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Systematic revision of the genus Styx Norton et Hall, 1967
Review of Palaeobotany and Palynology
Elsevier Publishing Company, Amsterdam Printed in The Netherlands
SYSTEMATIC REVISION OF T H E G E N U S S T Y X N O R T O N ET HALL, 1967 SATISH K. SRIVASTAVA
Chevron Oil Field Research Company, La Habra, Calif. (U.S.A.) (Received June 18, 1970) (Revised December 9, 1970)
SUMMARY
The genus Styx NORTON et HALL was based on an incomplete specimen. Its diagnosis is revised and emended here on the basis of complete and well preserved specimens. In its revised generic circumscription, Styx accommodates trilete megaspores with striate and/or reticulate exospore and three acrolamellae. It is distinct from Balmeisporites COOKSONet DETTMANNin lacking equatorial exoexinal outgrowths. The type-species Styx bella (KoNDINSKAYA) n. comb. is described in detail as revealed by stereoscan and light microscopes. The exospore of these megaspores appears to be three-layered rather than two-layered. The distribution of S. bella is given and its stratigraphical and paleoecological significance discussed. INTRODUCTION
COOKSON and DETTMANN (1958) instituted the genus Balmeisporites for acrolamellate megaspores with three equatorially situated equidistant reticulate outgrowths of the exoexine. KONDINSKAYA (1966) reported several acrolamellate megaspores with striate exospore from the Upper Cretaceous and Paleogene deposits of the west Siberian lowlands, and assigned them to the genus Balmeisporites COOKSONet DETTMANN, 1958. However, these Siberian megaspores do not have the equatorial exoexinal outgrowths. SRIVASTAVA and BINDA (1969) recovered several megaspores, similar to the above mentioned Siberian megaspores, from the Maastrichtian deposits of Alberta and Saskatchewan in Canada. They noticed the emphasis laid, in the generic diagnosis of Balmeisporites, on the presence of "three equidistant reticulate equatorial outgrowths of the exoexine", but felt it characteristic at the specific level only, rather than at the generic level. They followed KONDINSKAYA (1966) and assigned the Canadian acrolamellate striate megaspores to the genus Balmeisporites. Meanwhile, NORTON and HALL (1967) instituted the genus Styx to accommodate similar striate megaspores. The description of the genus Styx is Rev. Palaeobotan. Palynol., 11 (1971) 297-309
297
based on incomplete specimens, consequently the presence of acrolamellae was not mentioned in the original diagnosis. Recently the writer examined a few Australian specimens of Balmeisporites holodictyus to compare them with the Canadian and Siberian acrolamellate megaspores having a striate exoexine. The wing-like equatorial exoexinal outgrowths appear to be a convincingly generic characteristic of Balmeisporites as originally diagnosed by COOKSON and DETTMANN (1958) rather than a specific one as proposed by SRIVASTAVAand BINDA (1969). Thus megaspores without equatorial exoexinal outgrowths are not properly included in Balmeisporites. The erroneous captions and references to the figures of type-species in the original description (NORTON and HALL, 1967) were subsequently corrected by NORTON and HALL (1969). However, the type-species Styx minor NORTON, in: NORTON et HALL, 1967, is a junior synonym ofBalmeisporites bellus KONDINSKAYA, 1966. In the present paper, the generic diagnosis of Styx is revised on the basis of complete specimens and the type-species as revealed by stereoscan microscope is redescribed.
SYSTEMATICDESCRIPTION Genus Styx NORTON et HALL emend.
Balmeisporites bellus KONDINSKAYA,1966, p.119, p[.III, 3 (Fig.1 in the present paper) Styx NORTONet HALL 1967, p.104 Styx minor NORTON, 1967, in: NORTONet HALL, 1967, p.104, pl.I, C (non B) Type species. Styx minor NORTON, 1967 = Styx bella (KONDINSKAYA) n. comb.
Emended diagnosis. Megaspores trilete; acrolamellate, acrolamellae three, proximal; exoexine reticulate and/or striate; muri of variable length and breadth, anastomosing into various patterns; supratectal processes on exoexine echinate, echinae shape variable.
Remarks. Three acrolamellae in Styx distinguish it from the genus Arcellites MINER emend. ELLIS et TSCHUDY which has six acrolamellae. Although both Styx and Balmeisporites have three acrolamellae, Styx is distinct from Balmeisporites in lacking the equatorial exoexinal outgrowths. NORTON and HALL (1967) proposed the genus Styx to accommodate perinate trilete megaspores with echinate supratectal processes on the exospore. They did not mention the presence of acrolamellae on these megaspores. The illustrations of Styx minor and S. major (NORTON and HALL, 1967, pl. 1 C, B) indicate that Styx is acrolamellate and the generic diagnosis and specific descriptions are based on 298
Rev. Palaeobotan. Palynol., 11 (1971) 297-309
Fig.l. Styx bella (Balmeisporites belhts KONDINSKAYA), reproduction of the illustration of the type species from the original publication by KONDINSKAYA(1966, pHI1, 3).
incomplete specimens. The acrolamellate nature o f Styx minor is c o r r o b o r a t e d by its strong morphological resemblance to the megaspores described by KONDINSKAYA (1966) and by SRIVASTAVAand BINDA (1969) as Balmeisporites bellus, and by OLTZ (1969) as S t y x minor. Thus S t y x minor is a junior s y n o n y m o f Balmeisporites bellus KONDINSKAYA, 1966, which is here transferred to the genus S t y x NORTON et HALL emend. KONDINSKAYA (1966) distinguished several species a m o n g striate acrolamellate megaspores on the basis o f minor differences in the striate sculpturing on the exospore. Ultimately, such m i n o r differences m a y not prove to be o f any consequence. However, until more data is available, these species have been recognized as distinguished by KOND1NSKAYA (1966) and are transferred here to the genus Styx NORTON et HALL emend.
