Silphopsyllus desmanae, a species of the small subfamily Platypsyllinae of Leiodidae, lives in the fur of the semiaquatic Russian desman, and is apparently adapted to this highly specialized life style. Even though the morphology of adults of the species was described almost 70 years ago, we re-examined it with modern methods and documented its external and internal features in detail, and discuss them with respect to phylogeny and function. Our analyses of morphological data place Leptinillus as the sister group of the remaining genera of Platypsyllinae, and Leptinus as the sister group of Silphopsyllus + Platypsyllus. Platypsyllinae are supported by many putative autapomorphies: supraantennal ridges directed mesad but not extending beyond the antennal insertions and not forming a transverse ridge
tentorium without connected laminatentoria anterior to the tentorial bridge
submentum subrectangular
labrum about as wide as the maxillary-labial complex
elongate and posteriorly projecting lateral lobes of the mentum
antennomeres lacking periarticular gutters (and Hamann's organs)
cervical sclerites absent
precoxal prosternal region distinctly longer than the coxal rests
mesocoxal cavities situated closer to the body midline than to the lateral mesothoracic margins
metanepisterna fused with the metaventrite
metascutum laterally overlapping the meso- and metapleural regions
procoxae subglobose or only slightly elongate
mesocoxae subglobose. Platypsyllinae are most likely the sister group of Coloninae + Cholevinae. Eight unique apomorphies differentiating Platypsyllus from all the remaining Platypsyllinae are mainly adaptations for living in the fur of beavers. Silphopsyllus is much less adapted to life on a semiaquatic host than Platypsyllus.