Spiochaetopterus nonatoi, a new species of Chaetopteridae (Polychaeta) from Brazil: biogeographical consequences

A new species Spiochaetopterus nonatoi is described from the south-eastern coast of Brazil, the type locality being Flamengo Bight, 6-m depth (23 degr ees 30 'S 45 degrees 06 'W). This species is distinguishable front already erected species of the same genus by the following characteristics: oculate specimens of large size,, maximum segments, 197 (N = 15); maximum tube len gth, 45 cm; maximum body length, 20 cm; orange coloration of the fore part (peristomium and segment 1) and of the ventral shield on segments 6-7; shap e of the specialized enlarged cutting seta on A4 with an obliquely truncate d distal end: this slightly concave section is heart-shaped and clearly asy mmetrical segments B1 and B2 with one lobe on the neuropodia. This addition al description in the genus Spiochaetoplerus confirms the limited geographi cal area of each species in this genus. In spite of the probable ability of planktonic larvae of Spiochaelopterus to disseminate throughout the Atlant ic Ocean, the benthic adults of each species cover only a limited geographi cal area. In particular, the stem species S. costarum loses its cosmopolita n character.