Ancient beetles had a taste for dinosaur feathers

A recent discovery sounds like the start of another Jurassic Park restart, but this time the beetles take center stage instead of the mosquitoes. These new fossils preserved in amber show evidence that beetles fed on dinosaurs around 105 million years ago, according to a study published April 17 in the journal Proceedings of the National Academy of Sciences (PNA).

[Related: Entombed in amber, this tiny crab hails from the age of dinosaurs.]

The most impressive and complete specimen was found in the Rábago/El Soplao amber deposit in northern Spain. The amber contains shed fragments, or smolts, of small beetle larvae closely surrounded by some pieces of soft feathers. The feathers once belonged to an unknown theropod dinosaur that was either avian or non-avian. Flying and Earth-bound theropods typically shared indistinguishable feather types during the Early Cretaceous period. According to the team, the feathers do not belong to modern birds, since that group of animals appeared approximately 30 million years later, during the Late Cretaceous.

On Earth today, vertebrates and arthropods, like ticks and lice today, have a complex ecological relationship that has probably coexisted for more than 500 million years. Interactions between the two are thought to have shaped the evolutionary history of both vertebrates and arthropods, but evidence for arthropod-vertebrate relationships remains extremely rare in the fossil record, according to the team behind this study.

They found that the larval molts preserved in this study were related to modern skin beetles, or dermestids. These beetles feed on organic materials that decompose over time, sometimes disturbing dried museum specimens hidden in cabinets. However, dermestids play a key role in recycling organic matter, commonly living in bird nests and in mammalian places where hair, fur, or feathers accumulate.

Molt remains of feather-feeding beetle larvae intimately associated with portions of soft feathers of an unidentified theropod dinosaur in Early Cretaceous amber from Spain. Insets show the head with powerful jaws of one of the molting larvae (top) and the pigmentation pattern of the second-order feather branches (bottom), with the main stem of a feather to the right of the amber fragment. The amber fragment is only 6 millimeters wide. CREDIT: Spanish Geological and Mining Institute of the Higher Council for Scientific Research (CN IGME-CSIC)

The authors found that some of the portions of feathers and other remains were in intimate contact with dermestid beetle molts and have some evidence of damage or decomposition.

“This is compelling evidence that fossil beetles almost certainly fed on feathers and that they shed their host,” the study co-author and geologist at the Spanish Geological and Mining Institute of the Superior Council said in a statement. of Scientific Investigations of Spain, Enrique Peñalver. “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.”

[Related: These beetles sniff out fungus-infected trees to find their next target.]

It is not yet clear whether the feathered theropod host benefited from the beetle larvae feeding on the shed feathers and whether it could have occurred in a nest setting, where the host was sitting on the eggs.

“However, the theropod was most likely not harmed by the larvae’s activity, as our data shows that the larvae did not feed on live plumage and lacked defensive structures that, among modern dermestids, can irritate the skin. of the nest hosts, even killing them”, co-author. and paleobiologist from the Oxford University Museum of Natural History, Ricardo Pérez-de la Fuente, said in a statement.

Three other amber pieces that had an isolated beetle moult that were at a different stage of the beetle’s life cycle were also studied, allowing for a better understanding of the role their feathery diet played.

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