Scientists have discovered an insect that went extinct for more than 120 million years and featured many of the traits associated with modern butterflies including markings on the wing called eye spots.
Known as Kalligrammatid lacewings, paleobotanists for the past century have known they lived in Eurasia during the Mesozoic. But it’s taken recent discoveries of well-preserved fossils from two sites in northeastern China to demonstrate how similar they were to modern butterflies. Thanks to extensive lakes that limited oxygen exposure in these areas during mid-Jurassic through early Cretaceous time, paleontologists have been able to recover exquisitely preserved fossils that retain much of their original structure.
"Poor preservation of lacewing fossils had always stymied attempts to conduct a detailed morphological and ecological examination of the kalligrammatid," Indiana University’s David Dilcher, who was part of the team that made the discovery published in the journal Proceedings of the Royal Society B, said in a statement. "Upon examining these new fossils, however, we've unraveled a surprisingly wide array of physical and ecological similarities between the fossil species and modern butterflies, which shared a common ancestor 320 million years ago."
Dilcher, who also discovered the first flower last year, found that this insect from the Jurassic period survived in a manner similar their modern sister insects by visiting plants with "flower-like" reproductive organs producing nectar and pollen. They probably used their long tongues to probe nectar deep within the plant and also possessed hairy legs that allowed for carrying pollen from the male flower-like reproductive organs of one plant to the flower-like female reproductive organs of another.
Eventually, this system of pollination by long-tongued lacewings traveling between plants with exposed reproductive parts - called gymnosperms - gave way to more familiar system of insect pollinators and modern flowers, or angiosperms, in which the reproductive parts of the plants are contained with a protective seed.
This butterfly-like behavior is striking considering that modern butterflies didn’t appear on Earth for another 50 million years.
It is an example of what scientists call convergent evolution where two distantly related animals develop similar characteristics independently. In this case, the butterfly-like insect is an extinct "lacewing" of the genus kalligrammatid called Oregramma illecebrosa. Another genus of this insect - of the order Neuroptera – live on today and are commonly known as fishflies, owlflies or snakeflies.
“Here, we’ve got coevolution of plants with these animals due to their feeding behavior, and we’ve got coevolution of the lacewings and their predators,” Dilcher said. It’s building a web of life that is more and more complex.”
The researchers, which also included Conrad Labandeira, a curator at the Smithsonian Institution's National Museum of Natural History, and Dong Ren of Capital Normal University in Beijing, China, where the fossils are housed, found that the Kalligrammatid lacewings probably were important pollinators during mid-Mesozoic times.
“Various features of the mouthparts all indicate that these things were sucking fluids from the reproductive structures of gymnosperm plants,” Labandeira said in a statement, of a finding that was confirmed by an analysis of material lingering within the food tube of one fossil, which was found to contain only carbon. Had the insect been feeding on blood, its final meal would have left traces of iron.
Researchers were also able to find the presence of scales on wings and mouthparts, which, like the scales on modern butterflies, likely contained pigments that gave the insects vibrant colors. Based on similarities between Kalligrammatid wing patterns and those found on modern nymphalid butterflies (a group that includes red admirals and painted ladies), Labandeira said Kalligrammatids might have been decorated with red or orange hues.
From there, researchers did a chemical composition of various regions of the Kalligrammatid’s patterned wings including the eyespots. In modern butterflies with eyespots such as the modern owl butterfly, the dark center of the mark is formed by a concentration of the pigment melanin. It seems the Kalligrammatids, too, had melanin at the center of their eyespots.
“That, in turn, suggests that the two groups of insects share a genetic program for eyespot production,” Labandeira said. “The last common ancestor of these insects lived about 320 million years ago, deep in the Paleozoic. So we think this must be a developmental mechanism that goes all the way back to the origins of winged insects.”