Percussiopalpus, Jaloszynski & Hlavac, 2023

Jałoszyński, Paweł, Hlaváč, Peter & Anlaş, Sinan, 2023, Percussiopalpus gen. n. from Turkey, a free-living relative of cave-dwelling Thaumastocephalus, and revised placement of Thaumastocephalini (Coleoptera: Staphylinidae: Pselaphinae), Zootaxa 5277 (1), pp. 71-90 : 87

Placement of Percussiopalpus

The peculiar structure of the maxillary palpus, with palpomeres 1–3 identically shaped as those in Thaumastocephalus , 2 and 3 bearing bizarre filaments with apical spherical appendages, and a similarly shaped palpomere 4 suggest a close relationship between Percussiopalpus and Thaumastocephalus . Moreover, the antennae with an identical structure (especially the shape of the scape, pedicel, and antennomere 11), the prominent submental bulge, the shape of the head capsule in lateral view, ventral prothoracic and pterothoracic structures as well as the abdomen and legs show few differences between these two genera. Clearly, they are closely related and Percussiopalpus can be placed in Thaumastocephalini .

Percussiopalpus inusitatus is a free-living pselaphine, showing far-reaching adaptations to subterranean life, such as strongly reduced (but still present) eyes and reduced wings. However, its relatively stout body shape and weakly elongate appendages do not resemble the cavernicolous modifications found in Thaumastocephalus , which is strictly cavernicolous and have entirely lost cornea lenses. As is shared with many cave-dwelling beetles, Thaumastocephalus is slender and has greatly elongate appendages, and long sensory setae on the sides of the posterior region of the head. Interestingly, differences between the cavernicolous Thaumastocephalus and the free-living Percussiopalpus do not include only reductions in the former genus, but also additional pairs of metaventral and abdominal foveae that are lacking in Percussiopalpus but occur in Thaumastocephalus . This observation indicates that Thaumastocephalus is not simply a ‘reductive ecomorph’ that has evolved from within the Percussiopalpus lineage by adapting to life in caves and consequently losing some foveal and other external cuticular structures. For this reason, the new species discovered in Turkey is placed in a separate genus.