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Goodwynia dendroidea
1975 Multiplicisphaeridium dendroidium Morbey, p. 50–52, pl. 16, figs. 21–22, text-fig. 24.
Description:Very small, acavate, chorate toproximochorate, ovoidal to subspherical dinoflagellate cystswith a diverse array of furcate processes. The thin autophragmis typically scabrate, however rare specimens are granulate. The plate-centred processes are mostly hollow although some appear flattened, and are 1–5 μm in width. The hollow processes may be relatively simplewith denticulate or digitate distal terminations; more commonly they are variably furcate. These branched processes vary fromrelatively simple bifurcate projections to those with three or more orders of branching and bifurcate, trifurcate, or quadrifurcate distal terminations. The process tips may be blunt or pointed, and vary from stout to very delicate and slender. Themain process trunk is commonly weakly fibrous or ribbed. The cingulumismarked by an absence of spines or bymuch simpler, blunt, unbranched processes. The antapical process may be broader and/or longer than the surrounding hypocystal projections. The full tabulation formula is unclear, but appears similar to: 2+′, xa, ?5–6+″, xc, ?6–8‴, xp, ?1+⁗. The archaeopyle is uncertain, but appears to involve the loss of the apical and anterior intercalary plates.
Dimensions (based on 10 measured specimens):Overall length (excluding spines) 16 μm (18 μm) 20 μm; maximum width (excluding spines) 14 μm(17μm) 19 μm; length of spines 2–8 μm; width of spines<1–5 μm.
Local stratigraphical range: Goodwynia dendroidea is rare to frequent in the H. balmei Zone and the Lower R. rhaetica Subzone (late Norian to early Rhaetian), and very rare in the Upper R. rhaetica Subzone (late Rhaetian) in the Northern Carnarvon Basin.
Previous records: Goodwynia dendroidea was described by Morbey (1975) from theWestbury Formation of the Penarth Group (Rhaetian) in the Bunny Hill Borehole, Nottinghamshire, central England, and from the Swabian Facies to the Pre-planorbis Beds (Rhaetian) in the Kendlebachgraben of central Austria. Various Cambrian and Ordovician records of this species, such as Eisenack et al. (1976), Volkova et al. (1979), Downie (1982), and Hagenfeldt (1988) undoubtedly relate to superficially similar acritarchs with comparable processes but clearly lacking any dinoflagellate characteristics.
Remarks: Morbey (1975) noted that Goodwynia dendroidea (as Multiplicisphaeridium dendroidium occasionally possesses an “apical split-like pylome.” Although the apical position of this excystment aperture is consistent with the interpretation as an archaeopyle herein, the “split-like” structure of this opening is not so definitive. However, some dinoflagellate cysts do have “split-like” archaeopyles (Norris and Hedlund, 1972). Despite this, it is only rare specimens (from the many observed herein) that show an apparently multi-sided, straight-edged archaeopyle. This is more easily observed on specimens in polar view. The archaeopyle could easily appear to be “split-like” in lateral view as is the case for most specimens.
Comparisons: Although Goodwynia dendroidea is closely comparable in morphology to Goodwynia spinosa sp. nov., it is distinguished by the consistent differences in the length, number, and shape of the processes, and the marginally larger cyst size. Goodwynia spinosa sp. nov has numerous simple spines (up to eight per plate), rather than the usual single process per plate of Goodwynia dendroidea (see Fig. 7a–f). The single processes of the latter are broader, more complex (commonly branched), more varied and longer than the dominantly distally blunt spines of Goodwynia spinosa sp. nov.
Description:Very small, acavate, chorate toproximochorate, ovoidal to subspherical dinoflagellate cystswith a diverse array of furcate processes. The thin autophragmis typically scabrate, however rare specimens are granulate. The plate-centred processes are mostly hollow although some appear flattened, and are 1–5 μm in width. The hollow processes may be relatively simplewith denticulate or digitate distal terminations; more commonly they are variably furcate. These branched processes vary fromrelatively simple bifurcate projections to those with three or more orders of branching and bifurcate, trifurcate, or quadrifurcate distal terminations. The process tips may be blunt or pointed, and vary from stout to very delicate and slender. Themain process trunk is commonly weakly fibrous or ribbed. The cingulumismarked by an absence of spines or bymuch simpler, blunt, unbranched processes. The antapical process may be broader and/or longer than the surrounding hypocystal projections. The full tabulation formula is unclear, but appears similar to: 2+′, xa, ?5–6+″, xc, ?6–8‴, xp, ?1+⁗. The archaeopyle is uncertain, but appears to involve the loss of the apical and anterior intercalary plates.
Dimensions (based on 10 measured specimens):Overall length (excluding spines) 16 μm (18 μm) 20 μm; maximum width (excluding spines) 14 μm(17μm) 19 μm; length of spines 2–8 μm; width of spines<1–5 μm.
Local stratigraphical range: Goodwynia dendroidea is rare to frequent in the H. balmei Zone and the Lower R. rhaetica Subzone (late Norian to early Rhaetian), and very rare in the Upper R. rhaetica Subzone (late Rhaetian) in the Northern Carnarvon Basin.
Previous records: Goodwynia dendroidea was described by Morbey (1975) from theWestbury Formation of the Penarth Group (Rhaetian) in the Bunny Hill Borehole, Nottinghamshire, central England, and from the Swabian Facies to the Pre-planorbis Beds (Rhaetian) in the Kendlebachgraben of central Austria. Various Cambrian and Ordovician records of this species, such as Eisenack et al. (1976), Volkova et al. (1979), Downie (1982), and Hagenfeldt (1988) undoubtedly relate to superficially similar acritarchs with comparable processes but clearly lacking any dinoflagellate characteristics.
Remarks: Morbey (1975) noted that Goodwynia dendroidea (as Multiplicisphaeridium dendroidium occasionally possesses an “apical split-like pylome.” Although the apical position of this excystment aperture is consistent with the interpretation as an archaeopyle herein, the “split-like” structure of this opening is not so definitive. However, some dinoflagellate cysts do have “split-like” archaeopyles (Norris and Hedlund, 1972). Despite this, it is only rare specimens (from the many observed herein) that show an apparently multi-sided, straight-edged archaeopyle. This is more easily observed on specimens in polar view. The archaeopyle could easily appear to be “split-like” in lateral view as is the case for most specimens.
Comparisons: Although Goodwynia dendroidea is closely comparable in morphology to Goodwynia spinosa sp. nov., it is distinguished by the consistent differences in the length, number, and shape of the processes, and the marginally larger cyst size. Goodwynia spinosa sp. nov has numerous simple spines (up to eight per plate), rather than the usual single process per plate of Goodwynia dendroidea (see Fig. 7a–f). The single processes of the latter are broader, more complex (commonly branched), more varied and longer than the dominantly distally blunt spines of Goodwynia spinosa sp. nov.