Even 100 million years ago, dinosaurs had to contend with blood-sucking parasites, according to a new study based on the oldest-known fossil specimen that preserved both parasite and host.
A piece of Burmese amber dating back to 99 million years ago has been found to contain a hard tick clinging to a feather, the first fossil evidence that ticks fed on dinosaurs. And how did paleontologists make the jump from feather to dinosaur?
“The fossil record tells us that feathers like the one we have studied were already present on a wide range of theropod dinosaurs,” said Ricardo Pérez-de la Fuente, research fellow at Oxford University Museum of Natural History and an author on the study, which appears in Nature Communications today. “Although we can’t be sure what kind of dinosaur the tick was feeding on, the mid-Cretaceous age of the Burmese amber confirms that the feather certainly did not belong to a modern bird, as these appeared much later in theropod evolution according to current fossil and molecular evidence.”
Researchers also found indirect evidence that ticks fed on feathered dinosaurs based on several specimens of a newly-identified species of extinct tick named Deinocroton draculi, or “Dracula’s terrible tick,” also preserved in amber and dating to the Cretaceous (145-66 million years ago).
One specimen of the ancient arachnid was frozen in time after it fed, engorged with so much blood from its host that it had grown to eight times its normal size. But since the enlarged tick had not been fully immersed in the amber resin, it was not possible for researchers to name its last meal.
A second amber specimen containing two ticks encased side-by-side provided additional clues. On these ticks, researchers identified setae (tiny hairs) from the larvae of dermestids, so-called skin beetles that today typically eat skin, hair, feathers, and other traces of organic materials left behind in nests. No mammal hairs have yet been found in Cretaceous amber, suggesting that the skin beetles, and the tick, were active in a nest belonging to feathered dinosaurs.
“The simultaneous entrapment of two external parasites—the ticks—is extraordinary, and can be best explained if they had a nest-inhabiting ecology as some modern ticks do, living in the host’s nest or in their own nest nearby,” said David Grimaldi, curator in the Museum’s Division of Invertebrate Zoology and author on the study.
The study, led by Enrique Peñalver from the Spanish Geological Survey (IGME), draws on these findings to shed new light on the nearly 100-million-year parasitic relationship between ticks and their dinosaur hosts. “Ticks are infamous blood-sucking, parasitic organisms, having a tremendous impact on the health of humans, livestock, pets, and even wildlife, but until now clear evidence of their role in deep time has been lacking,” said Peñalver of the study.
But don’t get your hopes up for a real-life Jurassic Park scenario. Viable DNA can’t be extracted from ancient amber specimens because researchers have found that genetic material, even stored in ideal conditions, has an average half-life of just 521 years.