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Oligosphaeridium quattroccioae
Oligosphaeridium quattrocchioae Volkheimer 2010, p.236,238, figs.5H–M,6A–B,F–H.
Holotype: Volkheimer 2010, fig.6B. Age: late Valanginian–early Hauterivian.
Original description (Volkheimer, 2010)
Diagnosis. Oligosphaeridium quattrocchioae is differentiated essentially from other species of the genus by the distal complexity of the fenestrate processes; an Endo/Proc ratio of 2.9 (Relation between endocyst diameter and length of processes) and the fact that the antapical process is not especially large. Length of processes around one third of equatorial diameter.
Description. Skolochorate cysts of medium size, having a spherical to subspherical central body with eighteen hollow, tubiform processes and one (or two) slender, solid processes. Processes intratabular corresponding to the formula 4', 6", 6'", 1p, 1"", 1-2s. Processes formed from periphragm only. Tubiform processes infundibular and broadening distally, aculeate to broadly cauliflorate and exhibiting perforations of variable number, size, shape and location. Apical processes markedly more slender. One sulcal process constantly present; when a second sulcal process is present, it is very slender, unbranched and flexuous. Length of processes around one-third of equatorial diameter of central body. Surface of phragma without conspicuous ornament. Archaeopyle apical (type A); operculum free.
Derivation of name. In honour of the distinguished Argentinian palynologist Dr. Mirta Quattrocchio.
Holotype. Prep. MPLP 9041 A4/2H:15.3/95.4 (MPLP: Mendoza-Paleopalinoteca-Laboratorio-Paleopalinología) (fig. 6.B).
Paratype. Prep. MPLP 9041 A4/14C:26.2/94.9 (fig. 6.H).
Lodgement. Stored in the Unidad Paleopalinología del IANIGLA (Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales), CCT-CONICET-Mendoza. The coordinates indicated correspond to the microscope Leitz Dialux 20 located at IANIGLA.
Dimensions. Holotype: maximum diameter of body: 53 μm. Paratype: maximum diameter of body: 58 μm. Range of maximum diameter of body: 44 (55) 66 μm (55 specimens measured). Length of processes 13-25 μm.
Horizon and locality. Lower Member (=Pilmatué é Member) of the Agrio Formation, 23m above the lower limit of the Formation. Estancia Santa Elena, provincial road No.66, Neuquén province, Argentina.
Stratigraphic range. Lower Member (Pilmatué Member) of the Agrio Formation (Upper Valanginian to Lower Hauterivian).
Supplementary observations. The second sulcal process is exceptionally slender and may readily escape observation. It is not constantly present; it is visible on the specimen illustrated in figure 6.2, but lacking from the specimen sketched (fig. 6.1). No indication of an anterior sulcal process was seen in any specimen. The phragma surface is laevigate to finely granulate in all specimens seen. The apical processes are more slender than those on the loisthocyst, but have comparably complex terminations. Their proportionate length could not be measured.
The degree of complexity of the process tips is highly variable. In vertical view they may appear like a ragged-edged platform with an irregular scatter of perforation of variable size; in lateral view, they are seen to be secate to cauliflorate. Two processes on the loisthocyst, l'" (Iu) and lp (X), are markedly smaller than the others; the antapical process is of a size comparable to those of the pre- and postcingular paraplates.
For comparison with other skolochorate genera of dinoflagellate cysts see figure 3. Comparison with Oligosphaeridium pulcherrimum (Deflandre and Cookson) Davey & Williams, 1966 is close. Both species have fenestrations in the distal portions of the processes, but they differ in the Endo/Proc ratio, which is 1.9 in O. pulcherrimum, but 2.9 in O. quattrocchioae. The Endo/Proc ratio of O. patulum Riding and Thomas is 1.9, similar to O. pulcherrimum, but it presents non fenestrate processes. O. quattrocchioae finds also a close comparison with Oligosphaeridium byersense Duane, 1997, from the Early Cretaceous (Valanginian) of the Antarctic Peninsula, which is similar in Endo/Proc ratio (2.5 vs. 2.9). However it does not have fenestrate processes and the processes of that species are larger, buccinate rather than infundibular and of even greater distal complexity, adjacent processes being sometimes linked by trabeculae. Other species, such as Oligosphaeridium complex (White) Davey and Williams, have processes proportionately larger and, though of variable complexity, showing no close matches with Oligosphaeridum quattrocchioae. Oligosphaeridium complex subsp. brevispinum Jain, 1975 (p.182, pl. 1, figure 4) has short processes, but these are proportionately much thicker than in O. quattrocchioae, giving a totally different, heavier appearance to the subspecies mentioned.
Nevertheless, the size of processes is not reliable for differentiating chorate species, as process size is not only determined by genetics and therefore might not be a good characteristic to differentiate species in one genus. As an example, size of processes in Lingulodinium polyhedrum changes when salinity of sea water does. In normal salinity sea water this species forms normal cysts with normally long processes. But, when the cysts develop in less than normal salinity, the processes are shorter (Helenes, verbal communication).
