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Cometodinium habibii
Cometodinium habibii, Monteil, 1991
Holotype: Monteil 1991, Pl 3, fig. la-b
Locus typicus: Berriasian stratotype (Berrias, Ardeche; Southeastern France).
Stratum typicum: Early Berriasian (Boissieri Zone; Paramimounoum Sub-zone).
Age: Tithonian-earliest Valanginian-?Early Aptian
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Original description: [Monteil 1991, p. 442-443]:
Diagnosis:
Chorate (skolochorate) cysts with subspherical body.
Two-layered acavate cyst; periphragm and endophragm appressed, except where processes are formed. Hair-like processes, thin and numerous, flexuous, apparently nontabular, nonfibrous, cylindrical, hollow, distally closed, similar in size and shape. Basal third dichotomously divided (Pl. 3, fig. 5; Pl. 4, fig. 3). Tip evexate.
Archeopyle apical, type (4A), with angular margin, often difficult to discern; operculum adherent, sometimes tilted inside the cyst.
Paratabulation rarely expressed; occasionally indicated by archeopyle and/or paracingulum. Paratabulation probably gonyaulacacean, epicystal formula: ?pr, 4", Oa, 6", as (Pl. 5, fig. 3; Pl. 6, fig. 1).
Paracingulum may be suggested by alignment of two parallel, more or less equatorial rows of processes. Parasulcus not indicated.
Description:
The basal third of the processes is formed by a dichotomous three-dimensional system (Pl. 4, fig. 2, 3; Pl. 6, fig. 1). These characteristic processes are also shown by the specimens of Cometodinium sp. A (HABIB, 1972) illustrated by WILLIAMS & BUJAK (1980; pl. 9, fig. 5, 6). Obvious parasutures (Pl. 5, fig. 2) emphasize the existence of four paraplates (1", 2", 3", 4") composing the operculum (archeopyle apical, type (4A)). Moreover, the organization of processes on the operculum could be penitabular/intratabular (Pl. 5, fig. 2). All SEM observations show that the operculum is completely surrounded by the archeopyle parasuture. Although the parasuture between paraplates 1" and as does exist the operculum remains systematically attached (e. g. Pl 5, fig. 3) and is, therefore, of adherent type.
Dimensions:
Holotype Paratype Range (12 specimens):
Cyst diameter 60-65 µm 55-60 µm 50-70 µm
Central body diameter 42-44 µm 36-38 µm 35-50 µm
Length of prosesses up to 15 µm up to 15 µm up to 17 µm
Remarks:
the phenomenon of enantiomorphy observed in this species will be described below in chapter 2.
In HABIB & DRUGG (1987, Fig. 2) the range of Cometodinium habibii, as C. whitei, is discontinuous, Late Berriasian to Barremian. and Late Coniacian to Santonian. According to my observations the Upper Cretaceous specimens are here considered to represent a different species.
Affinities:
Cometodinium habibii sp nov. differs from all other species of the genus in having proximally dichotomous processes (Pl. 3, fig. 5). Prolixosphaeridium basifurcatum DODEKOVA (1969), has similar processes (Pl. 3, fig. 3, 4) but differs in having a cylindrical body, a free operculum and a surface between the processes being spinous, verrucate to granulate (DODEKOVA, 1969, p. 22) or even tuberculate (pers. obs.). In C habibii sp nov. the surface between the processes is typically psilate Phylogenetically, C habibii sp nov could be derived from P. basifurcatum.
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Stratigraphical and geographical distribution:
Numerous North Atlantic studies indicate a range from the base of Tithonian to the Early Aptian (HABIB, 1972; HABIB, 1976; HABIB & DRUGG, 1983; HABIB & DRUGG, 1987; RILEY & FENTON, 1984; ZOTTO et al, 1987). The new species has been reported by WILLAMS & BUJAK (1980), as Cometodinium sp. A (HAB B, 1972), from the Kimmeridgian-Portlandian boundary to the Valanginian in Northwestern Africa, and by HARRIS (1977), as Cometodinium sp. frorn the Late Jurassic/Early Cretaceous of the South Atantic Falkand Plateau. In Europe, this new species has been reported by ANTONESCU & AVRAM (1980), as Cometodinium ? sp., from the Valanginian to Early Barremian of Roumania and by HABIB & DRUGG (1983), as C. whitei, from the pre-Berriasian to post-Hauterivian of the Neocomian stratotype and parastratotype sections in southeastern France. In Southeastern France C. habibi sp nov ranges from the earliest Berriasian to earliest Valanginian in the Berriasian stratotype and the Va anginian hypostratotype (Monteil, in prep.). Higher in the stratigraphic column, forms showing a superficially similar morphology can be easily confused with C. habibii sp nov. These forms do not exhibit the typical dichotomously divided hair-like processes and are probably attributable to the genus Cleistosphaeridium. The new species C. habibii ranges from the base of the Tithonian to the Earliest Valanginian. It may questionably occur up to the Early Aptian.
