IvOM Life Sciences Miscellaneous Publications Royal Ontario Museum ■o o -o = cO Evolution of Archeopyle and Tabulation in Rhaetogonyaulacinean Dinoflagellate Cysts Gunter Dorhofer Edward H. Davies p.s. Ro 690 D64 1980 Digitized by the Internet Archive in 2012 with funding from Royal Ontario Museum http://archive.org/details/evolutionofarcheOOdrhf LIFE SCIENCES MISCELLANEOUS PUBLICATIONS ROYAL ONTARIO MUSEUM Evolution of Archeopyle GUNTER DORHOFER EDWARD H. DAVIES and Tabulation in Rhaetogonyaulacinean Dinoflagellate Cysts Publication dale: 29 February 1980 ISBN 0-88854-239-9 ISSN 0082-5093 ROYAL ONTARIO MUSEUM PUBLICATIONS IN LIFE SCIENCES The Royal Ontario Museum publishes three series in the Life Sciences: l ll i sc n si i s itiMKiRi noss, u numbered series of original scientific publications including monographic works i ii i si ii sc i s cit ( \sii in \i I'M'i ks. a numbered series of original scientific publications, primarily short and usually of taxonomic significance LIFE sciences miscellaneous publications, an unnumbered series of publications of varied subject matter and format. All manuscripts considered for publication are subject to the scrutiny and editorial policies of the Life Sciences Editorial Board, and to review by persons outside the Museum staff who are authorities in the particular field involved. I II I SCIENCES I DITORIAL BOARD Senior Editor: J H McANDREWS Editor: R D jwii S Editor: C McGOWAN (.1 mi k DORHOFER was a postdoctoral fellow of the Department of Geology, University of Toronto, and is with the Bundesanstalt fur Geowissenschaften und Rohstoffe, Niedersachsisehes Landesamt fiir Bodenforschung, D 3 Hannover 51, Stilleweg 2, Postfach 51 01 53, West Germany. i dw \ki> h da vies was a postgraduate student of the Department of Geology, University of Toronto, and is with Phillips Petroleum Company. Bartlesville, Oklahoma 74004, USA. Cover drawing: The excystment of Phallocysta (as envisioned by the second author E.H.D.) Canadian Cataloguing in Publication Data Dorhofer, Gunter, 1946- Evolution of archeopyle and tabulation in Rhaetogonyaulacinean dinoflagellate cysts (Life sciences miscellaneous publications ISSN 0082-5093) Bibliography: p. ISBN 0-88854-239-9 1. Dinoflagellata. Fossil - Paleontology — Meso/oic. 3. Evolution 4 Paleontology — Arctic regions 5. Paleontology - Germany. I. Davies. Edward H , 195ft- II. Royal Ontario Museum III. Title. IV. Series: Life sciences miscellaneous publication QE774.D5D64 563'. I C80-094086-5 QL1 T6539 © The Royal Ontario Museum, 1980 100 Queen's Park, ["oronto, Canada M5S 2C6 PRIMED AND BOUND IN CANADA AT THE ALGER PRESS Contents Abstract 5 Introduction 5 Imbrication, the Keystone Principle and Archeopyle Formation 6 Plate Series and Plate Designations 7 rerminologj 8 Materials and Methods 8 Stratigraphic Review of Cyst Characters of Pertinent Genera 9 Triassic-Lower Jurassic Dinoflagellates Suessia Morbey 1975 10 Rhaetogonyaulax Sarjeant emend. Harland et al. 1975 10 Heibergella Bujak and Fisher 1976 11 Dapcodinium Evitt 1961 11 Sverdrupiella Bujak and Fisher 1976 1 1 Noricysta Bujak and Fisher 1976 emend. 1 1 Hebecysta Bujak and Fisher 1976 I 1 Late EarK Jurassic and early Middle Jurassic Dinoflagellates 1 1 Comparodinium Morbey 1975 1 1 Dodekovia gen. nov. 1 1 Phallocysta gen. nov. 1 1 Susadinium gen. nov. 12 Pareodiniacean Cysts (Middle Jurassic-Lower Cretaceous) 12 Pareodinia Deflandre 1975 12 Glomodinium Dodekova 1975 12 Paragonyaulacysta Johnson and Hills 1973 emend. 12 Komewuia Cookson and Eisenack 1960 12 Netrelytron Sarjeant 1961 12 Gochteodinia Norris 1978b 12 Pseudoceratiacean Cysts (Upper Jurassic-Lower Cretaceous) 12 Imbatodinium Vozzhennikova 1967 13 Aptea Eisenack 1958 13 Pseudoceratium Gocht 1967 13 Vfuderongia Cookson and Eisenack 1958; Phoberocysta Millioud 1969 14 Odontochitina Deflandre 1935 14 Tenua Eisenack 1958; Doidyx Sarjeant 1966; Canningia Cookson and Eisenack 1960; Cyclonephelium Deflandre and Cookson 1955 14 Intercalary Plates and Horn Development in Pseudoceratiacean Cysts 15 Intercalary Plates 15 Horn Positions: Antapical versus Postcingular 15 Discussion 16 Systematic Palaeontology 22 Remarks on Suprageneric Classification 22 Description 23 Family Rhaetogonyaulacaceae Norris emend. 23 Dapcodinium Evitt emend. 23 Dapcodinium inornatum (Morgenroth) comb. nov. 23 Dapcodinium semitabulatum (Morgenroth) comb. nov. 23 Dapcodinium wapellense (Pocock) comb. nov. et emend. 23 Noricysta Bujak and Fisher 1976 emend. 23 Noricysta fimbriata Bujak and Fisher 1976 emend. 24 Sverdrupiella Bujak and Fisher 1976 24 Sverdrupiella mbinensis Bujak and Fisher 1976 24 Family Phallocystaceae fam. nov. 24 Comparodinium Morbey emend. Wille and Gocht 24 Comparodinium aquilonium sp. nov. 24 Dodekovia gen. nov. 26 Dodekovia svzygia sp. nov. 26 Dodekovia gochtii (Dodekova) comb. nov. 26 Phallocysta gen. nov 26 Phallocysta eumekes sp. nov. 27 Susadinium gen. nov. 28 Susadinium scrofoides sp. nov. 28 Family Pareodiniaceae Gocht emend. 30 Gochteodinia Norris 1978b 30 Gochteodinia villosa (Vozzhennikova) Norris 1978b 30 Gochteodinia verrucosa (Vozzhennikova) comb. nov. 30 Komewuia Cookson and Eisenack 1960 30 Komewuia diceras (Cookson and Eisenack) comb. nov. 30 Komewuia glabra Cookson and Eisenack 1960 31 Paragonyaulacysta Johnson and Hills emend. 31 Paragonyaulacysta calloviensis Johnson and Hills emend. 31 Paragonyaulacysta retiphragmata sp. nov. 31 Pareodinia Deflandre emend. Gocht 1970 32 Family Pseudoceratiaceae Eisenack emend. 33 Apiea Eisenack emend. Davey and Verdier emend. 33 Aptea polymorpha Eisenack emend. 34 Canningia Cookson and Eisenack emend. 36 Heterosphaeridium Cookson and Eisenack 1968 36 Heterosphaeridium heteracanthum (Deflandre and Cookson) Eisenack and Kjellstrorn 1971 36 Imbatodinium Vozzhennikova emend. 36 Imbatodinium kondratjevi Vozzhennikova emend. 37 Imbatodinium exiguum (Alberti) comb. nov. 37 Imbatodinium gochtii (Alberti) comb. nov. 37 Imbatodinium jaegeri (Alberti) comb. nov. 37 Imbatodinium longicornutum (Alberti) comb. nov. 37 Imbatodinium micropodum (Eisenack and Cookson) comb. nov. 37 Imbatodinium pelliferum (Alberti) comb. nov. 38 Imbatodinium sp. 38 Odontochitina Deflandre emend. Davey 1970 39 Odontochitina operculata (O. Wetzel) Deflandre and Cookson 1955 39 Odontochitina nuda (Gocht) comb. nov. 39 Pseudoceratium Gocht emend. 39 Pseudoceratium pelliferum Gocht emend. 39 Family Batiacasphaeraceae fam. nov. pro. 39 Batiacasphaera Drugg emend. 40 Batiacasphaera circularis (Cookson and Eisenack) comb. nov. 40 Batiacasphaera capitata (Cookson and Eisenack) comb. nov. 40 Batiacasphaera echinata (Gitmez and Sarjeant) comb. nov. 40 Batiacasphaera minor (Cookson and Hughes) comb. nov. 40 Batiacasphaera pilosa (Ehrenberg) comb. nov. 40 Batiacasphaera ringnesii (Manum and Cookson) comb. nov. 40 Batiacasphaera rioulti (Sarjeant) comb. nov. 41 Batiacasphaera rotundata (Cookson and Eisenack) comb. nov. 41 Batiacasphaera taugourdeaui (Varma and Dangwal) comb. nov. 41 Batiacasphaera torulosa (Davey and Verdier) comb. nov. 41 Batiacasphaera verrucosa (Sarjeant) comb. nov. 41 Batiacasphaera villersense (Sarjeant) comb. nov. 41 Family Areoligeraceae Evitt emend. Sarjeant and Downie 41 Cyclonephelium Deflandre and Cookson emend. 41 Summary and Conclusions 42 Acknowledgements 42 Literature Cited 43 Evolution of Archeopyle and Tabulation in Rhaetogonyaulacinean Dinoflagellate Cysts Abstract Jurassic to Lower Cretaceous dinoflagellate cysts from Arctic Canada and Germany demonstrate evolutionary lineages from a Triassic ancestral stock (Rhaetogonxaulax- type). These lineages are based on archeopyle formation, tabulation, and horn development. The evolution of archeopyles can be interpreted as an overlap scheme (imbrication) of plate boundaries. Initial archeopyle formation tends to remain stable through time in the preferred mid-dorsal keystone position. Earliest cyst genera formed disintegration archeopyles which later genera stabilized into fused opercular pieces of definite position, representing all major archeopyle types. A lineage within the Suborder Rhaetogonyaulacineae was developed from the Triassic ancestral stock through the Early to Middle Jurassic phallocystacean cysts, then through the pareodiniacean cysts of the Middle Jurassic to Early Cretaceous times through to the pseudoceratiacean cysts of the Late Jurassic to Early Late Cretaceous. The Pseudoceratiaceae have two intercalary plates within the operculum resulting in the asymmetrical archeopyle suture. Relevant genera of the Rhaetogonyaulacineae are reviewed and reinvestigated using scanning electron and interference contrast microscopy. The families Pseudoceratiaceae, Rhaetogonyaulacaceae, and Pareodiniaceae are emended. The families Phallocystaceae and Baticasphaeraceae are proposed. The first four families together constitute the suborder Rhaetogonyaulacineae. Three new genera are proposed: Dodekovia, Phallocxsta, and Susadinium. Nine genera are emended: Aptea, Batiacasphaera, Canningia, Cxclonephelium, Dapcodinium, Imbatodinium, Noricysta, Paragonxaulacxsta , and Pseudoceratium. Five new species are proposed: Comparodinium aquilonium, Dodekovia sxzxgia, Paragonxaulacxsta retiphragmata, Phallocxsta eumekes, and Susadinium scrofoides. (dinoflagellata; archeopyle; evolution; Mesozoic; Canada; Germany; SEM) inirouUC llOfl ^g t^e Rhaetogonyaulacineae, Hystrichosphaeridiineae, Gonyaulacystineae, and the Deflandreineae. We have Studies on the phylogeny and evolution of dinoflagellates investigated most genera of the rhaetogonyaulacinean are lacking in previous palynological literature. The suborder from the Jurassic-Cretaceous of the Sverdrup following hypotheses attempt to fill this void and to stir Basin, Arctic Canada and from the northwest German interest in dinoflagellate evolution. Neocomian. This work has revealed evidence on ar- Norris (1978a, b) revised the classification of dino- cheopyle and tabulation evolution, flagellate cysts at the suprageneric level. He recognized Within the suborder Rhaetogonyaulacineae Norns four suborders based mainly on archeopyle types. These (1978a, b) recognized three families, the Rhaeto- gonyaulacaceae, Sverdrupiellaceae, and Pareodiniaceae, which he differentiated mainly by distinct tabulation pattern, presence of pericoels. and smooth autophragm respectively. The classification did not include further details on archeopyle formation within the suborder. The classification incorporates a concept of dinoflagel- late evolution from ancestral rhaetogonyaulacacean through pareodiniacean cysts to members of the suborders Deflandreineae and Gonyaulacystineae. Members of the suborder Hystrichosphaeridiineae were thought to have been derived from early forms in the Late Triassic. According to Norris (1978a, b) the earliest known dinoflagellate cysts are characterized by "suessioid" tabulation, namely one "'in which plate number is high and variable, the diagnostic character being a well developed anterior intercalary series, some or all of which form an archeopyle" (Norris, 1978a,: 306). It was our intent to trace the development of important morphologi- cal characters along phylogenetic paths. The studies of Late Triassic and Early Jurassic dinoflagellate cysts indicate links between early suessioid genera and later pareodiniacean cysts. The studies on Early Cretaceous material have shown that this trend continues to the pseudoceratiacean cyst types. The principles on which the phylogenetic patterns are based, namely imbrication and the keystone principle and their relationship to archeopyle formation as well as the terminology used, are discussed to lay the foundation for the critical examination of generic relationships. The morphological and structural characters of each pertinent genus are reviewed in ascending stratigraphic order to acquaint the reader with the fossil record of rhaetogonyaulacinean dinoflagellate cysts. The discussion of those genera sketches the phylogenetic paths taken during the evolution of the Rhaetogonyaulacineae from the Triassic through to the Early Cretaceous and suggests possible radiation to other basic cyst types. A systematic section circumscribes and itemizes the taxonomic concepts of families, genera, and species used to support the hypotheses proposed. Imbrication, the Keystone Principle and A rcheopyle Formation Both tabulation and mode of archeopyle formation have been recognized as being of prime importance for the evolution and classification of dinoflagellate cysts (Evitt, 1967; Norris, 1978a). Gocht and Netzel (1974, 1976) and Diirr and Netzel (1974) have also presented direct evidence from the fine thecal structure of modern dinoflagellates. They showed the presence of an overlap pattern of plates in both Gonyaulax polyedra Stein (Diirr and Netzel, 1974) and several species of Peridinium Ehrenberg (Gocht and Netzel, 1974, 1976). Beginning with plate 1', each successive plate, proceeding from ventral to dorsal position on both right and left sides, overlaps the adjacent plate like shingles on a roof. This structure is closed in mid-dorsal position, in Peridinium by plates 2a and 4" and in Gonyaulax by plate 3". The precingular plates are attached to the cingular plates by an "adcingular Falz" (adcingular lap-joint), a griplike structure on the cingulum. Plate 4" in Peridinium and plate 3" in Gonyaulax are the "Firstziegelplatten" (keystone plates). A similar overlap scheme is developed on the hypotract starting with lp and ending with plate 3" '. The overlap scheme as recognized by Gocht and Netzel (1974:394—397) is here termed imbrication, referring to the order of plate boundary overlap on dinoflagellate cysts and thecae. Gocht and Netzel ( 1976) pointed out that the keystone position corresponds to the archeopyle position in cysts. They emphasized the importance of the adcingular lap-joints in determining the archeopyle mode and position. If the lap-joints are strong, intercalary