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Trithyrodinium suspectum subsp. ukrainense
Trithyrodinium suspectum subsp. ukrainense Dodsworth, 2004, p.130–131,133–134, pl.1, figs.1–8.
Holotype: Dodsworth, 2004, pl.1, figs.1,7.
Age: Cenomanian–Turonian.
Original decsription (Dodsworth, 204):
Trithyrodinium suspectum ukrainense subsp. nov. Plate 1, figs. 1–8
Designation of holotype. Plate 1, figs. 1 & 7. Slide 9104- 1(A) W48/2. Specimen dimensions: 49 µm long x 43 µm wide. The slide is curated in the Palynology Research Facility, University of Sheffield. The collection number for the type is ML5786.
Designation of paratypes. Paratype 1: Plate 1, fig. 5. Slide 9104-2(A) L48/3. Specimen dimensions: 63 µm long x 49 µm wide. Paratype 2: Plate 1, fig. 8. Slide 9106-2(A) X49/0. Specimen dimensions: 47 µm long x 46 µm wide.
Occurrence. The taxon occurs in Aksudere samples 9101-1 to 9123. The stratigraphic range is Upper Cenomanian to ?Lower Turonian.
Derivation of name. The taxon is named after the country Ukraine, in which it is first reported here.
Diagnosis. The taxon is a relatively small, thin walled and sparsely ornamented subspecies of Trithyrodinium suspectum. The endocyst is c. 0.5–0.75 µm thick and is ornamented with small (< 0.5–1 µm) grana/pilae that are isolated and evenly scattered or, to an extent, locally clustered. Areas devoid of any obvious ornament, c. 1–5 µm across are characteristic.
Description. The endophragm is subspherical to ellipsoidal in shape. The periphragm is subspherical to ellipsoidal with a short apical horn and two poorly developed antapical horns of nearly equal size, although the right antapical horn is usually slightly longer than the left one. The cyst is circumcavate. The periphragm may be partly or completely missing in some specimens. The endophragm is ornamented with grana. Grana are generally less than 1 µm in size but may develop into pilae up to 2 µm in length. The grana/pilae are isolated and evenly scattered, as seen on the paratype (Plate 1, fig. 8) or, to an extent, locally clustered in atabular patches, up to 15 µm in diameter, as seen on the holotype (Plate 1, fig. 7). Areas devoid of any obvious ornament, c.1–5 µm across, occur between grana/pilae. The periphragm is generally smooth but may possess sparse grana. Paratabulation is usually indicated by the archaeopyle(s) only. The archaeopyle is intercalary, type 3I/3I. The periarchaeopyle is rarely discernible. In the endocyst, excystment features are occasionally absent or restricted to sutures around three intercalary plates (e.g. Plate 1, fig. 8). One to three plates are lost in archaeopyle formation with sutures surrounding any of the three plates that remain attached. The cingulum is generally not indicated but on some specimens the position is indicated by folds in the endophragm and periphragm and by shallow local concavities at the lateral margins. The sulcus is not indicated.
The size is intermediate: Pericyst, average length = 54 µm, range 40–72 µm, average width = 46 µm, range 36–62 µm, measured specimens (n) = 52. Endocyst, average length = 45 µm, range 32–68 µm, average width = 42 µm, range 32–60 µm, n = 100.
