Gilboa - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 97

provided conclusive evidence of not only
the presence of spiders but also the oldest
use of silk known from the fossil record
(Shear et al ., 1989). It was later discovered
that the cuticle pattern matched other
fragments already described by Shear et al .
(1987) as a possible trigonotarbid, called
Gelasinotarbus ? fimbriunguis ( 100 ). Once
this was recognized, many more pieces
could be assembled, and much of the
anatomy of the spider, now called
Attercopus fimbriunguis , was reconstructed
(Selden et al ., 1991). Recreating a whole
animal from many tiny fragments was akin
to doing a jigsaw puzzle with only half of the
pieces and without the benefit of the
picture on the box! Legs, which were
tubular in life, were well preserved because
when they were flattened, both surfaces
were squashed together, strengthening the
fragment; other parts such as the body,
which consisted of large but single sheets of
cuticle, apparently disintegrated either
under pressure or during acid maceration.
Attercopus (its name comes from
attercop - an Old English word for a
spider) is not only the oldest spider but also
the only one known from the Devonian
Period; other putative records of Devonian
spiders were discussed and dismissed by
Selden et al . (1991). Material of Attercopus
has appeared in macerations from the

younger South Mountain locality.
Comparison with modern primitive spiders
suggests Attercopus was a burrower and used
silk to line its burrow.

Pseudoscorpions
These little animals (the largest alive today
measures less than 12 mm [0.5 in] in
length) resemble true scorpions in having
chelate pedipalps but they lack a tail.
Modern pseudoscorpions live in moss,
soil, bark, under stones, and in leaf litter.
They are predators on even tinier
invertebrates. Until the 1980s the oldest
fossil pseudoscorpion known was from
Baltic amber, about 38 million years in age
(Selden and Nudds, 2004, Chapter 13), so
when one emerged from the acid
maceration of Brown Mountain in 1990, it
extended the geological range of the
group 10-fold! The fossil was named
Dracochela deprehendor , and placed in
its own family, Dracochelidae, by
Schawaller et al . (1991). Dracochela is so
similar to living pseudoscorpions that the
family seems to fit into the modern
superfamily Chthonioidea (Harvey, 1992).

Mites
These minute arachnids are abundant in
nearly all terrestrial environments today
but rare in the fossil record. They are

100

100 Tarsus last leg segment
of the spider Attercopus
fimbriunguis, showing
characteristic fimbriate claws
upper paired claws and lower
median claw are quite similar
in size, setae, and slit sense
organs AMNH. Length
0.6 mm 0.02 in.