Billings' second operculum: a late Early Ordovician Maclurites (Gastropoda) from western Newfoundland and the Canadian Arctic

Abstract

An operculum of Maclurites, first described by Billings in 1865, is redescribed from the original material collected at Cape Norman, northwestern Newfoundland, and from additional specimens from Ellesmere Island, Canadian Arctic. Based on indirect evidence, a very late to latest Early Ordovician age is assigned to the strata of the St. George Group that contains this fossil. This operculum has a paleoequatorial distribution. On the basis of its geometry, the operculum is interpreted as having a "concentric" growth pattern rather than a spiral one. If so, the complex coiling pattern assumed for Maclurites may be in error. Speculation on functional morphology explains the shape of the operculum without recourse to any assumed coiling during growth and reinforces the interpretation of Maclurites as an exceedingly sedentary animal.