Beetle fossils found in Teruel show that they fed on dinosaur feathers

2023-04-18 00:25:17

Fossils of beetles trapped in amber found in the town of San Just (Teruel) have revealed that these insects fed on dinosaur feathers some 105 million years ago. The finding, published in the journal ‘Proceedings of the National Academy of Sciences’, shows a mutually beneficial or unilateral symbiotic relationship between the two species.

The main amber fragments studied contain molts of small beetle larvae closely surrounded by portions of down. The feathers belonged to an unknown theropod dinosaur that lived in the Early Cretaceous. The authors note that the feathers studied did not belong to modern birds as the group appeared about 30 million years later in the fossil record, during the Late Cretaceous.

Looking at modern ecosystems, we see how ticks infest livestock, frogs catch insects with acrobatic tongues, or some barnacles grow on the skin of whales. These are just some of the diverse and complex ecological relationships between vertebrates and arthropods, which have coexisted for more than 500 million years. The way these two groups have interacted over time is thought to have critically shaped their evolutionary history, leading to coevolution. However, evidence of these relationships is rarely found in the fossil record.

pests

Larval molts preserved in the amber were identified as related to modern skin beetles. These beetles, called dermestids, are often pests of stored goods or museum collections, feeding on organic materials that are difficult for other organisms to break down, such as natural fibers. However, they also play a key role in recycling organic matter in the natural environment, inhabiting bird or mammal nests, where feathers, hair or skin accumulate.

“In our samples, some of the portions of feathers and other remains, including minute fossil scats or coprolites, are in close contact with moults attributed to dermestids and show damage or signs of decomposition. This is compelling evidence that fossil beetles almost certainly fed on feathers and that they fell off their host,” explains Enrique Peñalver, from the Spanish Geological and Mining Institute (CN IGME-CSIC) and lead author of the study. .

Isolated moult of a feather-feeding beetle larva found in the Rábago/El Soplao amber outcrop, with detail of its powerful jaws. Molt length is less than two millimeters

CN IGME-CSIC

“The beetle larvae lived – feeding, defecating, molting – in accumulated feathers on or near a resin-producing tree, probably in a nest. A resin flow accidentally captured that association and preserved it for millions of years,” he says.

Three additional amber pieces, each containing an isolated beetle moult of a different stage of maturity but assigned to the same species, were also studied, “allowing for a better understanding of these tiny insects than is usually possible.” in paleontology,” says David Peris, from the Botanical Institute of Barcelona (CSIC-Barcelona City Council) and co-author of the study. The most impressive complete specimen was found in the Rábago/El Soplao amber deposit in Cantabria, about the same age as San Just.

What is not yet clear to the researchers is whether the feathered theropod host also benefited from the beetle larvae feeding on its feathers. For Ricardo Pérez-de la Fuente, from the Oxford University Museum of Natural History and co-lead author of the study, “it is most likely that the theropod did not suffer damage from the activity of the larvae, since our data show that they did not they fed on live plumage and lacked defensive structures that, among modern dermestids, can irritate the skin of nest hosts, and even kill them.”