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Egmontodinium polyplacophorum
Egmontodinium polyplacophorum Gitmez and Sarjeant, 1972
Holotype: Gitmez and Sarjeant, 1972, pl.8, figs.1-2, pl.11, figs.5-6,8, text-fig.24A-B
Paratype: Gitmez and Sarjeant, 1972
Locus typicus: Egmont Bight, Dorset, England
Stratum typicum: Middle-Late Kimmeridgian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Egmontodinium polyplacophorum Gitmez and Sarjeant, 1972, has an ovoidal cyst that is thin walled and without prominent granulation or punctation. Sutures variably ornamented with delicate crests or with rows of spinelets, simple or bifurcate and sometimes distally connected: the sutural ornamentation is most prominent around the antapex. Archeopyle apical. Size: overall length 60-80 µm, length without apex 50-68 µm, width 45-65 µm, maximum height of crests ca. 3-5 µm.
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Original diagnosis: Gitmez and Sarjeant, 1972, p.229
A species of Egmontodinium having an ovoidal cyst, thin walled and without prominent granulation or punctation. Sutures variably ornamented with delicate crests or with rows of spinelets, simple or bifurcate and sometimes distally connected; the sutural ornamentation is most prominent around the antapex. The tabulation is as for the genus, but shows some variation in detail through the presence or absence of additional small plates at sutural nodes.
Dimensions: Holotype: length of cyst 76 Ám, breadth 58 Ám, maximum height of crests 3.5 Ám. Paratype a: length 78 Ám, breadth 61 Ám, maximum height of crests 3 Ám. Paratype b: length (apex lacking) 65 Ám, breadth 59.5 Ám, maximum height of crests c. 5 Ám. Paratype c: length (apex lacking) 61 Ám, breadth 66 Ám, maximum height of crests c. 5 Ám. Range: overall length 60-80 Ám, length without apex 50-68 Ám, breadth 45-65 Ám, maximum height of crests c. 3 Ám. Measured specimens: 15.
Original description: Gitmez and Sarjeant, 1972, p.229, 231
The cyst surface is typically smooth, but may exhibit minute granulation or punctation. Ornament is normally confined to the sutures: in some instances, however, one or a few isolated spincs, or a short row of spines not traversing the plate, may be present within a plate boundary.
Four apical plates are developed, the first being the largest and situated in the anterior prolongation of the sulcus. They are surrounded by six (possibly sometimes by only five) elongate plates constituting the anterior circle, plate 3a-c being broader than the others in the holotype. The opercular suture opens along this circle, so that the plate boundaries with the apical plates are present in the operculum and those with the precingular plates on the cyst proper. The initial opening of the opercular suture appears to occur on the dorsal side: the operculum frequently retains a ventral attachment with the abandoned cyst. The holotype shows no opening: paratype (a) is partly open, though the operculum remains attached and almost in place; paratypes (b) and (c) lack the operculum.
The six precingular plates are almost of equal size. In the holotype, a small round plate is present at the node of the crest separating plates 3" and 4" and that bounding the operculum: no such plate has distinguished on the paratypes. The cingulum is made up of six elongate plates with clear boundaries. The sulcus is broad and occupies only the central part of the ventral surface, being separated from the apex by the large plate 1' and from the antapex by two posterior ventral plates and by two plates of the posterior circle. In the holotype, a small pate is present at the junction of the sulcus and plate 6'''. Of the six postcingular plates, the first is extremely small (as is the case in many species of Gonyaulacysta) and may be masked by its bounding crests: plate 2''' is also reduced, to accommodate the second posterior ventral plate, an equivalent of the posterior intercalary plate but displaced to the ventral side. The other four postcingular plates are quite large. The plates of the posterior circle are quite variable in form: in particular, plates 3pc and 5pc sometimes exhibit a remarkable "tail" extending along the sulcus separating two dorsal postcingular plates. The boundaries between the ventral posterior circle plates are in some instances distinguishable only with difficulty, if at all: the holotye is unusually clear in structure and exceptionally favourably orientated. The antapical plate is polygonal and quite large: on two specimens (paratypes a and c) it is partially subdivided by a row of proximally connected spines, but this row only traverses half the plate.
The ornamention of the sutures is highly variable, from rows of isolated, simple or bifurcate spines, with or without distal or (more commonly) proximal connections, to simple delicate crests of moderate height. The highest crests are generally those bounding the cingulum and antapex. (The character of the crests may be modified by accidents of preservation) The crests or spines are usually little more than onetenth of the cyst breadth in height: difficulty is often experienced in distinguishing particular crests.
