Thaumasioscolex didelphidis n. gen., n. sp (Eucestoda : Proteocephalidae) from the black-eared opossum Didelphis marsupialis from Mexico, the first proteocephalidean tapeworm from a mammal

Thaumasioscolex didelphidis n. gen., n. sp. is described from the intestine of the black-eared opossum Didelphis marsupialis L. (Marsupialia: Didelphi dae) from Los Tuxtlas, Veracruz, Mexico. The new genus differs from all pro teocephalidean genera in the morphology of the scolex that is formed by 4 w ell separated lobes each containing 1 noncircular sucker opening laterally inside the exterolateral cavity, a large-sized body (length up to 1 m), a l arge number of testes, the shape of gravid proglottids that are inversely c raspedote (the anterior border of a proglottid overlaps the posterior borde r of a preceding proglottid), eggs in groups mostly of 4-6 eggs each, and a n embryophore bearing digitiform projections on its external surface. This is the first tapeworm of the Proteocephalidea, the members of which were pr eviously reported exclusively from poikilotherm vertebrates (freshwater fis hes, amphibians, and reptiles), found in a homoiotherm vertebrate.