Styx diversispinulata (KONDINSKAYA)n. comb. Bahneisporites diversispinulatus KONDINSKAYA,1966, p.117, pl.I, 1 Styx longirimosa (KONDINSKAYA)n. comb. Balmeisporites Iongirimosus KONDINSKAYA, 1966, p. ll 9, pl.III, 2 Styx r a T a (KONDINSKAYA)n. comb. Balmeisporites r a r u s KONDINSKAYA, 1966, p.l17, pl.I, 2 Styx striatella (KOND1NSKAYA)n. comb. Balmeisporites striatellus KONDINSKAYA, 1966, p.118, pHI, 1 Rev. Palaeobotan. Palynol., 11 (1971) 297 309
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PLATEI SEM photomicrographs of Styx bella (KOND|NSKAYA)n. comb. (X shows the common spot in all SEM photomicrographs). 1. A complete specimen; × 250. 2. Photomicrograph from the top of the supratectal processes showing striations anastomosing into muri and supratectal processes on the exospore; × 1,250. 3. Outer layer of exospore has corroded, thus showing granular surface of striae. The ends of striae are recognizable at the distal end of the supratectal process; > 2,500.
PLATE I1 (p.302) SEM photomicrographs of Styx bella (KONDINSKAYA) n. comb. (X shows the common spot in all SEM photomicrographs). 1. A complete specimen; × 240. 2. Details of proximal part of the megaspore with acrolamellae, showing the grading of meshes and striae into the finer sculpture of the acrolamellae; ~ 600. 3. Showing primary striae and their fusion into the muri of larger meshes, and supratectal processes situated at the corners of the larger meshes: > 600. 4. Showing lateral fusion of striae and the details of the flared distal ends of the truncated supratectal processes; x 2,400. 5. Showing the outer layer effecting the lateral fusion of the striae. The outer layer is punctate and is corroded in part. The granular nature of exospore is seen clearly: " 6,000.
PLATE 1ll (p.303) photomicrographs of Styx bella (KOr~DINSKAYA) n. comb. (X, Y, and Z show common in respective SEM photomicrographs). Slightly corroded specimen showing striate pattern; 625. Broken part of the acrolamellae showing the inner layer of the exospore which is reticulate. Note the grading of larger sculpture elements into the finer elements of acrolamellae: • 1,250. 3, 4. Details of the middle layer of the exospore; :< 2,500.
SEM spots 1. 2.
PLATE IV (p.304) SEM photomicrographs of Styx bella (KONDINSKAYA) n. comb. (X shows the common spot in all SEM photomicrographs). 1. A small megaspore that may be immature; x 240. 2. Showing intact outer layer of the exospore which is punctate between striae; ~ 2,400. 3. Showing granular nature of the outer layer of the exospore, which is punctate between the striae; x 6,000. 4. Details of the exospore; × 12,000.
PLATE V (p.305) Light photomicrographs of Styx bella (KONDINSKAYA) n. comb. 1. A complete specimen showing composite striate sculpture on exospore; ~ 250. 2. A part of the exospore showing the punctate sculpturing between the striae; >, 400. 3. Details of the exospore on the margin of the megaspore showing the blending of larger sculpture elements into finer ones; × 1,000. 4. Showing the details of the distal ends of the supratectal processes on the exospore. Note that the individual ends of the striae are recognizable; ~: 1,000. 5. Showing the striations, with punctae between the striations; x 1,000. 6. Showing the reticulate inner layer of the exospore: ~ 1,000.
300
Rev. Palaeobotan. Palynol., 11 (1971) 297-309
PLATE
I
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PLATE 1I
@ (For legend see p.300.)
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P L A T E lII
U (For legend see p.300.)
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PLATE IV
is (For legend see p.300.)
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PLATE
V
4
2
5
(For legend see p.300.)
