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Goodwynia spinosa
Goodwynia spinosa sp. nov., Mantle et al. 2020, p. 47 - 48
Holotype: Mantle et al. 2020, Plate XIX, 4a–c
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (middle–upper Norian)
Original description: Mantle et al. 2020:
Description:
Very small, acavate, chorate to proximochorate, ovoidal to subspherical dinoflagellate cysts. The thin autophragm is scabrate with a covering of numerous very slender spines.
Processes/Spines: The majority of the spines are loosely clustered in plate-centred positions; the remainder are nontabular. These simple spines are mostly distally blunt, but they may also be acuminate, pilate, or have finely furcate tips. Rarely the bases of adjacent spines are fused, while several specimens also have marginally broader flattened processes up to 2 μm wide, with bifurcate or trifurcate branching. The cingulum is marked by reduced numbers, or the entire absence, of spines and is commonly distinctly concave in lateral profile.
Full tabulation formula: unknown, but may be summarised as: 2 +′, xa, ?5–6 +′′, xc, ?5–6 +′′′, xp, ?1 +′′′′
Archaeopyle: type is uncertain but appears to involve the loss of the apical and anterior intercalary plates.
Dimensions:
Overall length (excluding spines) 14 μm (17 μm) 20 μm; maximum width (excluding spines) 13 μm (15 μm) 17 μm; length of spines 1–5 μm; width of spines <1–2 μm
10 measured specimens
Remarks:
Although there is some intergradation between the highly cryptic, minute dinoflagellate cysts Goodwynia dendroidea sp. nov. And Goodwynia spinosa sp. nov. the majority of specimens of these two species are readily distinguishable. Therefore, it was considered appropriate to erect a new species, Goodwynia spinosa sp. nov. The latter has up to eight simple spines per plate, rather than the equivalent typically single, branched processes of Goodwynia dendroidea and is also marginally smaller.
Affinities/Comparisons:
Goodwynia spinosa sp. nov. is even harder to separate from the common Micrhystridium spp. in the Norian marine successions of the distal reaches of the Northern Carnarvon Basin than Goodwynia dendroidea, due to the numerous morphologically similar spines. However, unlike the predominantly distally acuminate spines of Micrhystridium and other small Triassic acanthomorph acritarchs, the slender processes of Goodwynia spinosa sp. nov. may be acuminate, blunt, pilate or rarely furcate, and they occur in discrete clusters. These plate-centred groupings of spines, the reduced distribution of spines across the cingulum and the combination archaeopyle (apical/anterior intercalary) further distinguish well-preserved specimens of Goodwynia spinosa sp. nov. from all small, acanthomorph acritarchs.
Holotype: Mantle et al. 2020, Plate XIX, 4a–c
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (middle–upper Norian)
Original description: Mantle et al. 2020:
Description:
Very small, acavate, chorate to proximochorate, ovoidal to subspherical dinoflagellate cysts. The thin autophragm is scabrate with a covering of numerous very slender spines.
Processes/Spines: The majority of the spines are loosely clustered in plate-centred positions; the remainder are nontabular. These simple spines are mostly distally blunt, but they may also be acuminate, pilate, or have finely furcate tips. Rarely the bases of adjacent spines are fused, while several specimens also have marginally broader flattened processes up to 2 μm wide, with bifurcate or trifurcate branching. The cingulum is marked by reduced numbers, or the entire absence, of spines and is commonly distinctly concave in lateral profile.
Full tabulation formula: unknown, but may be summarised as: 2 +′, xa, ?5–6 +′′, xc, ?5–6 +′′′, xp, ?1 +′′′′
Archaeopyle: type is uncertain but appears to involve the loss of the apical and anterior intercalary plates.
Dimensions:
Overall length (excluding spines) 14 μm (17 μm) 20 μm; maximum width (excluding spines) 13 μm (15 μm) 17 μm; length of spines 1–5 μm; width of spines <1–2 μm
10 measured specimens
Remarks:
Although there is some intergradation between the highly cryptic, minute dinoflagellate cysts Goodwynia dendroidea sp. nov. And Goodwynia spinosa sp. nov. the majority of specimens of these two species are readily distinguishable. Therefore, it was considered appropriate to erect a new species, Goodwynia spinosa sp. nov. The latter has up to eight simple spines per plate, rather than the equivalent typically single, branched processes of Goodwynia dendroidea and is also marginally smaller.
Affinities/Comparisons:
Goodwynia spinosa sp. nov. is even harder to separate from the common Micrhystridium spp. in the Norian marine successions of the distal reaches of the Northern Carnarvon Basin than Goodwynia dendroidea, due to the numerous morphologically similar spines. However, unlike the predominantly distally acuminate spines of Micrhystridium and other small Triassic acanthomorph acritarchs, the slender processes of Goodwynia spinosa sp. nov. may be acuminate, blunt, pilate or rarely furcate, and they occur in discrete clusters. These plate-centred groupings of spines, the reduced distribution of spines across the cingulum and the combination archaeopyle (apical/anterior intercalary) further distinguish well-preserved specimens of Goodwynia spinosa sp. nov. from all small, acanthomorph acritarchs.