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Jansonia thormalleus
Previous Australian usage: Microdinium ‘waisted’, Microdinium cf. ‘opacum’, Horologinella cf. Microdinium opacum (unpublished well reports), Horologinella? sp. A (Sinclair, 2012). Holotype: Plate XII, 8–10.
Diagnosis: A species of Jansonia with a subangular to subpolygonal ambitus and prominent pre- and postcingular lateral projections. Autophragm granulate, verrucate or adorned with muri forming an incomplete reticulum. Cingulum strongly constricted. Low-relief crests indicate a gonyaulacalean tabulation and inferred combination archeopyle; operculum free.
Etymology: ‘Thor’ referring to the Norse god Thor, and ‘malleus’ (Latin) meaning hammer, in reference to the cyst shape, which resembles symbolic depictions of Mjölnir (Thor's hammer).
Material: Palynological strew samples; 3417.61 m, 3388.5 m, Alaria- 1; 2841 m, 2842 m, 2844 m, Io-1; 3066.46 m, Pyxis-1; 3162.6 m, Laminaria-2.
Age: Oxfordian–Kimmeridgian (W. spectabilis–D. swanense zones; Fig. 5)
Lithostratigraphic occurrence: The Frigate Fm, lower Vulcan Fm and Iris Marl of the Bonaparte Basin. The Dingo Claystone, Jansz Sandstone and Eliassen Fm of the Northern Carnarvon Basin.
Description: A small, proximate, strongly lenticular dinoflagellate cyst, with a subangular to subpolygonal ambitus, prominent pre- and postcingular lateral projections and a pronounced and broadly rounded antapical protuberance that is laterally offset. Lateral precingular projections usually less pronounced than postcingular ones. Hypocyst significantly wider than epicyst; the combined height of the epicyst and cingulum roughly equals the height of the hypocyst. Low-relief ornamentation comprised of grana and verrucae that may coalesce to form a discontinuous reticulum and/or low-relief sutural crests, often more pronounced on the hypocyst. The cyst colour is characteristically brown to dark brown, generally darkest around the cingulum and sulcus, lightening apically, where the edges of the archeopyle margin may be colourless/translucent. Cingulum broad, weakly laevorotatory, and sulcus often bearing a distinctive flagellar scar. The low-relief sutural crests indicate a gonyaulacalean tabulation of formula:?pr,?4′,? 3–5a, 7″, 6c, 6″’, 1p, 1″”,?5–6 s (Fig. 11B, B'). Archeopyle inferred to be combination apical and anterior intercalary, Type (tAtI); operculum free.
Dimensions: (14 specimens measured)
Length: 18 (24) 29
Epicystal width: 14 (19) 22
Cingular width: 10 (16) 20
Hypocystal width: 19 (25) 31
Comparison and remarks: This new species is herein assigned to Jansonia based on the dark-brown, semi-opaque autophragm, smooth sutural crests, apical wall thinning, and reduced epicystal tabulation. This new species differs from all other species of Jansonia in having a subpolygonal ambitus with prominent pre- and postcingular lateral lobes. Jansonia thormalleus is superficially similar to Fostericysta eclipsiana (Riding and Helby, 2001d) Riding, 2005 but lacks the denticulate crests that are diagnostic of that genus. The thick dark brown to semi-opaque autophragm of Jansonia thormalleus excludes its attribution to Horologinella (Cookson and Eisenack, 1962) emend. Pestchevitskaya, 2006. The outline of Jansonia thormalleus varies, ranging from specimens having only protruding postcingular lateral lobes and a cingular constriction (Plate XII, 3, 13), to specimens with both prominent pre- and postcingular lateral projections (Plate XII, 11, 15). There is a morphological progression from Jansonia jurassica to Jansonia thormalleus reflected by a gradual increase in the width of the hypocyst (Plate XII, 1) and more prominent pre- and postcingular projections (Plate XII, 3–11). Older forms of Jansonia thormalleus, therefore, present a conical flask-like appearance (Plate XII, 3–4, 13). Thismorphological progression has a useful stratigraphic signal.