Rev. Palaeobotan. Palynol., 11 (1971) 297 309
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Distribution, Styx has been recorded from the Senonian-Danian deposits of Siberia (KoNDINSKAYA, 1966) and Maastrichtian of North America (NORTONand HALL, 1967; OLTZ, 1969; SNEAD, 1969; SRIVASTAVAand BINDA, 1969). Styx appears to be stratigraphically significant and a good indicator of local paleoecological conditions. Styx bella (KONDINSKAYA)n. comb. (Plate I, 1-3; 1I, 1-5; III, 1-4; IV, 1-4; V, 1-6) Balmeisporites bellus KONDINSKAYA,1966, p.l19, pl.lll, 3 Balmeisporites mollis KONDINSKAVA,1966, p.120, pl.lll, 4 Styx minor NORTON, 1967, in: NORTON et HALL, 1967, p.105, pl.l, C Balmeisporites bellus KONDI~SKAYA, 1966 (in: SRtVASTAVAand BXNDA, 19694 p.207, pl.1, 4--8, II, 1--3) Balmei~porites sp. D (in: SNEAD, 1969, p.57, pl.ll, 1,2)
Holotype. KONDINSKAYA(1966), pl. III, 3. Restated description (translated from KONDINSKAYA, 1966): Spore size including "sail" 190/~, spore diameter 88/~, height of "sail" 110/~. Spore outline round, with triradiate gaping slit, "sail" three-leaved (like blades of fan) with wide flange. Laesurae simple, gaping, length of leasurae less than the radius of spore body. Perispore sculpture granulate with spines of variable sizes (height ranging from 0.6 to 5/~) evenly distributed all over perispore. Granules present on "sail" also, which are confluent into cords (striae) running close together. Margins of "sail" thin, sinuous. Remarks on restated description. The proximally situated leaf-like exoexinal structures, called a "sail" by KQNDINSKAYA(1966), are here termed acrolamellae. In all plates of the present paper the photographs of the specimens have been oriented with their acrolamellae pointing upwards. The term exospore has been used here for the outer covering of the spore body in preference to perispore as used by KONDINSKAYA(1966). Detailed description (the description given by SR1VASTAVAand BINDA, 1969, is modified and emended after examining several specimens through the optical and stereoscan microscopes). Megaspores trilete, laesurae length equal to the spore radius; spore body circular in outline, covered by exospore; proximally exospore extended into three acrolamellae. Exospore layers are not very distinct. SRIVASTAVAand BINDA 0969) noted two layers in the exospore. However, a detailed examination of these megaspores indicates that the exospore is three-layered. 306
Rev. Palaeobotan. PalynoL, 11 (1971) 297-309
Inner layer thin, reticulate, meshes almost circular, about 3-5/t in diameter. Inner layer is distinct through the optical microscope (Plate V, 6). Middle layer thick, striate, striae 2-7/~ wide, striae form radiating patterns from several points, anastomose with neighboring striae forming thick muri _+ at right angles to the anastomosing striae (Plate II, 1-5); muri form a larger reticulate pattern, meshes triangular to polygonal, complete or incomplete, 10-15/~ in size, larger toward distal pole, smaller and broken ones toward proximal face grading into the finer sculpture of acrolamellae; striae anastomose at the corners of meshes at several levels (Plate I, 2, 3) where truncated conical supratectal processes are formed (Plate II, 5). Striae join laterally also at several stages with the neighboring ones forming irregular smaller meshes between striae (Plate II, 4, 5), meshes between striae may be complete (Plate IV, 2-4) or broken (Plate III, 3, 4). Outer layer thin, easily eroded, finely granular, pitted (Plate IV, 1-4), pits prominent between striae, meshes about 1.5/~ in diameter. Supratectal processes are truncated conical structures with flared free distal ends, and appear to be bundles of loosely fused striae at the "radiating centers" (Plate I, 2, 3). The ends of the striae are recognizable on the truncated ends of these cones (Plate III, 4; V, 4). Acrolamellae three, situated proximally on laesurae, conical in shape, emanate from the equatorial zone (Plate Ill, 1); distal sculpture elements of exospore grade proximally into finer elements of acrolamellae (Plate II, 2; Ill, 2; V,
1-3). Size range. Diameter of spore body 50-200/z; length of acrolamellae 45-150 p (50 specimens measured). Remarks on morphology. Styx bella varies considerably in size, ranging from 50 to 200/~ with all intermediate sizes. Very few specimens reach the conventionally accepted size for megaspores, i.e., 200 # or more. Distinction of species on the basis of size only is not favored in this case. Hence, Balmeisporites mollis has been treated here as a junior synonym of Styx bella. SRIVASTAVAand BINDA (1969) noted that striae in Styx bella are pitted. The stereoscan reveals that the outer-layer has pits between the striae (Plate l[, 4, 5), which gives the pitted appearance to striae in the optical microscope (Plate V, 1, 2). The pitted striae sensu SRIVASTAVA and BINDA (1969) are actually two striae separated by a row of pits (Plate IV, 1-4). Sometimes striae fuse laterally to form irregular large meshes (Plate III, 3, 4). SRIVASTAVAand BINDA(1969) observed two layers in the exospore. The actual number of exospore layers may be debatable. An LO analysis of the exospore indicates that there is at least one more layer below the striate layer of the exospore (Plate V, 4-6). SEM pictures do not show the inner layer distinctly. However, the Rev. Palaeobotan. Palynol., 11 (1971) 297-309
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reticulate inner layer is seen in the broken acrolamellae of one specimen (Plate III, 2). SRlVASTAVA and BINDA (1969) indicated that acrolamellae are formed by the outer layer of the exospore. A close examination of several specimens shows that actually all the exospore layers blend into finer elements of acrolamellae (Plate Ill, 2; V, 1-3).
