Ancient weevil pupal cases: Trace fossils from Australia’s Pleistocene

Steven Wade Veatch (USA) Curious pupal cases made by prehistoric weevils, together with worm burrows, are found as trace fossils in rock exposures of the Upper Bridgewater Formation along the western coastline of the Eyre Peninsula in South Australia (Flint, 1992; Flint and Rankin, 1991; Rankin and Flint, 1992). According to Parker and Flint (2005), the Upper Bridgewater Formation is a middle to late Pleistocene aeolian calcarenite (a wind-blown, consolidated gritty calcareous sandstone). These trace fossils are found inland from the coast for a distance of about 40km. Microscopic analysis of these ancient pupal cases shows they are made of gritty sand and gravel that were cemented by calcite over thousands of years. Fig. 1. Fossil pupal cases from the Bridgewater Formation resemble small elongated eggs. The cases have a hole where the fossil organism exited. These trace fossils are characterized by their strong cementation and a hollow interior. Scale in mm. (Specimen from the S W Veatch collection. Photo by S W Veatch.) These cases are thought to have contained the pupae Leptopius duponti, a medium-size, soil-inhabiting weevil or snout beetle of the family Curculionidae. The Curculionidae are one of the largest families of organisms, with at least 44,000 described species (Grimaldi and Engel, 2005). Adults of most species of this family have a characteristic elongate snout or nostrum. At the end of this well-developed snout is a small pair of mandibles for biting and chewing food. Taxonomic Classification:KingdomAnimaliaPhylumArthropodaClassInsectaOrderColeopteraSuborderPolyphagaSuperfamilyCurculionoideaFamilyCurculionidaeSubfamilyLeptopiinaeGenusLeptopiusSpeciesdupontiThe adult female Leptopius duponti not only relishes the foliage of … Read More