ANATOMY AND PHYLOGENETIC SIGNIFICANCE OF MICROPILINA-ARNTZI (MOLLUSCA, MONOPLACOPHORA, MICROPILINIDAE FAM NOV)

The anatomy of the neopilinoid limpet Micropilina arntzi (Waren & Hain , 1992, The Veliger 35:165-176) is described on the basis of graphic r econstructions of semithin serial sections. Hard parts, anatomical fea tures and reproductive biology of the minute species differ considerab ly from those of all other anatomically known neopilinoid species. The refore, Micropilinidae fam. nov. is erected for this genus. Micropilin a arntzi may be considered as partly paedomorphic with respect to the seriality of ventilatory (ctenidia), excretory or genital organs, or m ay represent an archaic condition within the Tryblidiida. Ontogenetic and comparative anatomical data strongly suggest that the serial repet ition of the various or an systems should be regarded as one of severa l autapomorphic features of the Neopilinoidea (Tryblidiida). (C) The R oyal Swedish Academy of Sciences.