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An illustration of a reconstruction of one of the Mesozoic whirligig beetles related to the striped whirligig examined in the study. Photo: Gray Gustafson.

Madagascar, an island off the southeastern coast of Africa, is home to its own unique species of birds, insects and reptiles. A team of researchers has found perhaps the oldest of all these fauna: a beetle whose origins trace back to the Triassic period.

The Malagasy striped whirligig beetle (Heterogyrus milloti) has been dated back to 206 million years ago using the fossil record and a methodology called “tip dating,” reports a team from the University of Kansas in the journal Scientific Reports.

The insect once inhabited much of Europe and Asia– but has now been reduced to just Madagascar, since the islands can provide refuge from continental extinction, they report.

“The remoteness of Madagascar is what may have saved this beetle,” said Grey Gustafson, lead author. “It’s the only place that still has the striped whirligig beetle because it was already isolated at the time of the Cretaceous-Paleogene extinction event – so the lineage was able to persist, and now it’s surviving in a marginal environment.”

The team looked at every known gyrinid species known to date, through the Triassic and Jurassic to the Mesozoic and into our current Cenozoic.

The “tip dating” involved Bayesian statistical analysis, and the extant species were included, based on observations using a scanning electron microscope.

The phylogenetic comparisons and family-tree tracing was done using a supercomputer cluster called “Ulam” at the Center for Advanced Research Computing at the University of New Mexico.

“This is unprecedented in Madagascar but echoes the survival of the Tuatara on New Zealand,” they write. “Both represent the last surviving species of formerly widespread Triassic-Jurassic lineages ‘rescued’ from extinction by microcontinental islands. Madagascar serving as such a refugium sets the island in a new perspective and demonstrates that increased attention to arthropods will likely change our view of this famous natural laboratory of evolution.”

The carnivorous aquatic beetle is elusive, only found on the surface of remote streams on the island. Part of this is due to the influx of cattle that ranchers bring to the area, which in turn brings feces that disrupts the nutrients in the ecosystem, driving the delicate insect out.

The Madagascar beetle, however, is nowhere near the oldest extant species on Earth. Jellyfish fossils have been dated to 550 million years and evidence exists that sponges (760 million years) and the horseshoe crab (450 million years) are all older.

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