Centropyxis cavitastoma
C. cavitastoma, after Bobrov, 2020

Centropyxis cavitastoma Bobrov, 2020

Diagnosis: The shell is circular from the ventral view, rarely wide-oval, flattened in lateral view, with the apertural part slightly more flattened than the opposite part of the shell. The ventral surface is invaginated, forming a vast funnel with a maximum depression in the apertural area. The aperture is located eccentrically, circular or broadly elliptical and is bordered by a crown of large mineral particles. The shell is grey, slightly yellowish. The ventral side is usually smooth and covered by colorless mineral plates of various size and shape. The dorsal side is ornamented with mineral particles of various size, among which there are very large ones, protruding from the general shell contour. The globoid formations of nanometric size are often found on the dorsal side.

Dimensions: According to Bobrov (2020): Shell length 100—123 µm, width 84—119 µm, apertural length 27—40 µm, apertural breadth 23—35 µm, shell height 48-55 µm. My measurements: Length 82—110 µm, mean 94 µm (n=14) in dry moss, Greece, 2024.

Habitat: The type locality of this species is surface soil on volcanic deposits under low temperature and high humidity conditions with Elymus sp. dominated on Adak Island, Aleutian archipelago, USA. Also found in dry mosses in Greece.

Geographical distribution: Aleutian archipelago, USA (Bobrov, 2020), Japan, 2024, Greece, Olympia, dry moss (Siemensma, 2024, unpubl.).

Remarks: Shells may appear oval, but this is often because the shell is at an angle.

Centropyxis cavitastoma
C. cavitastoma, after Bobrov, 2020
Centropyxis cavitastoma
C. cavitastoma, 2024
Centropyxis cavitastoma
C. cavitastoma, , largest diameter 82-110 µm, dry moss on rock, Greece, 2024
Ferry Siemensma, created August 28, 2024; last modified January 13, 2025
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