A new scissurelloid genus and species (Mollusca, Gastropoda) from the Late Triassic Cassian Formation

Abstract

Triassurella carnica n. gen. n. sp., a new scissurelloid limpet-shaped gastropod is described from the Late Triassic (early Carnian) Cassian Formation. It represents one of the few Triassic members of the slit-bearing non-nacreous vetigastropods of the Scissurelloidea-Fissurelloidea-group and suggests that diversity and disparity of this group are greater than previously known. Despite descriptive work on the Cassian fauna for more than 160 years, the Cassian Lagerstatte still produces new taxa. However, most of these new taxa are rare (sampling saturation) or minute (collecting bias).Triassurella carnica closely resembles the Recent hot vent limpetTemnocinclis and is probably closely related to it. In contrast toTemnocinclis, Triassurella lived in tropical shallow water. Thus, the finding ofTriassurella corroborates the on-shore/off-shore hypothesis for the vertical colonization of the ocean, which says that originations and innovations tend to occur first in near-shore, shallow-water environments and spread subsequently to deep-water off-shore environments.