Remarks on taxonomy. Styx minor is a junior synonym of Styx bella. Styx bella is distinct from Styx major in having anastomosing striae on the exospore; from Styx striatella, S. diversispinulata, S. rara, and S. Iongirimosa, it differs in having large closed meshes on the exospore. Distribution. Styx bella has been recorded from Senonian-Danian deposits of Siberia (KoNDINSKAYA, 1966), the Edmonton Formation (Maastrichtian) of Alberta, Canada (SRIVASTAVAand B1NDA, 1969), and the Hell Creek Formation (Maastrichtian) of Montana, U.S.A. (NORTON and HALL, 1967, 1969; OLTZ, 1969). The precise age of the Senonian deposits of Siberia is not known. However, S. bella has been recorded only from the Maastrichtian strata of North America, and appears to be a valuable stratigraphical marker. Paleoecological significance. The lithology of the sediments of the Edmonton Formation containing Styx bella suggests their deposition under fresh and brackish water conditions. Sediments were deposited in shallow fresh water basins, estuaries and deltas, or in littoral zones along the border of advancing and retreating seas. Some of the beds were deposited as mud fiats. Beds containing carbonaceous matter originated in enclosed basins or swamps (ALLANand SANDERSON,1945). A rich microspore assemblage associated with Sty.\" bella, recovered from the Edmonton Formation, is indicative of a humid subtropical climate (SRIVASTAVA, 1970), S. bella occurs in abundance in brackish sediments also, where it could have been transported by fresh water channels. The acrolamellae of these megaspores are well suited for long distance transportation by flotation. It appears that Styx bella flourished in stagnant fresh-water pools, marshes, and along streams and brooks. Through the fresh-water channels, it was readily transported to the deposition sites where sometimes it mingled with a brackish water assemblage. It occupied an environment somewhat similar to that of Azolla. Azolla megaspores and glochidia occur frequently with S. bella in the Edmonton Formation (SR1VASTAVA,1968). KONDINSKAYA(1966) noted that these megaspores are confined to lacustrine-palustrine deposits of Siberia in U.S.S.R. Similar paleoecological conditions are indicated in other areas of their occurrence in North America (NORTON and HALL, 1967; OLTZ, 1969).
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ACKNOWLEDGEMENTS 1 am grateful to Dr. (Mrs.) Mary Playford (Dr. M a r y D e t t m a n n ) for discussion c o n c e r n i n g the m o r p h o l o g y of Balmeisporites, lending the specimens of B. holodictyus for c o m p a r i s o n , a n d for constructive suggestions a b o u t the systematic revision of the genus S t y x . T h a n k s are due to Dr. Alfred R. Loeblich Jr., a n d Professor Helen T a p p a n for critically reading the m a n u s c r i p t ; to Mrs. Rosalind Srivastava for linguistic corrections; to Professor G l e n n E. Rouse for encouragement; a n d to Professor Geoffery Playford for cooperation a n d help in various ways. This work was completed during the tenure of a Killam Postdoctoral Fellowship at the University of British C o l u m b i a . The D e p a r t m e n t of Botany, University of British C o l u m b i a , Vancouver, C a n a d a , a n d the Chevron Oil Field Research C o m p a n y , provided necessary facilities in preparing the manuscript. REFERENCES ALLAN,J. A. and SANDERSON,J. 0. G., 1945. Geology of Red Deer and Rosebud Sheets, Alberta. Res. Council Alberta (Can.), Rept. 13:109 pp. CooKsoN, 1. C. and DETTMANN,M. E., 1958. Cretaceous "megaspores" and a closely associated microspore from the Australian region. Micropaleontology, 4: 3949. KONDINSKAYA, L. I., 1966. Fossil spores of water ferns in Upper Cretaceous and Paleogene deposits of the west Siberian lowland. In: A. F. CHLONOVA(Editor), Palynology of Siberia. Akad. Nauk U.S.S.R., pp.l16-122 (in Russian with English summary). NORTON, N. J. and HALL, J. W., 1967. Guide sporomorphae in the Upper Cretaceous-Lower Tertiary of eastern Montana (U.S.A.). Rev. Palaeobotan. Palynol., 2:99 110. NORTON, N. J. and HALL, J. W., 1969. Palynology of the Upper Cretaceous and Lower Tertiary in the type locality of the Hell Creek Forrnation, Montana, U.S.A. Palaeontographica, B, 125: 1-64.
OLTZ JR., D. F., 1969. Numerical analysis of palynological data from Cretaceous and Early Tertiary sediments in east central Montana. Palaeontographica, B, 128: 90-166. SNEAD, R. G., 1969. Microfloral diagnosis of the Cretaceous-Tertiary boundary, central Alberta. Res. Council Alberta (Can.), Geol. Div., Bull., 25:148 pp. SRIVASTAVA,S. K., 1968. Azolla from the Upper Cretaceous Edmonton Formation, Alberta, Canada. Can. J. Earth Sci., 5: 915-919. SRIVASTAVA,S. K., 1970. Pollen biostratigraphy and paleoecology of the Edmonton Formation (Maestricbtian), Alberta, Canada. Palaeogeography, Palaeoclimatol., Palaeoecol., 7: 221 276. SRIVASTAVA,S. K. and BINDA, P. L., 1969. Megaspores of the genus Balmeisporites from the Upper Cretaceous of Alberta and Saskatchewan, Canada. Rev. Micropal?ontol., 4:205 209.
