Cocoon-like trace fossils from the lacustrine-palustrine Bembridge Limestone Formation (Late Eocene), Southern England

摘要: In exposures of the Late Eocene Bembridge Limestone Formation at west end Isle Wight, calcareous ovoid-cylindrical trace fossils, ranging in length from 1 to over 47 mm long, but commonly 30 long and 15 diameter, occur sparingly distributed freshwater pedogenically-modified limestones yielding calcitic casts snails land snails. Although specimens fossils having both ends entire are usually preserved as calcite internal casts, occurrence rare hollow lined by drusy is evidence that they were chambers within sediment. The majority ruptured sub-terminally one before fossilization, probably escaping organism. Such partly entirely filled intraclastic lime mudstone. Rare attached a short burrow-fill composed similar mudstone about same diameter chamber. Most have surficial film chalky micrite or microspar, with without cemented micritic skin. some skin protects surface ornament lobate composite tobate-linear ridges 0.5 wide up 5 long. When weathered-out relief, these impart wrinkle-like fibrous texture, which can distinct helical trend. Whereas hitherto been interpreted tropical snails' eggs, differ latter shape, mode rupture occurrence. also lack an egg-shell microstructure cannot be reptile eggs. analogous foreign simple hymenopteran brood chambers, fossil Recent examples terminal cap seal, lacking specimens. Instead, may made other kinds insect for pupation, unknown organism aestivation hibernation.