or apical archeopyles can be formed instead of the keystone (precingular) types. In Peridinium the precingular plates are firmly attached to the adcingular lap-joint leaving plate 2a as the next preferred position for archeopyle formation in the overlap scheme. Gocht and Netzel (1976) suggest that in the early evolution of cysts the theca was still attached to the cyst during excystment and the archeopyle in the cyst would therefore correspond in a functional manner to the thecal keystone. However, such an explanation is not necessary, as it is evident from other thecal features which are "repeated" on the cyst body without any functional relation, "that the morphogenesis of theca and cyst wall did occur independently from each other, but is related to a similar cortical differentiation of the cell wall" (transl. from Berthold et al., 1976:330). This suggests a genetic control of cortex development, e.g. of both the thecal amphiesma (Loeblich, 1970) and the cyst phragma. Boltovskoy (1973) showed that under adverse condi- tions thecae of several Peridinium species form "ar- cheopyles", which are similar in position to the ar- cheopyle of the corresponding cysts. The (AIP) ar- cheopyle observed on the thecae only differs from the (AIP) cyst archeopyle in that the dorsal half of the epitheca is completely removed, whereas in the cysts the oper- culum is attached adcingularly. (We follow the Evitt System of symbols for archeopyle terminology but with the improvements outlined in Norris (1978a: 303), includ- ing the procedure of indicating compound opercular pieces by parentheses instead of superscript bars.) In our examination of archeopyles we noted that the keystone principle is applicable to fossil cysts from the earliest forms. Detailed scanning electron photomicro- graphs of Gonyaulacysta aldorfense Gocht 1970 (Gocht, 1970: pi. 30) and Hystrichosphaeropsis quasi-cribrata (O. Wetzel) Gocht 1976 (Gocht, 1976: figs. 14, 15) suggest imbrication and the keystone principle in fossil cysts, similar to thecae where "an external suture line can be discerned which is parallel but offset with respect to the internal suture line" (Gochl and Net/el, 1974:381). Imbrication in cysts is demonstrated in the archeopyle formation of Rhaetogonyaulax: "the archeopyle begins to develop bj initial splitting along the margins of some of the reflected intercalary plates . ." "One or more intercalar> plate-areas separate from each other and from the cyst, leaving the cyst otherwise intact. Further splitting results in the progressive loss of the remaining intercalary plate-areas, the apex as a unit, the anterior ventral and anterior sulcal plates. The order of these events has not yet been definitely determined, but it seems likely that the apex and the sulcal plates are the last to detach" (Harland et a].. 1975:851). This is also observable from the other early genera such as Sverdrupiella Bujak and Fisher 1976, Heibergella Bujak and Fisher 1976. Dapcodinium Evitt 1961. and Suessia Morbey 1975. The mid-dorsal keystone position always marks the initial archeopyle formation. We refer to this particular type of archeopyle formation as & disintegration archeopyle (see also Figs. 19, 20, 22, 23). Plate Series and Plate Designations Earliest dinoflagellate cysts differ from their later deriva- tives in that they have more plate series and more plates in a sencs. The Kofoid ( 1909) system oi plate designation is not applicable to the early forms, leading to the usage oi auxiliary terms such as "apical closing plates" (e.g. Wiggins, 1973), 'anterior pre-cingular plates", and "pre-antapical plates" (Morbey. 1975). The evolutional") trend from early dinoflagellates to the modern genera, such as Gonyaulax and Peridinium, represents a basic reduction in the number of plates and plate series This reduction can be accomplished in two ways (Fig. 1): 1) by fusion of several plates into a compound piece, later representing a single plate; and 2) by growth of a particular plate at the expense of other neighbouring plates. We have found evidence that both processes occurred during evolution, even though the first appears more prevalent. In the Kofoid system plates with identical designations on two different cysts are not necessarily homologous. The loss of a plate in a series is not indicated as the Kofoid designation of that plate is not lost but becomes a designation for the next higher numbered plate of that series: e.g., if plate 1" is reduced to the point where it is lost, plate 2" would assume the designation 1". All that would be recognized is a reduction of the number of plates in the precingular series by one. Similarly, if plates 2a and 3a were fused into one plate, the Kofoid system would designate the new plate as 2a with the la or with the 3a plate. It is difficult to identify these changes except as a RELICT SU T URES \ ADVANCED TA BULATION UNIDIRECTIONAL PLATE GROWTH t MULTIDIRECTIONAL PLATE FUSIO N PRIMITI VE (suessioid ) TABULATION Fig 1 Reduction ot plate numbers from primitive to advanced cvst types. 7 reduction in the number of plates in that series or as rudimentary sutural traces on the fused plate. The loss of a series of plates is an even more distinct change. If cysts similar to those of Suessia lost a series of plates, the series above or below would then take the place in designation of the lost series in the Kofoid system. For example, if the precingular series was reduced or fused with the cingular series, the anterior precingular series (Morbey, 1975) would then become the precingular series. The use of the Kofoid system, therefore, demands a change in designation of plates and plate series as reduction and /or fusion occurs. In lieu of a better system we will employ the Kofoid system during our discussion of evolutionary trends, but we alter designations of plates and plate series. For a better understanding of cyst evolution it will ultimately be necessary to employ a terminology based on homologous entities. also observed the PAS-bodies of Gonyaulax polyedra beneath the upper part of the sulcus. The eyespot occurs in motile and encysted living dinoflagellates. It may or may not be bounded by an envelope, which explains its variable shape and in W . coronata the eyespot remains in the cell, when the cytoplasm is extruded (Crawford and Dodge, 1971), a fact which could account for its preservation in fossil cysts. The function of the eyespot might be related to accumulation of waste products or digestion (Bibby and Dodge, 1972). The omphalos generally stains extremely well (as the eyespot; Schmitter, 1971). Its formation might be related to the presence of carotins in the eyespot since sporopollenin-like com- pounds are polymerized esters of carotins (Brooks et al., 1971). However, this possible relationship requires further investigation. In our study the omphalos is valuable in rapidly locating the ventral area of a cyst, especially in Pseudoceratiaceae and Rhaetogonyaulacaceae. Terminology We use descriptive terms as outlined in Williams et al., (1973). Evitt et al. (1976) proposed several alterations and several new terms that Norris (1978a) has criticized, in particular the introduction "of the term paraplate and numerous derivates with the prefix para-" as complicating the terminology. We agree with this criticism, because most thecal and cyst morphological features are controlled genetically (Norris, 1978a). Furthermore, the prefix "para-" not only has the meaning "near, beside" but also implies "inferior". The confusing term "proximochorate" had been used to describe well-developed ornament on proximate cysts in addition to that in the reduced chorate type as in Spiniferites Mantell (emend. Sarjeant 1970). Norris (1978a) has termed the latter type "spiniferate," i.e. outward ornament of reduced length, developed around a spherical main body. We use the term "apteate" for ornament, which is developed on a proximate cyst, but does not reach any great length. Apteate ornament is typically found in Aptea, Pseudoceratium, Cyc- lonephelium, and Gochteodinia. The term omphalos (from Greek omphalos, naval) is here proposed for the irregular subcircular to variably shaped thickening, which is often found ventrally at or near the apical end of the sulcus within the cyst body. The omphalos probably developed out of the accumulation body (eyespot, PAS-body) of the living dinoflagellate. In Woloszxnskiu coronata, the accumulation body consists "of a large number of pigment-containing lipid globules, which lie immediately beneath the theca in the vicinity of the sulcus" and "is situated adjacent to a flagellum" (Crawford and Dodge, 1971 : 702-703). Schmitter ( 1971) Materials and Methods The Canadian samples contributed by Davies are part of the material used in his Ph.D. thesis on the palyno- stratigraphy of the Sverdrup Basin, District of Franklin (Davies, 1979) under the supervision of Dr. G. Norris (Department of Geology, University of Toronto). See Fig. 2. Material from the German Lower Saxony Basin was obtained by Dorhofer as part of a post-doctoral research programme at the University of Toronto on Lower Cretaceous Palynostratigraphy. Localities and ages are given on Figs. 2 and 3. Light microscopy was done with the Leitz Orthoplan microscope no. 715326 in the Department of Geology, University of Toronto, using both interference contrast and bright field optics. All figures are accompanied by original sample numbers (e.g. WI 1410a or KBT 10/39.5/3), Royal Ontario Museum collection numbers (e.g. ROM 36409), and the stage coordinates (e.g. 49.8/100.3) of the above microscope; the upper right- hand corner of the slides corresponds to stage reading 0.0/90.0. The material is housed in the Royal Ontario Museum. Scanning electron microscopy was done with a Cambridge Stereoscan Mark 2a, at 20 kV electron gun potential. The specimens were coated with gold or with carbon and gold in a high vacuum unit following the gas evaporation method. The specimens are single mounted on small photographic film squares, which in turn are mounted in groups of four to eight on stubs. The stubs have received ROM collection numbers. Individual speci- mens can be located by counting clockwise on the stub starting from a small notch on the periphery. 120° 110° 100° 90° 80° -y / 1 1 v— ti # •%•. V* / *\EI let Ringnes Fig. 2 Location map, Sverdrup Basin, Arctic Canada. 1 . Panarctic Sandy Point L-46 well 2 Elf Wilkins E-60 well 3. Reindeer Peninsula 4. North Amund Ringnes Dome 5. Central Amund Ringnes Dome 6. Cape Ludwig 7. Jaeger River 8. Skaare Fjord Syncline 9. Forsheim Peninsula 10. Forsheim Anticline 11. Elf Jameson Bay C-31 well 12. North West Cornwall Island 13. Glacier Bay Stratigraphic Review of Cyst Characters of Pertinent Genera This review follows a lineage of progressive evolution of important cyst characters such as tabulation and ar- cheopyle. Although this section is descriptive, the concepts of plate fusion, plate reduction, imbrication, and the resulting stable mid-dorsal keystone position outlined above should be kept in mind. The review is in four sections that correspond with the four families of dinoflagellate cysts in Suborder Rhaetogonyaulacineae. These sections are discussed in ascending stratigraphic order: Rhaetogonyaulacaceae (Triassic-Lower Jurassic), Phallocystaceae (Lower- Middle Jurassic), Pareodiniaceae (Middle Jurassic-Lower Cretaceous), and Pseudoceratiaceae (Upper Jurassic Lower Cretaceous) r-55' --50e Fig. 3 Location map, northwest Germany. 1. KBT — wells. Peine, Aptian 2. KTH — wells, Hils embayment, Valanginian-Hauterivian locality Gehrden (Barremian) halfway between locality 2 and Hannover. 3. Salzgitter, Albian Triassic— Lower Jurassic Dinoflagellates Boreal Triassic marine algal cysts show distinctive dinoflagellate characters, namely specific tabulation pat- terns, distinctive modes of archeopyle formation, and cingular and sulcal furrows. These earliest dinoflagellate cysts are unique in their suessioid character (Norris, 1978a, b), that is having more plates and series than later dinoflagellates. This feature is considered primitive. The principal genera are reviewed below. Suessia Morbey 1975 Suessia was erected to accommodate cysts with an unusually high number of plates and series according to the following tabulation formula "?4', n a, n ap, n" , /; c, n" ', n p, n pa, 1 " ", n s. n may be up to 14 and the total number of plates may be over 60. "ap" and "pa" are the postapical and the preantapical series respectively. Suessia is the only dinoflagellate cyst genus known to have nine series. The earliest occurrences are in the Middle Norian (Wiggins, 1976). The archeopyle is of the disintegration type (Figs. 22e, f, 23a, C, d, f). Rhaetogonyaulax Sarjeant emend. Harland et al., 1975 Two species of Rhaetogonyaulax were first recorded from Britain (Sarjeant, 1963) both having spindle-shaped cysts. The archeopyle formation occurred by a progressive loss of plates in the mid-dorsal epitractal area (Sarjeant, 1963; Harland et al., 1975) initiating at the intercalary plates (disintegration archeopyle). The tabulation formula, as revised by Harland et al. (1975), is4-?6', 5-?6a, lav, 7", 7c, 7' ", lp, lpv, 3s, 3" ". The precingular series is 10 narrow m width. Shublikodinium Wiggins 1973 also has a disintegration archeopyle. an almost identical tabulation formula and a spindle shape. We follow Stover and Evitt (1978) in that the two genera are synonymous, with Shublikodinium junior to Rhaetogonyaulax. Heibergella Bujak and Fisher 1976 Heibergella was erected to accommodate untabulated, single walled cysts with an 1-31 archeopyle. The type species, H. asymmetrica Bujak and Fisher (1976). however, appears to exhibit sutural ornament. Hebecysta Bujak and Fisher 1976 Hebecysta is the earliest dinotlagcllate cysl known in which the archeopyle involves only three intercalary. plates. The tabulation is not well known but includes al least three intercalary and tour apical plates. It differs from Glomodinium Dodekova 1975 by its cavate nature. The precingular series is not as narrow as in Rhaetogonyaulax . Hebecysta occurs with Sverdrupiella in the early Late Norian. Dapcodinium Evitt 1961 Dapcodinium was reported from the Rhaetian to Sinemu- rian by Wiggins (1976), but ranges further into the Toarcian and Bajocian where it has been found in association with Phallocysta nov. gen., Comparodinium Morbey emend. Wille and Gocht (in press) and Susadinium gen. nov. It retains suessioid characters and the disintegration archeopyle. The tabulation formula is: 4'. 