Mussel of the

Page last updated
2 March 2023

Mussel of the Month

The March 2023 Mussel of the Month is Monocondylaea minuana. Monocondylaea is a genus of 8 recent species from South America.

Monocondylaea (Aplodon)
MNHN.Uruguay (type)

Monocondylaea paraguayana was Mussel of the Month back in September 2008, when we took the opportunity to discuss the changing diversity estimates of Neotropical freshwater mussels since the work of Haas (1969). There was a glimmer of taxonomic lumping by Simone (2006), and then a rebound requiring re-splitting from Pereira et al. (2014). Back in 2008, the thinking was that there were 3 species in the genus Monocondylaea. Today, we have eight (Graf & Cummings, 2021).

Despite the apparent taxonomic interest in Monocondylaea and the other genera of the Mycetopodidae, there hasn’t been much progress toward resting the classification of the family on a firm phylogenetic footing. The Monocondylaeinae is one of four subfamilies of the Mycetopodidae — the 2nd most species-rich with 18, and with 6 genera, it exceeds the genus-richness of the other 3 subfamilies combined. But, as is summarized on the cladomics page for the subfamily, no phylogenetic analysis has included more than two species of monocondylaeines* and never two in the same genus. Only weak tests the monophyly of the subfamily are available (and even then, it usually isn't recovered as monophyletic), and there has been no test of the monophyly of Monocondylaea, the most species-rich genus.

The state of cladistic knowledge isn’t much better for the Mycetopodidae itself. Although the family has more than 50 species in 11 genera, no phylogenetic analysis has included more than five species or represented more than two of the subfamilies! Are mycetopodids actually even a thing?**

We feel pretty confident that at least Monocondylaea minuana is a thing, and it is our current Mussel of the Month.

* As of this writing, the word “monocondylaeines” is unknown to
** It seems like that should be answered before anyone wants the revise taxonomy to claim that Mulleria is a mycetopodid and therefore mycetopodids are "mulleriids."


Phylum Mollusca
Class Bivalvia
Subclass Palaeoheterodonta
Order Unionoida

Superfamily ETHERIOIDEA Deshayes, 1830
Family MYCETOPODIDAE Gray, 1840
Subfamily MONOCONDYLAEINAE Modell, 1942

Genus Moncondylaea d'Orbigny, 1835

Species Monocondylaea minuana (d'Orbigny, 1835)

To find out more about the classification of Monocondylaea and the South American freshwater mussels, check out:
  • Graf, D.L. & K.S. Cummings. 2021. A 'big data' approach to global freshwater mussel diversity (Bivalvia: Unionoida), with an updated checklist of genera and species. Journal of Molluscan Studies 87(1). eyaa034 (36 pp.).
  • Haas, F. 1969. Superfamilia Unionacea. Das Tierreich 88: 1-663.
  • Pereira, D., M.C.D. Mansur, L.D.S. Duarte, A.S. de Oliveira, D.M. Pimpão et al. 2014. Bivalve distribution in hydrographic regions in South America: historical overview and conservation. Hydrobiologia 735: 15-44.
  • Simone, L.R.L. 2006. Land and Freshwater Molluscs of Brazil: An Illustrated Inventory of the Brazilian Malacofauna, Including Neighboring Regions of South America, Respect to the Terrestrial and Freshwater Ecosystems. EGB, Fapesp., Sao Paulo. 390 pp.

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