Observations on the Jurassic dinocyst genera Energlynia and Wanaea

Topotype material of all known species of the Jurassic dinocyst genera Energlynia and Wanaea has been examined, and forms the basis of a brief review of the genera. Observations and interpretations of specific morphological features are presented. A new species Wanaea thysanota is described and the diagnosis of Wanaea digitata emended.


INTRODUCTION
The organic-walled dinocyst genus Wanaea, originally of unknown affinity, was recognised as a dinoflagellate b m y Evitt (1961). Subsequently, Evitt (1963) suggested that all fossil dinoflagellates represent the cyst phase in the life-cycle of the dinoflagellate individual. Confirmation of Evitt's theory came from observations on Recent dinoflagellates by Rossignol (1963), Evitt & Davidson (1 964) and Wall & Dale (1968).
Wanaea was first described from Upper Jurassic deposits of Western Australia by Cookson & Eisenack (1958). They distinguished three species, W . spectabilis (the type species), W . clathrata and W . digitata. A fourth species W . fimbriata was described by Sarjeant in 1961 from the Oxford Clay of Yorkshire.
Morphologically, Wanaea consists of a large coneshaped hypocyst with a short antapical horn and a single prominent, lace-like paracingular flange, which is interrupted at the parasulcus (Fig. 1). The archaeopyle is epicystal, the operculum consisting of the entire epicyst. which is only slightly apically convex, and is circular to ellipsoidal in polar view. The cyst surface is essentially smooth, and non-tabulate.
In 1975, W . acollaris, a species of Bathonian age, now known t o range from the late Bajocian to late Callovian, was described from Bulgaria by Dodekova. W . acollaris lacked the prominent paracingular flange which characterised the other species o f Wanaea and, in addition, exhibited a faint gonyaulacoid paratabulation, the cyst surface variably smooth to granulate. In the following year, Sarjeant (1976) described forms which were in all probability conspecific with W . acollaris. However, Sarjeant erected a new genus Energlynia, with its type species E . kyrbasia to accommodate these cysts, suggesting that forms without a prominent paracingular flange should not be included in Wanaea. W . acollaris was subsequently transferred to Energlynia IJY Sarjeant (1978), who commented on the possible synonymy of E. kyrbasia and E. acollaris. Wanaea zoharensis Conway 1978, and Wanaea indotata Drugg 1978 were later described, both of which are referable to Energlynia o n the basis of overall morphology.
A full study of both Wanaea and Energlynia was made by Fensome (19Sl), who formally synonymised Energlyniu acollaris, E . kyrbasia and Wanaea zoharensis, and transferred Wanaea indotata t o Energlynia, maintaining it as a separate species, but acknowledging that "E. indotata may well prove to fall within the range of variation of E . acollaris". Fensome (op. cit.) also suggested a possible phylogenetic sequence from Energlynia acollarislE. indotata through the various species of Wanaea, based on the relative 'complexity' of the paracingular flange, with W . digitata (s.s.) and W . fimbriata being linked by an intermediate form Wanaea sp. A, split off from W . digitata (s.1.). Wanaeu sp. A is here given formal specific status as Wanaea thysanota sp. nov.

MATERIAL
In the study of dinocysts from Middle and Upper Jurassic strata from central England (Woollam 1980), the present author encountered numerous representatives of Wanaeu and, t o a lesser extent, Energlynia. Abundant specimens of other related dinocysts with epicystal archaeopyles, in particular Ctenidodinium, and also Energlynia, were subsequently observed while investigating the distribution of dinocysts in the Middle Jurassic rocks of southern England. T h e remarkable abundance o f dinocysts with epicystal archaeopyles in certain strata, combined with their obvious stratigraphic importance, stimulated an extensive review of the group to be undertaken. The results presented here represent part of that investigation, relating to Wanuea and Energlynia.
Topotype material of Wanaea spectabilis and W . cluthrata, held in the palynological collections of the Geology Department, University of Sheffield, and the type material of " Wanaea zoharensis", also housed in Sheffield, were examined. D r L. Dodekova  (i) Wanaea digitata; (ii) W . thysanota sp. nov.; (iii) W . spectabilis; (iv) W . fimbriata; (v) W . clathrata. Dr R. Helby and the National Museum of Victoria provided topotype material of Wanaea digitata. Topotype material containing Wanaea fimbriata, "Energlynia kyrbasia" and Energlynia indotata was collected from outcrop. Additional samples used in the study were also collected from outcrop. Well-preserved material of Energlynia indotata from Brora, Scotland was kindly provided by Dr R. Porter. Dr R. Morgan provided access to a number of colour transparencies of the Australian type specimens for examination.
The figured material is housed in the MPK collections of the Institute of Geological Sciences, Leeds.

