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Wanneria backhousei
Wanneria backhousei sp. nov., Mantle et al. 2020, p. 34
Holotype: Mantle et al. 2020, Plate V, 9a, b
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (Rhaetian)
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Original description: Mantle et al. 2020:
Description:
Small to medium, proximate to proximochorate, subspherical, ovoidal, or ellipsoidal dinoflagellate cysts with approximately equant epicysts and hypocysts.
Wall: autophragm is scabrate, microgranulate, or microreticulate with very low ridges delimiting most of the polygonal plates. These low, thin sutural ridges are sparsely surmounted by variably elongate spines (1–5 μm) that are sharply acuminate, with blunt rounded tips or have thin sinuous tips. The spinose ornament is both gonal and intergonal, and is consistently of low density, but this is somewhat variable. The spines may be sparsely distributed on the sutures, they may be exclusively gonal, or there may be significant areas which are entirely devoid of spines. These relatively smooth/sparse areas are largely restricted to the epicyst and the ventral surface, and at least a few postcingular and antapical spines are always present.
Tabulation: suessioid with nine latitudinal series (Fig. 4a). The cingulum is moderately laevorotatory, and is offset at the sulcus by up to half the height of a cingular plate.
Tabulation formulae are:
Sensu Morbey (1975): 1–2′, 4–6a, 8–9+ap, 11–15′′, 10–14+c, 10–12+′′′, 9+p, 5–6pa, 1+′′′′
Sensu Below (1987): 1–2n 4 , 4–6n 3 , 8–9+n 2 , 11–15n 1 , 10–14+c, 10–12+n1, 9+n2, 5–6n3, 1+n4
Archaeopyle: formed by the loss a simple opercular piece comprising all the climactal plates [(t’ + ta + tap)s]
Dimensions:
Overall length (excluding apical plates) 35 μm (45 μm) 52 μm; maximum width 36 μm (43 μm) 51 μm
20 measured specimens
Remarks:
Backhouse and Balme (2002) considered that their Wanneria sp. A (now Wanneria backhousei sp. nov.) warranted specific status. However, these authors also speculated that it may represent a facies-controlled morphotype of Wanneria listeri. Rare intermediate forms were also noted herein, but as most of the Norian and Rhaetian Wanneria species grade into each other to some degree, we contend that this taxon should be formalised. Further examination of well-preserved material may also reveal specimens with a larger number of plates for each latitudinal series than are noted herein.
Affinities/Comparisons:
Wanneria backhousei sp. nov. differs from Wanneria listeri in having a relatively low number of spines, by the weakly expressed tabulation and, in some associations, the more elongate ambitus.
Holotype: Mantle et al. 2020, Plate V, 9a, b
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (Rhaetian)
---------------------------------------------------------------------------------------------
Original description: Mantle et al. 2020:
Description:
Small to medium, proximate to proximochorate, subspherical, ovoidal, or ellipsoidal dinoflagellate cysts with approximately equant epicysts and hypocysts.
Wall: autophragm is scabrate, microgranulate, or microreticulate with very low ridges delimiting most of the polygonal plates. These low, thin sutural ridges are sparsely surmounted by variably elongate spines (1–5 μm) that are sharply acuminate, with blunt rounded tips or have thin sinuous tips. The spinose ornament is both gonal and intergonal, and is consistently of low density, but this is somewhat variable. The spines may be sparsely distributed on the sutures, they may be exclusively gonal, or there may be significant areas which are entirely devoid of spines. These relatively smooth/sparse areas are largely restricted to the epicyst and the ventral surface, and at least a few postcingular and antapical spines are always present.
Tabulation: suessioid with nine latitudinal series (Fig. 4a). The cingulum is moderately laevorotatory, and is offset at the sulcus by up to half the height of a cingular plate.
Tabulation formulae are:
Sensu Morbey (1975): 1–2′, 4–6a, 8–9+ap, 11–15′′, 10–14+c, 10–12+′′′, 9+p, 5–6pa, 1+′′′′
Sensu Below (1987): 1–2n 4 , 4–6n 3 , 8–9+n 2 , 11–15n 1 , 10–14+c, 10–12+n1, 9+n2, 5–6n3, 1+n4
Archaeopyle: formed by the loss a simple opercular piece comprising all the climactal plates [(t’ + ta + tap)s]
Dimensions:
Overall length (excluding apical plates) 35 μm (45 μm) 52 μm; maximum width 36 μm (43 μm) 51 μm
20 measured specimens
Remarks:
Backhouse and Balme (2002) considered that their Wanneria sp. A (now Wanneria backhousei sp. nov.) warranted specific status. However, these authors also speculated that it may represent a facies-controlled morphotype of Wanneria listeri. Rare intermediate forms were also noted herein, but as most of the Norian and Rhaetian Wanneria species grade into each other to some degree, we contend that this taxon should be formalised. Further examination of well-preserved material may also reveal specimens with a larger number of plates for each latitudinal series than are noted herein.
Affinities/Comparisons:
Wanneria backhousei sp. nov. differs from Wanneria listeri in having a relatively low number of spines, by the weakly expressed tabulation and, in some associations, the more elongate ambitus.