Page 101 - Introduction to Paleobiology and The Fossil Record

88 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Seaweeds (brown, green algae)

Sea grasses, mangroves (angiosperms)

Epibenthic, sessile (bryozoans,
forams, spirorbids)

High-level suspension feeders

Crinozoans, octocorals

Intermediate-level suspension feeders 25 cm

Low-level suspension feeders 5 cm

Giant bivalves, corals, sponges, Most brachiopods,
giant brachiopods bivalves, bryozoans
Figure 4.9 Epifaunal tiering of marine benthic communities; infaunal tiering recorded in trace fossil
assemblages is discussed on p. 205. (From Copper 1988.)

Trace fossil associations show that burrows extremely abundant primary producers to
may be organized in an infaunal, tiered hier- relatively few predators. A number of basic
archy (see Chapter 19). Ausich and Bottjer trophic or feeding strategies are known (Fig.

(1982) defined three levels with increasing 4.10). Several marine food chains (basically,
depth from the sediment–water interface: 0 to who eats what) have been documented includ-
−60 mm, −60 to −120 mm and −120 mm to ing those dominated by suspension feeders
−1 m. During the earliest Paleozoic, only the such as brachiopods, bryozoans and sponges.
first tier was consistently occupied, the second These fed mainly on phytoplankton and other

tier was occupied from the Late Silurian and, organic detritus. Suspension feeding was par-
finally, the third tier was populated in the ticularly common in Paleozoic benthos; the

Carboniferous. Tiering was also selectively Mesozoic and Cenozoic faunas were more
affected by extinction events, and tiers deeper dominated by detritus feeders, such as echi-
than 500 mm are rare after the Late Creta- noids, and food chains were generally longer
ceous because of predation by bony fi shes. and more complex (Fig. 4.11).
It might seem rather easy at fi rst sight to
Trophic structures: bottom or reconstruct a food chain for a fossil assem-
top of the food chain? blage, providing you can work out who ate
what. But that is easier said than done. One
Food pyramids form the basis of most eco- of the most spectacular fossil lake deposits,
logical systems, defining the energy fl ow dominated by amphibians, has been docu-

through a chain of different organisms from mented from the Upper Carboniferous of