Ancient beetles had a taste for dinosaur feathers

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

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

The most impressive and complete specimen was found in the amber deposit of Rábago/El Soplao in northern Spain. The amber contains shedded fragments–or molts–of small beetle larvae tightly surrounded by some pieces of downy feathers. The feathers once belonged to an unknown theropod dinosaur that was either avian or non-avian. Theropods that flew and those that were more Earth-bound 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 roughly 30 million years later during the Late Cretaceous. 

On Earth today, vertebrates and arthropods, like today’s ticks and lice, have a complex ecological relationship that has likely coexisted for more than 500 million years. The interactions between the two are believed to have shaped both vertebrate and arthropod evolutionary history, but evidence of arthropod-vertebrate relationships is still extremely rare in the fossil record, according to the team on 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 decay over time, sometimes bothering dried museum specimens tucked away in closets. However, dermestids do play a key role in recycling organic matter, commonly living in birds nests and in places on mammals where hair, skin, or feathers accumulate.

Animals photo
Molt remains of feather-feeding beetle larvae intimately associated with downy feather portions from an unidentified theropod dinosaur in Early Cretaceous amber of Spain. Insets show the head with powerful mandibles of one of the larval molts (top) and the pigmentation pattern of feather second order branches (bottom), with the main stem of one feather at the right of the amber fragment. The amber fragment is only 6 millimeters across. CREDIT: Geological and Mining Institute of Spain of the Spanish National Research Council (CN IGME-CSIC)

The authors found that some of the feather portions and other remains were in intimate contact with the molts of the dermestid beetles and have some evidence of damage or decay. 

“This is hard evidence that the fossil beetles almost certainly fed on the feathers and that these were detached from its host,” study co-author and Geological and Mining Institute of Spain of the Spanish National Research Council geologist Enrique Peñalver said in a statement. “The beetle larvae lived—feeding, defecating, molting—in accumulated feathers on or close to a resin-producing tree, probably in a nest setting. A flow of resin serendipitously 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 still unclear if the feathered theropod host benefited from the beetle larvae feeding on detached feathers and that it could have occurred in a nest setting, where the host was sitting on eggs.  

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

Three other pieces of amber that had isolated beetle molt that were in a different stage of the beetle life cycle were also studied, which allowed better understanding of the role that their feathery diet played.