Lobetelson mclaughlinae n. gen., n. sp. from the well-known Mazon Creek faunas of the Pennsylvanian (Carboniferous) of northeastern Illinois, USA, shares features in common with Belotelson magister (Packard, 1886), such as eight pairs of uniramous reptant thoracopods and a generalized caridoid body plan. The similarities are such that specimens of both species originally were mixed in museum and private collections of the fauna. However, L. mclaughlinae n. gen., n. sp. is distinguished by its more gracile thoracopods, extremely long rostrum (at least equal in length to the carapace), and a wide tail fan formed by broad lobate uropodal rami. In contrast, B. magister is now understood to possess more robust thoracopods, with a relatively short rostrum, and very styliform uropodal rami.
Crustacea, Decapoda, Belotelsonidea, Carboniferous, Mazon Creek fauna, Belotelson, Lobetelson n. gen., new genus, new species.