Pinguisoperla Chen, 2018

Chen, Zhi-Teng, 2018, Pinguisoperla, a new fossil genus of Perlidae (Insecta: Plecoptera) from mid-Cretaceous Burmese amber, Zootaxa 4425 (3), pp. 596-600 : 597

Genus Pinguisoperla Chen , gen. nov.

Type species. Pinguisoperla yangzhouensis gen. et sp. nov., by monotypy.

Diagnosis. The new genus is assigned to the family Perlidae by exhibiting typical family characters of the slender palpi, presence of tarsal euplantulae, short first tarsal segment, and the crossveins in basal half of forewing’s costal field. The new taxon can be separated from other extant and extinct genera of Perlidae by the combination of following characters: 1) body mostly dark; 2) head sub-quadrate, apical palpal segment slightly reduced; 3) pronotum trapezoidal with acute corners; tibia ventrally with two subapical spurs, apical tarsal segment with long apical bristles; 4) sternum 9 darkly sclerotized and distinctly extended backwards; paraprocts less developed; abdominal tip triangular; 5) first cercal segment strongly sclerotized, enlarged and elongated, curved outward and backward; subsequent cercal segments still thick but gradually tapering to apex; each cercal segment subapically fringed with long setae.

Etymology. The genus name contains the Latin Pinguis, which refers to the enlarged, plump basal segment of the cercus.

Remarks. In the family Perlidae , only males of the genus Caroperla Kohno, 1946 ( Perlidae : Acroneuriinae , Kiotinini ) have modified long basal cercal segment ( Kohno 1946, Sivec & Stark 2010). Caroperla includes three species and is only known from southeastern China, Japan, and Thailand ( DeWalt et al. 2018). The elongated and modified basal cercal segment, conspicuous abdominal hair brushes, recurved epiproct, and the reduced terminal palpal segment ( Sivec & Stark 2010) characterize the males of this perlid genus.

Based on the distinctly enlarged basal cercal segment, the new genus can be distinguished from all genera of Perlidae except for Caroperla . However, the new genus differs from Caroperla in several morphological characters: 1) although body size is similar, body color is dark in the new genus but generally pale brown to brown in Caroperla ; 2) basal cercal segment is unmodified and curved in the new genus, but modified and not curved in Caroperla ; 3) more than one cercal segments are enlarged in the new genus, but in Caroperla , only the first basal cercal segment is enlarged; 4) sternum 9 of the new genus is darkly sclerotized and distinctly extended backwards, but which is unmodified in Caroperla ; 5) paraprocts of the new genus is less developed, not distinctly elongated or recurved; 6) abdominal apex is triangular in the new genus but is rounded in Caroperla .

In view of the similarity with Caroperla , the new genus may be a stem group of the tribe Kiotinini Uchida, 1990 from subfamily Acroneuriinae Klapálek, 1914 . However, the tribe and subfamily assignment of the new genus is currently uncertain. Better preserved amber with clear abdominal sternal structures, paraprocts and epiprocts are expected to fulfill the accurate identifications.