Advances, diversions, possible relapses and additional problems in understanding the early evolution of the Articulata

Abstract

The authors review the available evidence concerning the early stages of radiation of the Articulata and support the hypothesis that there was probably a range of, perhaps incompletely, metameric organisms spanning, without definite borderlines, the early ancestors of arthropods, lobopods and annelids. By the early Cambrian, the stem lineages of the living articulate phyla were well‐identified, but there still survived a number of animals whose morphology spanned, to some extent, the gaps between the living taxa. The affinities between Annelida (sensu lato) and Mollusca are briefly discussed.

Key words:

• Articulata
• Evolution
• Morphology