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Elsevier Publishing Company, Amsterdam Printed in The Netherlands
SYSTEMATIC REVISION OF T H E G E N U S S T Y X N O R T O N ET HALL, 1967 SATISH K. SRIVASTAVA
Chevron Oil Field Research Company, La Habra, Calif. (U.S.A.) (Received June 18, 1970) (Revised December 9, 1970)
SUMMARY
The genus Styx NORTON et HALL was based on an incomplete specimen. Its diagnosis is revised and emended here on the basis of complete and well preserved specimens. In its revised generic circumscription, Styx accommodates trilete megaspores with striate and/or reticulate exospore and three acrolamellae. It is distinct from Balmeisporites COOKSONet DETTMANNin lacking equatorial exoexinal outgrowths. The type-species Styx bella (KoNDINSKAYA) n. comb. is described in detail as revealed by stereoscan and light microscopes. The exospore of these megaspores appears to be three-layered rather than two-layered. The distribution of S. bella is given and its stratigraphical and paleoecological significance discussed. INTRODUCTION
COOKSON and DETTMANN (1958) instituted the genus Balmeisporites for acrolamellate megaspores with three equatorially situated equidistant reticulate outgrowths of the exoexine. KONDINSKAYA (1966) reported several acrolamellate megaspores with striate exospore from the Upper Cretaceous and Paleogene deposits of the west Siberian lowlands, and assigned them to the genus Balmeisporites COOKSONet DETTMANN, 1958. However, these Siberian megaspores do not have the equatorial exoexinal outgrowths. SRIVASTAVA and BINDA (1969) recovered several megaspores, similar to the above mentioned Siberian megaspores, from the Maastrichtian deposits of Alberta and Saskatchewan in Canada. They noticed the emphasis laid, in the generic diagnosis of Balmeisporites, on the presence of "three equidistant reticulate equatorial outgrowths of the exoexine", but felt it characteristic at the specific level only, rather than at the generic level. They followed KONDINSKAYA (1966) and assigned the Canadian acrolamellate striate megaspores to the genus Balmeisporites. Meanwhile, NORTON and HALL (1967) instituted the genus Styx to accommodate similar striate megaspores. The description of the genus Styx is Rev. Palaeobotan. Palynol., 11 (1971) 297-309
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based on incomplete specimens, consequently the presence of acrolamellae was not mentioned in the original diagnosis. Recently the writer examined a few Australian specimens of Balmeisporites holodictyus to compare them with the Canadian and Siberian acrolamellate megaspores having a striate exoexine. The wing-like equatorial exoexinal outgrowths appear to be a convincingly generic characteristic of Balmeisporites as originally diagnosed by COOKSON and DETTMANN (1958) rather than a specific one as proposed by SRIVASTAVAand BINDA (1969). Thus megaspores without equatorial exoexinal outgrowths are not properly included in Balmeisporites. The erroneous captions and references to the figures of type-species in the original description (NORTON and HALL, 1967) were subsequently corrected by NORTON and HALL (1969). However, the type-species Styx minor NORTON, in: NORTON et HALL, 1967, is a junior synonym ofBalmeisporites bellus KONDINSKAYA, 1966. In the present paper, the generic diagnosis of Styx is revised on the basis of complete specimens and the type-species as revealed by stereoscan microscope is redescribed.
SYSTEMATICDESCRIPTION Genus Styx NORTON et HALL emend.
Balmeisporites bellus KONDINSKAYA,1966, p.119, p[.III, 3 (Fig.1 in the present paper) Styx NORTONet HALL 1967, p.104 Styx minor NORTON, 1967, in: NORTONet HALL, 1967, p.104, pl.I, C (non B) Type species. Styx minor NORTON, 1967 = Styx bella (KONDINSKAYA) n. comb.
Emended diagnosis. Megaspores trilete; acrolamellate, acrolamellae three, proximal; exoexine reticulate and/or striate; muri of variable length and breadth, anastomosing into various patterns; supratectal processes on exoexine echinate, echinae shape variable.
Remarks. Three acrolamellae in Styx distinguish it from the genus Arcellites MINER emend. ELLIS et TSCHUDY which has six acrolamellae. Although both Styx and Balmeisporites have three acrolamellae, Styx is distinct from Balmeisporites in lacking the equatorial exoexinal outgrowths. NORTON and HALL (1967) proposed the genus Styx to accommodate perinate trilete megaspores with echinate supratectal processes on the exospore. They did not mention the presence of acrolamellae on these megaspores. The illustrations of Styx minor and S. major (NORTON and HALL, 1967, pl. 1 C, B) indicate that Styx is acrolamellate and the generic diagnosis and specific descriptions are based on 298
Rev. Palaeobotan. Palynol., 11 (1971) 297-309
Fig.l. Styx bella (Balmeisporites belhts KONDINSKAYA), reproduction of the illustration of the type species from the original publication by KONDINSKAYA(1966, pHI1, 3).
incomplete specimens. The acrolamellate nature o f Styx minor is c o r r o b o r a t e d by its strong morphological resemblance to the megaspores described by KONDINSKAYA (1966) and by SRIVASTAVAand BINDA (1969) as Balmeisporites bellus, and by OLTZ (1969) as S t y x minor. Thus S t y x minor is a junior s y n o n y m o f Balmeisporites bellus KONDINSKAYA, 1966, which is here transferred to the genus S t y x NORTON et HALL emend. KONDINSKAYA (1966) distinguished several species a m o n g striate acrolamellate megaspores on the basis o f minor differences in the striate sculpturing on the exospore. Ultimately, such m i n o r differences m a y not prove to be o f any consequence. However, until more data is available, these species have been recognized as distinguished by KOND1NSKAYA (1966) and are transferred here to the genus Styx NORTON et HALL emend.