4a. 7", 6c. 6" ', 2p, 1" " (Evitt, 1961). Sverdrupiella Bujak and Fisher 1976 Sverdrupiella closely resembles Rhaetogonxaulax and Heibergella, but is defined as cavate. Bujak and Fisher (1976) have already demonstrated the wide variability within the genus, especially regarding archeopyle forma- tion and the degree of endoblast contraction. The latter is the sole difference between Heibergella and Sverdrupiella and, in view of the variability, appears a questionable generic criterion. All specimens we have investigated (Figs. 19, 20) possess a distinct disintegration archeopyle, initiating mid-dorsally between the apical and intercalary plate series. This corresponds to the second most preferred position with respect to the imbrication scheme. The pronounced cingular ornament suggests strong adcingular lap-joints. The ornament (spines, baculae, etc.) is not randomly distributed but is penitabular. The tabulation has not been determined in detail, but four series (including a narrow protoprecingular one) can be recognized on the epitract (Fig. 20C-E). In general the tabulation appears complex and similar to that of Rhaetogonyaulax. Noricysta Bujak and Fisher 1976 emend. Noricysta appears as early as the Early Norian, Bujak and Fisher (1976). It is cavate with an (AI) archeopyle and crests developed apically and antapically. It was described as untabulated. However, topotype material has yielded specimens with clear tabulation defined by sutural crests interpreted originally as folds (Figs. 24a-c, 22a, B, 21D-G). The tabulation formula is 6'. Ha, 10", 9c, 10" ', 6p, 6" ", ?s. Late Early Jurassic and Early Middle Jurassic Dinoflagellates Reports on dinoflagellate cysts from the late Early Jurassic are rare. Except for the widespread occurrences of Nannoceratopsis Deflandre 1938, only the "Maturo- dinium "-assemblage from the German Lias (Morgenroth, 1970) has been recorded. The high northern latitudes (Sverdrup Basin) have produced the new genera Phallocysta, Susadinium, and Dodekovia in which several important morphological features are developed that distinguish this complex from earlier dinoflagellates. Archeopyle types include (AI) + P, (A) + I and I. The number of intercalary plates is four or five, and the apical plate number is usually four. The epitractal plate series are reduced to three. Some genera have a shape similar to pareodiniacean cysts. Comparodinium Morbey 1975 Comparodinium has a 2A.i,4 archeopyle, as recently demonstrated by Wille and Gocht (in press). Its tabulation is 5', 5-6a, x" , xc, x" ', 5p, lpv, 1" ". The archeopyle is unusual and the suessioid tabulation indicates relation- ship with primitive genera. Dodekovia gen. nov. Dodekovia has a complex 3L-4 3P4-« archeopyle, which in overall shape resembles later gonyaulacean P-types. Yet, archeopyle development (Fig. 23B, E, H) in separate opercular pieces resembles earlier disintegration modes. The tabulation is 4', 5a, 9", 8c. 9" ', 2p, 2" ", 4s. Phallocysta gen. nov. Phallocysta has an elongated intercalary archeopyle consisting of three plates; the central intercalary is larger than the two flanking plates. The epitract is thin and of variable length, while the hypotract is thickened. The tabulation formula is 4', 5a, 6", ?6c, ?6" '. ?" ". Susadinium gen. nov. Susadmium has low protuberances in presumably in- tratabular position. Archeopyle formation occurs through the loss of three dorsal intercalary plates. The tabulation formula is 4?', 5a, 16", ?c, 5" ', ?1" ". The develop- ment of protuberances in the post- and precingular series is greater on the distal side, leaving a large sulcus. Pareodiniacean Cxsts (Middle Jurassic-Lower Cretaceous) Following Norris's (1978b) emended diagnosis for the family Pareodiniaceae, we regard these features as diagnostic (except number 5): 1 . Elongated proximate cyst body with an apical horn and infrequently one or two antapical horns. 2. One to three anterior intercalary plates. 3. Intercalary archeopyle with a transinistral 2a plate. 4. Geniculate (A-shaped) precingular-intercalary bound- ary. 5. Tabulation traces present or absent. The pareodiniacean cysts developed in the Bajocian- Aalenian, possibly Toarcian (Sarjeant, 1975). Earliest records are by Herngreen and De Boer ( 1 974) and Johnson and Hills (1973). Diversification accelerated in the Callovian-Upper Jurassic and declined in the Lower Cretaceous. Relevant genera are discussed below. Pareodinia Deflandre 1947 Pareodinia consists of elongate (tear-drop) shaped cysts with 21 archeopyles. The ornament is low. The tabulation when evident is 4', 2a, 6", ?6c, 16-1" ' , lp, 1" ", 3s. The age ranges from Bajocian to Albian. Glomodinium Dodekova 1975 Cysts with a 31 archeopyle should be kept apart from Pareodinia. Following Dodekova (1975) we agree with the erection of Glomodinium for such cysts and thus reject the emendations of Pareodinia by Johnson and Hills (1973) and by Wiggins (1975). Paragonyaulacysta Johnson and Hills 1973 emend. The genus Paragonyaulacysta was erected for forms from the Callovian of the Canadian Arctic which exhibit gonyaulaceanlike tabulation but differ by the presence of intercalary plates and an intercalary archeopyle (21 after Johnson and Hills 1973). Reinvestigation of the type species P. calloviensis Johnson and Hills 1973 has revealed a 31 archeopyle and the following tabulation formula: 4', 3a, 6", 6c, 6" ', 2p, 1" ", 2pv. Komewuia Cookson and Eisenack 1960 Komewuia has a 21 archeopyle and an apical and an antapical horn. The exact tabulation is not known. It ranges from Late Jurassic to Early Cretaceous. Netrelytron Sarjeant 1961 Netrelytron was erected for pareodiniacean cysts with a contracted endoblast, antapical horn and calyptra. The mode of archeopyle formation according to the illustration (Sarjeant, 1976:pl. 4, figs. 3, 5) is intercalary. Wiggins (1975) regarded the endoblasts of Netrelytron as "optical artifacts resulting from folding of the phragma" (Sarjeant, 1976:15). Sarjeant (1976), however, maintained the presence of a distinct endoblast. Gochteodinia Norris 1978b This genus was erected to separate spinose apteate forms with a 21 intercalary archaeopyle shown in Figs. 33f, G, 34g, and Evitt (1967: pi. 4, figs. 1-6), from Pareodinia and from Imbatodinium Vozzhennikova 1967. Pseudoceratiacean Cxsts (Upper Jurassic — Lower Cretaceous) Wall and Evitt (1975) have drawn attention to similarities between Cretaceous pseudoceratiacean cyst genera such as Pseudoceratium , Muderongia , Odontochitina, Phoberocysta, Endoceratium, and Aptea on the one hand to modern Ceratium Schrank 1 793 on the other. They have shown that all these genera exhibit at least some important ceratioid features. Their diagnostic criteria are sum- marized as: 1) presence of three or four coplanar horns, in apical, antapical, and postcingular position: 2) asymmet- rical hypotract, the left side being longer; and 3) basic gonyaulacean tabulation pattern, that is 4', 0a, 6", 5-6c, 6" ', lp, 1" ". Features 1 and 2 are present from almost all the cited Cretaceous genera, but the tabulation could only be determined in few instances. Wall and Evitt (1975) furnished partial tabulation formulae for Pseudoceratium pel life rum Gocht 1957, Endoceratium ludbrooki (Cookson and Eisenack) Vozzhennikova 1965, and Muderongia cf. mcwhaei Cookson and Eisenack 1958. All the preceding are type species and, therefore, the ceratioid affinity of these three genera on the basis of the tabulation formula could be considered established. No tabulation formula could be determined in the remaining genera Phoberocysta, Odontochitina. and Aptea. Imbatodinium, however, was considered by Wall and Evitt (1975) as non-ceratioid, because both hypotractal horns are in antapical position with none in postcingular. Huber and Nipkow (1923) showed that the development of horns is 12 sensitive to ecological factors inasmuch as small tempera- ture variations can easily suppress or enhance the development of one or more horns. The absence o( postcingular horns, therefore, does not exclude ceratioid affinities. Most pseudoceratiaceaen genera exhibit strong evidence for the possession of intercalary plates within the operculum. This character is very important in establish- ing the evolutionary ancestry of the Pseudoceratiaceae. The principal genera o\ this family are reviewed below, and then followed by discussions on the relevance of intercalary plates and horn position. Imbatodinium Vozzhennikova 1967 The development of the generic concept of Imbatodinium is closely related to that of Broomea Cookson and Eisenack 1958, Necrobroomea Wiggins 1975, and Batioladinium Brideaux 1975. Broomea ramosa Cookson and Eisenack 1958 exhibits a clear intercalary archeopyle, formed by the loss of a single plate, probably correspond- ing to plate 2a (Wiggins, 1975; Brideaux, 1975). Alberti (1961) described six new species from the Valanginian to Late Barremian of northwest Germany, which he provi- sionally assigned to Broomea, but noted that their archeopyles were not formed by the loss of an intercalary plate, because it was apparent that "in some species an apical part of the shell is often lacking" (Alberti, 1961:26, translation by Dorhofer). This was interpreted by subsequent authors as an (A) type archeopyle and, therefore, Brideaux (1975) followed Alberti's proposal and erected Batioladinium , to which he transferred most of Alberti "s "Broomea" species. Wiggins (1975) formulated the genus Necrobroomea, not knowing of Batioladinium. Earlier, however, Vozzhennikova (1967) had described the genus Imbatodinium, which included species with intercalary and apical archeopyles. The type species, /. kondrajevi Vozzhennikova 1967 was stated to have an apical archeopyle, also apparent from her illustrations and reillustrated in our material (Figs. 27d, E, 28a, 29b, C). We investigated specimens of Imbatodinium kondratjevi Vozzhennikova 1967, "Broomea" jaeger i Alberti 1961, "Broomea" longicornuta Alberti 1961, "Broomea" micropoda Eisenack and Cookson 1960, and "Broomea" pellifera Alberti 1961. All species conform in general shape, tabulation, and archeopyle, and belong to Im- batodinium, which has priority over Batioladinium and Necrobroomea. Well-preserved specimens of "Broomea" pellifera exhibited the tabulation 4', 2a, 6", 16-1" ' , ?l-2p, 1" ", ?pv (Fig. 33a-D). The archeopyle is formed by the loss of a compound operculum including all apical and anterior intercalary plates (4A2I). In all the above species the hypctract is attenuated, resulting in a low position of the cingulum on the cyst body. Two hypotractal horns are always present. Aptea Eisenack 1958 Aptea was erected as a monotypic genus, the type species being Aptea polymorphs Eisenack 1958. The sole ditterence from Pseudoceratmm is the considerable reduction in horn length. Aptea rugulosa Clarke and Verdier 1967 was added to the genus but differs significantly from Aptea polymorphs, as it bears two symmetrically placed antapical horns on the hypotract. This is a feature of Canningia Cookson and Eisenack 1960 to which Aptea rugulosa has been transferred (Stover and Evitt, 1978). Davey and Verdier (1974) emended the genus, erected Aptea securigera and transferred Cyc- lonephelium attadalicum Cookson and Eisenack 1962 and Cyclonephelium eisenackii Davey 1969 to the genus. In their emended generic diagnosis the following features were considered important: 1) asymmetrical rounded- triangular outline; 2) ornamentation with membranous crests and/or processes; and 3) indications of horn positions (apical, antapical, postcingular) by ornament and /or protuberances of the autophragm. They empha- sized the typical asymmetry which serves to separate Aptea from Cyclonephelium Deflandre and Cookson 1955, Canningia Cookson and Eisenack 1960, and Tenua Eisenack 1958. It is apparent that the only difference between Aptea and Pseudoceratium is the greater length of horns in the latter genus. This feature is probably of subgeneric significance, but for the present Aptea is retained apart from Pseudoceratium. Upper Aptian samples from northwest Germany contain abundant Aptea pohmorpha. A detailed description and emendation of the species is given below in the systematic section. The most important features are the tabulation formula 4', 2a, 6", 5-6c, 6" ', lp, 1" ", ?3-6s and a (4A2I) archeopyle. The same type of archeopyle was found in Imbatodinium indicating a close relationship between both genera. Pseudoceratium Gocht 1967 The original generic diagnosis of Pseudoceratium (Gocht, 1957:166) did not mention many features which now could serve as differential criteria. In the diagnosis of the type species P. pelliferum Gocht 1957, however, the following criteria were considered important: 1) asymmetrical-triangular outline; 2) development of three horns (apical, antapical, right postcingular); and 3) ornamentation with short spines, which may fuse at the bases. Tabulation could not be determined in any of Gocht's specimens and this feature was included in the generic- diagnosis, where allowance was made to include P. Inudum Gocht 1957: "shell smooth or clothed with short appendices" (transl.). Pseudoceratium 'nudum and P? . tetracanthum Gocht 1957 were only doubtfully included and the latter species was