Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered amo... more Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered among a diverse assemblage of plants and fungi in carbonate marine concretions at the Apple Bay locality along the shore of Holbert Inlet near the northern end of Vancouver Island, British Columbia, Canada. Lycopodialean stems are plectostelic and actinostelic, branch dichotomously, and are similar to both Lycopodicaulis oellgaardii and Lycoxylon spp. The Selaginella specimens represent the first anatomically preserved Selaginellales with excellent internal cellular preservation in the fossil record, and are described as Selaginella quatsinoense Rothwell et Stockey sp. nov. Stems have three and five exarch, monarch stelar segments, each of which is surrounded by an aerenchymatous endodermis with trabeculae. The leaf base is indented on the adaxial surface, suggesting the position of a ligule. These fossils document that species with diagnostic internal anatomy of modern Lycopodiales and Selaginellales evolved no later than the Valanginian of the early Cretaceous.
The generic name Weissia Roth well and Taylor is determined to be a later homonym of Weissia Hedw... more The generic name Weissia Roth well and Taylor is determined to be a later homonym of Weissia Hedwig. Weissia Rothwell and Taylor is therefore renamed Weissistachys, and the appropriate name transfer is made for the type species, Weissistachys kentuckiensis (Rothwell et Taylor) comb. nov.
Review of Palaeobotany and Palynology, Sep 1, 1988
... Printed in The Netherlands A REINTERPRETATION OF THE PALEOZOIC FERN NORWOODIA ANGUSTUM CHARLE... more ... Printed in The Netherlands A REINTERPRETATION OF THE PALEOZOIC FERN NORWOODIA ANGUSTUM CHARLES W. GOOD and GAR W. ROTHWELL ... have been as-signed to the Coenopteridales on the basis of vegetative features (eg, Morgan and Delevor-yas, 1954). ...
Review of Palaeobotany and Palynology, Apr 1, 1982
... 1965), features used in the elucidation of taxonomic problems (Hoskins and Cross, 1946; Taylo... more ... 1965), features used in the elucidation of taxonomic problems (Hoskins and Cross, 1946; Taylor, 1965), ovule ontogeny (Rothwell, 1971, 1980 ... pollen chamber of Stephanospermum costatum is conspicuous (Plate I, 1). Histologically, it possesses a prominent outer wall that often ...
International Journal of Plant Sciences, May 1, 2000
Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryo... more Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryopteris tridentata, occur in coal balls collected at the Pittsburgh and Midway Coal Company mine near Baxter Springs, Kansas. Included are the first fertile specimens of the species, evidence of complete vegetative frond architecture, and fronds that are specialized for vegetative propagation. Rhizomes are erect and unbranched, have helical phyllotaxis and short internodes, and typically display an ectophloic solenostele. Fronds are tripinnately compound with lobed pinnules that have open, dichotomous venation. Fertile pinnae or individual pinnules are interspersed among vegetative frond segments and produce sori of annulate sporangia beneath veins on the abaxial pinnule surface. Fertile pinnule lobes are rolled toward the abaxial surface to enclose the sori. Sporangia have a horizontally elongated biseriate annulus located near the short broad stalk and produce tetrahedral-shaped trilete spores with coarse spines. Epiphyllous branches diverge from the stipe or rachis, and some fronds produce only branches. This fern is reconstructed as having short stems. Helically arranged fronds are either pinnately dissected with lobed vegetative pinnules and abaxially rolled fertile pinnules or are specialized for vegetative propagation. The latter functioned as the foliar equivalent of stolons. While some characters of the B. tridentata plant are similar to those of Botryopteris forensis, generitype of the Botryopteridaceae, others are more comparable to those of Psalixochlaena cylindrica, generitype of Psalixochlaenaceae, suggesting the need for reevaluation of systematic relationships among species of the Botryopteridaceae and Psalixochlaenaceae.
The monostelic seed fern Schopfiastrum decussatum Andrews is described from a specimen collected ... more The monostelic seed fern Schopfiastrum decussatum Andrews is described from a specimen collected at a Middle Pennsylvanian petrifaction locality in southern Illinois. The specimen measures 24 cm long and is about 1.1 cm in diameter. Two petioles are attached to the axis and abundant foliar material is also present. Leaf arrangement is alternate and distichous. The stem consists of an exarch protostele surrounded by a prominent zone of secondary xylem. Secondary phloem and a vascular cambium are also preserved. The cortex is characterized by an undulating outer epidermal zone consisting of alternating ridges and furrows; internally this zone is delimited by conspicuous lacunae. Sclerenchyma bands occur in the outer cortex, with prominent resin canals present in the inner cortex. The fronds are represented by dichotomizing rachides, primary pinnae, and laminar pinnules. Features of the plant are compared to those of other Carboniferous pteridosperms, and a reconstruction of Schopfiastrum is included.
