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Wetzeliella draco
Wetzeliella draco (Gocht, 1955) Alberti, 1961
Now Rhombodinium. Originally (and now) Rhombodinium, subsequently Wetzeliella subgenus Rhombodinium.
Vozzhennikova, 1967, retained this species in Rhombodinium Gocht, 1955.
Holotype: Gocht, 1955, text-fig.1
Locus typicus: Northern Germany
Stratum typicum: middle Oligocene
Translation Gocht, 1955: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Gocht 1955, p. 85-87: Rhombodinium draco
Central body flattened, in outline approximately rhomboidal to kite-shaped, the margins are smooth and unindented. The apical horn pointed, or blunt; lateral horns strongly extended, at the distal end rounded or blunt, rectangular to the longitudinal axis or a little inclined to the apex. Antapical horns either fine pointed, or (mostly asymmetrical) fused to one appendage.
Dimensions: Range: Length: 124-150 µm; Width: 126-147 µm.
Additions (annotated): The membrane of shell and capsule is pale, soft, transpararent and smooth. The endophragm resembles in outline the periphragm, although it is rounded below the horns and does not or hardly rise in the horns. In all complete preserved specimens (one exception) a rounded-rectangular to trapezoidal archeopyle, which narrows towards the apex, is present in the epitheca, just below the apical horn.
Gocht, 1969, p.24-26:
The armor of W. draco occurred frequently in the Middle Oligocene samples, and was often very well preserved. The smooth variety is accompanied by one with spinules, mentioned by Alberti, 1961 from Freienwalde/Oder, which is described following the main form.
The body outline varies approximately within the range already defined in 1955.
Modifications affect chiefly the horns, which can be distally acuminate or even rounded out. The lateral horns occasionally show light notches (cf. Alberti, 1961) tracing a transverse furrow, which can be detected even without the notches as a fine line on the horns or- seldom- on the main body. The dextral antapical horn is always greatly reduced, but only seldom completely absent. The membrane of the outer armor is hyaline, that of the inner body somewhat scabrate. Both walls are thin and pale. On the horns, the theca has openings which vary in shape and show some degree of regularity only at the apical horn. Here, they are always on the ventral side and resemble an inverted "V" pointing upward. The lateral horns frequently have only one opening, while the antapical horns may have one, two, or more. Sometimes there is also an opening between the antapical horns. Similar holes in the outer membrane have already been known for a long time in other genera, e.g., Deflandrea, Scriniodinium, and Odontochitina. Frequently they occur only at the antapex, and in Deflandrea such apertures have been interpreted as flagellar slits (Eisenack, 1954). Since then, Eisenack, 1966 has observed, again in Deflandrea, typical pitted flagellar insertions in the region of the longitudinal furrow. This makes it possible to compare the antapical openings of Deflandrea with the membrane perforations in Wetzeliella and the other genera mentioned. Obviously such openings provide for contact between the content of the cell and the outside world; their precise function remains unknown. It is notable that they are limited almost exclusively to genera with inner bodies, and particularly species with smooth walls (without spines).
The distance between the outer and inner membrane laterally varies, but the two membranes do not touch each other here. Unformed organic substance is deposited in this space- usually only long, isolated flakes on the inner body, oriented with their long axis perpendicular to the body surface. Together they form more or less dense "caps", mainly under the horns, or as a narrow belt traversing the entire lateral margin. In the middle of the dorsal and ventral areas they are absent. Further accumulation leads to massive "horns" with smooth distal boundaries projecting far into the actual horns of the outer membrane. Such formations occur regularly in W. draco, but were observed also in other Wetzeliella species. Eisenack, 1954 describes them as "evaginations of the capsule (auricles)" in W. similis. They can be seen as flakes in Alberti"s illustrations. In the material from Meckelfeld, they were observed especially on W. samlandica, W. symmetrica, and W. sp. 2, but most conspicuously on W. solida, in which they can cover the entire inner body. Damaged tests of W. draco exhibit striking, serpentine lines of fracture, which were seen repeatedly. Even when the middle of the body was injured, the outer and inner membrane broke separately; hence, they are not fused. The archeopyle is like that of W. lunaris and W. meckelfeldensis: On the upper edge, the capsular pylome, which is smaller, exhibits a semilunar strip of membrane, while the pylome boundaries on the side towards the cingulum are congruent. The flagellar insertion is more conspicuous because of the smooth outer membrane without spines. The insertion is oblong, sloped downward to the right, and sometimes distinctly divided (transverse and longitudinal flagella? see Gocht, 1967). W. (Rh. J draco is hitherto known only from the Middle Oligocene.
Occurrence: Middle Oligocene.
Wetzeliella (Rhombodinium) draco var.
Alberti, 1961 described forms which undoubtedly were W. (Rh.) draco, but had processes which did not seem consistent with the genus Rhombodinium. He found a fairly complete range of transitional forms between smooth and spined. Similar specimens were found also in the Middle Oligocene strata at Meckelfeld.
There seem to be two major, extreme forms: one with many, short processes, and the other with fewer, but longer processes. The first is reminiscent of W. (W.) irtyschensis Alberti, and was mistakenly designated as such by Gocht, 1967. However, it is less symmetrical, and its inner body does not conform so closely to the lateral margin as in irtyschensis. The processes are short, often minute, and unbranched. The second form, which is usually more distinctly elongate, bears medium-sized to long, flexible processes which often end distally in two or three branches. The processes are never as numerous as on the short-spined extreme; they can even be sparse. On both forms, flagellar insertions were observed, as were also the flocculent organic deposits on the inner body. There are also perforations on the horns, but they are less frequent and less regularly shaped than on smooth individuals.
