Reconstruction of Friularachne rigoi. Lukas Panzarin

The researcher of the Institut Català de Paleontologia Miquel Crusafont (ICP) Fabio M. Dalla Vecchia and Paul A. Selden of the University of Kansas (KU) publish today in the online edition of the journal Acta Palaeontologica Polonica the description of a new species of mygalomorph spider, a group that includes extant tarantulas. Friularachne rigoi, the name given the new species, lived in northern Italy about 215 million years ago, when the early dinosaurs roamed this area, and it is one of the few spiders of the Triassic worldwide known.

Mygalomorph spiders are both famous and feared because of their big size and sometimes poisonous bite. However, the type specimen Friularachne rigoi, one of the oldest known ancestors of extant tarantulas, was an adult male less than half a centimeter long. Its fossils were found in the Carnic Prealps, in the Italian province of Udine in northeastern Italy, and they date back some 215 million years.

Only three other fossil spiders from this period, the Triassic, are known ranging from about 250 million years ago to about 200. The other three were found in France, the United States and South Africa. The mygalomorph spider published today in Acta Palaeontologica Polonica by paleontologists Fabio M. Dalla Vecchia (ICP) and Paul A. Selden (KU) is the second oldest known, only the French Rosamygale grauvogeli is geologically oldest. In fact, the evolutionary history of mygalomorph spiders is not well known because the fossil remains of spiders are extremely rare worldwide.

Fossil remains of Friularachne rigoi, with less than half centimetre of length. Paul A. Selden

The study has shown that Friularachne had thin legs and chelicerae (appendages used to grab prey) pointing forwards, comparatively large, and robust. Other appendages, the pedipalps, have expanded extremities and indicate that the only known individual of this spider was an adult male. Its abdomen was covered and protected by a broad shield (scutum). Friularachne presents some features that suggest it could belong to the superfamily Atypoidea, which would extend the fossil evidence of this superfamily back in time of over 100 million years. Calommata spiders, the extant genus of Atypoidea more similar to Friularachne, are also small and, in fact, it is not surprising that the oldest members of a lineage tend to be smaller than other more modern members.

Friularachne lived in the low islands emergent from the shallow tropical sea that covered most of the Alpine region 215 million years. It was contemporary with the early dinosaurs, whose fossil tracks have been found in the nearby Park of the Friulian Dolomites. In fact, the Triassic rocks of this area are internationally famous not only for its beauty, but also because of the fossil remains of reptiles, fish and crustaceans discovered in the last 30 years.

The new spider has been named Friularachne rigoi in honour of the region where it was found and its discoverer, mr. Robero Rigo. The fossils are in the Museo di Storia Naturale Friulano of Udine in Italy, with which the ICP has an agreement to develop joint research on several topics of the Mesozoic.