Cretotaenia Ponomarenko, 1977

Fikáček, Martin, Prokin, Alexander, Angus, Robert B., Pono, Alexander, Marenko, Yue, Yanli, Ren, Dong & Prokop, Jakub, 2012, Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga), Acta Entomologica Musei Nationalis Pragae 52 (1), pp. 89-127 : 99

† Cretotaenia Ponomarenko, 1977

Cretotaenia Ponomarenko, 1977a: 92 .

Type species. Cretotaenia pallida Ponomarenko, 1977 (by original designation).

Time range. Early Cretaceous, Berriasian to Hauterivian, ca. 146–135 mya.

Diagnosis. Larva: Head hyperprognathous; nasale simply triangular, epistomal lobes large, slightly overlapping nasale, bearing series of setae; mandible with two retinacular teeth; labium without ligula; each parietale with 6 stemmata situated in area of darker cuticle; all thoracic segments with large dorsal tergite; abdominal segments 1–8 each with a pair of dorsal sclerites and a pair of minute sclerites on each side above spiracle; tracheal system holopneustic, spiracular atrium absent; urogomphi large, 3-segmented.

Note. The genus was originally described as Adephaga incertae sedis by PONOMARENKO (1977a), but CROWSON (1981) later noted that it may rather be related to Helophorus . A detailed comparison of all preserved characters including those not mentioned in the original description confirmed this opinion: Cretotaenia precisely matches modern Helophorus larvae in nearly all preserved characters except the labium which does not protract as much anteriad, different arrangement of abdominal sclerites (two small sclerites are present laterally of dorsal large sclerite and dorsally of the spiracle in Cretotaenia , whereas Helophorus has a single large sclerite in this position) and the dorsally situated occipital foramen (situated posteriorly in Helophorus ). The phylogenetic analysis by FIKÁČEK et al. (2012) also confirms that Cretotaenia is related to the Helophoridae , and the genus is therefore included into the helophorid lineage in the present work. ZHERIKHIN et al. (1998) hypothesized that Cretotaenia pallida is likely a larval form of Laetopsia baissensis , which cannot be confirmed or rejected by our analyses even though both genera seem to represent basal extinct clades of the helophorid lineage.

At first view, the number of stemmata seems to be five on each parietale in the specimens examined. However, the arrangement of stemmata in the fossils precisely fits that in modern Helophorus (see FIKÁČEK et al. 2012, Fig. 1H ) in which five stemmata are situated dorsally in the area of darkened cuticle (and hence preserved in the fossils), whereas the largest stemma is rather isolated from the others, situated more ventrally outside of the area of darkened cuticle (and is therefore not preserved in the fossil). For that reason we consider Cretotaenia having 6 stemmata on each parietale.

Figures

Figs. 1–4. Hydrophilopsia longitarsalis Ponomarenko, 1987 (holotype). 1 – piece, general view; 2 – counterpiece, general view; 3 – detail of antenna; 4 – detail of the aedeagus. Scale bar: 2 mm (corresponds to Figs. 1–2). Abbreviations: acl – antennal club; aed – aedeagus; ant – antenna; cup – cupule; ins – intermediate antennomeres; ped – pedicel; sc – scapus.