Glycymeris septentrionalis is a species of marine bivalve mollusk in the family Glycymerididae. Native to the northeastern Pacific Ocean, it occurs along the coasts of Alaska, British Columbia, and adjacent regions. The species possesses a thick, subcircular shell with numerous radial ribs and a characteristic taxodont hinge composed of many small teeth. It inhabits sandy and gravelly seabeds in shallow water marine environments and at greater depths offshore.
Paleocene comparisons Fossils are known from the Pleistocene and Holocene of the northeastern Pacific, indicating that the species has persisted through multiple glacial–interglacial cycles and has survived for at least hundreds of thousands of years.
The variability of modern specimens have been used to inform interpretations of fossils. Specimens exhibit considerable variation in shell outline and in the size and shape of the hinge, even among specimens from a single locality. These observations suggest that morphological variability is a common characteristic of glycymerid bivalves and should be considered when distinguishing fossil species from the Upper Cretaceous and Paleocene.
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