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Lingulodinium hemicystum
Lingulodinium hemicystum McMinn, 1991
Holotype: McMinn, 1991, pl.3, figs.7,10,13
Age: Recent
Original description (McMinn, 1991)
Diagnosis: Large spherical to subspherical cyst, most commonly found as hemispheres, bearing numerous, bladelike, nontabular, hollow and closed, tapered processes. Archeopyle epicystal, type [AP].
Description: Large cyst most commonly found as hemispheres. The cyst wall is composed of a psilate to microgranulate, approximately 1µm thick endophragm and a thinner psilate periphragm. The periphragm supports up to 80 blade-shaped, nontabular, hollow, closed processes. These are typically 3-5µm in diameter at the base and taper upwards to a point; on some specimens processes are bulbous towards their base. The endophragm
and periphragm are appressed except beneath processes. The archeopyle is epicystal, type [AP], formed by
splitting of the cyst into two approximately equally sized hemispheres. A shallow sulcal notch or sulcal tab is discernible on better preserved specimens. There is no other expression of paratabulation.
Dimensions: Cyst diameter 50 (52) 65µm, process length 5 (10) 13µm; twenty specimens from Lake Macquarie were measured.
Remarks: Wall et al. (1973) emended the diagnosis of Lingulodinium to include forms with an archeopyle caused by the loss any number of precingular paraplates or having an epicystal archeopyle. In this study, in excess of 10,000 specimens of Lingulodinium were observed and none of these had anything other than an epicystal archeopyle. The consistency of this archeopyle type, together with other morphological features, warrants the separation of this morphotype as a separate species.
Comparison: Lingulodinium hemicystum is distinguished from Lingulodinium machaerophorum by the consistent presence of an epicystal archeopyle. It also lacks the striated process bases of L. machaerophorum (Wall et al. 1973) and the grana on the distal ends of the processes.
Distribution: Lingulodinium hemicystum is the dominant species in most Brisbane Water assemblages and is also either dominant or abundant in most assemblages from Lake Macquarie, Tuggerah Lakes, Port Jackson and Port Hacking. Only in Port Stephens is it less abundant but even there it is usually present. It has not previously been reported elsewhere.
Holotype: McMinn, 1991, pl.3, figs.7,10,13
Age: Recent
Original description (McMinn, 1991)
Diagnosis: Large spherical to subspherical cyst, most commonly found as hemispheres, bearing numerous, bladelike, nontabular, hollow and closed, tapered processes. Archeopyle epicystal, type [AP].
Description: Large cyst most commonly found as hemispheres. The cyst wall is composed of a psilate to microgranulate, approximately 1µm thick endophragm and a thinner psilate periphragm. The periphragm supports up to 80 blade-shaped, nontabular, hollow, closed processes. These are typically 3-5µm in diameter at the base and taper upwards to a point; on some specimens processes are bulbous towards their base. The endophragm
and periphragm are appressed except beneath processes. The archeopyle is epicystal, type [AP], formed by
splitting of the cyst into two approximately equally sized hemispheres. A shallow sulcal notch or sulcal tab is discernible on better preserved specimens. There is no other expression of paratabulation.
Dimensions: Cyst diameter 50 (52) 65µm, process length 5 (10) 13µm; twenty specimens from Lake Macquarie were measured.
Remarks: Wall et al. (1973) emended the diagnosis of Lingulodinium to include forms with an archeopyle caused by the loss any number of precingular paraplates or having an epicystal archeopyle. In this study, in excess of 10,000 specimens of Lingulodinium were observed and none of these had anything other than an epicystal archeopyle. The consistency of this archeopyle type, together with other morphological features, warrants the separation of this morphotype as a separate species.
Comparison: Lingulodinium hemicystum is distinguished from Lingulodinium machaerophorum by the consistent presence of an epicystal archeopyle. It also lacks the striated process bases of L. machaerophorum (Wall et al. 1973) and the grana on the distal ends of the processes.
Distribution: Lingulodinium hemicystum is the dominant species in most Brisbane Water assemblages and is also either dominant or abundant in most assemblages from Lake Macquarie, Tuggerah Lakes, Port Jackson and Port Hacking. Only in Port Stephens is it less abundant but even there it is usually present. It has not previously been reported elsewhere.