Styx diversispinulata (KONDINSKAYA)n. comb. Bahneisporites diversispinulatus KONDINSKAYA,1966, p.117, pl.I, 1 Styx longirimosa (KONDINSKAYA)n. comb. Balmeisporites Iongirimosus KONDINSKAYA, 1966, p. ll 9, pl.III, 2 Styx r a T a (KONDINSKAYA)n. comb. Balmeisporites r a r u s KONDINSKAYA, 1966, p.l17, pl.I, 2 Styx striatella (KOND1NSKAYA)n. comb. Balmeisporites striatellus KONDINSKAYA, 1966, p.118, pHI, 1 Rev. Palaeobotan. Palynol., 11 (1971) 297 309
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PLATEI SEM photomicrographs of Styx bella (KOND|NSKAYA)n. comb. (X shows the common spot in all SEM photomicrographs). 1. A complete specimen; × 250. 2. Photomicrograph from the top of the supratectal processes showing striations anastomosing into muri and supratectal processes on the exospore; × 1,250. 3. Outer layer of exospore has corroded, thus showing granular surface of striae. The ends of striae are recognizable at the distal end of the supratectal process; > 2,500.
PLATE I1 (p.302) SEM photomicrographs of Styx bella (KONDINSKAYA) n. comb. (X shows the common spot in all SEM photomicrographs). 1. A complete specimen; × 240. 2. Details of proximal part of the megaspore with acrolamellae, showing the grading of meshes and striae into the finer sculpture of the acrolamellae; ~ 600. 3. Showing primary striae and their fusion into the muri of larger meshes, and supratectal processes situated at the corners of the larger meshes: > 600. 4. Showing lateral fusion of striae and the details of the flared distal ends of the truncated supratectal processes; x 2,400. 5. Showing the outer layer effecting the lateral fusion of the striae. The outer layer is punctate and is corroded in part. The granular nature of exospore is seen clearly: " 6,000.
PLATE 1ll (p.303) photomicrographs of Styx bella (KOr~DINSKAYA) n. comb. (X, Y, and Z show common in respective SEM photomicrographs). Slightly corroded specimen showing striate pattern; 625. Broken part of the acrolamellae showing the inner layer of the exospore which is reticulate. Note the grading of larger sculpture elements into the finer elements of acrolamellae: • 1,250. 3, 4. Details of the middle layer of the exospore; :< 2,500.
SEM spots 1. 2.
PLATE IV (p.304) SEM photomicrographs of Styx bella (KONDINSKAYA) n. comb. (X shows the common spot in all SEM photomicrographs). 1. A small megaspore that may be immature; x 240. 2. Showing intact outer layer of the exospore which is punctate between striae; ~ 2,400. 3. Showing granular nature of the outer layer of the exospore, which is punctate between the striae; x 6,000. 4. Details of the exospore; × 12,000.
PLATE V (p.305) Light photomicrographs of Styx bella (KONDINSKAYA) n. comb. 1. A complete specimen showing composite striate sculpture on exospore; ~ 250. 2. A part of the exospore showing the punctate sculpturing between the striae; >, 400. 3. Details of the exospore on the margin of the megaspore showing the blending of larger sculpture elements into finer ones; × 1,000. 4. Showing the details of the distal ends of the supratectal processes on the exospore. Note that the individual ends of the striae are recognizable; ~: 1,000. 5. Showing the striations, with punctae between the striations; x 1,000. 6. Showing the reticulate inner layer of the exospore: ~ 1,000.
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PLATE
I
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PLATE 1I
@ (For legend see p.300.)
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P L A T E lII
U (For legend see p.300.)
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PLATE IV
is (For legend see p.300.)
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PLATE
V
4
2
5
(For legend see p.300.)
