Proposal of Spinulacorpus biforme (Smales, 2014) n. g., n. comb. and the Spinulacorpidae n. fam. to resolve paraphyly of the acanthocephalan family Rhadinorhynchidae Lühe, 1912.

Previous phylogenetic analyses of the Acanthocephala have demonstrated that the families Rhadinorhynchidae Lühe, 1912 and Transvenidae Pichelin & Cribb, 2001 are sister clades. However, a recent study found that the Rhadinorhynchidae is paraphyletic, due to the basal position of Rhadinorhynchus biformis Smales, 2014 relative to the Rhadinorhynchidae + Transvenidae. We reassess these relationships with new single-gene and concatenated phylogenetic analyses utilising cox1 mtDNA, 18S rDNA and 28S rDNA, including recently available sequences. Although topologies differed among single-gene analyses, the overall results support R. biformis as representative of a lineage distinct from those of the Rhadinorhynchidae and Transvenidae. Examination of additional specimens of R. biformis allowed us to identify morphological characters that further support this hypothesis. These results lead us to propose transfer of R. biformis to a new genus (Spinulacorpus n. g.) and family (Spinulacorpidae n. fam.) to resolve the paraphyly of the Rhadinorhynchidae.