Mesophthirus engeli: Cretaceous Feathered Dinosaurs Suffered from Lice
Paleontologists have found tiny nymphs of a previously unknown ancient insect species trapped in two pieces of 99-million-year-old (mid-Cretaceous period) Burmese amber, along with partially damaged dinosaur feathers, the damage of which was probably made by these insects’ feeding behaviors.
Named Mesophthirus engeli, the prehistoric parasitic insect was notably small — up to 0.5 mm for adults and 0.2 mm in the nymph stage.
It had wingless body, robust and short antennae, strong chewing mouthparts, and claws on its legs.
“Mesophthirus engeli shares many features of ectoparasitic function, i.e., wingless and dorsoventrally compressed body, reduced eyes, short antennae, robust and short legs unsuitable for quick movement or jump, pretarsus very small with one single claw, etc., which suggest that the insect had an ectoparasitic lifestyle,” said Capital Normal University paleontologists Taiping Gao and Dong Ren and their colleagues from China, the United States and the United Kingdom.
“Most significantly, these insects are preserved with partially damaged dinosaur feathers, the damage of which was probably made by these insects’ integument-feeding behaviors.”
The researchers found ten individuals of Mesophthirus engeli in two pieces of 99-million-year-old amber from the Hukawng Valley of Kachin State, in northern Myanmar, a village named Noije Bum about 18 km (11.2 miles) southwest of the town of Tanai. One of the pieces contained nine specimens and the other had only one specimen.
“All these ten nymphs look very similar in morphology but have minor distinctions, and they may be easily divided to two different groups,” the scientists explained.
“The members of the first group have relatively smaller body size (under 145 μm), much wider abdomens than their thoraxes, horizontal terminals of abdomens and apex of heads and compressed 5th antennomere.”
“In contrast, the specimens within the second group possess bodies over 157 μm in length, heads with arched top and clavate and smooth 5th antennomere.”
“We identify these two groups as two different but adjoining developmental stages of Mesophthirus engeli, and their abdomens and antennae might grow to extend with age, same as the body size.”
“The new findings provide the earliest known evidence about the origin of ectoparasitic insects feeding on feathers, which strongly support that the integument-feeding behaviors of insects appeared during or before the mid-Cretaceous along with the radiations of feathered dinosaurs including birds,” the paleontologists concluded.
A paper on the findings was published December 10, 2019 in the journal Nature Communications.
T. Gao et al. 2019. New insects feeding on dinosaur feathers in mid-Cretaceous amber. Nat Commun 10, 5424; doi: 10.1038/s41467-019-13516-4