Description of Armaparvus languidus n. gen. n. sp. Confirms Ultrastructural Unity of Cutosea (Amoebozoa, Evosea).

The American Type Culture Collection (ATCC) PRA-29 isolate has a publicly available transcriptome, which has led to its inclusion in recent phylogenomic analyses. The ATCC PRA-29 isolate was originally identified and deposited as "Pessonella sp." This taxon branches robustly within the recently discovered clade Cutosea, very distantly related to the clade in which the genus Pessonella is believed to branch based on morphological data. Using detailed light and electron microscopy, we studied the morphology and ultrastructure of ATCC PRA-29 as well as other cutosean amoebae to better elucidate the morphological affinity of ATCC PRA-29 to other amoebozoans. Here, we show that ATCC PRA-29 was misidentified by the original depositor as Pessonella and name it Armaparvus languidus n. gen. n. sp. We show that a cell coat of microscales separated from the cell membrane is a unique trait found in all known cutosean amoebae. As Cutosea represents a clade at the deepest bifurcation in the amoebozoan group Evosea and because this clade is currently taxon-poor, but likely represents a major understudied group it will be important to isolate and describe more cutosean amoebae in the future.