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Meiourogonyaulax baculata
Meiourogonyaulax baculata Mantle, 2009a, p.59, pl.14, figs.4a–b,5–6; text-fig.12C.
Holotype: Mantle, 2009a, pl.14, figs.4a–b.
Age Callovian.
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Original description (Mantle, 2009a)
Meiourogonyawlax baculata sp. nov. Plate 14, Figs 4-6; Text-fig. 12C
Diagnosis: Cysts proximate-proximochorate, acavate, with subcircular outline. Cyst wall single-layered. Autophragm perforate, microreticulate, and/or granulate. Paratabulation gonyaulacalean; indicated by aligned, robust, solid, short processes (typically bacula or clavae) or by spines interconnected by low crests (< 0.5 µm high). Further sculptural elements occur in intratabular positions. Archeopyle apical (type t4A); operculum free.
Description: The numerous processes covering the cyst vary in distribution, from being predominantly parasutural, with only a few intratabular elements, to being widely and randomly scattered across the entire cyst. These processes (1-5 µm long) are similarly variable in form and are baculate, clavate, buccinate, or subconical with broadly rounded, acuminate, bifid, or flared terminations, although baculate and clavate elements predominate. Some of the processes may be joined distally by thin trabeculae, but this is typically restricted to no more than 3 adjoining processes. The processes are commonly longest in gonal positions, Particularly along the paracingulum. This variation in process distribution and density means the paratabulation pattern is obvious on those cysts where parasutural elements predominate and less cleat on the cysts I with a denser covering of sculptural elements. However the paracingulum is invariably prominent. The paratabulation formula is standard gonyaulacalean (?pr, 4',6",-6c,5-6;",1""). The autophragm, (1-1.5 µm thick) is commonly perforate or microreticulate, but may also be granulate or rarely scabrate. The archeopyle is apical, with an angular margin and either undeveloped or deep accessory sutures. The operculum is I rarely attached and was not positively identified in the strew slides.
Dimensions (13 specimens): Length of cyst (excluding operculum) 43 (50) 59 µm; maximum width of cyst 55 (50) 67 µm; length of processes 1 (4) 6 µm; thickness of cyst wall 1-1.5 µm.
Holotype: SGM H8, EF N22/0. CPC no. 39262; PI. 14, Figs 4a, b. Total length of cyst (excluding operculum) 47 µm; I maximum width of cyst 60 µm; thickness of cyst wall 1 µm.
Type locality: Timor Sea, Bayu-Undan Field, Undan-3, core 2 at 3016 m (Elang Formation).
Etymology: Lat., baculum (rod-like); with reference to the commonesr process type adorning the autophragm.
Remarks: Meiorogonyaulax Sarjeant 1966 is distinguished from Lithodinia Eisenack emend. Gocht 1975 (modified by Stover & Evitt 1978: 60-61) on the basis of operculum type. These genera are characterized by compound and simple opercula respectively (Riding & Helby 2001: 81). The new species is assigned to Meiourogonyaulax as several compound opercula were observed still attached to the cysts. However, no opercula were observed in either the residues or the strew slides.
Comparison: Meiourogonyaulax baculata sp. nov. is distinguishable from other members of the genus by its combination of intratabular and parasutural sculptural elements. The numerous) stout, baculate and clavate processes are particularly distinctive. This species co-occurs with several others of Meiorogonyaulax and Lithodinia and poorly preserved specimens are often difficult to discriminate specifically. Meiorogonyaulax penitabulata Riding & Helby 2001 (2001d: 83, 85, 87; figs 11A-M, 12A-I) possesses variable spinose or denticulate elements surmounting low ridges, but these ridges or crest; are diagnostically penitabular. The processes of M. penitabulata are also typically thinner with a planar rather than subcircular cross-section and are commonly restricted to the penitabular ridges, whereas M. baculata commonly possesses intratabular sculptural elements. Lithodinia protothymosa Riding & Helby 2001 (2001d: 81-Bi; I figs lOA-L) is considerably larger with longer and broader processes than M. baculata and its processes are I connected by parasutural septa.
