Bowmanites pseudoaquensis, Libertín & Bek & Drábková, 2008

Libertín, Milan, Bek, Jiří & Drábková, Jana, 2008, Two new Carboniferous fertile sphenophylls and their spores from the Czech Republic, Acta Palaeontologica Polonica 53 (4), pp. 723-732 : 725

Bowmanites pseudoaquensis sp. nov.

Figs. 4–6 .

1998 Sphenophyllostachys aquensis (Remy) Boureau 1964 ; Bek 1998:

87–90, pl. 83. 1998 Sphenophyllostachys aquensis (Remy) Boureau 1964 ; Bek and

Opluštil 1998: 149–150, pl. 4: 8–10. Etymology: The morphology of the holotype closely resembles cones of Sphenophyllostachys aquensis . Holotype: NMP−E 6124. Type locality: Ovčín opencast mine, near Radnice , Radnice Basin , Czech Republic. Type horizon: Base of the Whetstone volcanic horizon, directly overlying the Lower Radnice Coal , Radnice Member , Kladno Formation , the Radnice Basin , lower Bolsovian, Pennsylvanian; Carboniferous.

Material.— Holotype (NMP−E 6124), and specimen NMP−E 6293 from Ovčín opencast mine, Radnice Basin.

Diagnosis.—Twelve lanceolate leaves per whorl. Tips of leaves pointed. Circular sporangia, sterile bracts arch−like bend apically. Subcircular to circular trilete spores. Thick−walled exine laevigate to finely scabrate.

Description.—Stems are monopodially branched, 1–2 mm wide with internodes 2–8 mm long and 1–3 mm wide ( Fig. 6A, B, D ). Leaves are 4–8 mm with narrow lanceolate margins ( Fig. 6 C ) and arranged in whorls ( Fig. 4A, B 2 ). Cones are 200 mm long and 4–5 mm wide and possess an apex with sterile leaves. Circular sporangia are about 1.5– 2 mm in diameter ( Figs. 4A 3 , 5A, G , 6E ). Sporangia occur between the axis of the cone and sterile bract on reduced sporangiophores ( Fig. 5A, G ). The surface of sporangia is finely rugose. Sterile bracts are hook−shaped; the apical margins are slightly wider at the end with rounded tips. Sterile stems are 1.0–2.5 mm in diameter.

Trilete spores are 110(121)150 µm in diameter ( Fig. 5B–F ). Circular to subcircular amb, simple laesurae, 1/2–2/3 of the radius. Exine laevigate to finely scabrate at the proximal contact area, 5–9 µm thick ( Fig. 5B–F ).

Remarks.—All the spores are closely similar and can be identified as Punctatisporites cf. obesus because the sculpture of the exine is sometimes very finely scabrate ( Fig. 5E, F ) and not laevigate as given in original diagnosis of P. obesus ( Potonié and Kremp 1954) .

Stratigraphic and geographic range.—Radnice Member, Kladno Formation, Lower Bolsovian, Radnice Basin, Czech Republic.

Figures

Fig. 4. Carboniferous (Bolsovian) fertile sphenophyll Bowmanites pseudoaquensis sp. nov., Ovčín opencast mine, Radnice Basin, Kladno Formation, Radnice Member. A. NMP−E 6123, general view of sterile stems with leaves arranged in verticils (A1); detail showing lanceolate leaves (A2); detail of nine lanceolate leaves arranged in verticils (A3). B. NMP−E 6124; cone with sterile apex (B1); detail of leafy stem (B2).

Fig. 5. Carboniferous (Bolsovian) fertile sphenophyll Bowmanites pseudoaquensis sp. nov., NMP−E 6124, Ovčín opencast mine, Radnice Basin, Kladno Formation, Radnice Member (A, G) and their spores of of Punctatisporites obesus−type (B–F). A. Detail showing the position of sporangia. Note that one sporangium occurs per sporangiophore between the sterile bract and the axis of a cone. B, D. Spores of Punctatisporites obesus−type; distal surfaces, SEM micrographs. C, E, F. Spore of Punctatisporites obesus−type. Proximal views. Note finely scabrate sculpture on the proximal surface (E, F) and slightly developed labrum. G. Detail of sub−terminally located sporangium on shortened sporangiophore.

Fig. 6. Carboniferous (Bolsovian) fertile sphenophyll Bowmanites pseudoaquensis sp. nov., NMP−E 6358, holotype, Ovčín opencast mine, Radnice Basin, Kladno Formation, Radnice Member. A. General view of the holotype showing sterile axis, leaves and several cones. B. Leaves on the central axis. C. Detail of the leaf tips. D. Leaves on the central axis. E. Terminal position of the cone.

Fig. 2. Carboniferous (Bolsovian) fertile sphenophyll Bowmanites brasensis sp. nov., NMP−E 6352, Matylda Mine, Břasy, Radnice Basin, Kladno Formation, Radnice Member. A. Stem with leaves divided twice and three times. B. Cone and stem. C. Monopodially branched stem with leaves. D. Detail of twice divided leaves. E. Monopodially branched stem with leaves arranged in verticils.

Fig. 3. Carboniferous (Bolsovian) fertile sphenophyll Bowmanites brasensis sp. nov., WBMP−F 03760 Matylda Mine, Břasy, Radnice Basin, Kladno Formation, Radnice Member. A. General view of the cone. B. Detail showing the position of sporangia with in situ spores (arrows) on the sporangiophore. C. Detail of in situ spores (arrows) in sporangia. Note the length of the sporangiophore. D. Position of sporangia between sterile bracts and the axis of a cone. E. Central body of a spore of Punctatisporites obesus−type; lateral view. F, G. Central bodies of spores of Punctatisporites obesus−type. Note the trilete mark and labrum. H. Central body of a spore of Punctatisporites obesus−type; distal view. I. Spore with exospore assigned to the dispersed species Punctatisporites obesus (Loose) Potonié and Kremp, 1954; proximal view.