Neoechinorhynchidae
Neoechinorhynchidae is a family of parasitic worms from the order Neoechinorhynchida. Species. Neoechinorhynchidae contains 4 subfamilies: Atactorhynchinae , Eocollinae , Gracilisentinae , Neoechinorhynchinae . Mayarhynchus. The genus Mayarhynchus is different from the other 17 genera in Neoechinorhynchidae by having a small proboscis has nine longitudinal rows of five hooks each, totaling 45 to 46 relatively weak rooted hooks. "M. karlae" has a small proboscis with nine longitudinal rows of five hooks each, totaling 45 to 46 relatively weak rooted hooks and a proboscis receptacle is nearly cylindrical and contains a single layered wall. The worm has a short trunk with a body wall  containing five dorsal and one ventral giant hypodermal nuclei. The lemnisci are broad and flat with large nuclei. In the male, the testes are in tandem, and the cement gland has eight large nuclei. In the female, the eggs are oval. Phylogenetic analysis has been conducted based on the cox1 gene, and the 28S ribosomal RNA gene were conducuted to compare with other species of Neoechinorhynchidae, confirming its correct family, however it determined that Neoechynorhynchus is not monophyletic. Atactorhynchinae. Atactorhynchus "A. duranguensis" has been found in the intestine of the Mezquital pupfish ("Cyprinodon meeki") a fish from in-land Mexico . Diagnostic features include: body small, stout, ventrally curved; small cylindrical proboscis armed with 16 alternating vertical rows of four or five hooks; anterior two or three hooks conspicuous, stout and larger than other hooks, and have large, rod-shaped roots with a markedly and abruptly enlarged base; three posterior hooks of each row are smaller and rootless; single-walled proboscis receptacle; lemnisci equal in length, elongate and robust; and cement gland syncytial, larger than testis. The new species is smaller than "A. verecundus" with smaller hook lengths and slightly smaller proboscis. "A. duranguensis" is also shaped differently: it has a  proboscis shape that is not widest at the apex, and the greatest width of the trunk is in about the middle contrasting "A. verecundus" where the trunk is widest posteriorly, and the proportion of large apical proboscis hooks in relation to the small basal hooks is different: the basal hooks of A. verecundus are about half the size of the anterior hooks and but only about a quarter of the size in "A. duranguensis". Unlike "A. verecundus", the base of the roots are markedly and abruptly enlarged in the new species. Finally, the eggs of the new species are smaller  (23-27 x 8-10 um) than those of "A. verecundus" (27-30 x 12-13 um). Floridosentis Tanaorhamphus Eocollinae. Eocollis Gracilisentinae. Gracilisentis Pandosentis Wolffhugelia Hosts. "Neoechinorhynchidae" species parasitize fish.