Local occurrence: Elang Formation; Wanaea indotata Interval Zone through Voodooia tabulata Interval Zone (Subzone VT5); rare.
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Holotype: Mantle, 2009a, pl.14, figs.4a–b.
Age Callovian.
-------------------------------------
Original description (Mantle, 2009a)
Meiourogonyawlax baculata sp. nov. Plate 14, Figs 4-6; Text-fig. 12C
Diagnosis: Cysts proximate-proximochorate, acavate, with subcircular outline. Cyst wall single-layered. Autophragm perforate, microreticulate, and/or granulate. Paratabulation gonyaulacalean; indicated by aligned, robust, solid, short processes (typically bacula or clavae) or by spines interconnected by low crests (< 0.5 µm high). Further sculptural elements occur in intratabular positions. Archeopyle apical (type t4A); operculum free.
Description: The numerous processes covering the cyst vary in distribution, from being predominantly parasutural, with only a few intratabular elements, to being widely and randomly scattered across the entire cyst. These processes (1-5 µm long) are similarly variable in form and are baculate, clavate, buccinate, or subconical with broadly rounded, acuminate, bifid, or flared terminations, although baculate and clavate elements predominate. Some of the processes may be joined distally by thin trabeculae, but this is typically restricted to no more than 3 adjoining processes. The processes are commonly longest in gonal positions, Particularly along the paracingulum. This variation in process distribution and density means the paratabulation pattern is obvious on those cysts where parasutural elements predominate and less cleat on the cysts I with a denser covering of sculptural elements. However the paracingulum is invariably prominent. The paratabulation formula is standard gonyaulacalean (?pr, 4',6",-6c,5-6;",1""). The autophragm, (1-1.5 µm thick) is commonly perforate or microreticulate, but may also be granulate or rarely scabrate. The archeopyle is apical, with an angular margin and either undeveloped or deep accessory sutures. The operculum is I rarely attached and was not positively identified in the strew slides.
Dimensions (13 specimens): Length of cyst (excluding operculum) 43 (50) 59 µm; maximum width of cyst 55 (50) 67 µm; length of processes 1 (4) 6 µm; thickness of cyst wall 1-1.5 µm.
Holotype: SGM H8, EF N22/0. CPC no. 39262; PI. 14, Figs 4a, b. Total length of cyst (excluding operculum) 47 µm; I maximum width of cyst 60 µm; thickness of cyst wall 1 µm.
Type locality: Timor Sea, Bayu-Undan Field, Undan-3, core 2 at 3016 m (Elang Formation).
Etymology: Lat., baculum (rod-like); with reference to the commonesr process type adorning the autophragm.
Remarks: Meiorogonyaulax Sarjeant 1966 is distinguished from Lithodinia Eisenack emend. Gocht 1975 (modified by Stover & Evitt 1978: 60-61) on the basis of operculum type. These genera are characterized by compound and simple opercula respectively (Riding & Helby 2001: 81). The new species is assigned to Meiourogonyaulax as several compound opercula were observed still attached to the cysts. However, no opercula were observed in either the residues or the strew slides.
Comparison: Meiourogonyaulax baculata sp. nov. is distinguishable from other members of the genus by its combination of intratabular and parasutural sculptural elements. The numerous) stout, baculate and clavate processes are particularly distinctive. This species co-occurs with several others of Meiorogonyaulax and Lithodinia and poorly preserved specimens are often difficult to discriminate specifically. Meiorogonyaulax penitabulata Riding & Helby 2001 (2001d: 83, 85, 87; figs 11A-M, 12A-I) possesses variable spinose or denticulate elements surmounting low ridges, but these ridges or crest; are diagnostically penitabular. The processes of M. penitabulata are also typically thinner with a planar rather than subcircular cross-section and are commonly restricted to the penitabular ridges, whereas M. baculata commonly possesses intratabular sculptural elements. Lithodinia protothymosa Riding & Helby 2001 (2001d: 81-Bi; I figs lOA-L) is considerably larger with longer and broader processes than M. baculata and its processes are I connected by parasutural septa.
Local occurrence: Elang Formation; Wanaea indotata Interval Zone through Voodooia tabulata Interval Zone (Subzone VT5); rare.
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