transferred to Muderongia (Alberti 1961: 14). At present P ''nudum and P. 13 dettmanniae Cookson and Hughes 1964 are the only smooth species included in Pseudoceratium. Pseudoceratium dettmanniae is clearly cavate and, there- fore, belongs to Endoceratium Vozzhennikova 1965 as suggested by Wall and Evitt (1975). Stover and Evitt (1978) recently made the transfer. Smooth asymmetrical forms with three horns are best kept in Odontochitina and, hence, P. Inudum is transferred to this genus. After these transfers, only ornamented species stay in Pseudoceratium. Neale and Sarjeant (1962) encountered forms which exhibited some traces of tabulation but in all other respects conformed with the morphology of P. pelliferum. The presence of faint tabulation traces was considered suffi- cient to separate the tabulated species P. (Eop- seudoceratium) gochtii Neale and Sarjeant 1962 (non Pocock 1962), who applied the same name to specimens of Imbatodinium jaegeri (Alberti 1961 comb, nov.) on subgeneric level. Eisenack (1961:284) had already dis- cussed the irrelevance of such tabulation traces for classification purposes on forms which otherwise con- form. For example he mentioned "Pseudoceratium" ludbrookiae, which was regarded as untabulated until specimens were found exhibiting clear tabulation. Hence, Eisenack (1964) rejected the subgeneric treatment of Pseudoceratium by Neale and Sarjeant (1962). Further- more, he mentioned that in P. gochtii "the tabulation is at least hard to recognize" (translation by Dorhofer: 325). It is interesting that the tabulation given by Neale and Sarjeant (1962) indicated the presence of an intercalary series. Wall and Evitt (1975) also observed specimens with tabulation traces from the same locality and called them P. pelliferum. They could not find support for the tabulation formula given by Neale and Sarjeant (1962) and rather suggested a basic ceratioid tabulation (without intercalaries). Davey (1974) and Duxbury (1977) also observed tabulated specimens of/', pelliferum but did not determine the tabulation formula. Singh's (1971 : pi. 67, fig. 1) illustration of P. expolitum Brideaux 1971 suggests breakage along a suture between apical and intercalary plates. Specimens off. pelliferum (Figs. 35f, 37B-E) also suggest the presence of two anterior intercalary plates, mainly based on the asymmetry of the archeopyle suture and a linear area devoid of ornament with a frequent indentation in the outline of the cyst in the area of the putative suture. Plate boundaries in Pseudoceratium are delineated by penitabular ornament. The tabulation ap- pears identical to that of Aptea. Muderongia Cookson and Eisenack 1958, PhoberocystaMilhoud 1969 The following discussion of Muderongia is mainly based on specimens of Muderongia simplex Alberti 1961, which were encountered from Arctic Canada and Germany. Many folded specimens resembled cysts illustrated by Alberti (1961) as Cantulodinium Alberti 1961. This genus has only been found in Alberti's samples together with Muderongia simplex. From our material we suggest that Cantulodinium constitutes only folded Muderongia and we, therefore, consider it synonymous. The presence of two intercalary plates is demonstrated in Fig. 36c, D, F. The form of the archeopyle resembles that of Aptea, indicating close relationships between the two genera. Muderongia differs from all other pseudoceratiacean genera (except Phoberocysta) in that it usually exhibits two almost bilaterally symmetrical postcingular horns and two antapical horns. Muderongia is cavate and always smooth. This is the sole difference from Pnoberocysta, which is always heavily ornamented (Millioud, 1969). In the position of horns, archeopyle suture and type, and cyst symmetry, this genus is very similar to Muderongia. Odontochitina Deflandre 1935 No tabulation has yet been observed in this genus and to judge from the featureless surface, it is unlikely that detailed tabulation will ever be determined. The basic pseudoceratiacean appearance of Odontochitina has been noted by many authors, most recently by Wall and Evitt (1975). Several excellently preserved specimens from the German Neocomian have shown some possible traces of tabulation; yet, no formula can be furnished. The position of the sulcus is apparent from Fig. 40a. The body surface is covered by numerous pits which in some areas are densely aligned, probably representing tabulation sutures. The archeopyle suture is asymmetrical as in Aptea. Both genera appear to be closely related, suggesting similar tabulation. Tenua Eisenack 1958, Doidyx Sarjeant 1966, Canningia Cookson and Eisenack 1960, Cyclonephelium Deflandre and Cookson 1955 Wall and Evitt (1975) discussed the possible relationship of these genera to the "Cretaceous ceratioid group". They cited several similarities between the two complexes including weak bilateral asymmetry, type (A) archeopyle, zigzag outline of archeopyle sutures and the offset of the sulcal notch to the left dorsal position. According to Wall and Evitt (1975) these genera lack three characteristics, which they consider typically ceratioid, namely, pro- nounced asymmetry of the hypotract, presence of postcin- gular horn(s), and Ceratium-type tabulation. On this basis they considered the entire complex non-ceratioid but closely related to the "true" ceratioids like Aptea and Endoceratium. The type species of Tenua (/. hystrix Eisenack 1958) is bilaterally symmetrical and has no indications of horns. It clearly exhibits dorsal and/or ventral reduction of its spine cover, similar to the reduction zones observable in Aptea and Cyclonephelium. The archeopyle suture is also similar to the latter genus, as it does not exhibit the strong asymmetry of Aptea or Pseudoceratium. The tabulation 14 has not yet been determined. The holotype specimen cannot be distinguished from Cyclonephelium. The only differences between Tenua hystrix and Cyclonephelium distinct urn Deflandre and Cookson 1955 are slightly longer and less densely arranged processes in the latter. Such a slight difference does not justify generic separa- tion: hence, Tenua is a junior synonym of Cyclonephelium (Davey, in press) which, however, should be restricted to apteate cysts. Chorate cysts of this type were transferred to Glaphyrocysta Stover and Evitt (1978). Bilaterally sym- metrical cysts with an uniformly dense cover of ornament, which subsequently were assigned to Tenua (in particular those from the Late Jurassic), are transferred to Batiacas- phaera Drugg emend. Neither in Cyclonephelium nor in "Tenua" could the presence of an intercalary series be established. The type species of Canningia (C. reticulata Cookson and Eisenack 1960) exhibits two pronounced antapical horns and two postcingular bulges. The former probably corresponds to plate positions lp, 1" " (right) and 6" ', 1" " (left) as shown by Wall and Evitt (1975) on Canninginopsis denticulata Cookson and Eisenack 1962, which is essentially similar to Canningia but with sutural ornament. It is not known whether an intercalary series is developed; however, some published illustrations would favour such an assumption, such as C. reticulata (Cookson and Eisenack 1960: pi. 38, fig. 2), C . colliveri (Cookson and Eisenack 1960: pi. 38, figs. 3,4). From this evidence it seems that some Canningia have intercalary plates included in the operculum, resulting in the large archeopyle often observed. Canningia constitutes a heterogeneous group and further research is warranted. The sole species of Doidv.x (D. anaphrissa Sarjeant 1966) has three horns developed in apical, antapical, and right postcingular positions. The cyst body is clearly asymmetrical, the ornament is apteate, and the archeopyle suture is identical to that of Aptea. Doidyx anaphrissa, therefore, was transferred to Aptea (Sarjeant and Stover, 1978); its transfer to Tenua by Benedek (1972:9, 10) was unwarranted. Within this complex clear intergradations are developed between the symmetrical group possessing intercalary plates and the symmetrical group without such plates. In the Late Barremian of Germany we have found cysts (Fig. 40B, F) with asymmetrical archeopyle sutures and slight asymmetrical body shape; only the apical horn is developed. The operculum contains intercalary plates. We regard these forms as extreme variants of Aptea anaphrissa. Intercalary Plates and Horn Development in Pseudoceratiacean Cysts Wall and Evitt (1975) regard forms as non-ceratioid if the hypotractal horns are situated antapically (instead of postcingularly) and the body is symmetrical. They stressed that the presence of intercalary plates would also indicate non-ceratioid affinities. These points are discussed below. Intercalary Plates As demonstrated above, Imbatodinium and Aptea possess intercalary plates. These plates are part of the operculum. The typical asymmetrical pseudoceratiacean suture appar- ent from Canningia, Muderongia, Phoherocysta , Odon- tochitina, Pseudoceratium, and Endoceratium suggests the same for these genera. Few of them exhibit any tabulation and only with the use of interference contrast microscopy and SEM was it possible to detect intercal- ary/apical sutures. Affinities among the pseudoceratia- cean taxa are stronger than resemblances to modern Ceratium; therefore, all the Cretaceous genera referred to as ceratioid (Wall and Evitt, 1975) should be regarded as pseudoceratiacean. Ceratium apparently has lost all signs of ancestral intercalary plates. Horn Positions: Antapical versus Postcingular Wall and Evitt (1975) argued against the relationship between "true Cretaceous ceratioids" and the "Broomea-group" . They consider the presence of post- cingular horns as essentially ceratioid. We have plotted in a schematic manner the position and development of horns in the entire pseudoceratiacean complex (Fig. 4). It shows that the earliest forms first developed two short antapical horns {Imbatodinium pelliferum, I. gochtii) which then became longer (Imbatodinium longicornutum Alberti, comb. nov.). Next was the development of two postcingu- lar horns in addition to the two antapical horns. At the same time the right antapical horn was already reduced (Muderongia, Phoberocysta). Further evolution led to the loss of the left postcingular and right antapical horn (Odontochitina, Pseudoceratium, Aptea). All horns are further reduced in Aptea, connecting the genus to forms devoid of horns (Cyclonephelium) or only showing slight bulges (Canningia). In the earliest forms (Imbatodinium) the cingulum is situated in the posterior half rather than centrally. Thus, the areas of origin of the antapical and the postcingular horns are close to each other. The pseudoceratiacean genera appear to have at least the potential ability to develop all five horns (Fig. 4, as shown in Canningia, Muderongia, or Phoberocysta). Specimens of Glomodinium from the Oxfordian/Kimmeridgian already exhibit a bulge in addition to the pronounced (?left) antapical horn (Fig. 29a), which might be interpreted as an incipient right antapical horn. Symmetry of pseudoceratiacean cysts is mainly expressed by the position of horns and the position of the anterior intercalary plates. Strong asymmetry, as a result of reduction of the right antapical horn, is always accom- panied by a strongly asymmetrical archeopyle suture 15 Par eodi m a Komewuia I mbatod inium gochti I longtcornut urn Phoberocysta Muderongia simplex Aptea Fig. 4 Horn development of pseudoceratiacean cysts from pareodiniacean cysts (dorsal view). inherent from a right-lateral shift of the intercalary plate position from the mid-dorsal area (Fig. 5). Typical asymmetrical genera are Odontochitina, Pseudoceratium, Aptea, Endoceratium. Earlier forms such as Imbatodinium, Muderongia simplex, and Phoberocysta, which are more symmetrical with regard to the horn development and position, also have the intercalary plates placed centrally in mid-dorsal position. The proposed lineage (Fig. 7) constitutes a gradual development of closely related morphological cyst types. In their experimental work on Ceratium hirundinella Huber and Nipkow (1923) have demonstrated that the angle of hypotractal divergence (between the right postcingular horn and the left antapical one) is positively related to water temperature. This angle increases with increasing temperature and decreases with decreasing water temperature. Also two-horned specimens developed in cold water, four-horned varieties in warm water. The earliest pseudoceratiacean forms have few horns and also have a very small spreading angle. This feature has been related to their possible derivation from high latitudinal cool-water areas (Dorhofer, in press). The evolution of forms with more horns and a larger spreading angle was possibly related to the shift of cool-water masses into somewhat lower (and warmer) latitudes shortly after the beginning of the Cretaceous, for example Muderongia, Phoberocysta. Discussion (Figs. 6, 7) The following discussion on the evolution of archeopyles and associated cyst characters is based on the premise that the keystone plate is a dominant structural feature and has remained in mid-dorsal position. The earliest dinoflagellates with undoubted tabulation have been recorded from the Late Triassic of Alaska and Arctic Canada (Wiggins, 1976, 1973; Fisher and Bujak, 1975; Bujak and Fisher, 1976). The Arctic Islands were shifted considerably northward during the Triassic and 16 medio - dorsal Muderongia dextro - lateral Aptea symmetrical asymmetrical Fig. 5 Relationship between bilateral symmetry and position of anterior intercalary plates in pseudoceratiacean cysts. Archeopyle (AI). Early Jurassic (Irving. 