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Distribution, Styx has been recorded from the Senonian-Danian deposits of Siberia (KoNDINSKAYA, 1966) and Maastrichtian of North America (NORTONand HALL, 1967; OLTZ, 1969; SNEAD, 1969; SRIVASTAVAand BINDA, 1969). Styx appears to be stratigraphically significant and a good indicator of local paleoecological conditions. Styx bella (KONDINSKAYA)n. comb. (Plate I, 1-3; 1I, 1-5; III, 1-4; IV, 1-4; V, 1-6) Balmeisporites bellus KONDINSKAYA,1966, p.l19, pl.lll, 3 Balmeisporites mollis KONDINSKAVA,1966, p.120, pl.lll, 4 Styx minor NORTON, 1967, in: NORTON et HALL, 1967, p.105, pl.l, C Balmeisporites bellus KONDI~SKAYA, 1966 (in: SRtVASTAVAand BXNDA, 19694 p.207, pl.1, 4--8, II, 1--3) Balmei~porites sp. D (in: SNEAD, 1969, p.57, pl.ll, 1,2)
Holotype. KONDINSKAYA(1966), pl. III, 3. Restated description (translated from KONDINSKAYA, 1966): Spore size including "sail" 190/~, spore diameter 88/~, height of "sail" 110/~. Spore outline round, with triradiate gaping slit, "sail" three-leaved (like blades of fan) with wide flange. Laesurae simple, gaping, length of leasurae less than the radius of spore body. Perispore sculpture granulate with spines of variable sizes (height ranging from 0.6 to 5/~) evenly distributed all over perispore. Granules present on "sail" also, which are confluent into cords (striae) running close together. Margins of "sail" thin, sinuous. Remarks on restated description. The proximally situated leaf-like exoexinal structures, called a "sail" by KQNDINSKAYA(1966), are here termed acrolamellae. In all plates of the present paper the photographs of the specimens have been oriented with their acrolamellae pointing upwards. The term exospore has been used here for the outer covering of the spore body in preference to perispore as used by KONDINSKAYA(1966). Detailed description (the description given by SR1VASTAVAand BINDA, 1969, is modified and emended after examining several specimens through the optical and stereoscan microscopes). Megaspores trilete, laesurae length equal to the spore radius; spore body circular in outline, covered by exospore; proximally exospore extended into three acrolamellae. Exospore layers are not very distinct. SRIVASTAVAand BINDA 0969) noted two layers in the exospore. However, a detailed examination of these megaspores indicates that the exospore is three-layered. 306
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Inner layer thin, reticulate, meshes almost circular, about 3-5/t in diameter. Inner layer is distinct through the optical microscope (Plate V, 6). Middle layer thick, striate, striae 2-7/~ wide, striae form radiating patterns from several points, anastomose with neighboring striae forming thick muri _+ at right angles to the anastomosing striae (Plate II, 1-5); muri form a larger reticulate pattern, meshes triangular to polygonal, complete or incomplete, 10-15/~ in size, larger toward distal pole, smaller and broken ones toward proximal face grading into the finer sculpture of acrolamellae; striae anastomose at the corners of meshes at several levels (Plate I, 2, 3) where truncated conical supratectal processes are formed (Plate II, 5). Striae join laterally also at several stages with the neighboring ones forming irregular smaller meshes between striae (Plate II, 4, 5), meshes between striae may be complete (Plate IV, 2-4) or broken (Plate III, 3, 4). Outer layer thin, easily eroded, finely granular, pitted (Plate IV, 1-4), pits prominent between striae, meshes about 1.5/~ in diameter. Supratectal processes are truncated conical structures with flared free distal ends, and appear to be bundles of loosely fused striae at the "radiating centers" (Plate I, 2, 3). The ends of the striae are recognizable on the truncated ends of these cones (Plate III, 4; V, 4). Acrolamellae three, situated proximally on laesurae, conical in shape, emanate from the equatorial zone (Plate Ill, 1); distal sculpture elements of exospore grade proximally into finer elements of acrolamellae (Plate II, 2; Ill, 2; V,
1-3). Size range. Diameter of spore body 50-200/z; length of acrolamellae 45-150 p (50 specimens measured). Remarks on morphology. Styx bella varies considerably in size, ranging from 50 to 200/~ with all intermediate sizes. Very few specimens reach the conventionally accepted size for megaspores, i.e., 200 # or more. Distinction of species on the basis of size only is not favored in this case. Hence, Balmeisporites mollis has been treated here as a junior synonym of Styx bella. SRIVASTAVAand BINDA (1969) noted that striae in Styx bella are pitted. The stereoscan reveals that the outer-layer has pits between the striae (Plate l[, 4, 5), which gives the pitted appearance to striae in the optical microscope (Plate V, 1, 2). The pitted striae sensu SRIVASTAVA and BINDA (1969) are actually two striae separated by a row of pits (Plate IV, 1-4). Sometimes striae fuse laterally to form irregular large meshes (Plate III, 3, 4). SRIVASTAVAand BINDA(1969) observed two layers in the exospore. The actual number of exospore layers may be debatable. An LO analysis of the exospore indicates that there is at least one more layer below the striate layer of the exospore (Plate V, 4-6). SEM pictures do not show the inner layer distinctly. However, the Rev. Palaeobotan. Palynol., 11 (1971) 297-309
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reticulate inner layer is seen in the broken acrolamellae of one specimen (Plate III, 2). SRlVASTAVA and BINDA (1969) indicated that acrolamellae are formed by the outer layer of the exospore. A close examination of several specimens shows that actually all the exospore layers blend into finer elements of acrolamellae (Plate Ill, 2; V, 1-3).