The occurrence of permineralized stem fragments with diagnostic equisetophyte anatomy in Petrifie... more The occurrence of permineralized stem fragments with diagnostic equisetophyte anatomy in Petrified Forest National Park, east-central Arizona provides an opportunity to characterize the internal structure of a Late Triassic (Norian Stage) equisetophyte. Features of Equisetocaulis muirii gen. et sp. nov. constitute the first evidence for internal anatomy of a Triassic equisetophyte from the Northern Hemisphere. Anatomically preserved stem fragments occur in pyrite nodules and are revealed on etched surfaces of nodule wafers. Stems range 7-16 mm in diameter, with a large hollow pith and 24-40 cauline bundles, each with a distinct carinal canal and several rows of radially aligned secondary tracheids. Cauline bundles converge at nodes to produce a ring of tracheids within the nodal diaphragms. Leaf traces and branch bases occur at nodes on alternating radii. These features confirm a close relationship between at least one of the equisetophytes from the Chinle Formation and modern species, amplify our knowledge of equisetophyte organization during a crucial period in the evolution of the clade, and further refine our understanding of the sequence of structural changes leading to crown group Equisetum L.
... Line indicates level at which stalk in 4 was sectioned. 422D bot (c), 20 x 70. (a = appendage... more ... Line indicates level at which stalk in 4 was sectioned. 422D bot (c), 20 x 70. (a = appendage, ca = cone axis, w = sporangial wall.) Page 5. 1198 SUSAN D. RIGGS AND GAR W. ROTHWELL IT. 4 1 - 1 ? .. r .-,VjZ . . - t - 'I " 0 ;.. rr .. . ,. _.-... 4 , t - ' " IZ IV Vw Irv. ? 't 4? F4 ..0 ...
... 1, fig. 1) clearly demonstrates that the ovules described by Rothwell (1971) are not C. oblon... more ... 1, fig. 1) clearly demonstrates that the ovules described by Rothwell (1971) are not C. oblongum. ... cupule or at the tip of a stalk. Conostoma ob-longum may have been borne on the inner obliquewall of a cupulate branching system such as in Eurystoma angulare (Long, 1960). ...
A large collection of anatomically preserved marattialean stem and trunk segments from the Upper ... more A large collection of anatomically preserved marattialean stem and trunk segments from the Upper Pennsylvanian of Ohio provides the basis for detailed structural and taxonomic studies of several Psaronius species. Nineteen of the specimens form an intergrading ...
A rich fossil biota from a Pennsylvanian age deposit of eastern North America contains numerous v... more A rich fossil biota from a Pennsylvanian age deposit of eastern North America contains numerous vegetative and fertile specimens that conform to a single species of primitive walchian conifers. Among the specimens is a compound pollen cone that comprises closely spaced, helically arranged, leaf‐like bracts with axillary dwarf shoots. The specimen looks superficially similar to an ultimate vegetative conifer shoot, but there are small appendages in the axil of each bract that represent the fertile dwarf shoots. Dwarf shoots consist of an axis that bears sterile scales and sporophylls with erect pollen sacs. Pollen found in the sacs is monosaccate and conforms to the sporae dispersae genus Potonieisporites Bhardwaj. This cone is a compound shoot system that is morphologically equivalent to the ovulate cones of conifers and to the pollen cones of Paleozoic cordaitaleans and modern gnetophytes. Therefore, it is fundamentally different from the simple pollen cones of other fossil and modern conifers. Discovery of this specimen unexpectedly supports molecular studies that predict a close relationship between Coniferales and Gnetales, and provides fossil evidence to help reconcile the discordant phylogenetic hypotheses of seed plant systematics that have been developed from morphological and molecular data.
Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern a... more Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern are described from the middle Miocene Yakima Canyon flora of central Washington State, USA. Identification of the W. virginica fossils is based on a combination of vegetative pinnules, rhizome and stipe anatomy, and fertile pinnules with indusiate sori and sporangia like those of extant W. virginica. Fronds are isomorphic. Vegetative pinnae are elongated and pinnatifid, with a secondary vein paralleling the midvein. Secondary veins of the pinnule lobe anastomose to form primary areoles and are either simple or dichotomize toward the margin. Rhizomes have a simple dictyostele with 3-5 cauline vascular bundles and often a sclerotic hypodermis. Leaf traces contain two large adaxial vascular bundles that occur laterally and adaxially, flanking an arc of 4-6 smaller bundles. Fertile pinnules have linear sori that are somewhat embedded in the laminae and are enclosed by a thin indusium. Leptosporangia display a vertical annulus and an elongated stalk. A second fern, Wessiea yakimaensis gen. et sp. nov., is represented by anatomically preserved branching rhizomes and attached frond bases that conform to the Onoclea-type pattern of rhizome and frond-base vasculature. Rhizomes have a simple dictyostele of 4-5 cauline meristeles. Leaf divergence is helical, with paired hippocampiform rachial traces. These two ferns occur in the same matrix with specimens of Osmunda wehrii. They demonstrate that filicalean fern assemblages similar to those of extant temperate floras were well established in western North America by the middle Miocene and further emphasize the exceptional species longevity of some homosporous pteridophytes.
The Upper Pennsylvanian (Conemaugh Group) Duquesne Coal west of Steubenville, Ohio represents a d... more The Upper Pennsylvanian (Conemaugh Group) Duquesne Coal west of Steubenville, Ohio represents a deltaic peat-accumulating swamp, and is one of the best known of coal swamp floras. In a few places, the peat was infiltrated and permineralized by calcium carbonate prior to coalification, thus producing coal balls in which both morphological and anatomical structure of the constituent plant parts are preserved. The plant material represents primarily the community that inhabited the peat-accumulating environment, but some remains from near-swamp environments also are represented. The flora is relatively diverse, consisting of over 55 megafossil taxa of isolated organs that were produced by at least 25 species of plants. All five major groups of Pennsylvanian coal-swamp plants (i.e., Lycopsida, Sphenopsida, Pteridopsida, Pteridospermopsida and Cordaitales) are represented.
Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered amo... more Anatomically preserved lycophytes of the Lycopodiales and Selaginellales have been discovered among a diverse assemblage of plants and fungi in carbonate marine concretions at the Apple Bay locality along the shore of Holbert Inlet near the northern end of Vancouver Island, British Columbia, Canada. Lycopodialean stems are plectostelic and actinostelic, branch dichotomously, and are similar to both Lycopodicaulis oellgaardii and Lycoxylon spp. The Selaginella specimens represent the first anatomically preserved Selaginellales with excellent internal cellular preservation in the fossil record, and are described as Selaginella quatsinoense Rothwell et Stockey sp. nov. Stems have three and five exarch, monarch stelar segments, each of which is surrounded by an aerenchymatous endodermis with trabeculae. The leaf base is indented on the adaxial surface, suggesting the position of a ligule. These fossils document that species with diagnostic internal anatomy of modern Lycopodiales and Selaginellales evolved no later than the Valanginian of the early Cretaceous.
The generic name Weissia Roth well and Taylor is determined to be a later homonym of Weissia Hedw... more The generic name Weissia Roth well and Taylor is determined to be a later homonym of Weissia Hedwig. Weissia Rothwell and Taylor is therefore renamed Weissistachys, and the appropriate name transfer is made for the type species, Weissistachys kentuckiensis (Rothwell et Taylor) comb. nov.
Review of Palaeobotany and Palynology, Sep 1, 1988
... Printed in The Netherlands A REINTERPRETATION OF THE PALEOZOIC FERN NORWOODIA ANGUSTUM CHARLE... more ... Printed in The Netherlands A REINTERPRETATION OF THE PALEOZOIC FERN NORWOODIA ANGUSTUM CHARLES W. GOOD and GAR W. ROTHWELL ... have been as-signed to the Coenopteridales on the basis of vegetative features (eg, Morgan and Delevor-yas, 1954). ...
Review of Palaeobotany and Palynology, Apr 1, 1982
... 1965), features used in the elucidation of taxonomic problems (Hoskins and Cross, 1946; Taylo... more ... 1965), features used in the elucidation of taxonomic problems (Hoskins and Cross, 1946; Taylor, 1965), ovule ontogeny (Rothwell, 1971, 1980 ... pollen chamber of Stephanospermum costatum is conspicuous (Plate I, 1). Histologically, it possesses a prominent outer wall that often ...
