Postaphanostoma, DORJES, 1968 TO THE

Atherton, Sarah & Jondelius, Ulf, 2022, Phylogenetic assessment and systematic revision of the acoel family Isodiametridae, Zoological Journal of the Linnean Society 194, pp. 736-760 : 745

REASSIGNMENT OF POSTAPHANOSTOMA DÖRJES, 1968 TO THE FAMILY MECYNOSTOMIDAE DÖRJES, 1968

Both species of Postaphanostoma included in our analyses, P. glandulosum Dörjes 1968 and P. nilssoni Kånneby & Jondelius, 2013 , grouped together as the highly supported sister-group of Mecynostomidae , separate from Isodiametridae . As with Faerlea , once again there has not been any detailed investigation into the body and reproductive musculature or sperm ultrastructure for any species of Postaphanostoma , and so it cannot be definitively stated if the animals of this group possess any of the morphological characteristics of Isodiametridae , Mecynostomidae or any other group. Indeed, the position of P. glandulosum and P. nilssoni as sister of Mecynostomidae in our phylogenetic analyses suggests such detailed morphological investigations should be of high priority for future studies. Unfortunately, no gene sequences of the type species of Postaphanostoma , P. atriomagnum Dörjes, 1968 , currently exist. However, there are also no significant morphological characters that distinguish P. glandulosum and P. nilssoni from the remainder of the genus with which to justify a separation, and so, rather than create confusion by forming a new genus in which to transfer the two species, we choose to reassign Postaphanostoma in its entirety to Mecynostomidae until such time as sequences or more detailed morphology can be assessed for the type.