New species of Mexicope, stat. nov. and Ianthopsis from Australia and a rediagnosis of Acanthaspidiidae (Isopoda : Asellota)

Abstract

Two new species, Mexicope westralia and Ianthopsis vanhoeffeni, are described from south-western and south-eastern Australia respectively. One species of Mexicope was known previously from the Gulf of Mexico and the Caribbean. New morphological evidence shows that Mexicope, hitherto considered as family incertae sedis, should be transferred to the Acanthaspidiidae. New diagnoses are presented for the family Acanthaspidiidae as well as the genera Mexicope and Ianthopsis. The distribution of species in the Acanthaspidiidae is summarised. The vertical distribution patterns of the three genera in the family (Acanthaspidia, Ianthopsis, Mexicope) are shown to be very different. It is suggested that the family originated in cold water of the southern hemisphere at lower shelf to upper bathyal depth (Ianthopsis) with subsequent evolution and radiation of Acanthaspidia in the deep sea and Mexicope in shallow warmer to tropical waters.