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A new miospore genus Ductilispora is described to accommodate simple acamerate miospores, …


Biology Articles » Paleobiology » Micropaleobiology » Some trilete spores from Lower Carboniferous strata of the Rio Blanco Basin, western Argentina » Systematic paleontology

Systematic paleontology
- Some trilete spores from Lower Carboniferous strata of the Rio Blanco Basin, western Argentina

Anteturma P ROXIMEGERMINATES R. Potonié 1970
Turma T RILETES Reinsch emend . Dettmann 1963
Suprasubturma A CAVATITRILETES Dettmann 1963
Subturma A ZONOTRILETES Luber emend . Dettmann 1963
Infraturma M URORNATI Potonié and Kremp 1954

Genus Ductilispora gen. nov.

Type species. Ductilispora circularis sp. nov.

Diagnosis. Spores radial, trilete, acavate. Amb subcircular to roundly subtriangular or triangular with convex or straight sides. Laesurae straight, simple or with slight lip development, length at least one-half of spore radius. Proximal face with reduced sculpture or laevigate. Distal face sculptured with folds like muri or thickenings of regular or irregular arrangement, infrequently branched or anastomosed.
Derivation of name. From the latin ductilis , easily deformable.
Comparison. Plicatispora Higgs et al . 1988 is characterised by a distal face sculptured with folds, and fine muri, but is distinguishable from Ductilispora gen. nov. in having laesurae extending almost to the spore margin and terminating into curvaturae. Amicosporites Cramer 1966, from the Upper Silurian of Spain, has a distal circular ridge, but differs by the fairly regular thickening, constantly annular. Knoxisporites Potonié and Kremp 1954 resembles the new taxon in having distal thickenings, but this genus was originally defined with a characteristic more o less uniform cingulum. Camptotriletes Naumova 1939 is distinguishable from Ductilispora gen. nov. by its sculpture with irregular and rather shapeless ridges of uneven irregular height (rudimentary cristae) or randomly placed welts that in part branch, and grade into rudimentary cristae.

Ductilispora circularis sp. nov.
Figures 1.A-F

Holotype. BA Pal 5406: T39/3, figures 1.A-B.

Diagnosis. Spores radial, trilete. Amb subcircular to suboval. Laesurae straight, with slight lip development; length at least three-quarters of spore radius. Distal face coarsely sculptured with a prominent ring-like thickening, more or less continuous (4-6 µm wide), fairly irregular in form, approximately conformable with amb. The thickened and unthickened exine is laevigate, 1.5-2 µm thick.
Dimensions. 38(55)65 µm (14 specimens).
Type locality and horizon. La Cortadera Creek, San Juan province, Argentina. Malimán Formation, Lower Carboniferous.
Distribution. Malimán and Cortaderas Formation, Lower Carboniferous.
Derivation of name. From latin circularis , of circular shape.
Comparison. Amicosporites splendidus , as described by Cramer (1966) from the Upper Silurian and Devonian of Spain, shows some resemblance to Ductilispora circularis sp. nov., but differs in having more regular annular ridges, laesurae extending to margin, thinner exine and amb rounded triangular. Ductilispora circularis sp. nov. resembles Knoxisporites ruhlandii Doubinger and Rauscher 1966, K . sp. cf. K . ruhlandii in Playford 1971 and K . stephanephorus Love 1960, but is distinguishable by lacking a cingulum. Moreover, K. ruhlandii and K. sp. cf. K . ruhlandii have a rounded boss-like exinal elevation of the distal polar region. On the other hand, K . stephanephorus , a species that is well known from Visean-Lower Namurian sediments of Britain and U.S.A., has two thickened rings equatorially, with interrradial connections, a thickened region on the distal pole and lips that broaden towards the equator. Dillspora disjunta (Neville in Neves et al ., 1973) Neville 1989 differs in having distal thickened polar boss and subpolar thickened ring, both of which may be variably developed, and an equatorial extension of the exine which is widest interradially, being reduced or absent at the apices.

Ductilispora longitudinalis sp. nov.
Figures 1.G-L

Holotype. BA Pal 5405: W39/0, figures 1.G-H.

