von Pseudovoltzia liebeana und seine Bedeutung für die Phylogenie der Koniferen. Palaeontogr., Abt. B 113, 1–29. Tomlinson, P.R., Takaso, T., 2002. Seed cone structure in conifers in relation to development and pollination: a biological approach. Can. J. Bot. 80, 1250–1273. Visscher, H., Kerp, J.H.P., Clement-Westerhof, J.A., 1986. Aspects of Permian palaeobotany and palynology; VI, towards a flexible system of naming Palaeozoic conifers. Acta Bot. Neerl. 35, 87–99. Winston, R.B., 1984. The Upper Pennsylvanian conifer Walchia garnettensis; structure and affinities. Palaeontogr., Abt. B 194, 97–108.