Newly discovered amber fossils from the Cretaceous period provide insights into the history of the development of notorious bloodsuckers. One specimen shows a species of tick that apparently represents a “missing link”: According to its mixed characteristics, it belonged to the family from which the two groups of parasites that plague animals and humans today developed. Another find expands on the previous evidence that ticks also bled the feathered dinosaurs: the amber shows a tick together with a feather.
Millions of years ago, it captured tree resin and then transformed it into a fascinating greeting from the past: Even small creatures and filigree structures were able to survive in amber over millions of years, which otherwise would not have left any fossil traces. Scientists have made many exciting discoveries in the transparent material in recent years, which provide insights into the development history of various living beings. The “gems of paleontology” also include amber that preserved the ancestors of notorious creatures: ticks.
The finds so far came mainly from Burmese amber from Myanmar that was around 100 million years old. A tick has even been found associated with a feather, suggesting it infested a feathered dinosaur. Nevertheless, the history of development and the behavior of the early representatives of the parasites still appear unclear. The findings of researchers led by Jason Dunlop from the Museum für Naturkunde – Leibniz Institute for Evolutionary and Biodiversity Research in Berlin have now provided new clues.
A tick with mixed characteristics
As Dunlop and his colleagues report, one of the new finds of ticks in a Burmese amber now provides clues to the origin of the two main groups of pests. As they explain, today’s species are divided into two lines that differ significantly in their characteristics: leather ticks have a flattened and soft body shell and their representatives primarily infest birds. The species that plague humans and many of our pets, on the other hand, belong to the so-called shield ticks: Wood ticks (Ixodes ricinus) and Co have comparatively robust body features, a solid back shield and different structures of the mouthparts than the leather ticks.
As the researchers report, the newly discovered fossil tick species has a surprising mix of characteristics: Among other things, it has the soft body of a leather tick, but it also has the large, protruding mouthparts that are typical of shield ticks. The researchers have therefore given the species the generic name “Khimaira” – based on the chimera, the mythical monster that combines body parts from different animals. The researchers interpret this tick as a “missing link”: It could be a representative of an extinct group from which the two main families we know today once developed.
An ancestor of “our” tick and a new tick feather fossil
However, another amber fossil makes it clear that there were also unambiguous ticks 100 million years ago: The researchers describe what is now the oldest known specimen of the tick genus Ixodes, a group that was previously only known from the much younger Baltic amber. Today’s Ixodes species include several ticks of medical importance, such as the common wood tick (Ixodes ricinus), which is also native to us. The new fossil is also particularly interesting because its characteristics suggest that it is closely related to present-day Australian species. It even sheds light on a question regarding former geographical connections: The finding seems to support a hypothesis according to which the location of Burmese amber, which is now in Southeast Asia, was once connected to Australia.
The current discoveries are rounded off by a new combination find of a tick and a feather. A juvenile of the Cornupalpatum burmanicum tick species was previously known to have been preserved in amber along with a feather that belonged to a feathered dinosaur. Dunlop and his colleagues now present another example of such a connection, which proves that the common end in the tree sap was probably no coincidence. According to the characteristics it is also a specimen of C. burmanicum – however, as can be seen from the wrapped genitals, it is an adult female. “The finding of two different life stages with dinosaur feathers supports the notion that this tick parasitized dinosaurs,” write Dunlop and his colleagues.
Source: Museum of Natural History – Leibniz Institute for Evolutionary and Biodiversity Research. Specialist article: Parasitology, doi: 10.1017/S0031182022000269