Diagnosis. Spores radial, trilete. Amb subcircular to suboval. Laesurae straight, with slight lip development; length at least three-quarters of spore radius. Distal face bearing one, more o less regularly disposed, transverse, central muri or thickening (2-4.5 µm wide al base, 3-7 µm high), length c. three-quarters of the spore radius, usually straight but sometimes strongly curved. Non-murornate exine laevigate to infragranulate, 1.5-2 µm thick.
Dimensions. Equatorial diameter 41(55)78 µm (23 specimens).
Type locality and horizon. La Cortadera Creek, San Juan province, Argentina. Malimán Formation, Lower Carboniferous.
Distribution. Malimán and Cortaderas Formation, Lower Carboniferous.
Derivation of name. From latin longitudinalis , relative to the length.
Comparison. Knoxisporites pristicus Sullivan 1968 is the most similar species, but this Tournaisian species differs in having ill defined thickening and a perceptible cingulum. Knoxisporites dissidius Neves 1961 is characterised by a hexagonal tendency of the equatorial outline, the slightly discordant fleshy cingulum and the pattern of distal thickenings.

Ductilispora corrugata sp. nov.
Figures 1.M-O

Holotype. BA Pal 5789: M 45/4, figures 1.M-N.

Diagnosis. Spores radial, trilete. Amb circular to subcircular. Laesurae straight, simple, extending to or almost to equator. Distal face sculptured with loosely distributed, smooth, rounded and low muri or thickenings infrequently branched and irregularly vermiculate (2-3 µm wide) and not closely packed overlapping. The thickened and unthickened exine is laevigate, 1.5-2.5 µm thick.
Dimensions. 48(58)70 µm (16 specimens).
Type locality and horizon. La Cortadera Creek, western San Juan province, Argentina. Cortaderas Formation, Lower Carboniferous.
Distribution. Cortaderas Formation, Lower Carboniferous.
Derivation of name. From latin corrugatus , corrugated, crumpled irregularly.
Comparison. Convolutispora superficialis , described by Felix and Burbridge (1967) from the Upper Mississippian to Lower Pennsylvanian of southern Oklahoma, resemblances Ductilispora corrugata sp. nov. However it is distinguishable by having indistinctly defined sculpture, forming weak convolutions; the elevated portions are broad with little sinuosity or ramification evident, weakly delimited lumina usually elongated, slight lips development and a thicker exine. Convolutispora vermiformis Hughes and Playford 1961 from the Late Devonian and Visean-Namurian has more coarsely lophate to lophoreticulate ridges, 4-12 µm in basal diameter and 4-6 µm high. D . corrugata sp. nov. is not included in the genus Convolutispora because its sculpture is irregularly vermiculate and not closely packed overlapping anastomosing. Knoxisporites literatus (Waltz) Playford 1963, differs by having a cingulum and distal surface bearing a few, coarse, irregular or regularly disposed muri enclosing broad lumina.

Infraturma A PICULATI Bennie y Kidston emend . Potonié 1956
Subinfraturma V ERRUCATI Dybová and Jachowicz 1957

Genus Verrucosisporites Ibrahim emend . Smith 1971

Type species. Verrucosisporites verrucosus Ibrahim 1933.

Verrucosisporites cortaderensis sp. nov.
Figures 1.P-S

Holotype. BA Pal 5756: Y: 47/0, figure 1.P.

Diagnosis. Spores radial, trilete; concave-convex. Amb circular to subcircular, margin modified due to projection of sculptural elements. Laesurae straight, simple, length to or almost the equator. Distal face convex densely and uniformly sculptured with verrucae that are broadly rounded or flattened in cross section and subcircular to irregular in basal outline [0.8(2-3) 7µm wide at base, 1(1-2) 5 µm high]. Subordinate coni, rounded or with sharp apices, and grana (1-2 µm broad and high) are present in variable proportion among specimens. Proximal face concave, with reduced sculpture. Exine between sculpture laevigate.
Dimensions. 50(70)87 µm (39 specimens).
Type locality and horizon. La Cortadera Creek, San Juan province, Argentina. Cortaderas Formation, Lower Carboniferous.
Distribution. Malimán and Cortaderas Formation, Lower Carboniferous.
Derivation of name. From Cortaderas Formation, the stratigraphic unit where this species is more abundant.
Comparison. Verrucosisporites morulatus (Knox) Smith and Butterworth 1967 is similar in having small proportion of conate, baculate and pilate sculptural elements, but differs by having originally spherical shape and the relatively loosely distributed sculptural elements. Verrucosisporites grandis McGregor 1960 is characterized by the sculpture with tendency towards biform elements at the equator and its bigger diameter. Verrucosisporites baccatus Staplin 1960 has irregularly disposed only grana and verrucae and is not concave-convex. Verrucosisporites cerosus (Hoffmeister, Staplin and Malloy) Butterworth and Williams 1958 is distinguishable by its sculpture including a proportion of pila which can only be seen at the margin.

