762 THE STRUCTURE OF EVOLUTIONARY THEORY
too rarely to generate enough cases for calculating a distribution of rates. Instead,
paleontologists worked by the false method of exemplification: validation by a
"textbook case" or two, provided that the chosen instances be sufficiently
persuasive. And even here, at this utterly minimal level of documentation, the
method failed. A few examples did enter the literature (see Fig. 9-2 for comparison
of an original claim with a secondary textbook version)— where they replicated by
endless republication in the time-honored fashion of textbook copying (see Gould,
1988a). But, in a final irony, almost all these famous exemplars turned out to be
false on rigorous restudy—see Hallam, 1968, and Gould, 1972, for stasis rather
than gradual increase in coiling in the Liassic oyster Gryphaea; Prothero and
Shubin, 1989, on stasis within all documented species of fossil horses, and with
frequent overlap between ancestors and descendants, indicating branching by
punctuational speciation rather than anagenetic gradualism; and Gould, 1974, on
complete absence of data for the common impression that the enormous antlers of
Megaloceros
9 - 2. Trueman's original claim for phyletic gradualism in the increased coiling of Gryphaea in
Lower Jurassic rocks of England (left). To the right, a textbook smoothing and simplification of
the same figure. Trueman's claim has been invalidated for two reasons: first, Gryphaea did not
evolve from Ostrea; and, second, subsequent studies have not validated any increase of coiling
within Gryphaea, despite Trueman's graphs. Nonetheless, once such figures become ensconced
in textbooks, they tend to persist even when their empirical justification has long been refuted in
professional literature.