The dinoflagellate cyst genus Epiplosphaera Klement 1960 - a reappraisal

The dinoflagellate cyst genus Epiplosphaera Klement 1960 and its species have been studied in material from the Oxfordian and Kimmeridgian of Poland. The taxonomic history of the genus is summarized and the morphology is discussed. The type species Epiplosphaera bireticulata differs from other representatives of the genus in having high septa which are dissected distally. Additional septa in E. bireticulata form a second reticulum inside the parasutural septa. Epiplosphaera reticulata differs from the other species by having low spines and low, smooth septa. The septa form a second reticulum within the parasutures, as in the case with E. bireticulata. Epiplosphaera areolata has high spines, but almost no reticulum or parasutures. Epiplosphaera reticulospinosa is intermediate between E. bireticulata and E. areolata. It has a mixture of both high and low septa between the spines. Epiplosphaera gochtii has low spines and few, low septa between some of the spines. Epiplosphaera ornata is regarded as a junior synonym of E. gochtii.


INTRODUCTION
A few dinoflagellate cysts from the Middle and Late Jurassic are characterized by being murochorate. Tabular and intratabular spines are connected with septa, giving the cyst a bireticulum. Klement (1960) described these cysts and created the genus Epiplosphaera and the closely related genus Ellipsoidictyurn to encompass these dinoflagellate cysts.
This paper reports chiefly on the study of some samples very rich in Epiplosphaera specimens. The material provided an excellent opportunity to study these cysts in the scanning electron microscope (SEM). They are very difficult to study in the light microscope due to the numerous high septa. Two almost simultaneous and opposing taxonomic proposals of Brenner (1988) and Courtinat (1989) respectively, are compared and reinterpreted using the material studied here.

Material
Epiplosphaera bireticulata, E. gochtii (including Sentusidinium ornatum), E. reticulata and E. reticulospinosa were found in large numbers in a sample from the Middle Oxfordian (Transversarium Zone) of the northeast margin of the Holy Cross Mountains (between Krak6w and Warszawa, Poland;  Fig. 1 ) are rich in Epiplosphaera specimens. The sample of the Transversarium Zone was given to me by Dr.
Gutowski, University of Warsaw. The other samples were core samples given to me by the University of Warsaw, or were collected by me from outcrops under the guidance of Drs B.A. Matyja and A. Wierzbowski, University of Warsaw.

Methods
The material has been processed following the preparationmethod described in Poulsen et al. (1990). Palynological slides have been studied using transmitted light microscopy. In  order to study these morphologically complex dinoflagellate cysts, some specimens were mounted as strew mounts on stubs and studied using scanning electron microscopy. Klement (1960) proposed the genus Epiplosphaera and described three new species belonging to this genus -E. bireticulnta (the type species), E. areolata and E . reticulospinosn. Sarjeant (1984) questionably included E . areolatn in Lithodinia. The transfer of E. arenlatn was not accepted by Brenner (1988), who retained this species in Epiploshaera. Brenner (1988)  The genus Epilosphara was originally described as: "Ellipsiodal shells with fine, irregularly polygonal, small-meshed reticulate ornamentation on the surface. Processes arising at the points of junction of the basal network are relatively short, simple or with short distal bifurcations, rarely isolated, mostly interconnected by fringes or by thick ledges perpendicular to the surface of the shell. These form either closed structures in theshapeof a second, much larger meshed polygonal network of crests, or run as liniar marginal fringes or produce a regularly trapezoidal pattern predominantly in the longitudinal and transverse directions.''-Translated from Klement (1960) by Stover & Evitt (1978). Klement (1960) described (in the holotype description) the archeopyleas a calotte-shaped split in one of the polar ends of the cyst. Stover and Evitt (1978) accepted Klement's description, the archeopyle type was, however, described as type [tAl with a free operculum in their synopsis and modified description.

Historical review
The paratabulation formula of this genus was neither described by Klement (1960) nor Stover & Evitt (1978), who also stated that the parasingulum and the parasulcus were not indicated. Brenner (1988), in his emendation of the genus, stated that the paratabulation is visibel, depending on the stateof reduction of the reticulumor preferential development of the parasutures. In the rich Polish assemblages indications of paratabulation are seen occasionally, including the species with the most complex reticulum of crests, i.e. E . bireticulata (PI. I, Fig. 4). The paratabulation is gonyaulacoid (Brenner, 1988).

