Anatomic description of Graptacme obtura (Scaphopoda: Dentaliidae) from Trindade Island, Brazil

Abstract

The genus Graptacme Pilsbry & Sharp, 1897 comprises 18 species worldwide, six of which occur in Brazil. Among them, only Graptacme obtura Fogarolli & Simone, 2024 is endemic to the country. This recently described species has so far been recorded only at Trindade Island, the most remote oceanic island of Brazil. This supports the increasing diversity being documented at the island together with several other animal groups. Herein, a detailed anatomical study is presented as a complement to the original description, representing the first anatomical account of the genus. Among the anatomical features presented, the more noteworthy are the oral tube with internal chambers and folds; the size and proportion of the muscles and cartilages which compose the odontophore; the shape, structure and cusps of the radula teeth; number of intestine loops and folds; shape and size of dorsal mantle border; the general shape of the foot and its epipodial lobes. These structures showed significant differences between the current species and other species with available anatomical studies in the literature, in addition to those characters traditionally used in scaphopod taxonomy, like the foot shape and radula.