The name Arhynchus[a] was chosen based on the characteristic absence of a proboscis in this species of Acanthocephala.

[4] The National Center for Biotechnology Information does not indicate that any phylogenetic analysis has been published on Apororhynchida that would confirm its position as a unique order in the class Archiacanthocephala.

[5] The lack of morphological features such as an absence of a muscle plate, a midventral longitudinal muscle, lateral receptacle flexors, and an apical sensory organ when compared to the other three orders of class Archiacanthocephala indicate it is an early offshoot (basal).

[6] The genus Apororhynchus consists of ectoparasitic worms that attach themselves beneath the skin and around the anus of birds.

[6][7] The distinguishing features of this order among acanthocephalans are a highly enlarged proboscis with limited motility and a reduced size of the hooks (or spines).

[6] Two regions of musculature are considerably different in Apororhynchus compared to the other acanthocephalan orders: the proboscis receptacle and receptacle protrusor are both reorganized in Apororhynchus with the muscles subdivided into strands extending from the cerebral ganglion, or nerve bundle, to the proboscis wall.

[6] Additional anatomical features that can be used to distinguish this genus among other acanthocephalans include a cerebral ganglion located under the anterior wall of the proboscis, long and tubular lemnisci (bundles of sensory nerve fibers) that run along a central canal, the lack of any protonephridia (an organ which functions as a kidney), and the presence of eight pear-shaped cement glands used to temporarily close the posterior end of the female after copulation.

[17] The parasite was discovered in 1931, in the Berlin Museum, taken from the digestive tube of a bird named at that time as "Oriolus cristatus", which was likely a crested oropendola (Psarocolius decumanus).

[17] Numerous fine hooks on the bulb-shaped proboscis, as well as the different host and location, distinguish it from A.

The species name amphistomi derives from a superficial resemblance to the amphistomate trematodes (flukes with stoma on opposite sides).

[17] It has been found in Kaua'i, Hawaii, parasitizing the now extinct Kauaʻi ʻakialoa (Akialoa stejnegeri).

[11] This parasite has been found in the black-winged pratincole (Glareola nordmanni) at Malye Chany Lake, in Russia,[26] and in the colon and cloaca of the Eastern yellow wagtail (Motacilla tschutschensis) in Chukotka and Kamchatka (including the Karaginsky Island), also in Russia.

The hook has a thin blade with a curved tip and root thickened with broadened base.

This stage involves penetrating the wall of the mesenteron or the intestine of the intermediate host and growing.

[31] Apororhynchus species exclusively parasitize avian hosts of different orders including owls, waders, and passerines.

[32] There are no reported cases of any Apororhynchus species infesting humans in the English language medical literature.