1974) causing geographic isolation of the Arctic Basin. Rising continentality in high latitudes is of prime importance for influencing world climate (Donn and Shaw, 1977). A pronounced increase in surface albedo due to increased continentality at high latitudes would result, causing cooler boreal climates. Thermal and geographical isolation of the Arctic Basin would have been the ideal situation for the development of dinoflagel- late cysts. Earliest cysts are proximate, which is a typical cool-water feature (Dorhofer, in press). Chorate acritarchs such as Micrhystridium Deflandre 1937 may have adapted to the stressed polar environment by development of a proximate cyst mode (Dorhofer, 1977a, b). These acritarchs would be expected to have primitive dinoflagel- late features such as suessioid tabulation and disintegration archeopyles. Such forms have been found in the Lower Jurassic (Fig. 21a, C). Further research on Triassic acritarchs is needed to demonstrate dinoflagellate cyst ancestry. Development of the ancestral dinoflagellate cyst stock probably occurred in the Late Triassic (latest Karnian; Wiggins, 1976) with Rhaetogonyaulax as the earliest known member (Figs. 4, 5). The Rhaetogonyaulax- complex arose during the Late Triassic from earliest forms with rounded apex and antapex ("Shublikodinium") to more spindle-shaped forms like R rhaetica (Sarjeant) Loeblich and Loeblich 1968. However, the basic form was maintained. Complex and strongly tabulated cysts with rounded body shape such as Suessia and its cavate counterpart Noricysta appear near the base of the Norian (Wiggins, 1976) and probably are directly related to the "Shublikodinium" types of Rhaetogonyaulax. Sverdrupiella and Heibergella also evolved directly from Rhaetogonyaulax in the Late Norian, maintaining the typical spindle shape and the primitive disintegration archeopyle, initiated by the loss of one to three anterior intercalary plates (Fig. 20D). Neither Rhaetogonyaulax nor Sverdrupiella have been recorded from sediments younger than Hettangian; however, genera that are very similar in shape, structure, and ornament such as Wanaea Cookson and Eisenack 1958 and Glossodinium Ioannides et al. 1977 occur in the Late Jurassic. Dapcodinium from the late Hettangian of Denmark (Evitt, 1961) and the late Pliensbachian of northwest Germany (Morgenroth, 1970) continued the primitive lineage. The disintegration ar- cheopyle is maintained, but, increasing stabilization is indicated by the fact that the apical series constitutes one opercular piece and often remains attached ventrally (Figs. 25e, G, 22d, g, I). In tabulation there is a reduction of the number of plates. Specifically, the intercalaries are reduced to four or five. Dapcodinium was observed in the Sverdrup Basin to range into the Toarcian to Bathonian. Comparodinium appeared in the latest Rhaetian (Mor- bey, 1975) and has been found up into the Toarcian to Bajocian of Arctic Canada and Germany (Wille and Gocht, in press). It is the earliest genus with a stabilized archeopyle (apical). The tabulation indicates affinities with Dapcodinium. The Toarcian is characterized by the first occurrence of 17 (4A2I) Imbatodinium -► Cyclonephelium 2a Pareodinia Glomodinium 31 4A/(4A) Lithodin/a Phal locysta Gonyaulacysta Gonyaulacysta (type 'aldorfense') 31 3P /?/)aefo<7onyau/ax RHAETOGONYAULACINEAE H YSTRICHOSPHAERID GONYAULACYST Fig. 6 Evolution of archeopylc types within the Rhaetogonyaulacineae, Hystrichosphaendiineae, and Gonyaulacystineae from a common ancestor with disintegration archeopylc. 18 CO o LU o CENOMANIAN ALBIAN APTIAN < LU o KIVMERIDGIAN if) CO < cr Z) "3 O CO CO < BARREMIAN HAUTERIVIAN VALANGINIAN BERRIASIAN TITHONI AN OXFORDIAN CALLOVIAN BATHONIAN BAJOCIAN TOARCIAN PLIENSBACH SINEMURIAN HETTANGIAN RHAETIAN NOR I AN KAR NIAN Q. 5 5 p - 11 X3 a ^= pseudoceratiacean on\aulac\sla reiiphrax,mtuu sp no\ . holotype, showing tabulation and archeopyle. Tabulation: 4', 3a, 6", 6c, 6' ", 2p. 2p\ . I archeopyle 31 t -3. SC sulcal crest 31 Provenience Savik Formation, 110 m below the top (1260 ft. cutting sample). Elf Jameson Bay C-31 well, Prince Patrick Island. District of Franklin, Northwest Territories, Canada. Holotype Slide JB 1260A, ROM 36529, 55.1/105.1. Figs. 29D-F. Size: 48 /urn. Diagnosis A species of Paragonyaulacysta with finely reticulate autophragm and punctate sutural crests. Tabulation 4', 3a, 6", 6c, 6" ', 2p, 2pv, 1" ", ?s; archeopyle 3Ii— 3. Remarks The reticulum consists of very fine irregular meshes (0.25-1.0 /xm). The height of the sutural crests is about 3 jam. In all other respects the species corresponds to P. calloviensis . Length 61(54)48 /urn; breadth 45(41)35 /xm. Stratigraphic Range Callovian, Elf Jameson Bay C-31 (307^06 m). Pareodinia Deflandre emend. Gocht 1970 Pareodinia Deflandre 1947:402. Pareodinia Deflandre emend. Gocht 1970: 153. Pareodinia Deflandre emend. Wiggins 1975:103. Type Species Pareodinia ceratophora Deflandre emend. Gocht 1970:153-156. Remarks The original generic diagnosis mentioned the globular shape and apical horn. Pareodinia ceratophora Deflandre 1947 was assigned as type species. The holotype is embedded in flint from a glacial boulder. It appears to be corroded and poorly preserved, seemingly having pyrite aggregates within the cyst. Gocht (1957) grouped Pareodinia with Pseudoceratium Gocht 1957, Odontochitina Deflandre 1935, Ceratocys- tidiopsis Deflandre 1937, and Nannoceratopsis Deflandre 1938 into the family Pareodinidae Gocht. Evitt (1961) included forms with an apical archeopyle in Pareodinia but later corrected this to include only intercalary archeopyles (Evitt 1967). Sarjeant (1966) erected P or anetr elytron to incorporate Pareodinia-Yike cysts with an endoblast. This was disputed by Wiggins (1975). Gocht (1970) noted that the type specimen of Pareodinia does not show any archeopyle, cingulum, or sutures, leaving only the variable shape to define the genus. He then examined topotype material and concluded that Pareodinia ceratophora has a 21 archeopyle. Pareodinia was emended to include forms of elongate shape with an apical horn and occasionally pointed antapex, smooth or granulate to slightly tabulated, having a kalyptra retained only under good preservation and gentle preparation, and having a 21 archeopyle. Sarjeant (1972) allocated two more species to the genus: Pareodinia groenlandica Sarjeant and P. apotomocerastes Sarjeant, both having 21 archeopyles. He also maintained Paranetrelxtron as a distinct genus (Sarjeant, 1972, 1976). Archeopyles of 31 type were found in pareodiniacean cysts by Johnson and Hills (1973), who emended Pareodinia Deflandre emend. Gocht to include both 21 and 31 archeopyles. Wiggins (1975) reviewed the family Pareodiniaceae and emended the genus Pareodinia to include species which accord to the tabulation formula 7a. cl., 6', 6a, 6", 7" ', 3" " (a. cl.: apical closing plates) and which have archeopyles formed by the loss of one, two, or three intercalary plates. After this emendation he regarded the following genera as synonymous with Pareodinia: Broomea Cookson and Eisenack 1958; Pluriarvalium Sarjeant 1962; Paranetrelxtron Sarjeant 1966; and Imbatodinium Vozzhennikova 1967. This emendation left the genus too widely circumscribed (Norris, 1978b). We consider Broomea as a distinct genus which has a II archeopyle (Wiggins, 1975; Norris, 1978b). We agree, however, in the treatment of Pluriar- valium as junior to Pareodinia. Latent tabulation traces are expected in all proximate cysts and the occasional presence does not justify generic separation (Gocht, 1970; Wiggins, 1975; see also discussion on Pseudoceratium). Only when strong sutural crests are developed such as in Paragonyaulacysta Johnson and Hills 1973 does the presence of tabulation warrant generic distinction. Differ- ent tabulation formulae for "Pluriarvalium" -types have been given by a number of authors: Sarjeant (1 962) — ?5\ l-3a, 6", 6" ', lp, lpv, 1" " Warren (1967) — 4', 2a, 6", ?6c, ?6-7" ', lp, 1" ", 3s Singh (1971) — ?4a, 6", 6" ' Wiggins (1975) — 7a. cl., 6', 6a, 6", 7" ', 3" " Brideaux and Fisher (1976) - • ?4', 2a, 6", 6c, 5-?6" ', lp, 1" ". Warren's (1967) and Brideaux and Fisher's (1976) interpretations differ only in the number of postcingular plates, which are difficult to determine. We agree with Warren's interpretations of ?6-7" '. We have found no evidence for more than two anterior intercalary plates and have not been able to identify any apical closing plates. 32 Family Pseudoceratiaceae Eisenack (1961) emend. Type Genus Pseudoceratium Gocht 1957. Emended Diagnosis Proximate (eavate or acavate, smooth to apteate); horns in up to five positions (1 apical, 2 antapical and 2 postcingular); ornament reduced or lacking, in penitabular or nontabular arrangement; tabulation is intermediate between suessiod and gonyaulacoid; archeopyle AI. This is expressed by the logogram AI, sus-gon, ap, l-2aa, 1-2 pc, pr, non-abs-pen. Aptea Eisenack emend. Davey and Verdier emend. Aptea Eisenack 1958:394. Doidyx Sarjeant 1966:206. Aptea Eisenack emend. Davey and Verdier 1974:641- 642. Type Species Aptea polymorpha Eisenack emend. Remarks Essentially we agree with the emendation of the genus us proposed by Davey and Verdier (1974) but some additional emending remarks are necessary to cir- cumscribe more closely the archeopyle. The archeopyle is (4A2I); tabulation formula: 4', 2a, 6", 5-6c, 6" ', lp, 1" ", ?3-6s. The apteate ornament is better developed in the circumferential area with both ventral and dorsal areas being virtually devoid of ornament. The ornament is usually penitabular with less frequent intratabular ele- ments. Some species of Aptea are considered to be transitional to eavate types, as the ornament is developed on an otherwise smooth autophragm; but the terminal ends of the processes tend to fuse. Total fusion would result in the formation of eavate forms like Endoce rati urn (Fig. 15). Endoceratium dettmannae en Endoceratium ludbrooki (ec) aut Aptea polymorpha Fig 15 Schematic transection through the cyst wall of species ol Endoi cratium and Aptea, to show the transition between eavate (EndtX eratium) and apteate forms {Aptea). ec: ectophragma; en: endophragma; aut: autophragma. 33 Transitional forms between Aptea and Endoceratium do exist. The type species E. ludbrookiae (Cookson and Eisenack) Vozzhennikova 1965 exhibits broad supporting ridges between the endophragm and periphragm (Norvick and Burger, 1976). As already partially expressed by Davey and Verdier (1974) the following criteria are particularly important in differentiating Aptea from similar genera: asymmetry of the cyst body, considerable reduc- tion of horns, always ornamented, (4A2I) type ar- cheopyle. Cyclonephelium Deflandre and Cookson 1955 and Batiacasphaera Drugg emend, are typically asymmet- rical and most probably have an (4A) archeopyle. Muderongia Cookson and Eisenack 1958 and Phoberocysta Millioud 1969 have two postcingular horns. Odontochitina Deflandre 1936 contains only smooth forms. Aptea is morphologically similar to Hetero- sphaeridium and Pseudoceratium, occupying an inter- mediate position between them. The processes become increasingly closer, longer, and more slender proceeding from Pseudoceratium to Heterosphaeridium (compare Figs. 36b, 37a, d). The following species agree with the emended generic diagnosis: Aptea poly mo rp ha Eisenack emend. Aptea anaphrissa (Sarjeant) Stover and Evitt 1978. Aptea attadalica (Cookson and Eisenack) Davey and Verdier 1974. Aptea eisenacki (Davey) Davey and Verdier 1974. Aptea securigera Davey and Verdier 1974. Aptea polymorpha Eisenack emend. Figs. 16, 37a, 38a-f, 39a-F Aptea polymorpha Eisenack 1958, p. 393. Emended Description Autoblast subcircular to egg-shaped in outline, dorsoven- trally flattened. Slight outward bulging occurs sometimes in the position of the three (occasionally four) horns which are marked by ornamental differentiation. These positions correspond to apical (left), antapical, and right postcingu- lar horns. Either or both of the latter two horns may not be developed in all specimens, the postcingular horn being suppressed first. The axis connecting the apical and antapical horns is always shifted to the left, the cyst being always asymmetrical. The autoblast is rather thick-walled. Its surface is finely pitted to granulate. Often sutures are marked by relatively broad pandasutural zones, represent- ing intercalary growth bands, characterized by striations perpendicular to the plate boundaries. Pandasutural areas 50 /» ■ \ 1.5- \ \ \ \ ■\ \ \ ■ 1.4- \ ■\. \ . \ \ . \ " 13- \ \ ■ i "■ WW w Doidyx £\ anaphrissa v 1.2- \ ■\ \ -~~~ 1- ^ \ \ 1 •■■'•• ""~--. \ . ".'"-.'! '.'