Scientists have recently excavated the fossilized remains of an ancient stick insect in China. The insect is a member of a newly discovered species that exhibited leaf mimicry over 126 million years ago.
The prehistoric insect lived sometime during the early Cretaceous period and scientists say that it is one of the early descendants of modern stick insects. The researchers who found the insect published their findings in the online journal PLOS ONE.
"Fossil species that can be conclusively identified as stem-relatives of stick- and leaf-insects (Phasmatodea) are extremely rare, especially for the Mesozoic era," says the study. "This dearth in the paleontological record makes assessments on the origin and age of the group problematic and impedes investigations of evolutionary key aspects, such as wing development, sexual size dimorphism and plant mimicry."
Using a very early and primitive type of leaf mimicry, the insect used its appearance to conceal itself from its predators. The insect, which has been named Cretophasmomima melanogramma, may have lacked some of the more complex features found in modern stick insects but it had already evolved the necessary basic structures.
"As early as in the Early Cretaceous, some stem-Phasmatodea achieved effective leaf mimicry," the study says. "The diversification of small-sized arboreal insectivore birds and mammals might have triggered the acquisition of such primary defenses."
The fossilized remains were found in the Yixian Formation in China. This is an area widely known among paleontologists for producing a relatively large number of well-preserved fossils from the early Cretaceous Period. The team found two specimens in a single layer. The first specimen was male and the second was female. The scientists also noticed something intriguing about the fossils.
"I realized there was something interesting about the coloration pattern of the wings," said Olivier Béthoux, one of the co-authors of the study. Béthoux is also a paleontologist from the National Museum of Natural History's Center of Paleobiodiversity and Paleoenvironment Research in Paris.
Béthoux found that the ancient stick insect had wings that contained an interesting pattern. The wings had darkly colored parallel lines and scientists were initially unsure of the reason for the patterns. After looking at another fossil of an ancient plant related to the gingko that the researchers found nearby, the scientists found a similar pattern on the plant's leaves. This means that the ancient stick insect evolved to mimic to leaves of this similarly ancient plant called Membranifolia admirabilis.
"We know from the same locality where the stick insect was discovered that there are a bunch of predators; including tiny tree-climbing dinosaurs and mammals with insect-eating teeth, as well as birds," Béthoux said.