International Journal of Plant Sciences, May 1, 2000
Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryo... more Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryopteris tridentata, occur in coal balls collected at the Pittsburgh and Midway Coal Company mine near Baxter Springs, Kansas. Included are the first fertile specimens of the species, evidence of complete vegetative frond architecture, and fronds that are specialized for vegetative propagation. Rhizomes are erect and unbranched, have helical phyllotaxis and short internodes, and typically display an ectophloic solenostele. Fronds are tripinnately compound with lobed pinnules that have open, dichotomous venation. Fertile pinnae or individual pinnules are interspersed among vegetative frond segments and produce sori of annulate sporangia beneath veins on the abaxial pinnule surface. Fertile pinnule lobes are rolled toward the abaxial surface to enclose the sori. Sporangia have a horizontally elongated biseriate annulus located near the short broad stalk and produce tetrahedral-shaped trilete spores with coarse spines. Epiphyllous branches diverge from the stipe or rachis, and some fronds produce only branches. This fern is reconstructed as having short stems. Helically arranged fronds are either pinnately dissected with lobed vegetative pinnules and abaxially rolled fertile pinnules or are specialized for vegetative propagation. The latter functioned as the foliar equivalent of stolons. While some characters of the B. tridentata plant are similar to those of Botryopteris forensis, generitype of the Botryopteridaceae, others are more comparable to those of Psalixochlaena cylindrica, generitype of Psalixochlaenaceae, suggesting the need for reevaluation of systematic relationships among species of the Botryopteridaceae and Psalixochlaenaceae.
The monostelic seed fern Schopfiastrum decussatum Andrews is described from a specimen collected ... more The monostelic seed fern Schopfiastrum decussatum Andrews is described from a specimen collected at a Middle Pennsylvanian petrifaction locality in southern Illinois. The specimen measures 24 cm long and is about 1.1 cm in diameter. Two petioles are attached to the axis and abundant foliar material is also present. Leaf arrangement is alternate and distichous. The stem consists of an exarch protostele surrounded by a prominent zone of secondary xylem. Secondary phloem and a vascular cambium are also preserved. The cortex is characterized by an undulating outer epidermal zone consisting of alternating ridges and furrows; internally this zone is delimited by conspicuous lacunae. Sclerenchyma bands occur in the outer cortex, with prominent resin canals present in the inner cortex. The fronds are represented by dichotomizing rachides, primary pinnae, and laminar pinnules. Features of the plant are compared to those of other Carboniferous pteridosperms, and a reconstruction of Schopfiastrum is included.
The occurrence of permineralized stem fragments with diagnostic equisetophyte anatomy in Petrifie... more The occurrence of permineralized stem fragments with diagnostic equisetophyte anatomy in Petrified Forest National Park, east-central Arizona provides an opportunity to characterize the internal structure of a Late Triassic (Norian Stage) equisetophyte. Features of Equisetocaulis muirii gen. et sp. nov. constitute the first evidence for internal anatomy of a Triassic equisetophyte from the Northern Hemisphere. Anatomically preserved stem fragments occur in pyrite nodules and are revealed on etched surfaces of nodule wafers. Stems range 7-16 mm in diameter, with a large hollow pith and 24-40 cauline bundles, each with a distinct carinal canal and several rows of radially aligned secondary tracheids. Cauline bundles converge at nodes to produce a ring of tracheids within the nodal diaphragms. Leaf traces and branch bases occur at nodes on alternating radii. These features confirm a close relationship between at least one of the equisetophytes from the Chinle Formation and modern species, amplify our knowledge of equisetophyte organization during a crucial period in the evolution of the clade, and further refine our understanding of the sequence of structural changes leading to crown group Equisetum L.
... Line indicates level at which stalk in 4 was sectioned. 422D bot (c), 20 x 70. (a = appendage... more ... Line indicates level at which stalk in 4 was sectioned. 422D bot (c), 20 x 70. (a = appendage, ca = cone axis, w = sporangial wall.) Page 5. 1198 SUSAN D. RIGGS AND GAR W. ROTHWELL IT. 4 1 - 1 ? .. r .-,VjZ . . - t - 'I " 0 ;.. rr .. . ,. _.-... 4 , t - ' " IZ IV Vw Irv. ? 't 4? F4 ..0 ...
