Gilboa - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 98

frequently overlooked because of their
small size (the majority are less than 2 mm
(0.08 in) long). Today's diversity of mites is
second only to that of insects, with some
30,000 extant species described. The most
abundant fossil mites are Pleistocene and
Holocene peats and mammoth sites of
the northern hemisphere, and reasonably
diverse faunas in the Baltic and Dominican
Republic ambers (Chapter 13). Mesozoic
mites are particularly rare. The oldest
known mites come from the Rhynie Chert
(Selden and Nudds, 2004, Chapter 5). At
Gilboa, Brown Mountain has yielded two
species of oribatid mites (Norton et al .,
1988) and one alicorhagiid (Kethley et al .,
1989). A few poorly preserved specimens
of oribatids similar to one of the
Brown Mountain oribatid families
(Devonacaridae) have been recovered
from South Mountain. Oribatids are
detritivores or fungivores in modern
ecosystems; alicorhagiids are known to
prey on nematodes. Mites play a major role
in soil and litter communities today and
doubtless did so in the Devonian Period.

fossils attributable to land animals
(including millipedes) occur in older rocks
(Shear and Selden, 2001). Body fossils
have been found in strata of middle
Silurian age in Scotland (Wilson and
Anderson, 2004). Others are known from
the Devonian of Scotland and Canada
(Shear et al ., 1996). A couple of specimens
of flat-backed millipedes were reported
from the Upper Devonian of the Delaware
Valley (Shear and Selden, 2001), but
the better known millipedes from
Gilboa belong to the extinct group
Arthropleurida. A new genus and species
of a supposed scorpion with gills covered
by circular plates ( 101 ), called
Tiphoscorpio hueberi , was described by
Kjellesvig-Waering (1986) from material
macerated from South Mountain by
Francis Hueber (1960). During a visit to
Bill Shear's laboratory in Virginia to
study the Gilboa arthropods, Paul Selden,
then of Manchester University (UK), saw
Hueber's slides of Tiphoscorpio fragments
and noticed their similarity to a quite
different animal, Eoarthropleura , from
the Devonian of Germany (Størmer,
1976). Arthropleurids occur in the fossil
record from the late Silurian to the
late Carboniferous. Carboniferous
arthropleurids were gigantic, possibly 2 m
(7 ft) in length but, in contrast, the

Millipedes
Millipedes are predominantly feeders on
plant detritus and live mainly in soil and
leaf litter. They are the oldest land animals
known from body fossils, although trace

101

101 Plates originally described
as gill covers of an aquatic
scorpion but later shown to be
ventral plates on the body of
an arthropleurid myriapod see
text USNM. Width 1.6 mm
0.06 in.