Anatomy and Phylogenetic Significance of Micropilina arntzi (Mollusca, Monoplacophora, Micropilinidae Fam. Nov.)

The anatomy of the neopilinoid limpet Micropilina arntzi (Warén & Hain, 1992, The Veliger 35: 165–176) is described on the basis of graphic reconstructions of semithin serial sections. Hard parts, anatomical features and reproductive biology of the minute species differ considerably from those of all other anatomically known neopilinoid species. Therefore, Micropilinidae fam. nov. is erected for this genus. Micropilina arntzi may be considered as partly paedomorphic with respect to the seriality of ventilatory (ctenidia), excretory or genital organs, or may represent an archaic condition within the Tryblidiida. Ontogenetic and comparative anatomical data strongly suggest that the serial repetition of the various organ systems should be regarded as one of several autapomorphic features of the Neopilinoidea (Tryblidiida).