From Fensome et al., 2019:
Votadinium spinosum Reid, 1977, p.445–446, pl.2, figs.24–26. Holotype: Reid, 1977, pl.2, figs.24–26; Gurdebeke et al., 2019b, pl.7, figs.1–4. Motile equivalent: Protoperidinium claudicans (Paulsen, 1907) Balech, 1974, according to Reid (1977, p.445). Contrary to the opinion of Lentin and Williams (1993, p.666), this name is not illegitimate following ICN Article 52.2e, since Reid (1977, p.445) did not explicitly include the type of Peridinium claudicans in synonymy with his new species, Votadinium spinosum. Age: Holocene.

Locus typicus: Galway, Ireland
Stratum typicum: Recent

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Original diagnosis: Reid, 1977, p.446
Test heart shaped, with two antapical lobes separated by a shallow antapical depression in dorsal view and with a rounded apex. Compressed dorsoventrally to half the width of the test giving a lunulate to hour glass outline in apical view. Wall thin with a smooth surface and ornamented by short solid spines which are usually curved. Archeopyle intercalary 2A.
Dimensions: Holotype: Test 54 µm. Range: Test 49 X 51 - 54 X 63 µm. Spine Length 3-7 µm. Number of specimens measured 15.

Original description: Reid, 1977, p.446
The single layered wall <1 µm which has a brown colour is ornamented by spines of equal length which have an irregular distribution over the whole test except for the antapical sulcus where they are absent. The archeopyle truncates the apex obliquely. Its shape was not clearly seen, but is appears to be pentagonal. An inner thin hyaline layer and cytoplasm were present in many cysts.

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Remarks from Gurdebeke et al., 2019b, p. 325-326:


Votadinium spinosum Reid, 1977
Plate 7, figures 1–15

Synonymy.
1965 Peridinium sp. (cysts-form 5): Wall, p. 307, fig. 16.
1967 Cyst of Peridinium claudicans Paulsen: Wall & Dale, p. 350, pl. 1, fig. R.
1968 Peridinium claudicans Paulsen: Wall & Dale, p. 273, pl. 2, figs 1–2.
1975 Cyst of Peridinium claudicans Paulsen: Davey & Rogers, p. 217, pl. 1, fig. 10.
1977 Votadinium spinosum Reid: Reid, p. 445–446, pl. 2, figs 24–26.
1985 Votadinium spinosum Reid: Matsuoka, p. 58–59, pl. 14, figs 1–6.
1987 Votadinium spinosum: Matsuoka, p. 65–66, pl. 14, figs 1–5.
1987 Cyst of Protoperidinium claudicans: Akselman, pl. 1, figs 7–9.
1989 Votadinium spinosum; Kojima, fig. 6.5.
1990 Cyst of Protoperidinium claudicans (Paulsen) Balech: Bolch & Hallegraeff, p. 183, fig. 25.
1992 Votadinium spinosum Reid: Matsuoka, p. 51, pl. 2, fig. 9.
1993 Cyst of Protoperidinium claudicans; Nehring, fig. 5-J.
1994 Votadinium spinosum Reid: Matsuoka, pl. 2, fig. 3a–b.
1996 Cyst of Protoperidinium claudicans Qi et al., p. 96, pl. 3, fig. Q.
1997 Cyst of Protoperidinium claudicans: Nehring, p. 313, fig. 17.
1998 Cyst of Protoperidinium claudicans: Montresor et al., fig. 3a.
2000 Votadinium spinosum: Cho, p. 27, pl. 3, fig. 1.
2000 Cyst of Protoperidinium claudicans: Ishikawa & Taniguchi, fig. 4-J.
2000 Protoperidinium claudicans: Rubino et al., p. 276, fig. 2g.
2002 Votadinium spinosum Reid: Prauss, pl. 3, fig. 7.
2003 Protoperidinium claudicans: Morquecho & Lechuga-Devéze, fig. 3.
2004 Cyst of Protoperidinium claudicans: Harland et al., pl. 1, fig. 3.
2004 Cyst of Protoperidinium claudicans: Joyce, p. 176, fig. 14a,b.
2004 Protoperidinium claudicans (Paulsen) Balech: Orlova et al., figs 44–46.
2004 Votadinium spinosum: Pospelova et al., pl. 2, fig. 12.
2004 Votadinium spinosum: Radi & de Vernal, pl. 1, fig. 11.
2005 Protoperidinium claudicans: Joyce et al., fig. 11.
2005 Votadinium spinosum: Pospelova et al., fig. 7.7.
2007 Votadinium spinosum: Cremer et al., figs 191–192.
2008 Votadinium spinosum: Vilanova et al., pl. 1, fig. K.
2010 Votadinium spinosum: Krepakevich & Pospelova, pl. 3f.
2010 Votadinium spinosum: Limoges et al., pl. 3, fig. 11.
2010 Votadinium spinosum: Matsuoka & Shin, fig. 2E.
2010 Votadinium spinosum: Pospelova et al., pl. 6, fig. 4.
2010 Votadinium spinosum: Satta et al., pl. 2, fig. n.
2010 Votadinium spinosum: Shin et al., fig. 4-H.
2010 Votadinium spinosum: Uzar et al., fig. 26.
2011 Votadinium spinosum: Aydin et al., fig. 12a,b.
2011 Cyst of Protoperidinium claudicans: D’Silva et al., fig. 2.15.
2011 Votadinium spinosum: Price & Pospelova, pl. 4, fig. 5.
2012 Votadinium spinosum: Candel et al., fig. 2.8.
2012 Cyst of Protoperidinium claudicans: Furio et al., fig. 2.17.
2012 Protoperidinium claudicans: Srivilai et al., fig. 2Q.
2013 Votadinium spinosum: Bringue et al., p. 41, pl. 3, fig. 6.
2013 Votadinium spinosum: Candel et al., pl. 2, fig. 6.
2013 Votadinium spinosum: Limoges et al., pl. 2, fig. 4.
2013 Cyst of Protoperidinium claudicans: Narale et al., fig. 3g.
2013 Protoperidinium claudicans (Paulsen) Balech: Orlova & Morozova fig. 3n,o.
2016 Votadinium spinosum Bringue et al., p. 805, pl. 3, fig. 6.
2018 Votadinium spinosum Reid: Matsuoka et al., p. 128, fig. 5.g.

Motile stage equivalent. Protoperidinium claudicans (Paulsen 1907) Balech 1974, according to Reid (1977, p. 445).

Remarks. The holotype of Reid (1977) was re-photographed
and is illustrated here for the sake of completeness (Plate 7, figures 1–4). It shows a broad (wider than long) heart-shaped cyst with broadly rounded antapical horns separated by a shallow antapical concavity and a rounded apex. The thin smooth wall is ornamented with short (3–7 mm; Reid 1977) solid spines. There is a large 2a archeopyle, which may involve apical plates. These general characteristics are also visible in the SEM image (Plate 7, figure 13), where the archeopyle is open and the operculum has been shed. The cyst wall and spines appear to be microgranular, and the solid spines have minute fenestrae at their bases (Plate 3, figures 5–7). It is possible that V. spinosum represents a species complex, as suggested by Matsuoka and Head (2013). This hypothesis needs to be further evaluated through cyst–theca and morphological studies.

Comparison. This species differs from all other Votadinium species in having a granular wall and bearing spines, and from V. psilodora, V. elongatum, V. nanhaiense, V. pontifossatum and V. reidii in having L/W < 1 and the archeopyle involving the apical part of the cyst.