The family-group level classification of Thaiconcha callifera has changed in the last couple months. This summer, the relatively new genus of Thaiconcha was classified in the Subtribe PILSBRYOCONCHINA (Tribe PSEUDODONTINI, Subfamily GONIDEINAE), but now it is classified in the Subtribe PSEUDODONTINA. However, Thaiconcha didn’t get transferred to a new subtribe because new information changed the best-estimate of its phylogenetic relationships. Rather, the classification nomenclature was shuffled because of the shifting identity of Pseudodon inoscularis.
These Mussel of the Month posts have been following the story of the shifting sands of pseudodontine classification since Pseudodon in July 2018. In the past, the taxa of the current PSEUDODONTINI were classified in only two genera: Pseudodon and Pilsbryoconcha (Graf & Cummings, 2007). The type species of Pseudodon is P. inoscularis. Where that species goes, so goes the name Pseudodon.
A few years ago, it was discovered that the old “Pseudodon” wasn’t monophyletic. Most species of the old “Pseudodon” shared a more recent common ancestor with Pilsbryoconcha instead of other species of “Pseudodon.” These non-pseudodon were split into new genera based on the existence of available genus names like Monodontina and Bineurus. As phylogenetic sampling increased in subsequent studies, new genera were introduced to name clades as necessary: Nyeinchanconcha, Sundadontina, and Thaiconcha (this month’s mussel). These genera were divided among two subtribes: PSEUDODONTINA for Pseudodon and PILSBRYOCONCHINA for all the rest.
At first, Pseudodon inoscularis (again, the type of the genus) was mistakenly placed in Monodontina because specimens identified as “P. inoscularis” grouped with Monodontina vondembuschiana (PILSBRYOCONCHINA) rather than Pseudodon (PSEUDODONTINA). Of course, it was realized that that situation was impossible: if anything was going to be called Pseudodon then it had to be Pseudodon inoscularis. Fortunately, this realization coincided with the discovery that the specimens identified as “Monodontina inoscularis” actually represented species of Sundadontina. The species that had been recently named Pseudodon avae was reconsidered as representing the real Pseudodon inoscularis.
But then Bolotov et al. (2023) found that the new P. inoscularis wasn’t the real P. inoscularis. After sampling some new specimens that better fit the type locality, it turned out the new real Pseudodon inoscularis was recovered in a clade with the species of Monodontina. So, “Pseudodon” isn’t Pseudodon. Monodontina needs to be called Pseudodon. Rather than leave the old “Pseudodon” without a name, the name Indopseudodon was created.
But it doesn’t end there! Just as the name Pseudodon follows Pseudodon inoscularis, so does the name of the subtribe. The tribe that was the PILSBRYOCONCHINA is now called PSEUDODONTINA becuase it contains Pseudodon, and the old PSEUDODONTINA is now the INDOPSEUDODONTINA (with only one genus, Indopseudodon). Thaiconcha* was among the genera that got reclassified from PILSBRYOCONCHINA to PSEUDODONTINA because of the principle of priority.
The table below depicts the changing classifications of the specimens used in phylogenetic analyses of the Pseudodontini (click to view a PDF). The shifting identity of “inoscularis” is highlighted. There is also an Excel spreadsheet that provides a more detailed summary listing Genbank accession numbers of the COI sequences of those specimens.
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* Remember Thaiconcha? This is a Mussel of the Month post about Thaiconcha. |