... 1, fig. 1) clearly demonstrates that the ovules described by Rothwell (1971) are not C. oblon... more ... 1, fig. 1) clearly demonstrates that the ovules described by Rothwell (1971) are not C. oblongum. ... cupule or at the tip of a stalk. Conostoma ob-longum may have been borne on the inner obliquewall of a cupulate branching system such as in Eurystoma angulare (Long, 1960). ...
A large collection of anatomically preserved marattialean stem and trunk segments from the Upper ... more A large collection of anatomically preserved marattialean stem and trunk segments from the Upper Pennsylvanian of Ohio provides the basis for detailed structural and taxonomic studies of several Psaronius species. Nineteen of the specimens form an intergrading ...
A rich fossil biota from a Pennsylvanian age deposit of eastern North America contains numerous v... more A rich fossil biota from a Pennsylvanian age deposit of eastern North America contains numerous vegetative and fertile specimens that conform to a single species of primitive walchian conifers. Among the specimens is a compound pollen cone that comprises closely spaced, helically arranged, leaf‐like bracts with axillary dwarf shoots. The specimen looks superficially similar to an ultimate vegetative conifer shoot, but there are small appendages in the axil of each bract that represent the fertile dwarf shoots. Dwarf shoots consist of an axis that bears sterile scales and sporophylls with erect pollen sacs. Pollen found in the sacs is monosaccate and conforms to the sporae dispersae genus Potonieisporites Bhardwaj. This cone is a compound shoot system that is morphologically equivalent to the ovulate cones of conifers and to the pollen cones of Paleozoic cordaitaleans and modern gnetophytes. Therefore, it is fundamentally different from the simple pollen cones of other fossil and modern conifers. Discovery of this specimen unexpectedly supports molecular studies that predict a close relationship between Coniferales and Gnetales, and provides fossil evidence to help reconcile the discordant phylogenetic hypotheses of seed plant systematics that have been developed from morphological and molecular data.
Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern a... more Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recognized onocleoid fern are described from the middle Miocene Yakima Canyon flora of central Washington State, USA. Identification of the W. virginica fossils is based on a combination of vegetative pinnules, rhizome and stipe anatomy, and fertile pinnules with indusiate sori and sporangia like those of extant W. virginica. Fronds are isomorphic. Vegetative pinnae are elongated and pinnatifid, with a secondary vein paralleling the midvein. Secondary veins of the pinnule lobe anastomose to form primary areoles and are either simple or dichotomize toward the margin. Rhizomes have a simple dictyostele with 3-5 cauline vascular bundles and often a sclerotic hypodermis. Leaf traces contain two large adaxial vascular bundles that occur laterally and adaxially, flanking an arc of 4-6 smaller bundles. Fertile pinnules have linear sori that are somewhat embedded in the laminae and are enclosed by a thin indusium. Leptosporangia display a vertical annulus and an elongated stalk. A second fern, Wessiea yakimaensis gen. et sp. nov., is represented by anatomically preserved branching rhizomes and attached frond bases that conform to the Onoclea-type pattern of rhizome and frond-base vasculature. Rhizomes have a simple dictyostele of 4-5 cauline meristeles. Leaf divergence is helical, with paired hippocampiform rachial traces. These two ferns occur in the same matrix with specimens of Osmunda wehrii. They demonstrate that filicalean fern assemblages similar to those of extant temperate floras were well established in western North America by the middle Miocene and further emphasize the exceptional species longevity of some homosporous pteridophytes.
The Upper Pennsylvanian (Conemaugh Group) Duquesne Coal west of Steubenville, Ohio represents a d... more The Upper Pennsylvanian (Conemaugh Group) Duquesne Coal west of Steubenville, Ohio represents a deltaic peat-accumulating swamp, and is one of the best known of coal swamp floras. In a few places, the peat was infiltrated and permineralized by calcium carbonate prior to coalification, thus producing coal balls in which both morphological and anatomical structure of the constituent plant parts are preserved. The plant material represents primarily the community that inhabited the peat-accumulating environment, but some remains from near-swamp environments also are represented. The flora is relatively diverse, consisting of over 55 megafossil taxa of isolated organs that were produced by at least 25 species of plants. All five major groups of Pennsylvanian coal-swamp plants (i.e., Lycopsida, Sphenopsida, Pteridopsida, Pteridospermopsida and Cordaitales) are represented.
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