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Observations

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Odd Insect Fossils Suggest Early Carnivorous Lifestyle

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insect fossil new orderA recently described swarm of fossil insects unearthed from a 100 million-year-old South American formation are a Frankensteinian riot of mismatched parts: lengthy praying mantis-like front legs; long, slim wings like a dragonfly; and wing-vein patterns to match those of modern-day mayflies. So unusual is their form that scientists are cataloguing the creatures into a completely new taxonomic order. They are hopeful that these strange bugs will divulge secrets about how early insects lived—and about modern insect diversity.


Thanks to a happy happenstance of geology, a rich shallow sea ecosystem that covered part of what is now northeastern Brazil was captured in the fossil record more than 100 million years ago. In the famous Crato Formation, fossilized insect larvae are so common that local brick workers have developed nicknames for them. And scientists have been taking a closer look at these bugs, with some surprising findings.


The "very peculiar combination of derived characters" (as the authors of the new study describe them) provide a clearer understanding of how contemporary insects evolved. The new order, Coxoplectoptera, is described in a paper published online July 19 in Insect Systematics & Evolution.


Within the new order (in the group Palaeoptera, for those keeping score), one family is particularly curious. The members of the Mickoleitiidae clade had large compound eyes and a prominent, dragon flylike chest. The species M. longimanus, named for its especially long front legs, had four slender wings that were more than twice the length of its body.


insect fossil new order larvaThe Brazil rocks have been particularly generous in divulging fossilized larvae of these odd bugs. Ranging from 10 to 32 millimeters in length, these larvae also boast some interesting anatomical features that provide some clues about their way of life. The researchers examined 21 specimens and concluded that they might have hung out partially hidden in burrows and used their antenna and "raptorial" front legs to catch prey.


As the researchers, led by Arnold Staniczek, of the State Museum of Natural History in Stuttgart, Germany, noted in their paper, "the morphology of the larvae does not allow definite conclusions of their lifestyle." But more clues about their lives can be gathered by going back to the rocks themselves. One adult M. longimanus was found on the same rock plate as a juvenile prehistoric fish (Dastilbe): its destiny was to spend eternity seconds away from becoming dinner.


Images courtesy of Staatliches Museum für Naturkunde Stuttgart

The views expressed are those of the author and are not necessarily those of Scientific American.

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