Abstract
Clisospira ellitsgaardi sp. nov. is described from the Cape Schuchert Formation (Early Silurian) of Washington Land, western North Greenland. The cancellate ornamentation of the sinistrally coiled molluscan shell is produced by the interference of successive crenulate growth lamellae. The wide frill of C. ellitsgaardi may have hindered sinking into soft bottom sediment or increased shell stability by increasing the surface area of the underside of the shell. The strongly tangential aperture probably indicates that C. ellitsgaardi effectively clamped its shell against the substratum when disturbed.
Highlights
Clisospira ellitsgaardi sp. nov. is described from the Cape Schuchert Formation (Early Silurian) of Washington Land, western North Greenland
When the shell is placed in standard orientation for description, with the apex upward and the aperture facing the observer, the aperture lies to the right of the axis of coiling
The shell is sinistral, i.e. coiling is anticlockwise when the shell is viewed from the apex, and the aperture lies to the left in standard orientation
Summary
Linsley & Kier (1984) followed Horny (1964) in assigning Clisospira and Ferrogyra Horny, 1964 to this subfamily. The frill of the Greenland Silmian species is wider and its outer areas show replacement of the cancellate ornamentation by abundant, fine, strongly prosoc1ine ribs. Clisospira rugosa Koken, 1925, as figured by Wangberg-Eriksson (1979) from the Ordovician of 6stergotland, Sweden, does not dosely resemble the type species, as illustrated by Knight (1941) It may not be a Clisospira, and as such is readily distinguished from C. ellitsgaardi by its higher spire, lack of cancellate ornamentation and lack of the wide, flat frill. Ferrogyra antiqua (Perner, 1903), the type and apparently only known species of the genus, appears to have a similar rate of whorl expansion to that of C. ellitsgaardi, but lacks cancellate ornamentation. Cancellate ornamentation is present in Laeogyra gracilis Perner, 1925 of Wangberg-Eriksson (1979), Pervertina Horny, 1964 and lnvertospira Horny, 1964; all three Ordovician forms show cancellate ornamentation, but lack the frill characteristic of C. ellitsgaardi
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