Galeripora purdoni Taylor B, Porfirio-Sousa, Jones, Seaquist, Siemensma, Taylor E & Tice, 2026
Basionym: Arcella artocrea var. pseudocatinus Deflandre, 1928
Description based on preprint: Taylor B et al., 2026 (bioRxiv; not yet formally published).

Diagnosis: Shell irregularly circular in apical view. Dorsal surface domed and densely pitted with small depressions, becoming smooth toward the margins. Ventral surface smooth and concave in active specimens, bearing numerous pores (>30, sometimes >100) that are loosely scattered across the surface rather than confined to the circumapertural region. Pores are larger and more abundant near the aperture, becoming smaller and sparser toward the shell margin. Aperture central, circular to ovoid, deeply invaginated, with a slightly everted collar. All exposed surfaces thinly coated with organic material that conceals the areolar building units. During encystment, the ventral surface everts and forms a domed or conical protuberance over the spherical resting cyst.

Dimensions: Shell diameter 179–254 μm (mean 212 μm, n=56); height 77–102 μm (mean 83 μm); aperture diameter 77–102 μm (mean 83 μm, n=56); apertural invagination 34–43 μm high (mean 39 μm, n=56); ratio of aperture to shell diameter 0.18–0.24 (mean 0.21).

Ecology: Type location: calcareous woodland fen, among hummocks of Sphagnum and embedded forest litter.

Geographical distribution: Ontario, Canada

Remarks: Galeripora purdoni is distinguished from congeners by molecular markers in the mitochondrial COI gene and by the exceptionally large number of pores scattered across its ventral surface. In ventral view, it can be differentiated from G. discoides, G. marichusae, G. megastoma, G. polypora, and G. scutelliformis by the small size of its aperture relative to the overall shell diameter. In lateral view, it differs from all varieties of A. artocrea and G. arenaria by the absence of a distinct border or basal rim on the shell margin (and from the latter also by its much larger size). The dorsal (apical) surface of the shell is distinguished from that of G. catinus and G. balari by the lack of ridges, folds, or facets. Galeripora succelli has a similar size and profile, but its test is described as flattened at the margins (i.e. with a “keel”), and its pores are restricted to a ring around the aperture. Other species in the genus—G. bathystoma, G. bufonipellita, G. galeriformis, G. halaurula, G. naiadis, and G. sitiens—may share individual characters with G. purdoni, but all are much smaller in size.

One taxon, described by Decloitre (1972) as Arcella arenaria var. irregularis, has a loose scattering of variably sized pores around the aperture, somewhat like that of G. purdoni. However, Decloitre’s variety is much smaller (70-80 μm, less than half the size of G. purdoni), and was reported from lichen on olive trees.

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