Page 93 - Introduction to Paleobiology and The Fossil Record

80 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Paleoecological investigations require a
PALEOECOLOGY
great deal of detective work. It is relatively
Pebbles and shells on the beach give us clues easy to work out what is going on in a living
about their sources. Paleontologists can recon- community (Fig. 4.1). Ecologists are very
struct ancient lifestyles and ancient scenes interested in the adaptations of animals and
based on such limited information, and this is plants to their habitats, the interactions
the basis of paleoecology. Paleoecology is the between organisms with each other and their

study of the life and times of fossil organisms, environment, as well as the flow of energy and
the lifestyles of individual animals and plants matter through a community. Ecologists also
together with their relationships to each other study the planet’s life at a variety of levels
and their surrounding environment. We know ranging through populations, communities,
a great deal about the evolution of life on our ecosystems and the biosphere as a whole. By
planet but relatively little about the ways sampling a living community, ecologists can
organisms behaved and interacted. Paleoecol- derive accurate estimates of the abundance
ogy is undoubtedly one of the more exciting and biomass of groups of organisms, the
disciplines in paleontology; reconstructing diversity of a community and its trophic struc-
past ecosystems and their inhabitants can be ture. But fossil animals and plants commonly
great fun. But can we really discover how are not preserved in their life environments.
extinct animals such as the dinosaurs or the Soft parts and soft-bodied organisms are
graptolites really lived? How did the bizarre usually removed by scavengers, whereas hard
animals of the Burgess Shale live together and parts may have been transported elsewhere or
how did such communities adapt to environ- eroded during exposure (see Chapter 3). In a
mental change? living nearshore community (Fig. 4.1) the
It is impossible to journey back in time to soft-bodied organisms, such as worms, would
observe extraordinary ancient communities, rapidly disappear together with the soft parts
so we must rely on many lines of indirect of the bony and shelly animals, for example

evidence to reconstruct the past and, of course, the fishes and the clams; the multiskeletal
some speculation. This element of speculation organisms such as the bony fishes would dis-

has prompted some paleontologists to exclude aggregate and animals with two or more shells
paleoecology from mainstream science, sug- would disarticulate. Fairly quickly there
gesting that such topics are better discussed would only be a layer of bones and shells left
at parties than in the lecture theatre. Emerg- with possibly some burrows and tracks in the
ing numerical and statistical techniques, sediment. Moreover, some environments are
however, can help us frame and test hypothe- more likely to be preserved than others;
ses – paleoecology is actually not very differ- marine environments survive more commonly
ent from other sciences. than terrestrial ones.
More recently, too, paleoecology has devel- Although fossil assemblages suffer from
oped much wider and more serious signifi - this information loss, paleoecological studies
cance in investigations of long-term planetary must, nevertheless, have a reliable and sound
change; ecological data through time now taxonomic basis – fossils must be properly

form the basis for models of the planet’s identified. And although much paleoecologi-
evolving ecosystem. The infl uential writings cal deduction is based on actualism or unifor-
of James Lovelock have extravagantly echoed mitarianism, direct comparisons with living
the suspicions of James Hutton over two cen- analogs, some environments have changed
turies ago, that Earth itself can be modeled as through geological time as have the lifestyles
a superorganism. The concept of Gaia and habitats of many organisms. For example,
describes the planet as a living organism some ecosystems such as the “stromatolite
capable of regulating its environment through world” – sheets of carbonate precipitated by
a careful balance of biological, chemical and cyanobacteria (see p. 189) – existed through-
physical processes. Ecological changes and out much of the Late Precambrian, returning
processes through time have been every bit as during the Phanerozoic only after some major
important as biodiversity changes; these extinction events and only for a short time
studies form part of the relatively new disci- (Bottjer 1998). Nevertheless, a few basic prin-
pline of evolutionary paleoecology. ciples hold true. Organisms are adapted for,