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Gagiella mutabilis
Gagiella mutabilis Backhouse, 1988
Holotype: Backhouse, 1988, pl.27, fig.1a-b
Locus typicus: Perth Basin, Western Australia
Stratum typicum: Valanginian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gagiella mutabilis Backhouse, 1988. Cyst, according to Backhouse (1988, p. 86, 88-89), asymmetrically quadrilobate, trilobate, or ovoid, usually laterally compressed with the parasulcal notch close to the lateral margin. Strongly lobate forms bear a lobe in the posterior parasulcal position and some alos bear a lobe in the 4" paraplate position. Autophragm rugulate, reticulate, spinose or granulate. Lobate forms rugulate, ovoid forms reticulate, granulate or rarely spinose with individual elements up to 2 µm. Lobate forms have an archeopyle margin which indicates 5 precingular plates. Size: length (without operculum) 41-84 µm, width 38-63 µm.
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Original description: Backhouse, 1988, p.86
Cyst asymmetrically quadrilobatc. trilobate, or ovoid. usually laterally compressed with the parasulcal notch close to the lateral margin. Strongly lobate forms bear a lobe in the posterior parasulcal position and some also bear a lobe in the 4" paraplate position (Fig. 23). Autophragm 1.0 to 1.5 Ám thick, bearing rugulate.
reticulate, spinose or granular surface features. Lobate forms rugulate (rugulae less than 1 Ám high); ovoid forms reticulate, granulate or, rarely, spinose, with individual elements up to 2 Ám high. Paratabulation indicated only by archeopyle suture. Paracingulum indicated on some ovoid forms by a narrow groove 2-3 Ám wide, offset approximately 4,llm. Some large lobate forms display a broad bulge in paracingular zone. Archeopylc apical, type [tA], operculum free; constituent paraplates not differentiated. Sulcal notch deep and narrow; primary archeopylc suture and accessory sutures indicate 5 or 6 precingular paraplates and 4 apical paraplates (Fig. 25).
Lobate forms posscss an archeopyle suture indicating 5 precingular paraplates including a wide 3" paraplate. Transition to a subovoid shape accompanied by splitting of the 3" paraplate into two narrow paraplates by development of a short accessory suture (Figs 23 to 25). Ovoid forms lack any expression of lateral or antapical lobes and possess archeopyle sutures indicating 6 distinct precingular paraplates.
Dimensions: Length of holotype 85 Ám, width 49 Ám. Range of length without operculum (58 specimens) 41(59)84 Ám, width 38(53)63 Ám.
Remarks: Gagiella mutabilis displays considerable variation in shape and surface sulpture. Attempts to subdivide the species have proved impracticable. Forms intermediate between the various morphological types are common, and the whole group spans a relatively thin stratigraphic section ol the Perth Basin. The morphological lineage represented by Ihese cysts is continued by the appearance of smooth subspherical cysts at the same level as the paracingulate forms of G. mlltabilis (Pl. 27, figs 16-18). These smooth cysts possess a thick autophragm and 6 precingular paraplates (figs 24, 25). and are referable to the genus Batiacasphaera. They may be the precursor of subspherical Early Cretaceous cysts with 6 precingular paraplate archeopyle sutures such as Batiacasphaera asperata. Gagiella mutabilis may have derived from cysts of the Pentafidla type during the period of Neocomian tectonism in the Perth Basin.
Gagiella mutabilis is the cyst of a dinoflagellate species which inhabited a restricted-marine, or possibly non-marine environment. It is recorded in large numbers in the Gage Sandstone Member in sections devoid of Late Jurassic and Early Cretaceous marine cysts.
Holotype: Backhouse, 1988, pl.27, fig.1a-b
Locus typicus: Perth Basin, Western Australia
Stratum typicum: Valanginian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gagiella mutabilis Backhouse, 1988. Cyst, according to Backhouse (1988, p. 86, 88-89), asymmetrically quadrilobate, trilobate, or ovoid, usually laterally compressed with the parasulcal notch close to the lateral margin. Strongly lobate forms bear a lobe in the posterior parasulcal position and some alos bear a lobe in the 4" paraplate position. Autophragm rugulate, reticulate, spinose or granulate. Lobate forms rugulate, ovoid forms reticulate, granulate or rarely spinose with individual elements up to 2 µm. Lobate forms have an archeopyle margin which indicates 5 precingular plates. Size: length (without operculum) 41-84 µm, width 38-63 µm.
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Original description: Backhouse, 1988, p.86
Cyst asymmetrically quadrilobatc. trilobate, or ovoid. usually laterally compressed with the parasulcal notch close to the lateral margin. Strongly lobate forms bear a lobe in the posterior parasulcal position and some also bear a lobe in the 4" paraplate position (Fig. 23). Autophragm 1.0 to 1.5 Ám thick, bearing rugulate.
reticulate, spinose or granular surface features. Lobate forms rugulate (rugulae less than 1 Ám high); ovoid forms reticulate, granulate or, rarely, spinose, with individual elements up to 2 Ám high. Paratabulation indicated only by archeopyle suture. Paracingulum indicated on some ovoid forms by a narrow groove 2-3 Ám wide, offset approximately 4,llm. Some large lobate forms display a broad bulge in paracingular zone. Archeopylc apical, type [tA], operculum free; constituent paraplates not differentiated. Sulcal notch deep and narrow; primary archeopylc suture and accessory sutures indicate 5 or 6 precingular paraplates and 4 apical paraplates (Fig. 25).
Lobate forms posscss an archeopyle suture indicating 5 precingular paraplates including a wide 3" paraplate. Transition to a subovoid shape accompanied by splitting of the 3" paraplate into two narrow paraplates by development of a short accessory suture (Figs 23 to 25). Ovoid forms lack any expression of lateral or antapical lobes and possess archeopyle sutures indicating 6 distinct precingular paraplates.
Dimensions: Length of holotype 85 Ám, width 49 Ám. Range of length without operculum (58 specimens) 41(59)84 Ám, width 38(53)63 Ám.
Remarks: Gagiella mutabilis displays considerable variation in shape and surface sulpture. Attempts to subdivide the species have proved impracticable. Forms intermediate between the various morphological types are common, and the whole group spans a relatively thin stratigraphic section ol the Perth Basin. The morphological lineage represented by Ihese cysts is continued by the appearance of smooth subspherical cysts at the same level as the paracingulate forms of G. mlltabilis (Pl. 27, figs 16-18). These smooth cysts possess a thick autophragm and 6 precingular paraplates (figs 24, 25). and are referable to the genus Batiacasphaera. They may be the precursor of subspherical Early Cretaceous cysts with 6 precingular paraplate archeopyle sutures such as Batiacasphaera asperata. Gagiella mutabilis may have derived from cysts of the Pentafidla type during the period of Neocomian tectonism in the Perth Basin.
Gagiella mutabilis is the cyst of a dinoflagellate species which inhabited a restricted-marine, or possibly non-marine environment. It is recorded in large numbers in the Gage Sandstone Member in sections devoid of Late Jurassic and Early Cretaceous marine cysts.