■■. '■■' ■ / 7* \ 1 1 - t ! ' \ / -^^ 1.0- i i it i i \ ex 0° 50° 60° 70° 80° 90° 100° Fig. 17 Hypotractal horn divergence of Apleu pohmorphu Eisenack 1958 "Doidyx" anaphrissa is plotted to indicate Us close affinity 35 case is the disappearance of the postcingular horn once L/ W is greater than 1.6; at the other extreme, forms with low extension ratios might exhibit indications of a left postcingular horn. The horn positions, however, become harder to determine with decreasing L/W as the horn bulges become indistinct and the outline almost circular. The presence of a fourth horn is restricted to these compact varieties. The archeopyle is (4A2I); its suture is zigzag in shape and asymmetrical, the left part being strongly deflected to the apex, the right part to the cingulum. Ventrally a sulcal notch is developed between plates 1' and 6", and another notch occurs where the 5" and 6" meet at the archeopyle suture. Dorsally the suture line dips down at the junctions of 2', 2", 3", and of 3', 3", 4". The presence of intercalary plates is responsible for the asymmetry of the archeopyle suture and of the autoblast. The sutures between the intercalary and the apical plates are very faint. symmetrical and the antapex founded. We, therefore, consider only the following species as belonging to Canningia: Canningia reticulata Cookson and Eisenack 1960 C. aspera Singh 1971 C. colliveri Cookson and Eisenack 1960 ?C. granulata Morgenroth 1966 C. hirtella (Alberti) Millioud 1969 C. rugulosa (Clarke and Verdier) Stover and Evitt 1978 C. scabrosa Cookson and Eisenack 1970 C. senonica Clarke and Verdier 1967. The remaining species have been transferred to Batiacas- phaera Drugg emend. Heterosphaeridium Cookson and Eisenack 1968 Canningia Cookson and Eisenack emend. Canningia Cookson and Eisenack 1960:251. Canningia Cookson and Eisenack emend. Cookson and Eisenack 1961:72. Type Species Canningia reticulata Cookson and Eisenack 1960. Remarks The emendation by Cookson and Eisenack (1961) to include forms with rounded antapices is unwarranted because the generic concept became too wide and heterogenous (Singh, 1971 :322). As originally proposed, only species which clearly indicate the presence of two antapical horns should be included. Furthermore, some species, such as the type species, C . reticulata indicate the presence of two postcingular horns by slight bulges. The wider generic concept would make the genus almost indistinguishable from Batiacasphaera Drugg emend. The type species Canningia reticulata exhibits an asymmetrical archeopyle suture suggesting an (AI) ar- cheopyle and pseudo-ceratiacean affinity. The genus is therefore emended: proximate dinoflagel- late cysts with roughly five-sided to almost circular outline. Apex prominent, antapex broadly indented between two rounded antapical horns. Cingulum occa- sionally indicated by faint surface ornamentation and/ or slight bulges representing postcingular horns. Surface smooth or with low but variable ornament. Archeopyle (AI), formed along an asymmetrical zigzag suture line. Tabulation was not determined. Some species presently in Canningia do not exhibit the (AI) archeopyle and are omitted from the genus. Their archeopyle suture is Type Species Heterosphaeridium conjunctum Cookson and Eisenack 1968. Heterosphaeridium heteracanthum (Deflandre and Cookson) Eisenack and Kjellstrom 1971 Fig. 36a, B Hystrichosphaeridium heteracanthum Deflandre and Cookson 1955:276, pi. 2, fig. 5. Heterosphaeridium heteracanthum (Deflandre and Cook- son) Eisenack and Kjellstrom 1971 : 451, pi. 4, fig. 4. Remarks Recent work (Dorhofer, in preparation) presents evidence for a (4A) + (21) archeopyle indicating pseudoceratiacean affinity. The archeopyle initiates as a (4A2I) type (Fig. 36b); breakdown of the operculum into two opercular pieces occurs later and is probably due to weak apical / intercalary sutures. Imbatodinium Vozzhennikova emend. Imbatodinium Vozzhennikova 1967:52. Batioladinium Brideaux 1975:1240. Necrobroomea Wiggins 1975 : 1 1 1 . Type Species Imbatodinium kondratjevi Vozzhennikova emend. 36 Emended Diagnosis Elongate proximate dinoflagcllate cysts with an apical horn and two hypotractal (antapical) horns; surface of autophragm smooth or with very low granules, verrucae, or spines. Tabulation, when evident, is 4', 2a. 6", 6c, 6-7" '. l-2p. 1" ", ?pv. ?s. The epitract is enlarged relative to the hypotract leaving the cingulum close to the antapex. Archeopyle (4A2I). The operculum occasionally remains attached to the sulcus. The emendation is necessary to describe the tabulation and to state the presence of an (AD archeopyle instead of an apical one. Remarks This genus differs from all pareodiniacean genera by its mode of archeopyle formation. It differs from Phoberocxsta . Pseudoceratium . and Aptea by the lack of ornament, the horn positions, and the posteriorly displaced cingulum. Muderongia, Odontochitina, and En- doceratium are cavate and also possess postcingular homs. The following species accord with the emended diagnosis: Imbatodinium kondratjevi Vozzhennikova emend. /. exiguum (Alberti) comb. nov. / gochtii (Alberti) comb. nov. /. imbatodinensis Vozzhennikova 1967 /. jaegeri (Alberti) comb. nov. /. longicornutum (Alberti) comb. nov. /. micropodum (Eisenack and Cookson) comb. nov. /. pelliferum (Alberti) comb. nov. The main distinguishing criteria are surface ornamenta- tion, which is always very low, and length of horns. Surface patterns are best recognized under the SEM, and are illustrated for several species (Figs. 3lB, 32a-C). Imbatodinium kondratjevi Vozzhennikova emend. Figs. 30A-E, 31A-F, 34c, E Imbatodinium kondratjevi Vozzhennikova 1967:55, pi. 9, figs. 1-9; pi. 10, figs. 1-6; pi. 11, figs. 1-3; pi. 15, figs. 1^. One aberrant specimen displayed 21 archeopyle The ornament is corrugated-granular. A mid-ventral internal thickening (omphalos) is usually present (as in all pseudoceratiaceans studied) (Fig. 30b). The left antapical horn is generally longer. The cingulum is not always as well pronounced as the original description suggests Imbatodinium exiguum (Alberti) comb. nov. Broomea exigua Alberti 1961 :26, pi. 5, fig. 14. Batioladinium"! exiguum (Alberti) Brideaux 1975:1240. Necrobroomea exigua (Alberti) Wiggins 1975: 111. Imbatodinium gochtii (Alberti) comb. nov. Broomea gochtii Alberti 1961 : 27, pi. 5, figs. 8-10. Necrobroomea gochtii (Alberti) Wiggins 1975:111. Imbatodinium jaegeri (Alberti) comb. nov. Broomea jaegeri Alberti 1961:26, pi. 5, figs. 1-7. Batioladinium jaegeri (Alberti) Brideaux 1975:1240, figs. 1-3. Necrobroomea jaegeri (Alberti) Wiggins 1975: 111. Imbatodinium longicornutum (Alberti) comb. nov. Fig. 32E Broomea? longicornuta Alberti 1961:27, pi. 5, figs. 18-21. Batioladinium longicornutum (Alberti) Brideaux 1975:1240. Necrobroomea longicornuta (Alberti) Wiggins 1975 : 1 1 1 . Remarks The species is emended to include reference to an (AI) archeopyle, probably involving four apical and two intercalary plates. In all other respects our specimens from the Sverdrup Basin conform with the original description. The presence of two anterior intercalary plates could be established under the interference contrast microscope; however, all sutures are very faint and are not easily photographed. These sutures are not expressed by sculptural elements and are not normally visible with SEM, suggesting that they constitute differentiations within the phragma or are expressed on its inner surface. Imbatodinium micropodum (Eisenack and Cookson) comb. nov. Fig. 32a, D Broomea micropoda Eisenack and Cookson 1960:7, pi. 2, figs. 8, 9. Batioladinium micropodum (Eisenack and Cookson) Brideaux 1975:1240. Necrobroomea micropoda (Eisenack and Cookson) Wig- gins 1975:11 1. 37 Imbatodinium pelliferum (Alberti) comb. nov. Figs. 18, 33a-d Broomea pellifera Alberti 1961:26, pi. 5, figs. 11-13. Batioladinium"! pelliferum (Alberti) Brideaux 1975:1240. Remarks We do not agree with Wiggin's treatment of "Broomea" pellifera as a junior synonym of "Broomea" micropoda. The ornament of "B" micropoda is "coarsely and closely granular" (Eisenack and Cookson 1960:7) whereas ornament of "B" pellifera is a short "fur-like" cover of densely arranged thin hairs (Alberti 1961; our own observations). /. pelliferum exhibits faint sutural ornament under interference contrast illumination with tabulation of 4', 2a, 6", 6c, 6' ' ', ?p, ?" ", ?s. Imbatodinium sp. Fig. 32b, f Description Elongated proximate dinoflagellate cyst with a long apical hom, and two short antapical horns of which one (left) is longer. Usually no tabulation indicated except by the outline of the archeopyle suture, which is asymmetrical suggesting a (4A2I) archeopyle. Surface finely reticulate, diameter of lumina 0.1-0.5 /xm. Size: 89 p.m. Remarks Positive identification under the light microscope is difficult. This species appears similar to /. micropoda: the surface ornament, visible only under SEM, is the sole difference. This species has been identified only from the Aptian of Germany (KBT 48.5 m, Peine). Fig. 18 Imbatodinium pelliferum (Alberti) comb, nov., showing tabulation and archeopyle. Tabulation: 4'. 2a. 6". 6c, 6" '. ?p, ?" ", ?s; archeopyle (4A2I). O: omphalos 38 Odontochitina Deflandre emend. Davey 1970 Odontochitina Deflandre 1935:234. Odontochitina Deflandre emend. Davey 1970:354. Type Species Odontochitina operculata (O. Wetzel) Deflandre and Cookson 1955. Odontochitina operculata (O. Wetzel) Deflandre and Cookson 1955 Fig. 40a Ceratium operculatum O. Wetzel 1933:170, pi. 2, figs. 21, 22. Odontochitina silicorum Deflandre 1935:234, pi. 9, figs. 8-10. Odontochitina operculata (O. Wetzel) Deflandre and Cookson 1955:291, pi. 3, figs. 5, 6. Remarks The asymmetrical archeopyle suture suggests pseudoceratiacean affinity and an (AI) archeopyle. Odontochitina nuaa (Gocht) comb. nov. Pseudoceratium! nudum Gocht 1957: 168, pi. 18, figs. 3, 4, 6. Remarks This species is transferred to Odontochitina because of its smooth periphragm and its cavate nature. Pseudoceratium Gocht emend. Pseudoceratium Gocht 1957:166. Type Species Pseudoceratium pelliferum Gocht 1957. Emended Diagnosis Dorsoventrally flattened proximate dinoflagellate cysts of asymmetrical triangular shape with three long horns in apical, antapical, and postcingular positions. A fourth horn (left postcingular) is occasionally weakly developed. Ornament apteate, consisting of peni- and infratabular elements. Tabulation traces occasionally apparent, for- mula: 4'. 2a. 6", 5— 6c, 6" ', 1" ", ?3-6s. Archeop (4A2I), operculum occasionally attached ventralK Remarks The genus is emended to have apteate ornament, and intercalary plates. Odontochitina is smooth and cavate The sole difference between Pseudoceratium and Aptea is the length of the horns which are reduced in Aptea. If this feature should prove not to justify generic separation, Aptea would become a junior synonym. Muderongia and Phoberocysta approach bilateral symmetry by exhibiting two distinct postcingular horns. Pseudoceratium pelliferum Gocht emend. Figs. 35f, 37B-E Pseudoceratium pelliferum Gocht 1957: 166, pi. 18, figs. 1, 2. Remarks The species is here emended to account for the presence of two anterior intercalary plates, which are included in the operculum; archeopyle (4A2I); ornament apteate, short and numerous penitabular and intratabular processes, the latter possibly following latent sutures between fused plates (Fig. 37c, E). The surface between the processes is finely corrugated-reticulate (Fig. 37d). Horn positions correspond to one each in apical, left antapical, and right postcingular positions. A slight left postcingular bulge (Fig. 37b) possibly indicates a fourth horn. Suborder Hystrichosphaeridiineae Family Batiacasphaeraceae fam. nov. pro Canningiaceae Sarjeant and Downie Type Genus Batiacasphaera Drugg emend. Family Diagnosis and Remarks A new name is desirable for the family Canningiaceae because Canningia has been transferred to the family Pseudoceratiaceae. Batiacasphaeraceae is a substitute for the Canningiaceae and retains the original diagnosis for Canningiaceae Sarjeant and Downie (1974) that includes genera with an A-archeopyle (Norris, 1978b). Canningia, because it has an AI archeopyle is transferred to the family Pseudoceratiaceae. The logogram for the Batiacas- phaeraceae is Pr, A, non, pcin. 39 Batiacasphaera Drugg emend. Batiacasphaera Drugg 1970:813, fig. 6a-b. Batiacasphaera Drugg emend. Morgan 1975:161. Sentusidinium Sarjeant and Stover 1978. Type Species Batiacasphaera compta Drugg 1970. Remarks The genus is emended to include the remaining species of "Tenua" after the holotype of "Tenua" was transferred to Cyclonephelium (Davey, in press); it also includes those species which were removed from Canningia because they lack indented antapices and asymmetrical archeopyle sutures (see p. 00; Drugg, 1970:813; Morgan, 1975:161). Cassidium Drugg 1967 is very similar to Batiacasphaera and could possibly take priority if the exact type or archeopyle, i.e. presence or absence of intercalaries, could be established. Drugg's illustration ( 1 967 : pi. 3, fig. 15) suggests a pseudoceratiacean operculum (with two inter- calaries). Besides species transferred below, the genus contains the following: Batiacasphaera compta Drugg 1970 B. baculata Drugg 1970 B. macrogranulata Morgan 1975. Norvick and Burger (1976) suggested possible synonymy of Batiacasphaera with Memhranosphaera Samoilovich 1961 ex. Norris and Sarjeant 1965, as Drugg's (1967, 1970) diagnosis of both genera overlap. At present Memhranosphaera differs by small size and a ventrally attached operculum, which bears a pronounced sulcal tongue. Both criteria are probably of subgeneric signifi- cance. Examination of the holotype specimen is necessary to determine whether a periphragm is present. This feature would differentiate it from Batiacasphaera. Most of the species transferred below to Batiacasphaera were included in the genus Sentusidinium Sarjeant and Stover (1978), which circumscribes the same species as Batiacasphaera as emended above. Characters within the morphological group of proximate cysts with a spherical body and a (4A) archeopyle are few and at present do not justify generic separation. However, the complex is probably polyphyletic, as affinities with lithodiniacean (Jurassic forms) and areoligeracean (Cretaceous and later forms) cysts are indicated. Further research might reveal discriminating characters. The following species are transferred to Batiacaspha- era. Batiacasphaera circularis (Cookson and Eisenack) comb. nov. Canningia circularis Cookson and Eisenack 1971:219, pi. 8, fig. 6. Batiacasphaera capitata (Cookson and Eisenack) comb. nov. Hxstrichosphaeridium capitatum Cookson and Eisenack 1960:252, pi. 39, fig. 9. Tenua capitata (Cookson and Eisenack) Gitmez and Sarjeant 1972:189, pi. 1, figs. 11-12. Batiacasphaera echinata (Gitmez and Sarjeant) comb. nov. Tenua echinata Gitmez and Sarjeant 1972:190, pi. 1, figs. 1-9. Batiacasphaera minor (Cookson and Hughes) comb, nov. Canningia minor Cookson and Hughes 1964:43, pi. 8, figs. 1-3, 5. Batiacasphaera pilosa (Ehrenberg) comb. nov. Xanthidium pilosum Ehrenberg 1843:61-63. Xanthidium pilosum Ehrenberg 1 843-Ehrenberg 1854, pi. 37, figs. 8, 4. Ovum Hispid um (Xanthidium) pilosum (Ehrenberg) Lohman 1904:21-25. Hxstrichosphaera pilosa (Ehrenberg) O. Wetzel 1933:43, pi. 4, fig. 23. Hxstrichosphaeridium pilosum (Ehrenberg) Deflandre 1937:79. Battisphaeridium pilosum (Ehrenberg) Sarjeant 1960: pi. 13, figs. 11, 12; pi. 14, fig. 11. Cleistosphaeridium pilosum (Ehrenberg) Davey et al. 1966:170. Tenua pilosa (Ehrenberg) Sarjeant 1968:231, pi. 2, fig. 7. Batiacasphaera ringnesii (Manum and Cookson) comb. nov. Canningia ringnesii Manum and Cookson 1964: 15, pi. 2, fig. 10. 