MORPHOLOGY AND TAXONOMIC NOTES
The following remarks are brief comments on important aspects of the morphology and taxonomy of Energlynia and Wanaea.
Genus Energlynia Sargeant, 1976. Description: cysts proximate, broadly biconical; hypocyst large, cone-shaped with a short antapical horn; epicyst rclatively small, slightly apically convex, circular in polar view. Archaeopyle epicystal; operculum simple, compound, corresponding to all paraplates of the epicyst, attached ventrally. Paratabulation absent, or indistinct, gonyaulacoid, indicated by low parasutural or rows of spinelets; paracingulum may be more distinct, indicated by a low ridge or nebulous rim. Remarks: No regularly occurring accessory archaeopyle sutures have been observed in the present study. This is in contrast to the observations of Sarjeant (1976), Stover & Evitt (1978 and Fensome (1981). However, random splitting of the operculum occasionally occurs along parasutures andlor within paraplate areas, probably caused by damage during compression and flattening of the epicyst.
Under normal working conditions, the consistent recognition of species of Energlynia is difficult. The pronouncement of Fensome (1981), recognising only E . acollaris and E . indotutu as separate species, is provisionally accepted here. However, examination of the topotype specimens of E . acollaris and its junior synonym "E. kyrbasia" illustrated in PI. 1, figs. 1 , 2 , 4 , 5 , shows clear differences in size, details of shape and surface ornament, and paratabulation development between the two "species". They may possibly be explained as ecophenotypic varieties. E . indotata (Pl. 1,  figs. 3 , 6, 7) is characterised by a relatively smooth cyst wall with a nebulous paracingular rim; P1. 1, fig. 3 shows a faintly paratabulate, detached epicyst of E . indotata. Cookson & Eisenack, 1958emended Fensome, 1981 Description: Cysts proximochorate (pterate), broadly biconical; hypocyst large, cone-shaped with a short antapical horn; epicyst relatively small, slightly apically convex, circular in polar view. Archaeopyle epicystal, operculum simple, compound corresponding to all paraplates of the epicyst, attached ventrally. Paratabulation generally absent except for a single prominent, lace-like, paracingular flange, interrupted at the parasulcus. The flange consists of radially arranged processes, variably inter-connected, and may form a perforate meshwork. Remarks: Fensome (1981) emended the generic diagnosis of Wanaea, restricting the genus to forms generally lacking paratabulation, with the exception of a single paracingular flange (some specimens of W . fimbriata seen in this study show very faint parasutural lines on the epicyst-see P1. 2, figs. 3 , 5). This modified the generic synopsis of Stover & Evitt (1978) who mistakenly noted that forms with two paracingular flanges exist (which is clearly not the case), and who also followed Dodekova's informal enlargement of the generic diagnosis to include forms with indications of paratabulation, other than a paracingular flange, now placed in Energlynia.

Genus Wanaea
In both Wanaea and Energlynia the principal archaeopyle suture occurs along an equatorial line, interpreted as running above the anterior margin of the paracingulum. The archaeopyle suture divides the operculum, the complete epicyst, from the hypocyst. Suturing is not entire, the operculum remaining attached over a short length of the equatorial margin corresponding in position to the line of interruption of the paracingular flange. The area of attachment is interpreted as the parasulcus (Fig. 1A). Loss of the operculum which occasionally occurs is almost certainly due to secondary damage to the rather flimsy parasulcal "hinge". N o regularly occurring accessory archaeopyle sutures have been observed in the present study, although secondary splitting of the operculum was observed in a small proportion of specimens, probably due to compression and flattening of the epicyst.
Species recognition in Wanaea is based on the morphology of the paracingular flange (Fig. 1B). Four species have been delineated in this way: W . spectabilis, W. clathrata, W . digitata and W . fimbriata. In addition, Fensome (1981) split off a fifth species from W . digitata, informally designated W . sp. A. The latter species is found commonly in Europe in the late Callovian and early Oxfordian, and is quite different from W. digitata (s.s.), found only in Australia in the late Jurassic. Wanaea sp. A. of Fensome (op. cit.) is therefore given formal specific status herein, as Wanaea thysanota sp. nov., and W . digitata emended accordingly, being restricted to the Australian type material.

Derivation of name.
Greek, thysanotos, fringed. Diagnosis. Epicyst slightly apically convex, hypocyst broadly conical, with a short rounded antapical horn. Archaeopyle epicystal, an equatorial line of schism partially separating the simple compound operculum (the entire epicyst), from the hypocyst. Cyst wall smooth, paratabulation generally absent, except for a prominent lace-like (posterior paracingular) equatorial flange which is interrupted along a line corresponding to the area of attachment of the operculum (parasulcus). The equatorial flange consists of radially arranged processes, varying in length from 10 to 20 pm, occa5sionally linked but generally free distally, simple, bifurcate or capitate, coalescing towards their bases to form a variably perforate crest. Remarks. This species is erected to accommodate forms previously placed in W . digitata, but which do not accord with the type material of the latter. Energlynia acollaris (Dodekova, 1975) Sarjeant, 1978 calloviense Zone, Lower Callovian, Brora, Scotland.

Wanaea digitata
Fensome (198 1) has postulated a phylogenetic sequence based o n increasing complexity of the paracingular crest, from W . spectabilis to W . digitata, then W . thysanota ( W . sp. A), W . fimbriata and finally W . clathrutu. This sequence is difficult to envisage given the spatialhemporal distribution of the individual species as outlined above.