Pinworm nematodes of the genus Syphacia (Nemata : Oxyurida : Oxyuridae) have a global distribution, and infect the caecum of rodents. Within the Australian Bioregion, 17 species of Syphacia infect a range of rodent hosts. Pinworms are traditionally thought to have coevolutionary relationships with their hosts, but the evolution and dispersal of Australian rodents and their helminths remains unclear. This combination of factors allowed us to investigate the likely relationships of Australian Syphacia species based on phylogenetic analysis, overlaid with the ecology and relationships of host species. We conducted a phylogenetic analysis using morphological characters of the species of Syphacia from the Australian Bioregion in order to examine the relationships between species, and to investigate how host evolution and phylogeny could inform (or be informed) by parasite phylogeny. Application of the taxon pulse theory of parasite speciation by matching host species to parasites shed some light on the timing of speciation of rodent hosts. We found that species of Syphacia had reasonably close host–parasite relationships, with additional evidence for ecological fitting or host switching occurring. Evidence provided here suggests strongly that most elements of the Stockholm Paradigm are at play in structuring the relationships we observe in this pinworm–mammal system.