A synoptic review of the family Dendronotidae (Mollusca: Nudibranchia): a multilevel organismal diversity approach

A synoptic review of the family Dendronotidae is presented based on morphological and molecular data.
Three genera are recognized: Dendronotus, Pseudobornella, and Cabangus gen. nov. Two new Dendronotus
species are described, D. yrjargul sp. nov. and D. nordenskioeldi sp. nov., which reveal fine-scale differences.
Dendronotus yrjargul sp. nov. from mid-Norway and the Arctic regions is a sister species to the North
Pacific D. kalikal. These two species are showing clear morphological and ontogenetic differences but are
close in genetic distance. In contrast, Dendronotus nordenskioeldi sp. nov. from the Laptev Sea is externally
similar to the white morphs of D. lacteus or D. frondosus, but according to the molecular data and radular morphology it is distinct from any of its congenerics. Comparison of molecular and morphological data
of D. niveus from the type locality (White Sea) and material from other localities with those from the
American North Atlantic coast (type locality of D. elegans) reveals their substantial similarity. Therefore,
D. niveus is considered a junior synonym of D. elegans. The present review of the family Dendronotidae
contributes to a general discussion on the species concepts and on a recent proposal of multilevel
organismal diversity.