(1) Background: Integrative taxonomy has been important in the comprehension of relationships among nematode parasites. Philometridae is a highly diverse family of these organisms, but poorly-known regarding genetic characterization and evolution. An integrative taxonomic analysis was performed to improve the knowledge of the evolutionary history of Philometridae. (2) Methods: Phylogenies were reconstructed based on genetic sequences alone and integrated with morphological/life history traits, which were phylogenetically mapped. The host–parasite cophylogeny was evaluated. (3) Results: Previously unpublished 28S rDNA sequences are given for some species. The phylogeny from this marker, although limited by data scarcity, showed similar patterns as that from 18S rDNA. Clades shared common features related to the structure of the esophagus and of the tail in males (especially the gubernaculum), site of infection, habitat, host taxa and geographic origin; most of these features were phylogenetically informative. The integrative phylogeny was better resolved. A cophylogenetic signal was present mainly in clades of freshwater species. (4) Conclusions: The speciation process in Philometridae is not unique or uniform; host capture, host–parasite co-evolution and allopatric (especially in freshwater) events may be occurring simultaneously in different lineages, places and times. Cases of plesiomorphy retention probably occur. Evolutionary convergence of poorly-informative characters is suggested, even though they are important for species diagnosis.

Em fevereiro de 2021, espécimes de copépodes parasitas foram coletados infestando as brânquias de Pygocentrus nattereri Kner e Serrasalmus rhombeus (Linnaeus) no Rio Caraipé, Estado do Pará, Brasil. Os copépodes foram fixados e preservados em etanol a 70%. Para a análise morfológica, os copépodes foram clareados em ácido lático a 85% e observados por microscopia de luz. Os espécimes coletados foram identificados como E. yumaricus pelo primeiro somito pedígero não fundido ao cefalossoma, uma maxílula sem espinhos, uma cerda falciforme semi-pinnada no último segmento exopodal da perna 1, endópodos segmentados em 2 nas pernas 1 e 4, e os segmentos endopodais da antena e segmentos abdominais lisos. No Brasil, E. yumaricus foi reportado infestando P. nattereri, S. rhombeus e Serrasalmus eigenmanni Norman em pelo menos seis localidades diferentes, todas na Amazônia Central. Portanto, os achados deste trabalho representam o primeiro registro desta espécie de ergasilídeo não apenas no Estado do Pará, mas também na Bacia Tocantins-Araguaia, ampliando o conhecimento sobre a diversidade e distribuição deste notável copépode parasita.