Long-lasting daddy longlegs

Rare fossils of harvestmen unearthed in China

Scientists have unearthed the fossils of two new species of harvestmen, a delicate type of creature better known to many folks as daddy longlegs.

MODERN ANTIQUITY The well-preserved fossil of this harvestman — a creature better known as a daddy longlegs — has traits remarkably similar to those of some living species. Details of the arachnid’s legs, mouthparts and genitals (all shown in inset) allow researchers to place the new species in a family that still exists today. Huang et al./ Naturwissenschaften

Though there are more than 6,400 known modern-day species of harvestmen  — which aren’t spiders but are closely related — only 26 species have been identified in the fossil record, notes Paul Selden of the University of Kansas in Lawrence. Typically, these exceptionally fragile arachnids aren’t preserved as fossils. More than half of known fossil harvestmen had been trapped in tree sap that later hardened into amber.

The two new species, described by Selden and his colleagues in an upcoming Naturwissenschaften, were entombed in fine-grained volcanic ash that fell in what is now north central China about 165 million years ago. The harvestmen — and the ash — either dropped into a lake or were washed there soon after the ash fell, Selden notes. Little is left of those ancient harvestmen: The fossils are, for the most part, 3-D outlines of fragile bodies that disappeared long ago. Those tiny molds, however, preserved even small details of the creatures, including their mouthparts, genitals and the joints of their legs.

One of the new species, a creature with a 5-millimeter-long body and a legspan of about 80 millimeters, is remarkably similar to modern-day harvestmen — so much so that Selden and his colleagues have placed it in a family, or group of species, that still exists. “If you saw one of these creatures today, you wouldn’t look twice at it,” he notes.

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