Millipede from South Australia rediscovered and described 90 years after it was first collected

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The new species Colobothrix deckeri is in the millipede family Dalodesmidae. It is remarkable because it is the first in its moisture-loving family to be found in a part of Australia with a low annual rainfall, between 400 and 500 mm (16 and 20 inches).

The new species is also unusual for the shape of its sphaerotrichomes, which are tiny ball-shaped structures found on the legs of mature males in Dalodesmidae and some other millipedes. Sphaerotrichomes normally have a long, pointed seta emerging from the ball. The new species has been placed in the new genus Colobothrix, which means "stunted hair," because the seta on its sphaerotrichomes is reduced to a short, blunt rod.

Colobothrix deckeri was named by Australian myriapodologist Robert Mesibov in honor of German colleague Peter Decker, who played a key role in the story behind the species' rediscovery, as described in the journal ZooKeys. The first specimen of C. deckeri was collected in 1936 and deposited as an unidentified millipede in the South Australian Museum (SAMA). In 2015, Decker found the specimen among many he borrowed from the museum for his Ph.D. work on another millipede family, Paradoxosomatidae.

Decker recognized the specimen as a dalodesmid and sent images of its microscopic characters to Mesibov, who is a dalodesmid specialist. The specimen was the first evidence for Dalodesmidae in dry South Australia, and in 2016 and 2017 Mesibov searched the 1936 locality on South Australia's lower Yorke Peninsula for fresh material. Both searches were unsuccessful, although the two trips yielded a new paradoxosomatid.

Meanwhile, arachnologists Michael Rix and Danilo Harms had been sampling spiders and associated litter invertebrates on Kangaroo Island, South Australia, about 50 km (31 miles) south of the 1936 locality. In 2010, they discovered a remarkable new species of assassin spider from a single site in the relatively wet northwestern corner of the island. They also collected several specimens of the new, still unidentified millipede at the same site and deposited them in the Western Australian Museum (WAM).

Early this year, Mesibov found the WAM millipede record online. He emailed WAM curator Mark Harvey, who kindly provided several images of the millipede collected by Rix and Harms, with close-ups of its diagnostic characters. The images showed that the 2010 Kangaroo Island specimens were the same species that had been collected in 1936 on the Yorke Peninsula.