40 Batiacasphaera rioulti (Sarjeant) comb. nov. Type Species Tenua rioulti Sarjeant 1968:231. pi. 1. figs. 12. 22; pi. 2, tigs. 1, 2. 4. Batiacasphaera rotundata (Cookson and Eisenack) comb. nov. Canningia rotundata Cookson and Eisenack 1961 : 72, pi. 12. figs. 1-5. Batiacasphaera taugourdeaui (Varma and Dangwal) comb. nov. Tenua taugourdeaui Varma and Dangwal 1964:68, pi. 2, fig. 9. Batiacasphaera torulosa (Davey and Verdier) comb, nov. Canningia torulosa Davey and Verdier 1973:180, pi. 1 figs. 2, 5, 8. Batiacasphaera verrucosa (Sarjeant) comb. nov. Tenua verrucosa Sarjeant 1968:232, pi. 1, fig. 17; pi. 2, figs. 3, 6. Batiacasphaera villersense (Sarjeant) comb. nov. Tenua villersense Sarjeant 1968:231, pi. 1, fig. 16; pi. 2, figs. 5, 10. Family Areoligeraceae Evitt emend. Sarjeant and Downie Cyclonephelium distinction Defiandre and Cookson 1955 (illustrated herein. Figs. 33E, 40c). Emended Diagnosis Dorsoventrally flattened proximate dinoflagellatc cysts. Outline symmetrical, subcircular to ovoidal, occasionally slightly asymmetrical. Apex often bulges out into a short blunt apical horn. No hypotractal horns present. Variable apteate ornament consisting of capitate spines or baculae which may or may not fuse distally and/or proximally. The intra- and penitabular ornament is pronounced in the circumferential area. In the ventral and dorsal areas the ornament is reduced or lacking. Tabulation formula: 4', 6", 5-6c, 6" ', lp, 1" "; archeopyle (4A). Remarks This genus is now restricted to forms with apteate ornament. The symmetrical shape of the archeopyle does not suggest the presence of intercalary plates, thus separating the genus from all pseudoceratiacean genera. It is not chorate as the emendation by Davey et al. (1966) suggested. Chorate species of Cyclonephelium have been transferred recently to the new genus Glaphyrocysta Stover and Evitt 1978. The type species of Tenua (T. hystrix Eisenack 1958) is synonymous with Cyc- lonephelium (Davey, in press). All other species previ- ously attributed to Tenua have evenly distributed and sometimes dense apteate ornament, and are transferred to Batiacasphaera Drugg 1970. The following species accord with the emended diagnosis: Cyclonephelium compactum Defiandre and Cookson 1955 C . areolatum Cookson and Eisenack 1960 C . clathromarginatum Cookson and Eisenack 1962 C. denseharhatum Cookson and Eisenack 1960 C. distinctum Defiandre and Cookson 1955 C . hughe sii Clarke and Verdier 1967 C . hystrix (Eisenack) Davey (in press) C. membraniphorum Cookson and Eisenack 1962 C. paucimarginatum Cookson and Eisenack 1962 C. paucispinum Davey 1969 ?C. vannophorum Davey 1969 C. vitilare Cookson 1965. Cyclonephelium Defiandre and Cookson emend. Cyclonephelium Defiandre and Cookson 1955:285. Tenua Eisenack 1958:410. Cyclonephelium Defiandre and Cookson emend. Cookson and Eisenack 1962:493. Cvi lonephelium Defiandre and Cookson emend. Williams and Downie 1966:223. The emendation separates two stratigraphically different complexes, since Cyclonephelium is generally restricted to the Cretaceous and Glaphyrocysta to the Upper Creta- ceous and Tertiary. Summary and Conclusions 1. Upper Triassic to Lower Jurassic cysts examined exhibit primitive suessioid characters such as complex tabulation and disintegration archeopyles. Noricysta and Dapcodinium are emended. 2. New genera ancestral to the pareodiniaceans are proposed from the Lower to Middle Jurassic of Arctic Canada (Phallocysta, Susadinium, Dodekovia). They are compared with genera known from this interval and placed in an evolutionary lineage with ancestral suessioid forms. 3. Pareodiniacean and pseudoceratiacean genera from the Upper Jurassic to Lower Cretaceous of Arctic Canada and northwest Germany are reviewed and reinvestigated, and a close phylogenetic relationship is proposed. Several genera are emended: Paragonyaulacysta, Aptea, Canningia, Im- batodinium , Muderongia, Pseudoceraiium , Batiacasphaera , Cyclonephelium , Komewuia . 4. Both pareodiniacean and pseudoceratiacean genera have intercalary plates and differ principally in the mode of archeopyle formation: I in the former and (AI) in the latter. The tabulation formula for both families is 4', 2-3a, 6", 5-6c, ?6-7" ', ?lp, 1" ". 5. Horn development in the Pseudoceratiaceae has phylogenetic significance but may also be related to ecological factors such as water temperature. 6. Archeopyle formation is closely related to the imbrication (Gocht and Netzel, 1976) of plate margins; the mid-dorsal keystone position of the archeopyle has essentially not changed since the Triassic and is probably homologous in most families. Apparent differences are due to Kofoidian plate nomenclature. 7. Different archeopyle types are determined by the strength of adcingular lap-joints and the state of fusion between neighbouring plate series. 8. Sequential lineages are documented explaining all major archeopyle types (I, AI, A, AIP, P) within the Rhaetogonyaulacineae from a common Triassic stock. The possible evolutionary steps are outlined below: (a) Possible evolution of proximate dinoflagellate cysts from Micrhystridium-type achritarchs with disin- tegration archeopyles and suessioid tabulation within the Triassic. (b) Radiation of suessioid proximate cysts in the Late Triassic, i.e. Rhaetogonyaulax, Sverdrupiella, Heibergella, Noricysta, Suessia. (c) Through plate fusion the archeopyle became more stabilized in position in cysts such as Dapcodinium and Comparodinium in the Early Jurassic. (d) Through further plate fusion the Phallocystaceae evolved with a stabilized 31 archeopyle and an intercalary series of 4-5 plates, in the late Early and early Middle Jurassic. (e) The evolution of the Pareodiniaceae from Phal- locysta through Glomodinium with a 31 archeopyle and later reduction to 21 in Pareodinia in the Middle Jurassic and II as in Broomea in the Middle to Late Jurassic. (f) The development of antapical horns in the Pareodiniaceae as in Komewuia during the Late Jurassic. (g) Fusion of the 2a to the apical series thus forming a (4A2I) archeopyle of the Pseudoceratiaceae such as Imbatodinium in the late Late Jurassic and early Early Cretaceous. (h) Elaboration in horn number and length within the Pseudoceratiaceae in the Early Cretaceous, (i) Further fusion of the apical and intercalary plates into one apical series forming the 4A archeopyle of some members of the Batiacasphaeraceae such as Cyclonephelium in the Early Cretaceous, (j) Possible formation of the precingular archeopyle through fusion of the dorsal intercalary plates with the dorsal precingular plates as in Dodekovia (3I3P) leading to the Gonyaulacystineae in the Middle Jurassic. (k) Possible evolution of peridinioid cysts through pseudoceratiacean cysts such as Muderongia simplex involving a shift in structure towards symmetry. 9. The supra-generic classification of Norris (1978a, b) closely parallels our phylogenetic concepts; some taxa, however, have been reassigned. Two new families are proposed: Phallocystaceae and Batiacas- phaeraceae. The family Pseudoceratiaceae is emended and transferred to the suborder Rhaetogonyaulacineae. The families Rhaeto- gonyaulacaceae and Pareodiniaceae are emended. Acknowledgements We thank the following for critically reading the manuscript and for their helpful suggestions: W.W. Brideaux, J. Bujak, R.J. Davey, W.R. Evitt, H. Gocht, H. Netzel, G. Norris, L.E. Stover, J. P. Verdier, W. Wille, and two anonymous reviewers. P.B. O'Donovan assisted with photography and G. Gomolka assisted with scanning electron microscopy. Appreciation is expressed to Elf Oil Co. 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Sibirskoye Otdeleniye, Institut Geologii i Geofiziki, Trudy. 347 pp. v. \ I I n 1965 1967 Microplankton, pollen, and spores from Ihe Lower Jurassic in Britain. Micropaleontology 11:151-190. Fossil microplankton in deep-sea cores from the Caribbean Sea. Palaeontology 10:95-123. 46 Unless otherwise stated, all illustrations of Figs. 19^0 were taken with interference contrast optics and enlarged to scale A on Fig. 38. See Fig. 38 for scale B. Fig. 19 Scanning electron micrographs. All specimens are from sample Elf Jameson Bay C-31 JB 3300, Heiberg Fm., Arctic Canada. A-G Sverdrupiella sabinensis Bujak and Fisher 1976. A Ventral view x 730, E Enlarged part of epitract, x 1460. Note the archeopyle initiation at top left (white arrow) and mid-ventral claustrum (CL). ROM 36982. B Left lateral view of epitract with initial disintegration archeopyle, x 1460, D Enlarged portion of B, x 3640, ROM 36976. C Right lateral view with mid-dorsal disintegration archeopyle. Note also the large claustrum (CL), x 1460, ROM 36982. F Detail of surface texture showing blunt spines in penitabular positions, x 3955, ROM 36976. G Apical view showing mid-dorsal initiation of disintegration archeopyle. Sulcal area indicated by s. x 1430, ROM 36976. 48 49 Fig. 20 A-B Heibergella salebrosacea Bujak and Fisher 1976 showing mid-dorsal initiation of disintegration archeopyle (arrow), Jameson Bay C-31, JB 3330, ROM 36956, 49.7/99.6, Heiberg Fm., Arctic Canada. C-E Sverdrupiella sabinensis Bujak and Fisher 1976, showing disintegration archeopyle. Jameson Bay C-31, JB 3300; ROM 36595, 48.4/107.2. Heiberg Fm., Arctic Canada. C Focus on apical plate series, which remained attached ventrally. D Focus on intercalary and precingular plate series, showing penitabulary arranged spines; also note ventral claustrum (CL). E Focus on narrow "protoprecingular" series (arrow). 50 X if H^V'^ m '^\ * B 51 Fig. 21 Scanning electron photomicrographs. All specimens of Nor icy sta from sample SP 2541-45, Panarctic Sandy Point L-46, Heiberg Formation, Arctic Canada. A, c "Micrhystridium" sp. exhibiting a disintegration archeopyle initiating in the mid-dorsal intercalary region, the keystone position. A x 2045. C x 1220. ED 1030-4, Savik Fm., Ellef Ringnes Island, Arctic Canada, ROM 36987. B Noricysta fimbriata Bujak and Fisher 1975, showing complex tabulation, x 1580, ROM 36983. D Noricysta fimbriata, exhibiting initial archeopyle development, x 1225, ROM 36985. E Noricy sta fimbriate, showing complex tabulation, x 2400, ROM 36983. F, G Noricy sta fimbriate. Detail of surface textures and sutural ornament, x 3640. G x 2075, ROM 36983. 52 53 Fig. 22 A-B Noricysta fimbriate Bujak and Fisher 1976, showing disintegration archeopyle involving the apical series and initial breakdown of the precingular series. Panarctic Sandy Point L-46, SP 2541^5A, ROM 36964, 34.9/99.7, Heiberg Fm., Arctic Canada. C Noricysta fimbriate Bujak and Fisher 1976, showing archeopyle initiation between the apical and intercalary plate series (arrow). Panarctic Sandy Point L-46, SP 2541-45A, ROM 36964, 44.6/103.2, Heiberg Fm., Arctic Canada. D Dapcodinium sp. A, showing intercalary initiated disintegration archeopyle with the apical series remaining attached (A). Elf Jameson Bay C-31, JB 1950A, ROM 36552, 35.7/103.8, Savik Fm., Arctic Canada. E-F Suessia swabiana Morbey 1975, antapical view showing complex tabulation and plates of the "protoprecingular" series (arrow), Panarctic Sandy Point L-46, SP 2541^45A, ROM 36964, 45.0/99.3, Heiberg Fm., Arctic Canada. G, l Dapcodinium sp. B, showing disintegration archeopyle. The apical (A) and intercalary (I) series are indicated. Panarctic Sandy Point L-46, SP 1880, ROM 36965, 41.3/107.0. Wilkie Point Fm., Arctic Canada. H Sverdrupiella sabinensis Bujak and Fisher 1976, showing disintegration archeopyle. Same specimen as Fig. 20. c-E. Scale B. Elf Jameson Bay C-31 , JB 330-A, ROM 36596, 48.4/ 107.2, Heiberg Fm.. Arctic Canada. 54 I D 55 Fig. 23 Scanning electron photomicrographs. A, c, D, F, G. Suessia swabiana Morbey 1975, Panarctic Sandy Point L-46, SP 2541—45, Heiberg Fm., Arctic- Canada. A, c Right lateral view showing initial archeopyle development. A x 3045, C x 1220, ROM 36985. D x 1220, ROM 36985. F Dorsal view showing advanced stages of the disintegration archeopyle. x 1220, ROM 36985. G Right lateral view demonstrating plate fusion adcingularly. SP 2541^45A, x 1460, ROM 36983. B, E, H Dodekovia syzygia sp. nov. Savik Fm., Reindeer Peninsula, Ellef Ringnes Island. ED1030-4A, ROM 36992. B, E Left lateral view exhibiting precingular and intercalary plates separating from the archeopyle. B x 3045. E x 3045. H Right lateral view with 3P3I archeopyle. x 1220. 56 57 Fig. 24 a-c Noricysta fimbriata Bujak and Fisher 1976, showing sutural crests and folds. Note omphalos (OM) on B. Panarctic Sandy Point L-46, SP 2541^5/a, ROM 36964, 35.7/95.4, Heiberg Fm., Arctic Canada. D, E, G Phalhcysta eumekes sp. nov., lateral view showing epitracral tabulation and omphalos (OM). Elf. Wilkins E-60, WI 1410a, ROM 36452, 39.2/103.5. F Susadinium scrofoides sp. nov., lateral view showing intercalary archeopyle. Reindeer Peninsula, ED1029-6a, ROM 36624, 44.3/105.2, Savik Fm., Arctic Canada. H Susadinium scrofoides sp. nov., Panarctic Sandy Pt. L-46, SP 1935^0a, ROM 36966, 46.3/107.2, Savik Fm., Arctic Canada. I Susadinium scrofoides sp. nov., holotype. Dorsal view showing intercalary archeopyle. Reindeer Peninsula, ED 1038-2a, ROM 36598, Savik Formation, Arctic Canada. J Dapcodinium wapellense (Pocock) comb, nov., Elf Wilkins E-60, WI 2070a, ROM 36474, 43.2/102.1, Savik Fm., Arctic Canada. K Susadinium scrofoides sp. nov. , Elf Wilkins E-60, WI 1950a, ROM 36470, 47.3/105.0, Savik Fm., Arctic Canada. 