Mussel of the

Page last updated
5 December 2019

Mussel of the Month

The December 2019 Mussel of the Month is Parvasolenaia rivularis. Parvasolenaia is a genus of three species found in East Asia.

USNM 472449. Ning-kouo-fou [Ning-kuo, Anhui], China.

Parvasolenaia is new genus of Recent freshwater mussels described in 2019. Back in June 2018, we commented on the burst of new genera that had been described in 2017 and 2018. Including the genera from 2019 in the tally, we have had 10 newly described taxa in the last three years: Cambarunio, Indochinella, Leaunio, Leoparreysia, Paetulunio, Parvasolenaia, Parvaspina, Sagittunio, Trapezidens, and Yaukthwa. That doesn’t include all the genera that have been resurrected from synonymy during the same period —Bineurus, Cumberlandia, Eurynia, Indonaia, Monodontina, Obovalis, Pletholophus, Pseudodontoideus, Pseudunio, Sinohyriopsis, etc. To put those 10 new genera over the last 3 years into context, only nine genera were described in the 18 years from 1988 to 2016, and only 5 of those are currently treated as valid. The other four were Soviet-style Comparatory Genera.

The surge in generic splitting is almost completely the result of two recent trends in freshwater mussel taxonomy. The first factor is the burst of new data and molecular phylogenetic results for North American and (especially) East Asian freshwater mussels (e.g., Lopes-Lima et al., 2017; Bolotov et al., 2017; Konopleva et al., 2019). The other factor is a change in attitude among molecular systematists to give names to clades recovered in molecular phylogenetic studies. Over the last decade, the pendulum has swung from merely pointing out when genera were not found to be monophyletic to naming genera and species for lineages that conflict with existing taxonomy.

The three species of Parvasolenaia were, until this year, classified in the genus Solenaia. However, Huang et al. (2019) recovered two of those species in a clade with Ptychorhynchus pfisteri — although we can’t put much confidence in clades with Bayesian posterior probabilities of 0.50 and 0.80.

A piece of Fig. 2 from Huang et al. (2019).

There is nothing sacrosanct about the traditional freshwater mussel genera. Taxa should be split up or lumped together when new data become available. Hopefully, Parvasolenaia will face some more rigorous phylogenetic testing in the near future.

* Although there is still a month left in the year.


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily UNIONOIDEA Rafinesque, 1820
Family UNIONIDAE s.s
Subfamily GONIDEINAE Ortmann, 1916
Tribe GONIDEINI s.s.

Genus Parvasolenaia Huang & Wu in Huang et al., 2019

Species Parvasolenaia rivularis (Heude, 1877)

To find out more about Parvasolenaia and the other new mussel genera, check out:
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