Gilboa - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 102

modern Ground Pine; Rellimia , a more
shrubby or bushy progymnosperm also
occurs there. The flora at South Mountain
has a similar structure to that at Brown
Mountain but consists of more, and
different genera. Both seem to have
been preserved in gently flowing, possibly
even stagnant, water bodies within the delta
environment. Of especial interest at these
localities, however, are the animal
remains. We find predatory arachnids
(e.g. trigonotarbids, spiders, pseudoscor-
pions) and myriapods ( Devonobius
and scutigeromorphs), and detritus-feeders
(e.g. eoarthropleurids, microdecemplicids,
and mites) but no true herbivores (i.e.
animals which feed on living plant material
to digest).
It is most likely that the trophic system
at these localities and, indeed, at all
Devonian localities of early terrestrial
ecosystems, differed from the more
familiar ones we see today in lacking
herbivory. Shear and Selden (2001)
discussed this in great detail, and
concluded that the lack of herbivores is
most likely genuine (they have not simply
all been soft-bodied and thus not
preserved), but that herbivory had yet to
evolve. Modern herbivores utilize a flora of
fungi and other microbes in their guts to
break down plant material which the
animal has cut into pieces and chewed.
Their guts are really fermentation
chambers, and the animals rely on the flora
because they lack the necessary enzymes to
break down such materials as cellulose

themselves. Detritus-feeders simply eat the
already broken-down plant material from
the forest floor, together with the
decomposing microbes and fungi. We can
envisage a progression from detritivory to
herbivory in animals which imprison the
microbes in their guts and thus bypass the
external decomposition of plant material.
This seems not to have occurred until
much later in the Paleozoic.

C OMPARISON OF G ILBOA WITH
OTHER EARLY TERRESTRIAL BIOTAS
Other famous localities preserving early
terrestrial ecosystems include the late
Silurian Ludford Lane, Shropshire,
England (Jeram et al ., 1990) and the
Lower Devonian Rhynie Chert of
Scotland (Selden and Nudds, 2004,
Chapter 5). These localities have many
similarities in their trophic structure: they
all lack herbivores and seem to have had a
predator-detritivore food chain. There
are some differences in their flora,
however. The flora in the Silurian was
much simpler than in the Devonian; the
plants were simple, dichotomously
branching axes with terminal sporangia,
such as Cooksonia . In the early Devonian
(e.g. Rhynie Chert), these simple plants
were joined by primitive club-moss-like
plants such as Asteroxylon which was a
creeping form that had a main stem with
side branches, all covered with scale-like
'leaves'. By the Middle Devonian,
evidence from Gilboa shows that full-scale
forests had developed.

F URTHER R EADING
Anderson, L. I. and Trewin, N. H. 2003. An
Early Devonian arthropod fauna from
the Windyfield Cherts, Aberdeenshire,
Scotland. Palaeontology 46 , 467-509.
Arnold, C. A. 1937. Observations on fossil
plants from the Devonian of eastern
North America. III. Gilboaphyton
goldringiae , gen. et sp. nov. from the
Hamilton of eastern New York.
Contributions from the Museum of

Paleontology, University of Michigan
5 , 75-78.
Banks, H. P. 1966. Devonian flora of New
York State. Empire State Geogram
4 ,10-24.
Banks, H. P., Bonamo, P. M. and Grierson,
J. D. 1972. Leclercqia complexa gen. et
sp. nov., a new lycopod from the late
Middle Devonian of eastern New York.
Review of Palaeobotany and
Palynology 14 , 19-40.