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Microdinium sinuatus
1986 Microdinium sp. B of Ioannides, p. 29, pl. 15, fig. 16.
Holotype. Plate 3, figure 2; GSCA slide no. P42196-03 (¼GSCC slide no. P5189-15H); coordinates 8.8x91.0; EF S56/3; Nunavut Palaeontology Collection no. NUPB 993; section 5, Maud Bight, Bylot Island. Bylot Island formation.
Etymology. The epithet, a noun in apposition, is from the Latin sinuatus meaning bend or curve in reference to the vermiculate nature of the surface ornamentation.
Diagnosis. A species of Microdinium in which the main indications of paratabulation, when present, are the paracingulum, which can be delineated by ridges, and the separation of the precingular paraplates laterally by accessory archaeopyle sutures. Some ridges may parallel the outline of the paraplates, but others are haphazardly orientated. The ornamentation is expressed by discontinuous membranous rugula or vermicula, some of which show alignment, especially reflecting parasutures. Occasional small acuminate protuberances about 1cm high are present, both in parasutural and intratabular locations.
Comments. Microdinium sp. B of Ioannides (1986, pl.15, fig. 16) appears to be synonymous with Microdinium sinuatus. However, Ioannides (1986) refrained from formalising the taxon because of the limited number of specimens (seven) and the ‘imprecise definition of the tabulation’. We do not consider these factors to be obstacles since the taxon is easily recognisable.
Size. Holotype: length 22um, width 28um. Range of six specimens: length with operculum missing, 23–42um, width 29–44um.
Age. Late Coniacian to late Campanian.
Holotype. Plate 3, figure 2; GSCA slide no. P42196-03 (¼GSCC slide no. P5189-15H); coordinates 8.8x91.0; EF S56/3; Nunavut Palaeontology Collection no. NUPB 993; section 5, Maud Bight, Bylot Island. Bylot Island formation.
Etymology. The epithet, a noun in apposition, is from the Latin sinuatus meaning bend or curve in reference to the vermiculate nature of the surface ornamentation.
Diagnosis. A species of Microdinium in which the main indications of paratabulation, when present, are the paracingulum, which can be delineated by ridges, and the separation of the precingular paraplates laterally by accessory archaeopyle sutures. Some ridges may parallel the outline of the paraplates, but others are haphazardly orientated. The ornamentation is expressed by discontinuous membranous rugula or vermicula, some of which show alignment, especially reflecting parasutures. Occasional small acuminate protuberances about 1cm high are present, both in parasutural and intratabular locations.
Comments. Microdinium sp. B of Ioannides (1986, pl.15, fig. 16) appears to be synonymous with Microdinium sinuatus. However, Ioannides (1986) refrained from formalising the taxon because of the limited number of specimens (seven) and the ‘imprecise definition of the tabulation’. We do not consider these factors to be obstacles since the taxon is easily recognisable.
Size. Holotype: length 22um, width 28um. Range of six specimens: length with operculum missing, 23–42um, width 29–44um.
Age. Late Coniacian to late Campanian.