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Striatodinium lineatum
Striatodinium lineatum Riding and Helby, 2001f, p.168,170, figs.14A–P.
Holotype: Riding and Helby, 2001f, figs.14A–B.
Age: Oxfordian–earliest Kimmeridgian.
Original description (Riding & Helby, 2001f)
Description. A species of Striatodinium which is slightly dorsoventrally flattened and has a dense ornamentation, consisting of outer, generally continuous, penitabular ridges, within which there may be numerous subparallel, occasionally coalescing, longitudinal ridges or aligned rows of elements. The ridges are low, 0.5-1µm in height, sooth distally and narrow (c. 1µm in width). These ridges may be long, short, discontinuous and sinuous. The paratabulation is marked by the smooth pandasutural bands between the penitabular fields. The paracingulum is well marked, with hexagonal paraplates, bearing an outer, often interrupted penitabular ridge. Within the penitabular fields the overall longitudinal lineation of accessory ridges is maintained.
Dimensions (µm; n=43): Min. (Mean) Max.
Length of entire cyst: 41 (46) 54
Length of loisthocyst: 33 (42) 50
Length of operculum: 9 (10) 11
Length of precingular paraplate series*: 14 (17) 20
Length of paracingulum: 4 (5) 6
Length of postcingular paraplate series*: 20 (22) 25
Equatorial width of cyst: 26 (30) 35
* - measured in dorsal view.
The measured specimens are from sidewall core samples from Octavius-2 well at 2905.00m and 2907.00m, Tenacious West-1 well at 3040.00m and outcrop sample 81FH63, from Kimmeridgian lowermost part of the Lelinta Formation (Fageo Group) of Misool, eastern Indonesia (Hasibuan, 1990).
Comments. Striatodinium lineatum is a distinctive species due to the prominent, dense, longitudinal ridges and aligned low relief elements, which cover the autophragm, apart from the smooth pandasutural bands. The vast majority of the specimens studied are loisthocysts. The few opercula which were encountered are flattened cones, relatively low in height, and lacking an apical horn. The pandasutural bands, which define the individual paraplates, are not always clearly developed, particularly in specimens in which the ridges are less prominent. Normally the paratabulation is best developed on the dorsal side. The less well preserved forms may have sparser, more discontinuous ridges. It is possible therefore that the ridges are susceptible to physico-chemical degradation.
Comparison. Striatodinium is smaller than S. otti and also differs in having additional nontabular, longitudinal ornamentation and lacking prominent penitabular crests.
Derivation of name: From the Latin linea, meaning line or thread and referring to the longitudinal ridges which impart a linear pattern to this species.
Holotype and type locality: Figures 14A-B, CPC 35726, sample 81FH63, outcrop material from the lower part of the Lelinta Formation (Kimmeridgian), Misool, eastern Indonesia (Hasibuan, 1990).
Stratigraphical distribution: Striatodinium lineatum ranges fromn the Oxfordian to Kimmeridgian upper part of the Wanaea clathrata Zone (6bi) to the basal part of the Kimmeridgian Dingodinium swanense Zone (6aiiib). It occurs consistently over this interval in the Timor Sea region (and Misool), but is extremely rare to the south in the Carnarvon Basin, Western Australia.
Holotype: Riding and Helby, 2001f, figs.14A–B.
Age: Oxfordian–earliest Kimmeridgian.
Original description (Riding & Helby, 2001f)
Description. A species of Striatodinium which is slightly dorsoventrally flattened and has a dense ornamentation, consisting of outer, generally continuous, penitabular ridges, within which there may be numerous subparallel, occasionally coalescing, longitudinal ridges or aligned rows of elements. The ridges are low, 0.5-1µm in height, sooth distally and narrow (c. 1µm in width). These ridges may be long, short, discontinuous and sinuous. The paratabulation is marked by the smooth pandasutural bands between the penitabular fields. The paracingulum is well marked, with hexagonal paraplates, bearing an outer, often interrupted penitabular ridge. Within the penitabular fields the overall longitudinal lineation of accessory ridges is maintained.
Dimensions (µm; n=43): Min. (Mean) Max.
Length of entire cyst: 41 (46) 54
Length of loisthocyst: 33 (42) 50
Length of operculum: 9 (10) 11
Length of precingular paraplate series*: 14 (17) 20
Length of paracingulum: 4 (5) 6
Length of postcingular paraplate series*: 20 (22) 25
Equatorial width of cyst: 26 (30) 35
* - measured in dorsal view.
The measured specimens are from sidewall core samples from Octavius-2 well at 2905.00m and 2907.00m, Tenacious West-1 well at 3040.00m and outcrop sample 81FH63, from Kimmeridgian lowermost part of the Lelinta Formation (Fageo Group) of Misool, eastern Indonesia (Hasibuan, 1990).
Comments. Striatodinium lineatum is a distinctive species due to the prominent, dense, longitudinal ridges and aligned low relief elements, which cover the autophragm, apart from the smooth pandasutural bands. The vast majority of the specimens studied are loisthocysts. The few opercula which were encountered are flattened cones, relatively low in height, and lacking an apical horn. The pandasutural bands, which define the individual paraplates, are not always clearly developed, particularly in specimens in which the ridges are less prominent. Normally the paratabulation is best developed on the dorsal side. The less well preserved forms may have sparser, more discontinuous ridges. It is possible therefore that the ridges are susceptible to physico-chemical degradation.
Comparison. Striatodinium is smaller than S. otti and also differs in having additional nontabular, longitudinal ornamentation and lacking prominent penitabular crests.
Derivation of name: From the Latin linea, meaning line or thread and referring to the longitudinal ridges which impart a linear pattern to this species.
Holotype and type locality: Figures 14A-B, CPC 35726, sample 81FH63, outcrop material from the lower part of the Lelinta Formation (Kimmeridgian), Misool, eastern Indonesia (Hasibuan, 1990).
Stratigraphical distribution: Striatodinium lineatum ranges fromn the Oxfordian to Kimmeridgian upper part of the Wanaea clathrata Zone (6bi) to the basal part of the Kimmeridgian Dingodinium swanense Zone (6aiiib). It occurs consistently over this interval in the Timor Sea region (and Misool), but is extremely rare to the south in the Carnarvon Basin, Western Australia.