In a study published in the journal ‘Current Biology’, vertebrate paleontologists from the University of Uppsala and entomologists from the National Sun Yat-sen University (Taiwan), the Friedrich-Schiller-Universität Jena (Germany) and the University of Guadalajara ( México) describes a small beetle Triamyxa coprolithica , the first insect described from fossil feces , probably from a Silesaurus opolensis dinosaur, which ingested it in large quantities.
The study used synchrotron microtomography to reconstruct the beetles in 3D while they were still trapped in fossilized fecal matter, dating back 230 million years . The good state of conservation of these fossils allowed a detailed description of the new genus of beetles and a comparison with other more modern ones.
Triamyxa coprolithica represents a hitherto unknown extinct lineage of the suborder Myxophaga, whose modern representatives are small and live on algae in humid environments. For its part, Silesaurus opolensis was a relatively small dinosaur ancestor, with an estimated body weight of 15 kilograms. It also had a beak at the tip of its jaws that could have been used for rooting in leaf litter and perhaps pecking insects from the ground, somewhat like modern birds .
The coprolite contains nearly complete fossils, as well as isolated heads, pronotes, elytra, and other sclerites, all embedded in the phosphate-rich coprolite matrix.
The conservation of beetles in coprolite is similar to that of amber specimens, which normally produce the best preserved insect fossils. However, amber was mainly formed during a relatively recent geological period .
The coprolite fragment was scanned at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. The coprolite was mounted in a tube that was scanned in a 4mm vertical series in half acquisition mode, that is, the center of rotation was set to the field of view side of the camera, resulting in a double increased field of view. The distance between the sample and the chamber (propagation distance) was 2800 mm.
Other types of 3D preservation of insects include specimens preserved as mineralized replicas (eg, silicified, phosphated, or pyritized), as voids, in flint, or within vertebrate coprolites (fossil droppings). In recent years, it has become apparent that coprolites can act as microenvironments in which organic inclusions can be better conserved than in host rock. This study thus shows that coprolites may be valuable for studying the early evolution of insects and, at the same time, the diet of extinct vertebrates.