Holotype: Gitmez and Sarjeant, 1972, pl.8, figs.1-2, pl.11, figs.5-6,8, text-fig.24A-B
Paratype: Gitmez and Sarjeant, 1972
Locus typicus: Egmont Bight, Dorset, England
Stratum typicum: Middle-Late Kimmeridgian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Egmontodinium polyplacophorum Gitmez and Sarjeant, 1972, has an ovoidal cyst that is thin walled and without prominent granulation or punctation. Sutures variably ornamented with delicate crests or with rows of spinelets, simple or bifurcate and sometimes distally connected: the sutural ornamentation is most prominent around the antapex. Archeopyle apical. Size: overall length 60-80 µm, length without apex 50-68 µm, width 45-65 µm, maximum height of crests ca. 3-5 µm.
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Original diagnosis: Gitmez and Sarjeant, 1972, p.229
A species of Egmontodinium having an ovoidal cyst, thin walled and without prominent granulation or punctation. Sutures variably ornamented with delicate crests or with rows of spinelets, simple or bifurcate and sometimes distally connected; the sutural ornamentation is most prominent around the antapex. The tabulation is as for the genus, but shows some variation in detail through the presence or absence of additional small plates at sutural nodes.
Dimensions: Holotype: length of cyst 76 Ám, breadth 58 Ám, maximum height of crests 3.5 Ám. Paratype a: length 78 Ám, breadth 61 Ám, maximum height of crests 3 Ám. Paratype b: length (apex lacking) 65 Ám, breadth 59.5 Ám, maximum height of crests c. 5 Ám. Paratype c: length (apex lacking) 61 Ám, breadth 66 Ám, maximum height of crests c. 5 Ám. Range: overall length 60-80 Ám, length without apex 50-68 Ám, breadth 45-65 Ám, maximum height of crests c. 3 Ám. Measured specimens: 15.
Original description: Gitmez and Sarjeant, 1972, p.229, 231
The cyst surface is typically smooth, but may exhibit minute granulation or punctation. Ornament is normally confined to the sutures: in some instances, however, one or a few isolated spincs, or a short row of spines not traversing the plate, may be present within a plate boundary.
Four apical plates are developed, the first being the largest and situated in the anterior prolongation of the sulcus. They are surrounded by six (possibly sometimes by only five) elongate plates constituting the anterior circle, plate 3a-c being broader than the others in the holotype. The opercular suture opens along this circle, so that the plate boundaries with the apical plates are present in the operculum and those with the precingular plates on the cyst proper. The initial opening of the opercular suture appears to occur on the dorsal side: the operculum frequently retains a ventral attachment with the abandoned cyst. The holotype shows no opening: paratype (a) is partly open, though the operculum remains attached and almost in place; paratypes (b) and (c) lack the operculum.
The six precingular plates are almost of equal size. In the holotype, a small round plate is present at the node of the crest separating plates 3" and 4" and that bounding the operculum: no such plate has distinguished on the paratypes. The cingulum is made up of six elongate plates with clear boundaries. The sulcus is broad and occupies only the central part of the ventral surface, being separated from the apex by the large plate 1' and from the antapex by two posterior ventral plates and by two plates of the posterior circle. In the holotype, a small pate is present at the junction of the sulcus and plate 6'''. Of the six postcingular plates, the first is extremely small (as is the case in many species of Gonyaulacysta) and may be masked by its bounding crests: plate 2''' is also reduced, to accommodate the second posterior ventral plate, an equivalent of the posterior intercalary plate but displaced to the ventral side. The other four postcingular plates are quite large. The plates of the posterior circle are quite variable in form: in particular, plates 3pc and 5pc sometimes exhibit a remarkable "tail" extending along the sulcus separating two dorsal postcingular plates. The boundaries between the ventral posterior circle plates are in some instances distinguishable only with difficulty, if at all: the holotye is unusually clear in structure and exceptionally favourably orientated. The antapical plate is polygonal and quite large: on two specimens (paratypes a and c) it is partially subdivided by a row of proximally connected spines, but this row only traverses half the plate.
The ornamention of the sutures is highly variable, from rows of isolated, simple or bifurcate spines, with or without distal or (more commonly) proximal connections, to simple delicate crests of moderate height. The highest crests are generally those bounding the cingulum and antapex. (The character of the crests may be modified by accidents of preservation) The crests or spines are usually little more than onetenth of the cyst breadth in height: difficulty is often experienced in distinguishing particular crests.