Mussel of the

Page last updated
4 May 2022

Mussel of the Month

The May 2022 Mussel of the Month is Trapezidens exolescens. Trapezidens is a genus of five species endemic to Myanmar.

USNM 85473. Tavoy [Dawai], Burmah [Myanmar]. (lectotype)

We tried a decade ago to enshrine this species as Mussel of the Month. Back then, it was a widespread species called Trapezoideus exolescens. In the intervening 10 years, T. exolescens sensu lato has been shattered into multiple species in 5 genera: Trapezoideus, Yaukthwa, Indonaia, Lens, and Trapezidens. The last of these is the current resting place of Trapezidens exolescens sensu stricto. The other species of Trapezidens have been assembled from pieces of Lamellidens (Bolotov et al., 2017; Konopleva et al. 2020).

The details of the history of the disintegration of the old Trapezoideus has been document under the genera linked above. We made sure to use the type specimen of the valid senior synonym in the picture this time so that so matter what splitting happens in the future, T. exolescens as Mussel of the Month will survive the revision. Or maybe the pendulum will swing the other way, and the next mania will be lumping…


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily UNIONOIDEA Rafinesque, 1820
Family UNIONIDAE s.s.
Subfamily PARREYSIINAE Henderson, 1935
Tribe LAMELLIDENTINI Modell, 1942

Genus Trapezidens Bolotov, Vikhrev & Konopleva in Bolotov et al., 2017

Species Trapezidens exolescens (Gould, 1843)

To find out more about the revision of Trapezidens and other southern Asian freshwater mussels, check out:

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