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Lunnomidinium
From Williams et al., 2017:
[Lunnomidinium, Lindström, 2002, p. 253, 255.
Type species: Lunnomidinium scaniense, Lindström, 2002 (pl.1, figs.1-6)]
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Original description: [Lindström, 2002]:
Diagnosis:
Proximate to proximochorate, acavate dinoflagellate cysts with seven or more latitudinal rows of paraplates arranged in a suessiacean pattern, with an epicystal {tAtItP} archeopyle; the principal suture is formed along the anterior margin of the paracingulum.
Description:
Proximate to proximochorate, acavate dinoflagellate cysts. Autophragm of low relief, with intratabular ornamentation or protuberances. Paracingulum always evident as a broad transverse constriction, parasulcus evident as ventral groove; both devoid of intratabular ornamentation. Paratabulation either indicated by low parasutural ridges or sutures, or not expressed. Archeopyle epicystal {tAtItP}, principal archeopyle suture located immediately anterior to paracingulum. Operculum adnate ventrally, but occasionally found free.
Remarks:
Lunnomidinium has similar paratabulation to other fossil genera in the family Suessiaceae; i.e. Beaumontella Below 1987, Noricysta Bujak and Fisher 1976, Suessia Morbey 1975, Umbriadinium Bucefalo Palliani and Riding, 1997, and Wanneria Below 1987. The principal difference is in the archeopyle type. Beaumontella has an apical archeopyle, while Noricysta, Suessia, Wanneria and Umbriadinium all have combination archeopyles, which in excystment may involve all the epicystal paraplates except the ones in the precingular series ( Bucefalo Palliani and Riding, 1997). In Lunnomidiniumthe archeopyle is epicystal, with the suture running immediately anterior to the cingular paraplates. Another characteristic of Lunnomidinium is the presence of intratabular (paraplate centered) ornamentation, which may occur on the apical, precingular, postcingular, posterior intercalary, and some of the antapical paraplates. In Beaumontella and Umbriadinium intratabular spines are present in all the paraplate series on the epi- and the hypocyst, and occasionally also in the paracingulum ( Bucefalo Palliani and Riding, 1997). Cysts of the extant suessiacean dinoflagellate Polarella glacialis Montresor et al. 1999 also bear intratabular processes on the epi- and hypocyst (Montresor et al., 1999). In its general shape, Lunnomidinium resembles Parvocysta Bjaerke 1980 and Susadinium Dörhöfer and Davies 1980, but it can be separated from these Jurassic genera because of its suessiacean paratabulation consisting of at least seven paraplate series, with more paraplates in each series, and also by having an epicystal archeopyle.Susadinium and Parvocysta are included in the peridinialean family Heterocapsaceae, which has six paraplate series, and is characterized by five apical paraplates, and an apical intercalary archeopyle ( Fensome et al., 1993). The suessiacean paratabulation and the epicystal {tAtItP} archeopyle distinguishes Lunnomidinium from the gonyaulacalean genus Moorodinium Backhouse, 1988, which is similar in general shape, but has a tAtP archeopyle and six paraplate series (Backhouse, 1988).
[Lunnomidinium, Lindström, 2002, p. 253, 255.
Type species: Lunnomidinium scaniense, Lindström, 2002 (pl.1, figs.1-6)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lindström, 2002]:
Diagnosis:
Proximate to proximochorate, acavate dinoflagellate cysts with seven or more latitudinal rows of paraplates arranged in a suessiacean pattern, with an epicystal {tAtItP} archeopyle; the principal suture is formed along the anterior margin of the paracingulum.
Description:
Proximate to proximochorate, acavate dinoflagellate cysts. Autophragm of low relief, with intratabular ornamentation or protuberances. Paracingulum always evident as a broad transverse constriction, parasulcus evident as ventral groove; both devoid of intratabular ornamentation. Paratabulation either indicated by low parasutural ridges or sutures, or not expressed. Archeopyle epicystal {tAtItP}, principal archeopyle suture located immediately anterior to paracingulum. Operculum adnate ventrally, but occasionally found free.
Remarks:
Lunnomidinium has similar paratabulation to other fossil genera in the family Suessiaceae; i.e. Beaumontella Below 1987, Noricysta Bujak and Fisher 1976, Suessia Morbey 1975, Umbriadinium Bucefalo Palliani and Riding, 1997, and Wanneria Below 1987. The principal difference is in the archeopyle type. Beaumontella has an apical archeopyle, while Noricysta, Suessia, Wanneria and Umbriadinium all have combination archeopyles, which in excystment may involve all the epicystal paraplates except the ones in the precingular series ( Bucefalo Palliani and Riding, 1997). In Lunnomidiniumthe archeopyle is epicystal, with the suture running immediately anterior to the cingular paraplates. Another characteristic of Lunnomidinium is the presence of intratabular (paraplate centered) ornamentation, which may occur on the apical, precingular, postcingular, posterior intercalary, and some of the antapical paraplates. In Beaumontella and Umbriadinium intratabular spines are present in all the paraplate series on the epi- and the hypocyst, and occasionally also in the paracingulum ( Bucefalo Palliani and Riding, 1997). Cysts of the extant suessiacean dinoflagellate Polarella glacialis Montresor et al. 1999 also bear intratabular processes on the epi- and hypocyst (Montresor et al., 1999). In its general shape, Lunnomidinium resembles Parvocysta Bjaerke 1980 and Susadinium Dörhöfer and Davies 1980, but it can be separated from these Jurassic genera because of its suessiacean paratabulation consisting of at least seven paraplate series, with more paraplates in each series, and also by having an epicystal archeopyle.Susadinium and Parvocysta are included in the peridinialean family Heterocapsaceae, which has six paraplate series, and is characterized by five apical paraplates, and an apical intercalary archeopyle ( Fensome et al., 1993). The suessiacean paratabulation and the epicystal {tAtItP} archeopyle distinguishes Lunnomidinium from the gonyaulacalean genus Moorodinium Backhouse, 1988, which is similar in general shape, but has a tAtP archeopyle and six paraplate series (Backhouse, 1988).