Linoproductoidea

Linoproductoids commonly had long but simple trails, and fine, regular ribbing across the entire shell. Thick and symmetrical ventral spines were present on the hinge and diverse across the remainder of the valve, while the dorsal valve lacked spines (except in grandaurispinins and certain gigantoproductins).^[2]

Initially, the surface of the ventral valves of linoproductoids had posterior and anterior spines of around the same thickness. Very early in the Carboniferous, the group evolved two additional spine-distribution patterns: one with the thickest spines confined to the hinge margin and another where they are confined to the trail. Three families were established based on these three patterns.^[3]