Comparisons. Trithyrodinium suspectum ukrainense has features in common with Trithyrodinium suspectum sensu stricto and Trithyrodinium evitii. T. suspectum sensu stricto differs in being larger, possessing a thicker endocyst and denser ornament. The type material described by Manum and Cookson (1964) documented specimen length 91–118 µm, width 65–78 µm and wall thickness 2.5–4 µm (n = 4). Davey (1969) assigned smaller, thinner walled specimens to T. suspectum, length 61–68 µm, width 56–59 µm and wall thickness 1.5–2 µm (n = 5). Ioannides (1986) gave measurements for endocyst length 55–75 µm, width 55–72 µm and wall thickness 1.5–3.5 µm. In T. suspectum sensu stricto, the endophragm ornament of grana/rod-like structures is reported by all these authors to be more densely packed, lacking the c.1–5 µm spaces developed between ornament elements seen in T. suspectum ukrainense. Trithyrodinium evitii and T. suspectum ukrainense are comparable in terms of size and endophragm wall thickness. T. evitii differs in lacking prominent periphragm apical and antapical horns, possessing a smooth to minutely ornamented endophragm that is sometimes covered with a brown organic layer and lacking the distinct grana/pilae of T. suspectum ukrainense.
Discussion. In carbonate samples taken from below and above the black shales at Aksudere, slightly thicker walls (c. 0.75–1 µm thick, excluding ornament) were recorded from some specimens. These are assigned to T. cf. suspectum ukrainense (Table 1). Many specimens observed from black shales in this study are from preparations that have been oxidised with Schulze’s solution (Text-Fig. 2). This may have resulted in slight bleaching or even thinning of endophragm walls. In a previous work (Schrank, 1988), extended oxidation has been shown to affect the degree of cavation in certain peridinioids. Specimens from unoxidised carbonate preparations in the present study (e.g. Plate 1, fig. 6) are of similar size and exhibit similar cavation and ornament to those from the extended oxidation preparations. Nøhr-Hansen & Dam (1999) demonstrated that oxidation with concentrated nitric acid and subsequent treatment with potassium hydroxide resulted in the removal of a brown non-sporopollenin organic layer that surrounds the endocyst of T. evitii. Layers of this type were not observed on T. suspectum ukrainense endocysts from unoxidised kerogen or extended oxidation preparations. The specimens present in the Aksudere material are considered to be close in morphology to specimens that are often included in the taxon Trithyrodinium suspectum. They are sufficiently alike and sufficiently different from the type material of T. suspectum, in terms of size, wall thickness and possessing areas devoid of ornament, to warrant the erection of the new subspecies T. suspectum ukrainense.
Holotype: Dodsworth, 2004, pl.1, figs.1,7.
Age: Cenomanian–Turonian.
Original decsription (Dodsworth, 204):
Trithyrodinium suspectum ukrainense subsp. nov. Plate 1, figs. 1–8
Designation of holotype. Plate 1, figs. 1 & 7. Slide 9104- 1(A) W48/2. Specimen dimensions: 49 µm long x 43 µm wide. The slide is curated in the Palynology Research Facility, University of Sheffield. The collection number for the type is ML5786.
Designation of paratypes. Paratype 1: Plate 1, fig. 5. Slide 9104-2(A) L48/3. Specimen dimensions: 63 µm long x 49 µm wide. Paratype 2: Plate 1, fig. 8. Slide 9106-2(A) X49/0. Specimen dimensions: 47 µm long x 46 µm wide.
Occurrence. The taxon occurs in Aksudere samples 9101-1 to 9123. The stratigraphic range is Upper Cenomanian to ?Lower Turonian.
Derivation of name. The taxon is named after the country Ukraine, in which it is first reported here.
Diagnosis. The taxon is a relatively small, thin walled and sparsely ornamented subspecies of Trithyrodinium suspectum. The endocyst is c. 0.5–0.75 µm thick and is ornamented with small (< 0.5–1 µm) grana/pilae that are isolated and evenly scattered or, to an extent, locally clustered. Areas devoid of any obvious ornament, c. 1–5 µm across are characteristic.