Division Pyrrhophyta Pascher 1914
Class Dinophyceae Fritsch 1929 Order Peridiniales Haeckel 1894 Genus Epiplosphaera Klement 1960emend. Brenner 1988 Type species. Epiplospliaera bireticulntn Klement 1960. Diagnosis. (translated from Brenner, 1988: "Proximochorate dinoflagellate cyst with an apical archeopyle. The cyst wall consists of a thin inner membrane and a solid to fine porous main cyst wall. The surface of the cyst bears an ornament of septa from which normally short bifid spinesarise. The spines are often interconnected by delicate septa or membranes. The septa form an irregular network, which occurs in different stages of reduction. The reduction of the ridge network takes place either by shortening, producing an incomplete network, or by preferential development of the parasutures. Depending on the stage of reduction, the paracingulum, the parasulcus, or the parasutures are recognized. The paratabulation is gonyaulacoid." Remarks. Although this species was originally described as one in which paratabulation is indicated by the archeopyle only (Klement, 1960;Stover & Evitt, 19781, indications of paratabulation may be visible in certain, rather specific, orientations (e.g. PI. 1, Fig. 4). The gonyaulacoid paraplate pattern is indicated by the archeopyle sutures (Pl. 3, Figs 2,6). No irregular break is noticed in the archeopyle sutures; the operculumis free as previouslystated by Stover& Evitt (1978).
Comparison. Epiplospkaera differs from Ellipsoidictyurn in having spines, which are interconnected muri or septa that are typically uneven distally. Ellipsoidictyurn lacks spines and has muri that are essentially uniform in height so that the outline of the cyst is fairly smooth, not irregular and jagged as in Epiplosphaera. Aldorfia and Valensiella have an autophragm with an ectophragm, the archeopyle of Aldorfia is precingular. Egmontodinium and Histiophora has both well expressed parasutures with only minor indication of a non-tabular reticulum (see Brenner, 1988, fig. 19). Klement 1960 (Pl. Remarks. Courtinat (1989) regarded this species as a junior synonym of Epiplosphaera reticdata (Valensi) Courtinat 1989. The spines and crests of E. bireticulata are in the type material between 12-15 l m . Epiplosphaera reticdata is described by Valensi (1953) as a species with spines about 3pm in length. The crests of E. bireticulata are high and dissected whereas the crests of E. reticiilata are low and smooth (Valensi, 1953, pl. 2, figs4,5,14,19and pl. 13,fig.6 Magnification: Scale bars represent 10pm. Fig. 1 taken under SEM, all others taken in transmitted light. All specimens are from I'oland

Epiplosphaera areolata
Epiplosphaera gochtii (Fensome 1979 Remarks In accordance with the emendation of Epiploslzaera by Brenner (1988), this species is best placed in this genus, rather than in Ellipsordict!/irm or in Sentirsidiniurn as it has spines interconnected by septa, which is not characteristic of the two latter genera. Fensome (1979) and Courtinat (in Courtinat & Gaillard, 1980) published, independently and within a few months of each other, descriptions of two new species, E. goclztii and E. ornata, that, I believe, are clearly conspecific. The two species have identical shaped spines which, however, original were described with minor differences in length and thickness (Fensome, 1979;Courtinat, in Courtinat & Gaillard 1980). In the type material of E. gochtii from East Greenland the length of the spines was between 4-6 pm (Fensome, 1979). In the type material of E . ornata, the length of the spines was between 5-8 pm (Courtinat in Courtinat and Gaillard, 1980). In the Polish material, E . gochtii occurs in large numbers in one sample.

4.
Remarks. The emendation of Epiplosphaera Klement 1960, by Brenner (1988 justifies the transfer of E. reticulata to Epiplosphaera as done by Courtinat (1989); it has low spines and indications of paracingulum and parasulcus and is, therefore, best placed in Epiplosphaera rather than in Ellipsoidictyurn which is characterized by the lack of spines. Courtinat (1989) considered E. bireticulata to be a junior subjective synonym of E. reticulata. This is in my view highly questionable; they differ in spine length and crest height.
Furthermore the septa of E. reticulata are smooth (Valensi, 1953, pl. 2, figs 4, 5), whereas the crests of E . bireticulata are dissected. E. reticulata is similar to E. bireticulata in having a reticulum with low smooth crests and similar form of the spines. E. reticulata differs from E. bireticulata in having much lower spines and crests. The synonymy proposed by Courtinat (1989) is rejected in this paper. Age. Early Bajocian to Late Kimmeridgian. In the Polish material studied, E. reticdata occurs from the Middle Oxfordian (Transversarium Zone) to the Late Kimmeridgian (Eudoxus-Autissiodorensis Zones). The holotype is of Bajocian ageand the paratypeof Bathonianage (Valensi, 1953). Sarjeant (1979) reported the range of this species as Early Bajocian to mid Callovian. Thomas &Cox (1988) (Smelror 1988) comb. nov. Remarks. This species is attributed to Valensiella because the cyst wall organisation is an autophragm with an ectophragm (Smelror, 1988). The species cannot be placed in Ellipsoidictyum as it is a genus without an ectophragm.

CONCLUSIONS
Based on the scanning electron microscopy and transmitted light microscopy of the Polish material the genus Epiplosphaera is believed to consist of five species at present, i.e. E . bireticulata (the type species) and E. areolata, E. gochtii, E. reticulata and E. reticulospinosa. Epiplosphaera bireticulata and E. reticulata are not regarded as synonyms, as suggested by Courtinat (1989).
Sentusidiniurn ornaturn is regarded as a junior subjective synonym of E. gochtii and not of Epiplosphaera reticulospiirosa as proposed by Courtinat (1989).

I thank Drs. Bronislaw Andrzej Matyja and Andrzej
Wierbowski (University of Warsaw) for their assistance, while I was collecting the samples from Poland, and for providing core samples. Dr. Gutowski (University of Warsaw) is thanked for the samples he provided. Dr. Stefan Piasecki (Greenland Geological Survey) provided the opportunity to examine Fensome's type material of Epiploshaera gochtii.
Dr. James Riding (British Geological Survey) is thanked for stimulating discussions of the material described in the manuskript. IamgratefultoDrs KarenDybkjr,StefanHultberg, Jon Ineson and Svend Stouge (Geological Survey of Denmark) for useful comments to improve the manuscript. Yvonne Husfeldt prepared the samples. Peter Moors made the photographs. Benny Scharck helped in the production of the plates. Hanne Danielsen did the typing.
The SEM study was carried out at the British Geological