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Fossils of a new species of ‘bird-eating’ spider which is 240 million
years old have been discovered in eastern France, more than doubling the
length of the fossil record for these creatures.

Their location suggests that this type of spider was widespread during
the Triassic period which could have been the ‘Age of the Mygalomorphs’.

Bird-eating spiders, otherwise known as mygalomorphs, are best known
for their deadly representatives such as the large hairy tarantula and the
Australian funnel-web. But despite their name most of these creatures are
small and live quietly in silk-lined burrows, trapping nothing more impressive
than the occasional insect.

Paul Selden of the University of Manchester and Jean-Claude Gall of
the Louis Pasteur University in Strasbourg found the new species in rocks
from a quarry in the Vosges mountains of France. They have named it Rosamygale
grauvogeli (Palaeontology, vol 35, p 211).

Previously, the earliest known mygalomorphs, described in 1990, were
about 100 million years old. Selden and Gall found 10 specimens of the new
species, preserved in exceptional detail. They are part of the primitive,
modern family Hexathelidae, the funnel-webs.

Seldon was struck by their long spinnerets, the organs on the end of
the abdomen for spinning silk. Mygalomorph spiders with spinnerets as long
as these usually weave funnel-shaped webs for capturing insects.

Rosamygale had bristly legs and a body like that of a modern funnel-web
spider, but it was smaller; even the biggest of the fossils has a body less
than 7 millimetres long.

The spiders lived in a hot, tropical land. ‘The rocks were laid down
in a delta or lagoon where a large river met the Zechstein Sea, a shallow
sea that covered much of Europe at the time,’ says Selden. ‘Occasional influxes
of water swept land plants and animals into temporary pools, which later
dried up in the heat.’ The spiders were found in a layer of clay from such
a pool together with land-dwelling myriapods, scorpions and insects.

According to Selden, the fossils have retained such detail because
of the circumstances of their death. ‘This strata is famous for exceptional
preservation of fossils,’ he says. ‘As the water in the pools dried up,
a thin scum of bacteria settled on the dead plants and animals, stopping
them from decaying any further.’

The new species provides important information about the ancient distribution
of this type of spider. ‘In Triassic times, the area that is now the Vosges
mountains was on the edge of the supercontinent Pangaea,’ says Selden.
‘The Zechstein Sea was a large bay on its eastern edge, providing a tropical
climate with wet and dry seasons. Most of the rest of the continent was
fairly arid, making an ideal habitat for spiders.’

Selden speculates that this period of geological history could have
been a golden age for these spiders. ‘It is possible that the mygalomorphs
were far more diverse and numerous than they are today, filling ecological
niches that are today home to the more advanced araneomorph spiders, our
familiar garden types.