Biology Reference
In-Depth Information
groups (e.g., Euasterids) in younger strata, and an explanation (or an ac-
knowledged realization) offered for any signifi cant difference. For example,
the Asteraceae, with multiple fl owers on a single head (asters, chrysanthe-
mums), are among the most advanced of the fl owering plants, so reports
or assumptions about their presence in the Cretaceous or early Tertiary
should be made with caution and received with a healthy skepticism. The
developing phylogeny for the angiosperms is shown in fi gure 3.6. Similar
phylograms are actively being developed for other plant and animal groups,
for example, for the bryophytes at Duke University (www.biology.duke.
edu/bryology), for the ferns by Schuettpelz and Pryer (2007), and at the
Arnold Arboretum at Harvard University for gymnosperms (see the site
Gymnosperms on the Tree of Life, or Gymnosperm AToL, http://www.huh
.harvard.edu/research/mathews-lab/).
Each of these contexts—sea level, temperature, phylogeny—can serve
as a guideline for assessing identifi cations and for accurately interpreting
the paleontological record. Other contexts mentioned previously are faunal
history, orogeny, plate tectonics, geomorphic features, and sedimentology.
These frameworks should not constrain novel reports or innovative think-
ing, however, because new paradigms often arise from the unexpected. The
value of context is that during a time of increasing responsibility for pro-
viding correct identifi cations, it gives cause for refl ection before placing in
the literature information that is now being used for such a wide variety
of important purposes. Fossils are used to add a time dimension to evo-
lutionary scenarios, propose relationships between organisms, and recon-
struct environments within which new groups of plants, animals, and early
humans appeared, migrated, and evolved. The fossil record is also being
used, together with models of energy fl ow, spatial heterogeneity, regional
(historical) effects, and biological/evolutionary factors (e.g., the stochastic
distribution of highly speciose plant groups), to explain and predict zones
of unusual species richness in underexplored regions so as to prioritize
conservation efforts (Distler et al. 2009; Graham 2009). The modern rain
forest was once depicted as ancient, unchanging, and enduring, with the
implicit rationalization that it could be lumbered, burned, farmed, and rav-
aged with impunity because it had always recovered or had persisted unal-
tered for millions of years. Subsequent paleobotanical studies have shown
that concept to be wrong on all counts. There is a lot riding these days on a
proper reading of fossils as a basis for detecting past lineages and for recon-
structing past environments, and context is one way to improve the chances
of getting it right.