Occurrence: Middle Oligocene.
Now Rhombodinium. Originally (and now) Rhombodinium, subsequently Wetzeliella subgenus Rhombodinium.
Vozzhennikova, 1967, retained this species in Rhombodinium Gocht, 1955.
Holotype: Gocht, 1955, text-fig.1
Locus typicus: Northern Germany
Stratum typicum: middle Oligocene
Translation Gocht, 1955: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Gocht 1955, p. 85-87: Rhombodinium draco
Central body flattened, in outline approximately rhomboidal to kite-shaped, the margins are smooth and unindented. The apical horn pointed, or blunt; lateral horns strongly extended, at the distal end rounded or blunt, rectangular to the longitudinal axis or a little inclined to the apex. Antapical horns either fine pointed, or (mostly asymmetrical) fused to one appendage.
Dimensions: Range: Length: 124-150 µm; Width: 126-147 µm.
Additions (annotated): The membrane of shell and capsule is pale, soft, transpararent and smooth. The endophragm resembles in outline the periphragm, although it is rounded below the horns and does not or hardly rise in the horns. In all complete preserved specimens (one exception) a rounded-rectangular to trapezoidal archeopyle, which narrows towards the apex, is present in the epitheca, just below the apical horn.
Gocht, 1969, p.24-26:
The armor of W. draco occurred frequently in the Middle Oligocene samples, and was often very well preserved. The smooth variety is accompanied by one with spinules, mentioned by Alberti, 1961 from Freienwalde/Oder, which is described following the main form.
The body outline varies approximately within the range already defined in 1955.
Modifications affect chiefly the horns, which can be distally acuminate or even rounded out. The lateral horns occasionally show light notches (cf. Alberti, 1961) tracing a transverse furrow, which can be detected even without the notches as a fine line on the horns or- seldom- on the main body. The dextral antapical horn is always greatly reduced, but only seldom completely absent. The membrane of the outer armor is hyaline, that of the inner body somewhat scabrate. Both walls are thin and pale. On the horns, the theca has openings which vary in shape and show some degree of regularity only at the apical horn. Here, they are always on the ventral side and resemble an inverted "V" pointing upward. The lateral horns frequently have only one opening, while the antapical horns may have one, two, or more. Sometimes there is also an opening between the antapical horns. Similar holes in the outer membrane have already been known for a long time in other genera, e.g., Deflandrea, Scriniodinium, and Odontochitina. Frequently they occur only at the antapex, and in Deflandrea such apertures have been interpreted as flagellar slits (Eisenack, 1954). Since then, Eisenack, 1966 has observed, again in Deflandrea, typical pitted flagellar insertions in the region of the longitudinal furrow. This makes it possible to compare the antapical openings of Deflandrea with the membrane perforations in Wetzeliella and the other genera mentioned. Obviously such openings provide for contact between the content of the cell and the outside world; their precise function remains unknown. It is notable that they are limited almost exclusively to genera with inner bodies, and particularly species with smooth walls (without spines).
The distance between the outer and inner membrane laterally varies, but the two membranes do not touch each other here. Unformed organic substance is deposited in this space- usually only long, isolated flakes on the inner body, oriented with their long axis perpendicular to the body surface. Together they form more or less dense "caps", mainly under the horns, or as a narrow belt traversing the entire lateral margin. In the middle of the dorsal and ventral areas they are absent. Further accumulation leads to massive "horns" with smooth distal boundaries projecting far into the actual horns of the outer membrane. Such formations occur regularly in W. draco, but were observed also in other Wetzeliella species. Eisenack, 1954 describes them as "evaginations of the capsule (auricles)" in W. similis. They can be seen as flakes in Alberti"s illustrations. In the material from Meckelfeld, they were observed especially on W. samlandica, W. symmetrica, and W. sp. 2, but most conspicuously on W. solida, in which they can cover the entire inner body. Damaged tests of W. draco exhibit striking, serpentine lines of fracture, which were seen repeatedly. Even when the middle of the body was injured, the outer and inner membrane broke separately; hence, they are not fused. The archeopyle is like that of W. lunaris and W. meckelfeldensis: On the upper edge, the capsular pylome, which is smaller, exhibits a semilunar strip of membrane, while the pylome boundaries on the side towards the cingulum are congruent. The flagellar insertion is more conspicuous because of the smooth outer membrane without spines. The insertion is oblong, sloped downward to the right, and sometimes distinctly divided (transverse and longitudinal flagella? see Gocht, 1967). W. (Rh. J draco is hitherto known only from the Middle Oligocene.
Occurrence: Middle Oligocene.
Wetzeliella (Rhombodinium) draco var.
Alberti, 1961 described forms which undoubtedly were W. (Rh.) draco, but had processes which did not seem consistent with the genus Rhombodinium. He found a fairly complete range of transitional forms between smooth and spined. Similar specimens were found also in the Middle Oligocene strata at Meckelfeld.
There seem to be two major, extreme forms: one with many, short processes, and the other with fewer, but longer processes. The first is reminiscent of W. (W.) irtyschensis Alberti, and was mistakenly designated as such by Gocht, 1967. However, it is less symmetrical, and its inner body does not conform so closely to the lateral margin as in irtyschensis. The processes are short, often minute, and unbranched. The second form, which is usually more distinctly elongate, bears medium-sized to long, flexible processes which often end distally in two or three branches. The processes are never as numerous as on the short-spined extreme; they can even be sparse. On both forms, flagellar insertions were observed, as were also the flocculent organic deposits on the inner body. There are also perforations on the horns, but they are less frequent and less regularly shaped than on smooth individuals.
Occurrence: Middle Oligocene.