Subinfraturma N ODATI Dybová and Jachowicz 1957

Genus Dibolisporites Richardson emend . Playford 1976

Type species. Dibolisporites echinaceus (Eisenack) Richardon 1965.

Dibolisporites malimanensis sp. nov.
Figure 1.T and figures 2.A-C

Holotype. BA Pal 5401: V40/4, figures 2.A-B.

Diagnosis. Spores radial, trilete. Amb circular to subcircular. Laesurae straight, with membranous lips, extending to or almost to equator. Proximal face is rarely discernible, frequently missing or ruptured, when present is hyaline and psilate. Distal face and equatorial regions sculptured with biform elements, each element is compound of coni with rounded apices (0.8-4 µm in basal diameter, 1-3 high µm), subpolygonales in plan view, surmounted by a simple, bifurcate, trifurcate or multifurcate short spine (0.5-1.2 high µm). The proportion of different elements varies considerably between specimens. Sculptural elements discrete and separated by areas 0.2-0.5 µm wide. Exine about 0.5 µm thick.
Dimensions. Equatorial diameter 35(46)73 µm (87 specimens).
Type locality and horizon. La Cortadera Creek, San Juan province, Argentina. Malimán Formation, Lower Carboniferous.
Distribution. Malimán and Cortaderas Formation, Lower Carboniferous.
Derivation of name. From Malimán Formation, the stratigraphic unit where this species is more abundant.
Comparison. The Late Carboniferous and Early Permian species, Dibolisporites disfacies Jones and Truswell 1992, differs from Dibolisporites malimanensis sp. nov. in being more regularly sculptured with biform elements composed of verrucae. Dibolisporites microspicatus Playford 1978 has lesser diverse sculpture, made by densely distributed biform elements of approximately hemispherical verrucae or grana surmounted by one (very rarely two) minute spines, and frequently coalescent in sinuous uniserial lines of up to 10 elements, or in groups of 3 or 4 elements and a thicker exine (1.3-1.8 µm). Dibolisporites confertus as described by Turnau and Jakubowska (1989), from the Early Devonian of central Poland, is similar to Dibolisporites malimanensis sp. nov., in having an ornament of densely set mammillate biform elements with often polygonal bases. However, the Polish species has more regular elements that rapidly taper and are surmounted by a very narrow spine. Verrucosisporites poligonalis Lanninger 1968 (p. 128, pl. 22-19) is ornamented by polygonal verrucae. Verrucosisporites ? Polygonalis Lanninger (in McGregor, 1973, p. 37-38, pl. 4-16, 17, 19, 25 and 26) is similar to Dibolisporites malimanensis sp. nov. in having biform elements but differs in the uniform sculpture.

Suprasubturma L AMINATITRILETES Smith and Butterworth 1967
Subturma Z ONOLAMINATITRILETES Smith and Butterworth 1967
Infraturma C INGULICAVATI Smith and Butterworth 1967

Genus Indotriradites (Tiwari) Foster 1979

Type species. Indotriradites korbaensis Tiwari 1964.

Indotriradites variabilis sp. nov.
Figures 2.D-H

1987 Hymenozonotriletes pseudoreticulatus Azcuy and Ottone, plate 2, figure 1.
1993 Hymenozonotriletes pseudoreticulatus Césari and Limarino, plate 1, figure 10.
1995 Hymenozonotriletes verrucosus Césari and Limarino, plate 1, figure 10.
1996 Grandispora pseudoreticulatus Ottone, plate 3, figure 3.
1996 Grandispora pseudoreticulatus Ottone and Rosello, plate 1, figure 12.

