Weird world of fossil worm cocoons

Stephen McLoughlin, Benjamin Bomfleur and Thomas Mörs (Sweden) Fossil hunters occasionally chance upon small glossy red to amber-coloured, roughly circular objects on bedding planes, when they crack open shales that were deposited in ancient swamps and rivers. These curious fossils range from about a millimetre in diameter up to the size of a fingernail (Fig. 1). When well preserved, they are egg shaped, but, in most cases, they have been flattened to a thin flake in the rock by the weight of the overlying strata. Some specimens appear to have a net-like coating on the surface but, otherwise, they offer few clues as to their identity. Indeed palaeontologists have reported these objects for over 150 years and have variously interpreted them as the eggs of insects, parts of lichens, the food-catching devices of ancient invertebrates, the membranous coatings of seeds, or the linings of clubmoss sporangia. Many early palaeobiologists simply labelled them as ‘red eggs’ and avoided assigning them to any particular biological group. Fig. 1. A minute, acid-resistant fossil belonging (Figs. 4 and 5). We have to a category traditionally called ‘red eggs’; from the Early Cretaceous of Western Australia. These strange objects occur mostly in sediments deposited in continental settings, and they have been reported widely in the residues left over after palaeobotanists have dissolved rock samples in the search for fossil spores, pollen and leaf cuticle. Two conclusions can be gleaned from these occurrences: The mysterious fossils likely belong to a land- or freshwater-based organism; andThese objects … Read More

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