Back
Goodwynia
Goodwynia, Mantle et al., 2020, p. 47
Type species: Goodwynia spinosa, Mantle et al., 2020
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Mantle et al. 2020]:
Description:
Small, acavate, chorate to proximochorate, ovoidal to subspherical dinoflagellate cysts with numerous spines or short, furcate processes.
There are slender spines which are mostly clustered in small groups in plate-centred positions, and broader processes which are typically restricted to a single element per plate. These larger processes vary considerably from flattened to hollow projections with branched, denticulate or digitate terminations. The compound, heteromorphic branching ranges from simple first-order bifurcation to third-order multi-furcate terminations. The cingulum may lack processes or contain fewer, simpler processes than the rest of the cyst. The antapical process may be broader and/or longer than the surrounding hypocystal projections.
The surface of autophragm varies from scabrate to granulate
The tabulation is indicated only by the plate-centred positions of the processes and the poorly defined principal archaeopyle suture
The tabulation formula is not fully known, but can be summarised as: 2+′, xa, ?5–6′′, xc, ?5–8′′′, xp, ?1+′′′′
The archaeopyle is type is uncertain, but appears to involve the loss of the apical and anterior intercalary plates
Remarks:
The dinoflagellate affinity of these tiny cysts is not easily proven. However, the consistent presence of an angular, straight-edged, opening with six or more sides, in an anterior position, strongly suggests a dinoflagellate cyst archaeopyle in Goodwynia gen. nov. This feature is formed by the loss of multiple plates, probably both apical and intercalary plates. Furthermore, the regular distribution and clustering of small spines, and/or the regular distribution of the larger processes, strongly suggests that these are plate-centred positions on a tabulate dinoflagellate cyst. Although the tabulation formula cannot be fully elucidated, the apparent presence of five or more precingular plates and six or more postcingular plates is again strong evidence of a dinoflagellate cyst affinity. The equatorial area either lacks processes, or has notably smaller spines, and is interpreted as the cingulum.
Affinities/Comparisons:
The very small size of Goodwynia gen. nov. (typically <20 μm in diameter, excluding the spines) makes it very difficult to separate from Micrhystridium or other small Late Triassic acanthomorph acritarchs. However, when examined at high magnifications, the consistent anterior position of the archaeopyle, the plate-centred processes or spines and the apparently prominent cingulum all readily distinguish Goodwynia gen. nov. from all spinose acritarchs. The largely Palaeozoic acritarch genus Multiplicisphaeridium is the most closely comparable. This genus possesses similar compound heteromorphic processes with multi-order furcate branches and distal terminations. However, it has a markedly different excystment aperture, often a split-like pylome rather than the large, broad multiplate archaeopyle of Goodwynia gen. nov. Multiplicisphaeridium also lacks the other dinoflagellate features of Goodwynia gen. nov., namely a cingulum and plate-centred processes.
There are no comparable Triassic dinoflagellate cysts except the proximochorate to chorate genus Beaumontella. The latter has substantially simpler processes and a greater number of plate series which strongly suggest close affinities to the suessioids.
Type species: Goodwynia spinosa, Mantle et al., 2020
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Mantle et al. 2020]:
Description:
Small, acavate, chorate to proximochorate, ovoidal to subspherical dinoflagellate cysts with numerous spines or short, furcate processes.
There are slender spines which are mostly clustered in small groups in plate-centred positions, and broader processes which are typically restricted to a single element per plate. These larger processes vary considerably from flattened to hollow projections with branched, denticulate or digitate terminations. The compound, heteromorphic branching ranges from simple first-order bifurcation to third-order multi-furcate terminations. The cingulum may lack processes or contain fewer, simpler processes than the rest of the cyst. The antapical process may be broader and/or longer than the surrounding hypocystal projections.
The surface of autophragm varies from scabrate to granulate
The tabulation is indicated only by the plate-centred positions of the processes and the poorly defined principal archaeopyle suture
The tabulation formula is not fully known, but can be summarised as: 2+′, xa, ?5–6′′, xc, ?5–8′′′, xp, ?1+′′′′
The archaeopyle is type is uncertain, but appears to involve the loss of the apical and anterior intercalary plates
Remarks:
The dinoflagellate affinity of these tiny cysts is not easily proven. However, the consistent presence of an angular, straight-edged, opening with six or more sides, in an anterior position, strongly suggests a dinoflagellate cyst archaeopyle in Goodwynia gen. nov. This feature is formed by the loss of multiple plates, probably both apical and intercalary plates. Furthermore, the regular distribution and clustering of small spines, and/or the regular distribution of the larger processes, strongly suggests that these are plate-centred positions on a tabulate dinoflagellate cyst. Although the tabulation formula cannot be fully elucidated, the apparent presence of five or more precingular plates and six or more postcingular plates is again strong evidence of a dinoflagellate cyst affinity. The equatorial area either lacks processes, or has notably smaller spines, and is interpreted as the cingulum.
Affinities/Comparisons:
The very small size of Goodwynia gen. nov. (typically <20 μm in diameter, excluding the spines) makes it very difficult to separate from Micrhystridium or other small Late Triassic acanthomorph acritarchs. However, when examined at high magnifications, the consistent anterior position of the archaeopyle, the plate-centred processes or spines and the apparently prominent cingulum all readily distinguish Goodwynia gen. nov. from all spinose acritarchs. The largely Palaeozoic acritarch genus Multiplicisphaeridium is the most closely comparable. This genus possesses similar compound heteromorphic processes with multi-order furcate branches and distal terminations. However, it has a markedly different excystment aperture, often a split-like pylome rather than the large, broad multiplate archaeopyle of Goodwynia gen. nov. Multiplicisphaeridium also lacks the other dinoflagellate features of Goodwynia gen. nov., namely a cingulum and plate-centred processes.
There are no comparable Triassic dinoflagellate cysts except the proximochorate to chorate genus Beaumontella. The latter has substantially simpler processes and a greater number of plate series which strongly suggest close affinities to the suessioids.