Silurian Megalodont Bivalves of the Canadian Arctic and Australia: Paleoecology and Evolutionary Significance

Abstract

The oldest occurrence (Early Silurian, Llandovery) of megalodont bivalves is reported from the Canadian Arctic. Megalodonts, although occurring through most of the Silurian, are abundant in Ludlow strata in three main areas: Australia, the Arctic, and the Michigan Basin. They occupied several different depositional environments, but they tended to be most common in shallow-water, protected back-barrier, lime mud-rich settings. Many of the Silurian megalodonts were reclined, mud-resting, epifaunal suspension feeders. Because of their abnormally large size, thick shell, probable high skeleton-to-body ratio, and epifaunal, tropical reef-associated habitat, many probably contained photosynthetic endosymbionts