Rare evidence of ‘arthropod-vertebrate relationships’ found preserved in ancient amber

“The beetle larvae lived − feeding, defecating, moulting − 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,” said Dr Enrique Peñalver, from the Geological and Mining Institute of Spain of the Spanish National Research Council (CN IGME-CSIC) and lead author of the study, in a statement. 

Dermestids, or modern skin beetles, were identified as larval molts preserved in amber. The authors claim that the feathers belong to an “unknown theropod dinosaur,” and not modern birds that existed back then, as documented in some of the fossil records of that time. 

The dinosaur could either be avian or non-avian, as both groups of theropods existed during the Early Cretaceous period. These dinosaur groups are likely to have shared feather types that were often indistinguishable.

Because the fossil record is scarce, this rare discovery provides valuable insights into arthropod-vertebrate relationships. For more than 500 million years, these two groups are said to have coexisted and interacted.

The official statement cites current ecosystem examples of vertebrate and arthropod relationships, such as how ticks infest cattle, and frogs eat insects with acrobatic tongues.

These few examples illustrate the diverse and complex ecological relationships that have existed for millions of years between vertebrates and arthropods. As a result, shaping the evolution of these two groups throughout history. 

Dr Ricardo Pérez-de la Fuente, from Oxford University Museum of Natural History and co-lead author of the study, concluded by saying: “It is unclear whether the feathered theropod host also benefited from the beetle larvae feeding on its detached feathers in this plausible nest setting. 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.” 

The details have been published in the journal Proceedings of the National Academy of Sciences.