Scientists have made a skin-crawling discovery: Ancient ticks, trapped in amber, that fed on the blood of feathered dinosaurs nearly 100 million years ago.
The specimens, described in the journal Nature Communications, include the oldest dinosaur parasite to be found together with remains from its extinct host — and offer a smoking gun in the long, intimate history between ticks and dinosaurs and their living descendants, birds.
"I was astonished," study coauthor Ricardo Perez-de la Fuente, a paleontologist at the Oxford University Museum of Natural History, said of the discovery. "It was something we weren't expecting at all."
Scientists have suspected that the blood-sucking bugs dined on dinosaurs for millions of years — in fact, they're still afflicting birds, dinosaurs' only living descendants, today. But it's been difficult to establish that relationship, let alone study it, because it's been a challenge to find fossils that include both ticks and the remains of the dinosaurs they lived on.
"Direct evidence … of an organism and the remains of another one, the host, is extremely rare in paleontology," Perez-de la Fuente said.
The big break came in the form of ancient Burmese amber specimens that had been bought online by private collectors who donated the finds to museums. (One of the collectors, Scott Anderson, is listed as a coauthor on the paper.)
One of the specimens, a 99-million-year-old hard tick known as Cornupalpatum burmanicum, was found actually entangled in a plume from a feathered dinosaur — a telling sign that the tick had latched onto the feather before it was trapped in golden sap.
"It was a very unexpected surprise," Perez-de la Fuente said.
The scientists had to work harder to establish the link between the other specimens, identified as Deinocroton draculi, and feathered dinosaurs. Attached to these ticks' bodies were tiny hairlike setae from specialized beetle larvae that live in nests and eat tough-to-digest organic material like skin or hair.
Given that many feathered dinosaurs are thought to have built nests, the beetle setae offer a clue as to where these ticks were getting their meals, the paleontologist said. (It can't have been from the nest of a modern bird because the evidence indicates that birds emerged much later, the scientist said.)
One of the ticks was also found engorged with blood — but that doesn't mean there will be a real-life Jurassic Park anytime soon, Perez-de la Fuente said.
For one thing, he pointed out, it would have to be called Cretaceous Park, named after the later period during which these amber fossils formed.
On a more serious note, the 1993 film featured dinosaurs brought to life thanks to a blood-engorged mosquito trapped in amber. But in reality, DNA has a very short half-life, and such genetic information would not be recoverable.
"DNA is a fragile molecule," he said.
The scientists say they hope to find more amber specimens bearing clues about this complex relationship – one that could tell them more about dinosaurs' ecology, environment and the spread of disease. And they suspect that this parasite-host relationship goes back much further than 300 years, though it will take more fossils to know for sure.
"We don't expect to get the oldest fossils from the fossil record," Perez-de la Fuente pointed out. "Ticks could have been up to 300 million years old, but we don't have paleontological evidence of that."
Ultimately, D. draculi went extinct — perhaps around the same time as the dinosaurs, wiped out thanks to the asteroid that slammed into Earth some 66 million years ago. But other tick species continued to thrive, as did the birds that some of them dined upon.
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