New Carboniferous fossils of Spilapteridae enlighten postembryonic wing development in Palaeodictyoptera

Abstract

A new palaeodictyopterid nymph Bizarrea obscura gen.n. et sp.n. (Spilapteridae) and a new adult specimen of Homaloneura cf. dabasinskasi Carpenter are described from the Pennsylvanian (Moscovian) ironstone nodules of Mazon Creek (IL, U.S.A.). Both taxa share enlarged prothoracic lobes (interpreted by some as winglets), heteronomous meso-and metathoracic wing pads or wings, a slender abdomen with pointed laterotergites, and a unique division of the abdominal segments by two transverse sulci. An alternative hypothesis for the placement of Bizarrea within Homoiopteridae is considered on the basis of its large body size and relatively short wing pads. Based on the morphology of the new material, postembryonic development of wing pads in Palaeodictyoptera (Palaeodictyopterida) is reconsidered. Detailed investigation of the abdominal segments, including examination by scanning electron microscopy, reveals the presence of subcircular, sclerotized structures partially covered at the bases of the nymphal laterotergites I-VII, ?VIII. Based on their position and shape, these structures are interpreted as abdominal spiracles, and thus a terrestrial or semiaquatic habitat for these immatures is hypothesized. Moreover, our discovery of the same, supposedly homologous structures in the enigmatic Vogesonymphidae (Permoplectoptera), from the Middle Triassic of Grès à Voltzia in France, is evidence for the parallel coexistence of ancestrally terrestrial and derived aquatic lineages of Ephemerida (Ephemeropterida) in early Mesozoic ecosystems.This published work has been registered in ZooBank, http://zoobank.org/urn:lsid: zoobank.org:pub

Paleozoic Nymphal Wing Pads Support Dual Model of Insect Wing Origins

“…Palaeodictyoptera are central to the debate regarding the evolutionary development of wings as their nymphal pads are unique among insects, whereby they were articulated and capable of controlled movement [16,17]. While palaeodictyopteran nymphs historically were speculated to have been aquatic [18], current evidence rather supports common terrestrial environments for both nymphs and adults, particularly based on their feeding and respiratory structures [10,19].…”

“…These then became narrower in later developmental stages. However, the record is patchy, and evidence for gradually narrowing wing pads through successive ontogenetic stages cannot be demonstrated convincingly [19]. Data from palaeodictyopterans implicate the retention of the developing wings within exuvial sheaths until the latest instars, a pattern of development known from exopterygotes and holometabolan pupae.…”

New palaeodictyopterans from the Late Carboniferous of the UK (Insecta: Palaeodictyopterida)

“…2015; Prokop et al . 2016a). Furthermore, our fossil shares the diagnostic characters of the genus Homaloneura Brongniart, 1885, in the presence of a nearly straight or slightly concave anterior wing margin (partially preserved in distal part) and simple cross-veins in the area between RA and RP; but other diagnostic characters, e.g., the form of the convex ridge, are not preserved.…”

“…Other available nymphs of this order bear only a pair of markedly long and stout cerci, comparable to adults (Wootton 1972; Prokop et al . 2016a, 2017). The lifestyle of these nymphs was initially considered as aquatic by some authors (Brongniart 1885, 1893; Handlirsh 1906), but further re-evaluation of available taxa was unable to confirm aquatic adaptations and, thus, rather supported a terrestrial mode of life for these insects (Wootton 1972; Shear & Kukalová-Peck 1989).…”

Hidden surface microstructures on Carboniferous insect Brodioptera sinensis (Megasecoptera) enlighten functional morphology and sensorial perception

“…These techniques have been more widely used in studies of fossils from younger strata, such as Mesozoic and Cenozoic amber inclusions and exceptionally preserved compressed fossils11121314. The broader application to the study of scarce insect fossils was accelerated recently with use of ESEM, which makes it possible to study uncoated specimens using this non-invasive technique15.…”