Description. The endophragm is subspherical to ellipsoidal in shape. The periphragm is subspherical to ellipsoidal with a short apical horn and two poorly developed antapical horns of nearly equal size, although the right antapical horn is usually slightly longer than the left one. The cyst is circumcavate. The periphragm may be partly or completely missing in some specimens. The endophragm is ornamented with grana. Grana are generally less than 1 µm in size but may develop into pilae up to 2 µm in length. The grana/pilae are isolated and evenly scattered, as seen on the paratype (Plate 1, fig. 8) or, to an extent, locally clustered in atabular patches, up to 15 µm in diameter, as seen on the holotype (Plate 1, fig. 7). Areas devoid of any obvious ornament, c.1–5 µm across, occur between grana/pilae. The periphragm is generally smooth but may possess sparse grana. Paratabulation is usually indicated by the archaeopyle(s) only. The archaeopyle is intercalary, type 3I/3I. The periarchaeopyle is rarely discernible. In the endocyst, excystment features are occasionally absent or restricted to sutures around three intercalary plates (e.g. Plate 1, fig. 8). One to three plates are lost in archaeopyle formation with sutures surrounding any of the three plates that remain attached. The cingulum is generally not indicated but on some specimens the position is indicated by folds in the endophragm and periphragm and by shallow local concavities at the lateral margins. The sulcus is not indicated.
The size is intermediate: Pericyst, average length = 54 µm, range 40–72 µm, average width = 46 µm, range 36–62 µm, measured specimens (n) = 52. Endocyst, average length = 45 µm, range 32–68 µm, average width = 42 µm, range 32–60 µm, n = 100.
Comparisons. Trithyrodinium suspectum ukrainense has features in common with Trithyrodinium suspectum sensu stricto and Trithyrodinium evitii. T. suspectum sensu stricto differs in being larger, possessing a thicker endocyst and denser ornament. The type material described by Manum and Cookson (1964) documented specimen length 91–118 µm, width 65–78 µm and wall thickness 2.5–4 µm (n = 4). Davey (1969) assigned smaller, thinner walled specimens to T. suspectum, length 61–68 µm, width 56–59 µm and wall thickness 1.5–2 µm (n = 5). Ioannides (1986) gave measurements for endocyst length 55–75 µm, width 55–72 µm and wall thickness 1.5–3.5 µm. In T. suspectum sensu stricto, the endophragm ornament of grana/rod-like structures is reported by all these authors to be more densely packed, lacking the c.1–5 µm spaces developed between ornament elements seen in T. suspectum ukrainense. Trithyrodinium evitii and T. suspectum ukrainense are comparable in terms of size and endophragm wall thickness. T. evitii differs in lacking prominent periphragm apical and antapical horns, possessing a smooth to minutely ornamented endophragm that is sometimes covered with a brown organic layer and lacking the distinct grana/pilae of T. suspectum ukrainense.
Discussion. In carbonate samples taken from below and above the black shales at Aksudere, slightly thicker walls (c. 0.75–1 µm thick, excluding ornament) were recorded from some specimens. These are assigned to T. cf. suspectum ukrainense (Table 1). Many specimens observed from black shales in this study are from preparations that have been oxidised with Schulze’s solution (Text-Fig. 2). This may have resulted in slight bleaching or even thinning of endophragm walls. In a previous work (Schrank, 1988), extended oxidation has been shown to affect the degree of cavation in certain peridinioids. Specimens from unoxidised carbonate preparations in the present study (e.g. Plate 1, fig. 6) are of similar size and exhibit similar cavation and ornament to those from the extended oxidation preparations. Nøhr-Hansen & Dam (1999) demonstrated that oxidation with concentrated nitric acid and subsequent treatment with potassium hydroxide resulted in the removal of a brown non-sporopollenin organic layer that surrounds the endocyst of T. evitii. Layers of this type were not observed on T. suspectum ukrainense endocysts from unoxidised kerogen or extended oxidation preparations. The specimens present in the Aksudere material are considered to be close in morphology to specimens that are often included in the taxon Trithyrodinium suspectum. They are sufficiently alike and sufficiently different from the type material of T. suspectum, in terms of size, wall thickness and possessing areas devoid of ornament, to warrant the erection of the new subspecies T. suspectum ukrainense.