Holotype: Monteil 1991, Pl 3, fig. la-b
Locus typicus: Berriasian stratotype (Berrias, Ardeche; Southeastern France).
Stratum typicum: Early Berriasian (Boissieri Zone; Paramimounoum Sub-zone).
Age: Tithonian-earliest Valanginian-?Early Aptian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Monteil 1991, p. 442-443]:
Diagnosis:
Chorate (skolochorate) cysts with subspherical body.
Two-layered acavate cyst; periphragm and endophragm appressed, except where processes are formed. Hair-like processes, thin and numerous, flexuous, apparently nontabular, nonfibrous, cylindrical, hollow, distally closed, similar in size and shape. Basal third dichotomously divided (Pl. 3, fig. 5; Pl. 4, fig. 3). Tip evexate.
Archeopyle apical, type (4A), with angular margin, often difficult to discern; operculum adherent, sometimes tilted inside the cyst.
Paratabulation rarely expressed; occasionally indicated by archeopyle and/or paracingulum. Paratabulation probably gonyaulacacean, epicystal formula: ?pr, 4", Oa, 6", as (Pl. 5, fig. 3; Pl. 6, fig. 1).
Paracingulum may be suggested by alignment of two parallel, more or less equatorial rows of processes. Parasulcus not indicated.
Description:
The basal third of the processes is formed by a dichotomous three-dimensional system (Pl. 4, fig. 2, 3; Pl. 6, fig. 1). These characteristic processes are also shown by the specimens of Cometodinium sp. A (HABIB, 1972) illustrated by WILLIAMS & BUJAK (1980; pl. 9, fig. 5, 6). Obvious parasutures (Pl. 5, fig. 2) emphasize the existence of four paraplates (1", 2", 3", 4") composing the operculum (archeopyle apical, type (4A)). Moreover, the organization of processes on the operculum could be penitabular/intratabular (Pl. 5, fig. 2). All SEM observations show that the operculum is completely surrounded by the archeopyle parasuture. Although the parasuture between paraplates 1" and as does exist the operculum remains systematically attached (e. g. Pl 5, fig. 3) and is, therefore, of adherent type.
Dimensions:
Holotype Paratype Range (12 specimens):
Cyst diameter 60-65 µm 55-60 µm 50-70 µm
Central body diameter 42-44 µm 36-38 µm 35-50 µm
Length of prosesses up to 15 µm up to 15 µm up to 17 µm
Remarks:
the phenomenon of enantiomorphy observed in this species will be described below in chapter 2.
In HABIB & DRUGG (1987, Fig. 2) the range of Cometodinium habibii, as C. whitei, is discontinuous, Late Berriasian to Barremian. and Late Coniacian to Santonian. According to my observations the Upper Cretaceous specimens are here considered to represent a different species.
Affinities:
Cometodinium habibii sp nov. differs from all other species of the genus in having proximally dichotomous processes (Pl. 3, fig. 5). Prolixosphaeridium basifurcatum DODEKOVA (1969), has similar processes (Pl. 3, fig. 3, 4) but differs in having a cylindrical body, a free operculum and a surface between the processes being spinous, verrucate to granulate (DODEKOVA, 1969, p. 22) or even tuberculate (pers. obs.). In C habibii sp nov. the surface between the processes is typically psilate Phylogenetically, C habibii sp nov could be derived from P. basifurcatum.
---------------------------------------------------------------------
Stratigraphical and geographical distribution:
Numerous North Atlantic studies indicate a range from the base of Tithonian to the Early Aptian (HABIB, 1972; HABIB, 1976; HABIB & DRUGG, 1983; HABIB & DRUGG, 1987; RILEY & FENTON, 1984; ZOTTO et al, 1987). The new species has been reported by WILLAMS & BUJAK (1980), as Cometodinium sp. A (HAB B, 1972), from the Kimmeridgian-Portlandian boundary to the Valanginian in Northwestern Africa, and by HARRIS (1977), as Cometodinium sp. frorn the Late Jurassic/Early Cretaceous of the South Atantic Falkand Plateau. In Europe, this new species has been reported by ANTONESCU & AVRAM (1980), as Cometodinium ? sp., from the Valanginian to Early Barremian of Roumania and by HABIB & DRUGG (1983), as C. whitei, from the pre-Berriasian to post-Hauterivian of the Neocomian stratotype and parastratotype sections in southeastern France. In Southeastern France C. habibi sp nov ranges from the earliest Berriasian to earliest Valanginian in the Berriasian stratotype and the Va anginian hypostratotype (Monteil, in prep.). Higher in the stratigraphic column, forms showing a superficially similar morphology can be easily confused with C. habibii sp nov. These forms do not exhibit the typical dichotomously divided hair-like processes and are probably attributable to the genus Cleistosphaeridium. The new species C. habibii ranges from the base of the Tithonian to the Earliest Valanginian. It may questionably occur up to the Early Aptian.