Linnaean vs. phylogenetic systematics & the DML & a last comment

[Stephan Pickering <stefanpickering2002@yahoo.com>]

  Scientific discussion on the DML is, indeed, the
stated purpose...thus, I would like to add a final
comment: "long dead animals" is inaccurate and, could,
possibly stymie the evolution of the List itself. You
state that we unable to study the "molecular biology,
social behaviour" of pre-K/T dinosaurs. Perhaps. The
K/T extinction events (bolide impact, fluctuating
sealevels and CO2, environmental stresses coupled with
temperature changes) eradicated a phenomenal array of
taxa, while others (even terrestrial, temperature
sensitive taxa) survived. Using bifurcation theory and
fast-slow dynamical systems to under how extinctions
are the results of natural selection, we can see that
natural selection maximises "fitness", and, as well,
can decrease it and cause maladaptations of
populations resulting in extinctions. These
maladaptions are, in part, genetic (mutations,
migration, drift), and genetic synergism among
dinosaur genomes toward the end-Cretaceous may have
caused "meltdowns" in some clades due to a combination
of drift and mutation. Ulf Dieckmann, Paul Marrow,
Richard Law (1995, Evolutionary cycling of
predator-prey interactions: population dynamics and
the Red Queen, Jour. Theoretical Biology
176(1):91-102) have called this evolution to
extinction.
   Before and after the K/T extinction events, changes
in ecology were transpiring faster than changes in
genomes, and natural selection was, then and now,
weak. A dinosaur genome had trait changes small
relative to fitness changes, so that breeding
populations exhibited little visible change. When
changes in dinosaur populations did occur, there were
profound ecological bifurcations, so that the mean
quantitative changes of genome traits were affected.
We could call this punctuated equilibria. Using
mathematic concepts applied to dinosaurs at the end
Cretaceous, there were four bifurcations leading to
mass extinctions: saddle-node bifurcation of
equilibria; subcritical Hopf; saddle-node bifurcation
of limit cycles; homoclinic and heteroclinic
bifurcations.
  All of these bifurcations are intertwined with
predator-prey systems among dinosaurs. Stasis
equilibrium among dinosaur populations were
interrupted, and death of populations occurred,
because ecological subsystems were unable to sustain
viable breeding flocks/herds of dinosaurs, or if
interacting dinosaur populations were unable to
achieve and maintain stasis (co-existence, e.g., mixed
species herds). And we can speak, as it were, of
dinosaur populations having exhibited extinction
"attractor" cycles of behaviour. Overfeeding,
infertility of eggs due climatic conditions, etc.,
could have reduced populations of some clades to the
level where extinction was rapid. Let me put it
another way: some fitness levels of dinosaurs toward
the end-Cretaceous probably fell below critical
fitness thresholds (as among other taxa, e.g.,
pterosaurs), so that what is called "delayed loss of
stability" killed off populations world wide, for
different reasons (the argument "cold" killed
dinosaurs, is more applicable to sauropods, as Roger
Seymour's excellent research demonstrates they were
not endothermic, than to other clades).
  Thus, to speak of "long dead animals" is not
correct. All of the events outlined above, at the K/T
boundary, killed numerous taxa. Some dinosaurs
survived in isolated geographical areas well into the
Paleocene (as James Fassett and Spencer Lucas have
explicated), but most died off...most, but not all.
Mammalian fliers, bats (and looking with wonder at the
Green River Shale juvenile male, 5 inch long bat with
a 12 inch wingspan, at YPM, Icaronycteris index, one
sees a mammalian pterosaur, so to speak), within 10
million years were ruling the night skies. And who
were "rulers" of the day skies? Dinosaurs,generally
toothless, flying theropods, Mr Rowe. And today, ~ 50
million years later, these flying theropods  have
radiated all over the globe. 
   As dinosaurologists, we can, with wonder, study
dinosaurs all around us, grapple with the intricacies
of their molecular biology, watch living social
behaviour of dinosaurs, rejoice in the fact that the
"beautiful beasts" we have dedicated our lives to, are
still accessible. A pigeon is not a stegosaur, and a
duck is not a dromaeosaur -- but, all are dinosaurs,
linked by genetics and evolutionary processes. These
flying theropods have flourished because, as Gregory
Paul has cogently noted, they have decoupled two
different locomotor modes, flying and walking, which
bats (and pterosaurs) were not able to do (other
factors have been explored by Jim Carey, especially
parental care), and have evolved, from the Cretaceous,
thermoregulatory and cardiovascular systems. The
post-K/T theropod history (from "terror birds" to
teratorns to  Harpagornis to moas to geese to
dinosaurs with songs that touched poets) is, to me, as
beautiful and awe-inspiring as the pre-K/T dinosaurs.
   All of these dinosaurs are subjects for the
Dinosaur Mailing List. And, I'm afraid, phylogenetic
systematics is more utilitarian (for molecular
genetics, cladistics, etc.) and reflective of living
taxa than Linnaeanism. It is not a question of
"better". It is a question of science itself evolving,
sharpening tools of observations.


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