Remarks on taxonomy. Styx minor is a junior synonym of Styx bella. Styx bella is distinct from Styx major in having anastomosing striae on the exospore; from Styx striatella, S. diversispinulata, S. rara, and S. Iongirimosa, it differs in having large closed meshes on the exospore. Distribution. Styx bella has been recorded from Senonian-Danian deposits of Siberia (KoNDINSKAYA, 1966), the Edmonton Formation (Maastrichtian) of Alberta, Canada (SRIVASTAVAand B1NDA, 1969), and the Hell Creek Formation (Maastrichtian) of Montana, U.S.A. (NORTON and HALL, 1967, 1969; OLTZ, 1969). The precise age of the Senonian deposits of Siberia is not known. However, S. bella has been recorded only from the Maastrichtian strata of North America, and appears to be a valuable stratigraphical marker. Paleoecological significance. The lithology of the sediments of the Edmonton Formation containing Styx bella suggests their deposition under fresh and brackish water conditions. Sediments were deposited in shallow fresh water basins, estuaries and deltas, or in littoral zones along the border of advancing and retreating seas. Some of the beds were deposited as mud fiats. Beds containing carbonaceous matter originated in enclosed basins or swamps (ALLANand SANDERSON,1945). A rich microspore assemblage associated with Sty.\" bella, recovered from the Edmonton Formation, is indicative of a humid subtropical climate (SRIVASTAVA, 1970), S. bella occurs in abundance in brackish sediments also, where it could have been transported by fresh water channels. The acrolamellae of these megaspores are well suited for long distance transportation by flotation. It appears that Styx bella flourished in stagnant fresh-water pools, marshes, and along streams and brooks. Through the fresh-water channels, it was readily transported to the deposition sites where sometimes it mingled with a brackish water assemblage. It occupied an environment somewhat similar to that of Azolla. Azolla megaspores and glochidia occur frequently with S. bella in the Edmonton Formation (SR1VASTAVA,1968). KONDINSKAYA(1966) noted that these megaspores are confined to lacustrine-palustrine deposits of Siberia in U.S.S.R. Similar paleoecological conditions are indicated in other areas of their occurrence in North America (NORTON and HALL, 1967; OLTZ, 1969).
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ACKNOWLEDGEMENTS 1 am grateful to Dr. (Mrs.) Mary Playford (Dr. M a r y D e t t m a n n ) for discussion c o n c e r n i n g the m o r p h o l o g y of Balmeisporites, lending the specimens of B. holodictyus for c o m p a r i s o n , a n d for constructive suggestions a b o u t the systematic revision of the genus S t y x . T h a n k s are due to Dr. Alfred R. Loeblich Jr., a n d Professor Helen T a p p a n for critically reading the m a n u s c r i p t ; to Mrs. Rosalind Srivastava for linguistic corrections; to Professor G l e n n E. Rouse for encouragement; a n d to Professor Geoffery Playford for cooperation a n d help in various ways. This work was completed during the tenure of a Killam Postdoctoral Fellowship at the University of British C o l u m b i a . The D e p a r t m e n t of Botany, University of British C o l u m b i a , Vancouver, C a n a d a , a n d the Chevron Oil Field Research C o m p a n y , provided necessary facilities in preparing the manuscript. REFERENCES ALLAN,J. A. and SANDERSON,J. 0. G., 1945. Geology of Red Deer and Rosebud Sheets, Alberta. Res. Council Alberta (Can.), Rept. 13:109 pp. CooKsoN, 1. C. and DETTMANN,M. E., 1958. Cretaceous "megaspores" and a closely associated microspore from the Australian region. Micropaleontology, 4: 3949. KONDINSKAYA, L. I., 1966. Fossil spores of water ferns in Upper Cretaceous and Paleogene deposits of the west Siberian lowland. In: A. F. CHLONOVA(Editor), Palynology of Siberia. Akad. Nauk U.S.S.R., pp.l16-122 (in Russian with English summary). NORTON, N. J. and HALL, J. W., 1967. Guide sporomorphae in the Upper Cretaceous-Lower Tertiary of eastern Montana (U.S.A.). Rev. Palaeobotan. Palynol., 2:99 110. NORTON, N. J. and HALL, J. W., 1969. Palynology of the Upper Cretaceous and Lower Tertiary in the type locality of the Hell Creek Forrnation, Montana, U.S.A. Palaeontographica, B, 125: 1-64.
OLTZ JR., D. F., 1969. Numerical analysis of palynological data from Cretaceous and Early Tertiary sediments in east central Montana. Palaeontographica, B, 128: 90-166. SNEAD, R. G., 1969. Microfloral diagnosis of the Cretaceous-Tertiary boundary, central Alberta. Res. Council Alberta (Can.), Geol. Div., Bull., 25:148 pp. SRIVASTAVA,S. K., 1968. Azolla from the Upper Cretaceous Edmonton Formation, Alberta, Canada. Can. J. Earth Sci., 5: 915-919. SRIVASTAVA,S. K., 1970. Pollen biostratigraphy and paleoecology of the Edmonton Formation (Maestricbtian), Alberta, Canada. Palaeogeography, Palaeoclimatol., Palaeoecol., 7: 221 276. SRIVASTAVA,S. K. and BINDA, P. L., 1969. Megaspores of the genus Balmeisporites from the Upper Cretaceous of Alberta and Saskatchewan, Canada. Rev. Micropal?ontol., 4:205 209.
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