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Re: David Hone on the Cope's Rule paper
Mike Keesey wrote:
You certainly can say that without contradicting David Hone, since in an
earlier paper he reached a similar conclusion: "Only the Cretaceous
sauropods [among large dinosaurs] do not follow the trend, and these are
characterized by their extreme variance of sizes" (Hone et al. 2005:594).
Hone, D. W. E., T. M. Keesey, D. Pisani & A. Purvis. 2005.
Macroevolutionary trends in the Dinosauria: Cope's rule. Journal of
Evolutionary Biology 18:587-595.
The thing is that the "Jablonski polygons" used to illustrate this point
actually separate the Cretaceous sauropods from the Jurassic sauropods. But
all Cretaceous sauropod lineages are known from the Jurassic (diplodocoids,
brachiosaurids, titanosaurs), and the ancestor-descendent pairings (which
were also used to test Cope's Rule) do cross the Jurassic-Cretaceous
boundary. So I'm not entirely sure why the Jablonski plot separated
Jurassic and Cretaceous sauropods - especially if the objective was to test
Cope's Rule over the entire evolution of the Sauropoda. If you combine the
plots (Jurassic+Cretaceous) into a single shape, most of the Late Jurassic
sauropods would fall outside the polygon, making them outliers.
Thus, when Hone et al. (2005) says "Only the Cretaceous sauropods do not
follow the trend", I guess I would extend this to the entire Sauropoda; if
the Cretaceous sauropods don't get bigger, then Cope's Rule does not hold
for the clade as a whole. That's why I quoted Carrano over Hone &c.
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