Acheronauta is a genus of extinct worm-shaped arthropod that lived in the early Silurian (Telychian-Sheinwoodian stages) Waukesha biota fossil site in southeast Wisconsin.

[1] Multiple phylogenetic analyses were performed, and it was found that this arthropod forms a previously undiscovered clade with the Devonian stem-arthropod Captopodus, and the somewhat enigmatic group Thylacocephala.

[4] While its specific placement in the mandibulate family tree has not been fully known, it is accepted to occupy a position near the base of the grouping.

[1] Before it was named, Acheronauta was recognized as one of the most abundant arthropod fossils from the biota (only behind the dalmantid trilobite Waukeshaaspis, and several leperditicopid ostracods).

The specific epithet translates to ‘sting like a bee’, which according to the authors of the paper is in honor of the American boxer Muhammad Ali.

This feature looks like the bivalved carapaces of other arthropods like the hymenocarines, but due to the lack of dorsally oriented fossils means that there is no confirmation of the presence of a hinge line.

On the anterior area of the head was an ocular somite that bore a pair of teardrop-shaped eyes that possessed facets.

[1] †Parioscorpio venator †Cascolus ravitis †Tanazios dokeron †Captopodus poschmanni †Acheronauta stimulapis †Thylacocephala †Occacaris oviformis Myriapoda †Ercaicunia multinodosa †Clypecaris pteroidea †Waptia fieldensis †Perspicaris dictynna †Canadaspis perfecta †Tokummia katalepsis †Branchiocaris pretiosa †Nereocaris exilis †Odaraia alata †Euthycarcinoidea †Fuxianhuia †Chengjiangocaris †Shankouia Argulus Ostracoda †Lepidocaris Triops Artemia Remipedia Cephalocarida Hexapoda Multicrustacea Three versions of a Bayesian phylogenetic analysis were cunducted because of the ambiguity of some of the features of A.

Additionally, Parioscorpio, which has remained enigmatic for over four years since its description in 2020,[5][6] was found to occupy a position between the Artiopoda and mandibulates, making it slightly related to A. stimulapis, and a basal taxon to the total-group mandibulata.

[7] Based on certain characteristics of this creature (including the specialization of its appendages, and its large size compared to many of the other taxa from the lagerstätte), this arthropod was found to be a scavenger as well as an opportunistic predator.

On the other hand, the large size of the appendages and their lack of setae would have probably limited the arthropod to the niche of ensnaring small prey, and not suspension feeding.

[1][3][8] Possibly hunting in the midwater was Thylacares brandonensis, a thylacocephalan arthropod, and in terms of geographical location, the closest relative to A.

[2] Hard shelled organisms like nautiloid cephalopods, brachiopods, clams, corals, crinoids, and sponges are rare in these sediments, and the ones that are found are not well preserved.