58 59 Fig. 25 Scanning electron photomicrographs. A-D Susadinium scrofoides sp. nov., ventral view, ED 1030-4, Savik Fm., Ellef Ringnes Island, Arctic- Canada. A x 3045. B x 3045, ROM 36983. C x 1220. D x 3045, ROM 36986. E Dapcodinium inornatum (Morgenroth) comb. nov. dorsal view, x 1220. Savik Fm., Ellef Ringnes Island, ROM 36987. F Mendicodinium sp., ventral view with epitractal archeopyle. ED 1030-1, x 1220, ROM 36988, Savik Fm., Ellef Ringnes Island, Arctic Canada. G Dapcodinium semitabulatum (Morgenroth) comb, nov., ventral view, apical series attached ventrally. x 1220, Savik Fm., Ellef Ringnes Island, Arctic Canada, ED 1030-1, ROM 36984. 60 61 Fig. 26 A-D Dodekovia syzygia sp. nov., holotype. A Bright field optics, dorsal view. D Bright field optics, ventral view. Notice plates around sulcus. B Dorsal view. C Ventral view. Reindeer Peninsula, ED 1030-4a, ROM 36628, 55.9/98.6, Jaeger Mb., Savik Fm., Arctic Canada. E Comparodinium aquilonium sp. nov., holotype. Initial archeopyle formation, two opercular pieces in place, focus on the intercalary opercular piece partly inside the autoblast. Elf Wilkins E-60, WI 1950-a, ROM 36470, 35.6/95.2, Savik Fm., Arctic Canada. F-G Dodekovia syzygia sp. nov., showing opercular plates in situ. Reindeer Peninsula, ED 1030-4a, ROM 36628, 56.1/99.0, Jaeger Mb., Savik Fm., Arctic Canada. H Phallocysta eumekes sp. nov., showing the angular outline of the archeopyle in lateral view. Reindeer Peninsula, ED 1031^ta, ROM 36631, 54.3/95.4, Jaeger Mb., Savik Fm., Arctic Canada. I Comparodinium aquilonium sp. nov., paratype. Exhibiting the angular archeopyle suture. Elf Wilkins E-60, WI 2070a, ROM 36474, 51.0/93.8, Savik Fm., Arctic Canada. J Phallocysta eumekes sp. nov., paratype. Due to twisting of epitract the archeopyle appears as an irregular slit. Elf Wilkins E-60, WI 1320A, ROM 36449, 45.1/98.2, Savik Fm., Arctic Canada. K Phallocysta eumekes sp. nov. holotype showing the 31 archeopyle. Reindeer Peninsula, ED 1031-4A, ROM 36631, 35.2/100.1, Jaeger Mb., Savik Fm., Arctic Canada. 62 k " 10 ^ jjl*" *t^T D N :M I X. If 3^ kill \ * • \ \ • : '. | 1 * • 1 1 I - f » ( • 1 I! | !• • L 63 Fig. 27 Scanning electron photomicrographs. All specimens are from sample ED 103 1—4, Jaeger Mb., Savik Fm., Reindeer Peninsula, Arctic Canada. A-D, G Phallocysta eumekes sp. nov., ROM 36986. A-c Left lateral view, x 1220. D Ventral view, x 1220. G Antapical view, x 1220. E, F, l Phallocysta eumekes sp. nov., ROM 36976. E Dorsal view, x 975. F Left lateral view, x 975. I Close-up of archeopyle, x 4440. H Phallocysta eumekes sp. nov., close-up of archeopyle, showing surface texture and double layered wall. x 4800, ROM 36976. 64 65 Fig. 28 Scanning electron photomicrographs. All specimens are from sample 1030-4, Savik Fm., Ellef Ringnes Island, Arctic Canada. A-H Comparodinium aquilonium sp. nov. A, D Right lateral view exhibiting initial archeopyle development. A x 1440. D x 3600, ROM 36986. B Left lateral view, x 1440, ROM 36983. C Ventral view of whole specimen, x 1440, ROM 36989. E, F Ventral view, showing initial archeopyle splitting. E x 1440. F x 3600, ROM 36989. G, H Right lateral view showing two opercular pieces slightly displaced, ROM 36989. G x 3600. H x 1440, ROM 36989. 66 67 Fig. 29 A Glomodinium sp. showing (31) archeopyle and hypotractal bulge as an indication of a lateral horn. Central Amund Ringnes Dome, ED 1009-7 Aa, ROM 36641, 47.5/101.6, Savik Fm., Arctic Canada. B Glomodinium tripartitum (Johnson and Hills) Dodekova 1975. Initial archeopyle formation, three intercalary plates detaching separately. Central Amund Ringnes Dome, ED 1009-la, ROM 36635, 43.0/105.7, Savik Fm., Arctic Canada. C Glomodinium tripartitum (Johnson and Hills) Dodekova 1975, showing three intercalary plates in place. Central Amund Ringnes Dome, ED 1009-la, ROM 36635, 40.3/101.4, Savik Fm., Arctic Canada. D-F Paragonyaulacysta retiphragmata sp. nov., holotype, showing pronounced sutural ridges and 31 archeopyle. Elf Jameson Bay C-31, JB 1260a, ROM 36529, 55.1/105.9, Savik Fm., Arctic Canada. 68 1 r *. % 17, t> . 69 Fig. 30 A-E Imbatodinium kondratjevi Vozzhennikova emend. All specimens are from the Deer Bay Fm., North Amund Ringnes Dome, Amund Ringnes Island, Arctic Canada. A Dorsal view, showing surface granulation and faint plate sutures. ED 1028-21A, ROM 36776, 43.8/99.6. B, D Dorsal view. Some sutures are discernible. Note the low position of the cingulum (C) and the pronounced omphalos (OM). ED 1028-21 A, ROM 36776, 43.5/106.8 i) Bright field optics, x 875. C Coarse variety, ED 1028-19A, ROM 36775, 33.8/1 10.2. E Ventral view, operculum removed, ED 1028-21c, ROM 36805, 46.7/95.1. 70 \ jc v^ #£7 ,0M r*i . ■ .0 ft . _^J*^ 71 Fig. 31 Scanning electron photomicrographs. All specimens are from sample ED 1028-21 , Deer Bay Fm., North Amund Ringnes Dome, Amund Ringnes Island, Arctic Canada. A-F Imbatodinium koruiratjevi Vozzhennikova emend. A, B Ventral view, showing sulcal area (S), cingulum (C) and faint archeopyle sutures (AS and arrows), ROM 36981. A x 975. B x 1940. C, F Oblique ventral view, showing archeopyle initiation. C x 1940. F x 900, ROM 36981. D, E Ventral view, showing archeopyle suture. D x 1860. E x 930, ROM 36981. 72 73 Fig. 32 Scanning electron photomicrographs. A, D Imbatodinium micropodum (Eisenack and Cookson 1960) comb, nov., ROM 36988. D Ventral view, showing incipient archeopyle formation; also note low position of cingulum (C), x 1220. A Enlarged postion of surface showing fine granular wall structure. (Compare the illustration in Davey 1974, pi. 7, fig. 8.) x 3045, KBT 10/39.5, Aptian, Germany. B, F Imbatodinium sp., ROM 36990. F Ventral view, x 1220. B Enlarged portion of surface, showing finely reticulate surface pattern, x 6080. KBT 9/48.5, Aptian, Germany. C, G Imbatodinium jaegeri (Alberti) comb, nov., ROM 36981. G Ventral view, note archeopyle suture, x 1765. C Enlarged portion of surface, showing chagrenate surface pattern, 4020. KBT 10/39.5, Aptian, Germany. E Imbatodinium longicornutum (Alberti) comb. nov. Left lateral view, operculum removed, surface smooth, x 970. Gehrden 31, Upper Barremian, Germany, ROM 36979. H Imbatodinium sp. Apex with archeopyle initiation, x 3045. KBT 10/39.5, Aptian, Germany. 74 75 Fig. 33 a-d Imbatodinium pelliferum (Alberti) comb, nov., exhibiting the archeopyle suture and faint tabulation traces. Note the low position of cingulum and pronounced omphalos (OM, on D). KTHl/30/5a, ROM 36967, 47.8/96.4, Hauterivian, Germany. E Cychnephelium distinctum Deflandre and Cookson 1955. Ventral view, showing ventrally attached operculum, x 770. KBT 10/39.5, Aptian, Germany, ROM 36992. F, G Gochteodinia villosa (Vozzhennikova) Norris 1978, ROM 36988. F Oblique dorsal view, apical horn partly broken off. Note the cingular area free of processes (C). x 650. G Enlarged portion, showing 21 archeopyle with opercular plates in place and processes presumably in penitabular position, x 1220, ED 1004-3, Jaeger River, Cornwall Island, Arctic Canada. E-G Scanning electron photomicrographs. 76 77 Fig. 34 a, B Endoceratium dettmannae (Cookson and Hughes) Stover and Evitt 1978, showing asymmetrical archeopyle suture (AS) and breakage of the operculum along the intercalary suture (IS) between the apical and the intercalary plate series. Also apparent are two pronounced postcingular horns, a pronounced left antapical horn, and a bulge indicating a right antapical horn. Note dark omphalos (OM). A scale B, Os 924/3s, ROM 36969, 55.3/96.5, Latest Albian, Germany. C Imbatodinium kondratjevi Vozzhennikova emend., operculum, ventral view on inside of dorsal intercalary plates. Compare with operculum of I. jaegeri (Fig. 35D). ED 1028-21C, ROM 36805. 43.0/ 107.7, Deer Bay Fm., North Amund Ringnes Island, Arctic Canada. D Muderongia simplex ventral view, showing 1' and 4'. The right postcingular horn is bent upwards. ED 1002^a, ROM 36715, 40.0/ 105.9. Deer Bay Fm., Cape Ludwig, Amund Ringnes Island, Arctic Canada. E Imbatodinium kondratjevi Vozzhennikova emend., apical part, showing archeopyle suture (AS) and intercalary plates (la, 2a). ED 1028-21A, ROM 36776, 38.5/95.8, Deer Bay Fm., North Amund Ringnes Island, Arctic Canada. F Komewuia glabra Cookson and Eisenack 1960, oblique dorsal view, showing 21 archeopyle, slightly granular surface, and kalyptra. No endoblast is developed; circular folds are due to compression. ED 1047-7A, ROM 36741, 44.2/ 107.4, Savik Fm., North West Cornwall Island, Arctic Canada. Scale B. G Gochteodinia villosa (Vozzhennikova) Norris 1978. Oblique dorsal view, exhibiting 21 archeopyle with opercula slightly displaced. ED 1041-1 A, ROM 36801 , 47.7/ 103.2, Deer Bay Fm., West Cornwall Island. Arctic Canada. Scale B. 78 IS ' JtS 3f^ OM AS. 2a VtfA 7 1a > • • "* sSft' jB^ * " -A. m ^K9 S> 79 Fig. 35 A, D Imbatodinium jaegeri (Alberti) comb, nov., showing asymmetrical archeopyle suture (AS) and faint elongate precingular plates. ED 1004-3b, ROM 36678, 38.8/93.6, Deer Bay Fm., Jaeger River, Cornwall Island, Arctic Canada. B, C Phoberocysta neocomica (Gocht) Millioud 1969, showing asymmetrical archeopyle suture, adjacent plate boundaries and postcingular horns. KTH l/20/4a, ROM 36970, 51.4/93.8, Hauterivian, Germany. E Imbatodinium jaegeri (Alberti) comb, nov., Operculum. ED 1004-3b, ROM 36678, 35.3/93.38, Deer Bay Fm., Jaeger River, Cornwall Island, Arctic Canada. F Pseudoceratium pelliferum Gocht 1957. Apical area showing the asymmetrical archeopyle suture and a possible intercalary suture (?IS). Mo 551 /5s, ROM 36971,49.3/99.9, Middle Albian (reworked), Germany. 80 V*r 3> « • I* AS - ?IS / 81 Fig. 36 Scanning electron photomicrographs. All Muderongia specimens are from sample ED 1002-4, Deer Bay Fm., Cape Ludwig, Amund Ringnes Island, Arctic Canada. A, B Heterosphaeridium heteracanthum (Deflandre and Cookson) Eisenack and Kjellstrom 1971. Complete specimen with partly detached operculum. Note the typical asymmetrical pseudoceratiacean shape of the latter, which dips down dorsally to the right. Also compare the nature of processes with that of Aptea polymorpha (Fig. 37a) and Pseudoceratium pelliferum (Fig. 37D). a x 1220. B x 3045, KBT 10/39.5. Aptian, Germany, ROM 36991. C, F Muderongia simplex Alberti 1961. Dorsal view, showing partly detached operculum and position of anterior intercalary plates (l-2a). C x 730. F x 1220, ROM 36985. D Muderongia simplex Alberti 1961. Isolated operculum, showing anterior intercalary plates, x 1525, ROM 36978. E Muderongia simplex Alberti 1961. Ventral view, showing incipient archeopyle formation, cingulum, and sulcal area, x 730, ROM 36979. G Muderongia simplex Alberti 1961. Apex, showing incipient archeopyle formation and double nature of the wall, x 1525, ROM 36980. 82 83 Fig. 37 Scanning electron photomicrographs A Aptea polymorpha Eisenack emend. Detail of processes, x 3065, KBT 10/39.5, Aptian, Germany, ROM 36993. B-E Pseudoceratium pelliferum Gocht 1957. Gehrden 31, Upper Barremian, Germany, ROM 36979. C Complete specimen, showing penitabular ornament, x 730. B Detail of cingular area, x 1460. D Detail of surface and processes. Compare with Fig. 1. Note archeopyle suture (AS), x 3640. E Detail of apical area and archeopyle suture (AS), x 1510. 84 85 Fig. 38 A. Aptea polxmorpha Eisenack 1958. Detail of ventral epitract, showing archeopyle suture, breakage along the intercalary suture (IS), and pronounced sulcal field (S). KBT 10/39.5/3, ROM 36968, 40.8/108.3. Aptian, Germany. B, C Aptea polxmorpha Eisenack 1958. Details of tabulation on the ventral area. Note the "projected" position of the flagellar pore (FP) and the unornamented ventral area. KBT 10/39.5/1, ROM 36972, 38.3/ 100.00, Aptian, Germany. D, E, F Aptea polxmorpha Eisenack 1958. Complete specimens, all from the German Aptian. Scale B. D Dorsal view, KBT 10/39.5/3, ROM 36968, 62.8/107.8. E Dorsal view, KBT 10/39.5/3, ROM 36968, 63.4/98.4. F Ventral view. Note the pronounced omphalos (OM). KBT 10/39.5/1, ROM 36972, 38.3/100.0. 86 87 Fig. 39 A Aptea polymorpha Eisenack 1958. Dorsal view, showing asymmetrical archeopyle suture, broad pandasutural zones, and detail of ornament. KBT 10/39.5/3, ROM 36968, 62.8/107.8, Aptian, Germany. B, c Aptea polymorpha Eisenack 1958. Dorsal view showing asymmetrical archeopyle suture, broad pandasutural zones and breakage along the suture between the two intercalary plates. KBT 10/39.5/3, ROM 36968, 63.4/98.4, Aptian, Germany. D, E Aptea polymorpha Eisenack 1958. Complete specimens all from the German Aptian. Scale B. D Dorsal view, KBT 10/39.5/3, ROM 36968, 45.8/106.6. E Ventral view, KBT 10/39.5/3, ROM 36968, 40.8/108.3. F Aptea polymorpha Eisenack 1958. Detail of E showing a faint intercalary suture (IS) and pronounced sulcal (S) and flagellar pore (FP) areas. KBT 10/39.5/3. ROM 36968, 40.8/108.3. 88 89 Fig. 40 A Odontochitina operculata (O. Wetzel) Deflandre 1955. Dorsal view showing asymmetrical archeopyle suture, a fold indicating the position of the cingulum (C), the sulcal groove (S) on the inside of the distal periphragm, and a pronounced omphalos (OM). Note pitted traces, possibly indicating plate boundaries. KBT 10/39.5/2, ROM 36973, 44.2/101.5, Aptian, Germany. B, F Aptea cf. anaphrissa (Sarjeant) Stover and Evitt 1978. Gehrden 31/2, ROM 36974, 47.8/102.7, Late Barremian, Germany. B Complete specimen with unornamented ventral area. Scale B. F Detail, showing asymmetrical archeopyle suture (AS) and intercalary notch (IS). C Cyclonephelium distinctum Deflandre and Cookson 1955, showing symmetrical archeopyle suture. Note the position of cingulum. KBT 10/39.5/2, ROM 36973, 35.0/107.6, Aptian, Germany. D Cribroperidinium orthoceras (Eisenack) Davey 1969. Operculum, exhibiting intratabular ridges. Mo 551 /4s, ROM 36975, 55.5/110.6, Late Albian, Germany. E Cribroperidinium sp. Detail of dorsal area. KBT 10/39.5/1 , ROM 36972, 58.2/ 100.0, Aptian, Germany. G Aptea anaphrissa (Sarjeant) Stover and Evitt 1978, with asymmetrical archeopyle suture, indications of two postcingular horns. KBT 10/39.5/2, ROM 36973, 50.5/103.6, Aptian, Germany. 90 91 /& ' ISBN 0-88854-239-9 ISSN 0082-5093