What is Paranoplocephala macrocephala (Douthitt, 1915) (Cestoda: Anoplocephalidae)?

We present a redescription for Paranoplocephala macrocephala (Douthitt, 1915) in the type host, Geomys bursarius (Shaw) (hereafter PMG), and compare it with a P. macrocephala-like taxon in Microtus pennsylvanicus (Ord) (hereafter PMM) and P. kalelai (Tenora, Haukisalmi & Henttonen, 1985) in Clethrionomys rufocanus (Sundevall) using uni- and multivariate (discriminant analysis) morphometric methods. P. kalelai was found to be most divergent among these three taxa using both uni- and multivariate analyses, supporting its status as an independent species. Most of the observed metrical differences between PMG and PMM were found to reflect the larger body size of PMM; the relative size of organs (ratios) did not usually differ significantly between these taxa. The length/width ratio of mature segments was found to be the only size-independent feature that reliably separates PMG and PMM. Since PMM and PMG are also qualitatively very similar, e.g. with respect to the distribution of testes and morphology of the terminal genital ducts, the present analysis could not provide conclusive evidence against their conspecificity. However, the morphological variability and wide host and geographical distribution of P. macrocephala-like cestodes in North American voles of the genus Microtus, and the patterns of host-specificity within Paranoplocephala, suggest that this complex probably includes several species.