Holotype: Volkheimer 2010, fig.6B. Age: late Valanginian–early Hauterivian.
Original description (Volkheimer, 2010)
Diagnosis. Oligosphaeridium quattrocchioae is differentiated essentially from other species of the genus by the distal complexity of the fenestrate processes; an Endo/Proc ratio of 2.9 (Relation between endocyst diameter and length of processes) and the fact that the antapical process is not especially large. Length of processes around one third of equatorial diameter.
Description. Skolochorate cysts of medium size, having a spherical to subspherical central body with eighteen hollow, tubiform processes and one (or two) slender, solid processes. Processes intratabular corresponding to the formula 4', 6", 6'", 1p, 1"", 1-2s. Processes formed from periphragm only. Tubiform processes infundibular and broadening distally, aculeate to broadly cauliflorate and exhibiting perforations of variable number, size, shape and location. Apical processes markedly more slender. One sulcal process constantly present; when a second sulcal process is present, it is very slender, unbranched and flexuous. Length of processes around one-third of equatorial diameter of central body. Surface of phragma without conspicuous ornament. Archaeopyle apical (type A); operculum free.
Derivation of name. In honour of the distinguished Argentinian palynologist Dr. Mirta Quattrocchio.
Holotype. Prep. MPLP 9041 A4/2H:15.3/95.4 (MPLP: Mendoza-Paleopalinoteca-Laboratorio-Paleopalinología) (fig. 6.B).
Paratype. Prep. MPLP 9041 A4/14C:26.2/94.9 (fig. 6.H).
Lodgement. Stored in the Unidad Paleopalinología del IANIGLA (Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales), CCT-CONICET-Mendoza. The coordinates indicated correspond to the microscope Leitz Dialux 20 located at IANIGLA.
Dimensions. Holotype: maximum diameter of body: 53 μm. Paratype: maximum diameter of body: 58 μm. Range of maximum diameter of body: 44 (55) 66 μm (55 specimens measured). Length of processes 13-25 μm.
Horizon and locality. Lower Member (=Pilmatué é Member) of the Agrio Formation, 23m above the lower limit of the Formation. Estancia Santa Elena, provincial road No.66, Neuquén province, Argentina.
Stratigraphic range. Lower Member (Pilmatué Member) of the Agrio Formation (Upper Valanginian to Lower Hauterivian).
Supplementary observations. The second sulcal process is exceptionally slender and may readily escape observation. It is not constantly present; it is visible on the specimen illustrated in figure 6.2, but lacking from the specimen sketched (fig. 6.1). No indication of an anterior sulcal process was seen in any specimen. The phragma surface is laevigate to finely granulate in all specimens seen. The apical processes are more slender than those on the loisthocyst, but have comparably complex terminations. Their proportionate length could not be measured.
The degree of complexity of the process tips is highly variable. In vertical view they may appear like a ragged-edged platform with an irregular scatter of perforation of variable size; in lateral view, they are seen to be secate to cauliflorate. Two processes on the loisthocyst, l'" (Iu) and lp (X), are markedly smaller than the others; the antapical process is of a size comparable to those of the pre- and postcingular paraplates.
For comparison with other skolochorate genera of dinoflagellate cysts see figure 3. Comparison with Oligosphaeridium pulcherrimum (Deflandre and Cookson) Davey & Williams, 1966 is close. Both species have fenestrations in the distal portions of the processes, but they differ in the Endo/Proc ratio, which is 1.9 in O. pulcherrimum, but 2.9 in O. quattrocchioae. The Endo/Proc ratio of O. patulum Riding and Thomas is 1.9, similar to O. pulcherrimum, but it presents non fenestrate processes. O. quattrocchioae finds also a close comparison with Oligosphaeridium byersense Duane, 1997, from the Early Cretaceous (Valanginian) of the Antarctic Peninsula, which is similar in Endo/Proc ratio (2.5 vs. 2.9). However it does not have fenestrate processes and the processes of that species are larger, buccinate rather than infundibular and of even greater distal complexity, adjacent processes being sometimes linked by trabeculae. Other species, such as Oligosphaeridium complex (White) Davey and Williams, have processes proportionately larger and, though of variable complexity, showing no close matches with Oligosphaeridum quattrocchioae. Oligosphaeridium complex subsp. brevispinum Jain, 1975 (p.182, pl. 1, figure 4) has short processes, but these are proportionately much thicker than in O. quattrocchioae, giving a totally different, heavier appearance to the subspecies mentioned.
Nevertheless, the size of processes is not reliable for differentiating chorate species, as process size is not only determined by genetics and therefore might not be a good characteristic to differentiate species in one genus. As an example, size of processes in Lingulodinium polyhedrum changes when salinity of sea water does. In normal salinity sea water this species forms normal cysts with normally long processes. But, when the cysts develop in less than normal salinity, the processes are shorter (Helenes, verbal communication).