Schizophoromorpha Ponomarenko, 2002

Shcherbakov, D. E. & Ponomarenko, A. G., 2023, The first known fossil hygropetric beetle larva related to Myxophaga (Coleoptera) from the Permian of European Russia, Russian Entomological Journal 32 (3), pp. 261-270 : 262-265

Infraorder Schizophoromorpha Ponomarenko, 2002

Family? Phoroschizidae Bouchard et Bousquet, 2020 (= Schizophoridae Ponomarenko, 1968 )

Circularva Shcherbakov et Ponomarenko , gen.n.

TYPE SPECIES. Circularva reichardti Shcherbakov et Ponomarenko , sp.n .

DIAGNOSIS. Small, flattened larva resembling sucking disc. Body contour almost perfectly circular, except for head angularly projecting anteriorly. Thoracic and abdominal tergites with lateral lobes (paranota, or paratergites, or dorsal laterotergites) feebly separated by depressed lines from disc; paranota widest at mesonotum, narrower and less distinctly separated towards posterior; disc widest at abdominal segment III. Head large, transverse, nearly diamond-shaped in dorsal view, longer than pronotum, jutting into body, so that pronotum U-shaped and mesonotum deeply arched. Stemmata on each side six, in sublateral group, facing dorsally. Thorax ~1.5 times shorter than abdomen. Meso- and metanotum and at least anterior abdominal tergites with posterior row of widely separated setigerous tubercles. Abdominal paranota of successive segments contiguous, not festoon-like. Posterolateral angles of abdominal tergites acute, in posterior tergites (especially IX) produced tooth-like. Long, filiform spiracular gills finely annulate proximally, originating sublaterally, directed caudally, ap-

Figs 1–4. Circularva reichardti gen. et sp.n., habitus: 1–2 — negative, 3–4 — positive impression. SEM: 1–3 — BSE, 4 — LVSTD. Scale bar 1 mm.

Рис. 1–4. Circularva reichardti gen. et sp.n., общий вид: 1–2 — обратный, 3–4 — прЯмой отпечаток. СЭМ: 1–3 — BSE, 4 — LVSTD. Длина масштабной линейки 1 мм.

264 First fossil hygropetric beetle larva from the Permian of Russia parently developed on all tergites from I to IX. Tergite X large, almost semicircular, completely visible from above.

COMPOSITION. Type species.

COMPARISON. The presence of long spiracular gills on the abdomen indicates that the fossil belongs to either Torridincolidae or their ancestors, Phoroschizidae (= Schizophoridae ; see Discussion). The new genus differs from presumed larvae of Schizophoromorpha in the disc-shaped body, from known torridincolid larvae in the large abdominal segment X, from Torridincolinae in the shorter thorax, and from Deleveinae in contiguous abdominal paranota.

The long spiracular gills and the disc-shaped body of the new genus, flattened like in torridincolids, suggest life in running water. The degree of larval body flattening is variable in Torridincolidae , being greatest in the last instar larvae of advanced genera [ Reichardt, 1973; Ge et al., 2010], so the new fossil is presumably a mature larva.

ETYMOLOGY. Latin circus (ring) and larva (ghost, mask); gender feminine.