Abstract
Simple SummaryA new false click-beetle (Eucnemidae) belonging to subfamily Anischiinae, formerly not known as fossils, extends the age of this small extant group 125 million years back. The structural specializations of the false click-beetle larvae are discussed. On the basis of this new piece of paleontological evidence, it is shown that these insects have changed their host preference from gymnosperms to angiosperms at least twice. It also indicates that the beetle larvae can switch their favored development substrate by adapting in different ways, either with or without morphological specialization.Rheanischia new genus, type species Rheanischia brevicornis new species (Eucnemidae, Anischiinae) is described from the Lower Cretaceous of Liaoning, China. The presence of this species in early Cretaceous deposits provides new insight into the evolution of basal lignicolous Eucnemidae clades. Both Anischiinae and Palaeoxeninae species diversified in a world dominated by gymnosperms, before the main radiation of angiosperms. More than 95% of modern eucnemid larvae have a Palaeoxenus-type highly modified head structure, but contrary to the Palaeoxenus larva, they develop in angiosperm wood. Anischiinae utilize angiosperms as well, but their head capsule shows no such modifications. These facts prove that highly specialized morphological features do not offer definite proof of similar way of life in the distant past, nor should non-modified structures be taken as proof for another kind of substrate choice. Eucnemidae have invaded angiosperms with two quite different morphological adaptations. This fact may have implications for the evolution of all clicking elateroids.
Highlights
The superfamily Elateroidea includes four families with species possessing a defensive “clicking” mechanism based on an advanced promesothoracic locking structure [1]
The first Mesozoic eucnemids were described from lower Cretaceous China [6] and upper Jurassic Australia [7]
Anischiinae other diagnostic characters: flagellomeres flattened, stout, bulbous in profile, antennae apically abruptly expanded to form weak, three-segmented club (Figure 3B); labrum attached underneath frontoclypeal region, faintly visible (Figures 1A and 3B)
Summary
The superfamily Elateroidea includes four families with species possessing a defensive “clicking” mechanism based on an advanced promesothoracic locking structure [1]. The second largest family, false click-beetles (Eucnemidae), includes more than 1700 extant species [4]. Their fossil history remained quite obscure until Muona [5] reviewed the early records and reported 18 genera with 34 species from the Baltic amber. Most of these were described from Eocene samples, but five genera (Microrhagus Dejean, Sieglindea Muona, Erdaia Muona, Euyptychus LeConte, Fornax Laporte) were reported both from the Miocene and Eocene. Our knowledge of the Mesozoic fauna was greatly expanded when Muona et al [10] showed that the previously described Chinese elaterid fossils included one Jurassic and six early Cretaceous eucnemids, all of them belonging to extant monotypic subfamilies (Pseudomeninae Muona, Schizophilinae Muona, and Palaeoxeninae Muona)
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