Hypnum orbicularicordatum Renauld & Cardot, Bull. Herb. Boissier 4: 19. 1896

Plants medium-sized to large, brownish yellow. Stems unbranched or sparsely branched (few shoots seen); axillary hair apical cell elongate-rectangular to short-linear. Stem leaves broadly ovate or broadly ovate-cordate; costa single, 90-109 µm wide near base, ending shortly below apex; alar regions indistinctly delimited, broadly oblong to transversely triangular, from margins 65-80% distance to costa; ; medial cells to 18(-20) µm wide proximally, 40-126 × 7-12(-14) µm in distal 1/3-1/2. Sexual condition unknown. Spores unknown.

Habitat unknown; elevation unknown; Nunavut.

It is unclear whether Calliergon orbicularicordatum is an expression of another Calliergon species from unfavorable conditions or if it should be recognized as a distinct species. K. Karczmarz (1971) reported C. orbicularicordatum from Alaska, Greenland, and Svalbard, but the features he used to distinguish this taxon are unclear.