Diagnosis: A species of Jansonia with a subangular to subpolygonal ambitus and prominent pre- and postcingular lateral projections. Autophragm granulate, verrucate or adorned with muri forming an incomplete reticulum. Cingulum strongly constricted. Low-relief crests indicate a gonyaulacalean tabulation and inferred combination archeopyle; operculum free.
Etymology: ‘Thor’ referring to the Norse god Thor, and ‘malleus’ (Latin) meaning hammer, in reference to the cyst shape, which resembles symbolic depictions of Mjölnir (Thor's hammer).
Material: Palynological strew samples; 3417.61 m, 3388.5 m, Alaria- 1; 2841 m, 2842 m, 2844 m, Io-1; 3066.46 m, Pyxis-1; 3162.6 m, Laminaria-2.
Age: Oxfordian–Kimmeridgian (W. spectabilis–D. swanense zones; Fig. 5)
Lithostratigraphic occurrence: The Frigate Fm, lower Vulcan Fm and Iris Marl of the Bonaparte Basin. The Dingo Claystone, Jansz Sandstone and Eliassen Fm of the Northern Carnarvon Basin.
Description: A small, proximate, strongly lenticular dinoflagellate cyst, with a subangular to subpolygonal ambitus, prominent pre- and postcingular lateral projections and a pronounced and broadly rounded antapical protuberance that is laterally offset. Lateral precingular projections usually less pronounced than postcingular ones. Hypocyst significantly wider than epicyst; the combined height of the epicyst and cingulum roughly equals the height of the hypocyst. Low-relief ornamentation comprised of grana and verrucae that may coalesce to form a discontinuous reticulum and/or low-relief sutural crests, often more pronounced on the hypocyst. The cyst colour is characteristically brown to dark brown, generally darkest around the cingulum and sulcus, lightening apically, where the edges of the archeopyle margin may be colourless/translucent. Cingulum broad, weakly laevorotatory, and sulcus often bearing a distinctive flagellar scar. The low-relief sutural crests indicate a gonyaulacalean tabulation of formula:?pr,?4′,? 3–5a, 7″, 6c, 6″’, 1p, 1″”,?5–6 s (Fig. 11B, B'). Archeopyle inferred to be combination apical and anterior intercalary, Type (tAtI); operculum free.
Dimensions: (14 specimens measured)
Length: 18 (24) 29
Epicystal width: 14 (19) 22
Cingular width: 10 (16) 20
Hypocystal width: 19 (25) 31
Comparison and remarks: This new species is herein assigned to Jansonia based on the dark-brown, semi-opaque autophragm, smooth sutural crests, apical wall thinning, and reduced epicystal tabulation. This new species differs from all other species of Jansonia in having a subpolygonal ambitus with prominent pre- and postcingular lateral lobes. Jansonia thormalleus is superficially similar to Fostericysta eclipsiana (Riding and Helby, 2001d) Riding, 2005 but lacks the denticulate crests that are diagnostic of that genus. The thick dark brown to semi-opaque autophragm of Jansonia thormalleus excludes its attribution to Horologinella (Cookson and Eisenack, 1962) emend. Pestchevitskaya, 2006. The outline of Jansonia thormalleus varies, ranging from specimens having only protruding postcingular lateral lobes and a cingular constriction (Plate XII, 3, 13), to specimens with both prominent pre- and postcingular lateral projections (Plate XII, 11, 15). There is a morphological progression from Jansonia jurassica to Jansonia thormalleus reflected by a gradual increase in the width of the hypocyst (Plate XII, 1) and more prominent pre- and postcingular projections (Plate XII, 3–11). Older forms of Jansonia thormalleus, therefore, present a conical flask-like appearance (Plate XII, 3–4, 13). Thismorphological progression has a useful stratigraphic signal.