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Islandinium minutum
Islandinium minutum (Harland and Reid in Harland et al., 1980, p.216,218, figs.2M-O) Head et al., 2001, p.629.
Originally Multispinula, subsequently Multispinula?, thirdly Algidasphaeridium?, fourthly (and now) Islandinium.
Taxonomic junior synonym: Cantiacidinium conicum (name not validly published), according to Head et al. (2001, p.629).
Holotype: Harland et al., 1980, fig.2O.
Age: Holocene.
Original description (Harland et al., 1980):
Type species: Multispinula quanta Bradford, 1975 ex Harland and Reid herein Multispinula minuta sp. nov. Fig. 2 M-0
1977. Dinoflagellate cyst E Reid & Harland; pl. 2, fig. II.
Derivation of name:. - Latin: minuta, small, with reference to the size of this species.
Diagnosis. - A small spheroidal cyst consisting of two wall layers carrying numerous, rigid to flexuous, solid, aculeate processes. Paratabulation and the archeopyle not observed.
Description. - Cyst small and spheroidal made up of two closely appressed wall layers, the periphragm making up the processes. Cyst wall smooth or ornamented by small granules. Processes numerous, rigid to flexuous and variable in length up to 1/6 to 1/5 the cyst diameter, aculeate, with hollow bases and solid shafts and tips. Paratabulation not present, even including recognition of paracingular or parasulcal areas. Archeopyle not observed.
Dimensions. - Holotype: Maximum diameter 40.0 µm, minimum diameter 30.0 µm, maximum process length 4.0 µm. Range: Maximum diameter 23.75 (36.81) 45.0 µm, minimum diameter 15.0 (30.80) 40.0 µm. maximum process length 3.75 (5.98) 8.75 µm. Measured specimens 21.
Holotype. - MPK 1306, Fig. 2 0.
Type horizon. - Recent sediment, sample CSA 1780, Dome Kopanoar, Canadian Arctic.
Variation. - Intraspecific variation appears restricted to size (compare Fig. 20 with Fig. 2N) and the relative length of the processes.
Environmental requirements. - This cyst is known, to date, only from Arctic sediments and may prove to be a reliable indicator of cool or cold climatic conditions. Its strict environmental requirements are, however, not known in detail.
Thecal equivalence. - Probably a cyst of Protoperidinium sp. indet., especially if its assignment to the genus Multispinula is correct. but otherwise unknown.
Remarks. - This cyst is assigned to Multispinula because of its process structure. Unfortunately failure to orientate specimens and the non-recognition of any definite archeopyle structure must throw some doubt on our generic assignment. ?M. minuta sp. nov. is most closely comparable to M. quanta Bradford which differs in being larger, although a significant intraspecific variation is admitted, and in possessing an intercalary archeopyle. A similarity to the cyst of Protoperidinium nudum (Meunier) Balech is also conceded but M. minuta appears to possess many more processes. It is also comparable to Cantiacidiniu, conicum Reid (ms), a cyst described by Reid (1972), which differs in possessing hollow processes and an archeopyle in the form of zig-zag split; otherwise the two forms are closely comparable and may be related.
Originally Multispinula, subsequently Multispinula?, thirdly Algidasphaeridium?, fourthly (and now) Islandinium.
Taxonomic junior synonym: Cantiacidinium conicum (name not validly published), according to Head et al. (2001, p.629).
Holotype: Harland et al., 1980, fig.2O.
Age: Holocene.
Original description (Harland et al., 1980):
Type species: Multispinula quanta Bradford, 1975 ex Harland and Reid herein Multispinula minuta sp. nov. Fig. 2 M-0
1977. Dinoflagellate cyst E Reid & Harland; pl. 2, fig. II.
Derivation of name:. - Latin: minuta, small, with reference to the size of this species.
Diagnosis. - A small spheroidal cyst consisting of two wall layers carrying numerous, rigid to flexuous, solid, aculeate processes. Paratabulation and the archeopyle not observed.
Description. - Cyst small and spheroidal made up of two closely appressed wall layers, the periphragm making up the processes. Cyst wall smooth or ornamented by small granules. Processes numerous, rigid to flexuous and variable in length up to 1/6 to 1/5 the cyst diameter, aculeate, with hollow bases and solid shafts and tips. Paratabulation not present, even including recognition of paracingular or parasulcal areas. Archeopyle not observed.
Dimensions. - Holotype: Maximum diameter 40.0 µm, minimum diameter 30.0 µm, maximum process length 4.0 µm. Range: Maximum diameter 23.75 (36.81) 45.0 µm, minimum diameter 15.0 (30.80) 40.0 µm. maximum process length 3.75 (5.98) 8.75 µm. Measured specimens 21.
Holotype. - MPK 1306, Fig. 2 0.
Type horizon. - Recent sediment, sample CSA 1780, Dome Kopanoar, Canadian Arctic.
Variation. - Intraspecific variation appears restricted to size (compare Fig. 20 with Fig. 2N) and the relative length of the processes.
Environmental requirements. - This cyst is known, to date, only from Arctic sediments and may prove to be a reliable indicator of cool or cold climatic conditions. Its strict environmental requirements are, however, not known in detail.
Thecal equivalence. - Probably a cyst of Protoperidinium sp. indet., especially if its assignment to the genus Multispinula is correct. but otherwise unknown.
Remarks. - This cyst is assigned to Multispinula because of its process structure. Unfortunately failure to orientate specimens and the non-recognition of any definite archeopyle structure must throw some doubt on our generic assignment. ?M. minuta sp. nov. is most closely comparable to M. quanta Bradford which differs in being larger, although a significant intraspecific variation is admitted, and in possessing an intercalary archeopyle. A similarity to the cyst of Protoperidinium nudum (Meunier) Balech is also conceded but M. minuta appears to possess many more processes. It is also comparable to Cantiacidiniu, conicum Reid (ms), a cyst described by Reid (1972), which differs in possessing hollow processes and an archeopyle in the form of zig-zag split; otherwise the two forms are closely comparable and may be related.