Mussel of the Month

This is the era of freshwater mussel revision. Old genera like Trapezoideus, Solenaia, and Pseudodon and being split and reclassified to give us new genera like Trapezidens, Sinosolenaia, and Sundadontina. This month our subject is Parreysia. (Each of those genera is hot-linked to a discussion about their recent taxonomic machinations.)

We already thought we covered Parreysia corrugata as Mussel of the Month in September of 2005. Back then, Parreysia was thought to be composed of almost 40 species in two subgenera, P. (Parreysia) and P. (Radiatula) (Graf & Cummings, 2007). Sixteen years later, when we updated the checklist (Graf & Cummings, 2021 and references cited therein), Parreysia sensu lato has been split into 4 genera (Parreysia sensu stricto, Leoparreysia, Radiatula, and Indonaia), and two species have been shifted to Scabies. The most recent work by Bolotov et al. (2022a-c) provides a good summary of the current state of those taxa. As of this typing, only 6 Recent species are currently classified under Parreysia. We have gone from a “garbage-pail,” catch-all genus to a tidy little package that is the sole genus in its own tribe (Parreysiini).

Furthermore, the specimen we thought was P. corrugata (the type of Unio tennentii Hanley & Theobald, 1876) is now classified by Bolotov et al. (2022a) as Parreysia plagiostoma. To get P. corrugata back on the map, this month we are depicting a type specimen of Unio favidens Benson, 1862. Parreysia favidens itself had been recognized as a valid species for more than 150 years, but Bolotov et al. (2022a) sunk that name (with its many subspecies and synonyms) and a half dozen other old species circumscriptions under the Parreysia corrugata we have today.

We look forward to catching up with you in another decade or so about the classification of Parryesia!