Holotype. BA Pal 5409: L51/1, figures 2.E-F (originally illustrated by Césari and Limarino, 1995, plate 1, figure 10).

Diagnosis. Spores radial, trilete, cavate, zonate. Amb subtriangular with convex sides and rounded apices, occasionally subcircular. Laesurae straight to slightly sinuous, with lips lenght to or almost to equatorial margin or in some instances to the flange margin as slender folding, 2-4.5 µm high. Proximal face laevigate. Central body distally sculptured with basally fused, simple and biform coni and spine, 2-7 µm µm high and 1.5-3 µm in basal diameter, often basally coalescent to produce a roughly reticulate appearance in some specimens, but it is a variable character between specimens. Equatorial flange about 1/5-1/6 of spore radius, having fairly uniform width on same specimen, outer margin irregularly dentate due to projecting of coni, 1-2 µm broad basally and long. Zone usually sculptured with minute cone and spinae.
Dimensions. Equatorial diameter 96(118)180 µm, diameter central body 55(71)105 µm (46 specimens).
Type locality and horizon. La Cortadera Creek, San Juan province, Argentina. Malimán Formation, Lower Carboniferous.
Distribution. This species, described originally from late Givetian-Early Frasnian age from Argentina (Ottone, 1996), has been subsequently reported from late Givetian-Early Frasnian age from Bolivia (Ottone and Rossello, 1996) and Early Carboniferous from Bolivia (Azcuy and Ottone, 1987), Malimán and Cortaderas Formation.
Derivation of name. From latin variabilis , that varies or can vary.
Comparison. In seeking an appropriate generic assignment of the studied specimens, several possibilities were analised. Kraeuselisporites as redefined by Scheuring (1974) is invariably acavate. Cristatisporites (Potonie and Kremp) Butterworth et al . 1964 has cristate, often biform sculpture and a cingulizona. Indotriradites as originally defined (Tiwari, 1964), subsequently enmended by Foster, 1979 and following other authors as Loboziak et al . (1999), is cavate (intexinal layer separated, at least distally and equatorially, from exoexine by a broad or narrow cavum), with the exoexine extended equatorially in a zona and bearing distal sculpturae. Therefore, the species here described is undoubtedly assignable to Indotriradites .
Hymenozonotriletes pseudoreticulatus , which was described by Menéndez and Pöthe de Baldis (1967) from the Middle Devonian of the Picuiba 1 boring of Paraguay, shows closest resemblance with Indotriradites variabilis sp. nov. However, that species was originally considered as acavate and characterized by a central body sculptured by concentric irregular ridges, partly anastomosed producing a roughly reticulate appearance. Taking into account that I. Malimanensis is cavate, with the distal sculpture usually discrete and that all the original material of H. Pseudoreticulatus is lost, a new specific taxon is here proposed.
Nevertheless, some specimens from southern Devonian-Lower Carboniferous sequences, which are very similar to the ones here described, were referred to H. pseudoreticulatus (Azcuy and Ottone, 1987; Ottone and Rosello, 1996; Ottone, 1996). Some of that material could be examined and indeed resembles Cortaderas and Malimán´s specimens. Ottone (1996) transferred H. pseudoreticulatus to the genus Grandispora , but this combination is here considered unsuitable. Grandispora , according to the emendation of McGregor 1973, and the usual use by several authors (Playford, 1991; Loboziak et al ., 1999; Higgs et al ., 2000, among others), includes cavate spores, with exoexine predominantly sculptured on all the distal face, which may also extend onto equatorial portions of the proximal surface. However, some species with a distinctive flange and sculpture located mainly on the central body have been included in this genus, for example, G. Macrotuberculata (Arkangelskaya) McGregor 1973, which do not fit within the original generic diagnosis.
Among the known species of Indotriradites , I . Dolianitii Loboziak et al. 1999 has smaller diameter, larger and closer spaced elements on or around the inner margin of zona and faint radial plication on the zona. Indotriradites daemonii Loboziak et al . 1999 differs by having smaller sculpture and dense radial plication on zona.


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