Thanks. I accept your answer. You have gotten me into the habit of expecting you to know a few details/things, after all.

I am satisfied that the lineal sequence of parent-to-offspring is somewhat complicated by the change in vertebra numbers between presumed blood relatives. I require a continuous chain of evidence/record, you know, because any thing else allows for intelligent episodic punctuated modifications of the life form. If the "jump" is from one life form to a distinctly different model, (as seems rather apparent in the biosphere) then I find that to be persisting in the "irreducible complexity" category. So sorry.

If there is a detailed (the devil is in the details?) Darwinian explanation, or a progressive step-by-step cellular biology explanation (explanatory, as well as predictive) at hand for that *needed* (as opposed to planned) variance in vertebra number, it certainly would be potentially interesting and impressive.

(added)

http://www.google.com/search?hl=en&ie=ISO-8859-1&q=%22devil+in+the+details%22+evolution&btnG=Search

http://209.85.173.104/search?q=cache:NcQEjZTl01IJ:www.ias.ac.in/jgenet/Vol82No3/AKCHIPPINDALEetal-JGENET-2003.pdf+%22devil+in+the+details%22+evolution&hl=en&ct=clnk&cd=1&gl=us&ie=UTF-8

"

After decades of research on the hundreds of selection
lines derived from the IV D. melanogaster population,
many of our earlier conceptions about the nature of life-
history evolution have been broken down or even rever-
sed. Here and in other papers (Leroi et al. 1994a,b; Archer
et al. 2003; Phelan et al. 2003; Chippindale et al., in press)
we have empirically demonstrated nonlinear and even re-
versing evolutionary correlations under long-term selection.
Far from being distraught by the lack of simple, pre-
dictable patterns in experimental evolution, we are instead
impressed by the ingenuity of selection, the complexity
of trait associations, and the sensitivity of animal popula-
tions to small changes in their environment. Some of the
problems plainly stem from grouping as simple ‘traits’ or
‘characters’ portions of the phenotype governed by many
loci and multiple discrete functional steps (e.g. develop-
ment, longevity). Under these circumstances it is inevi-
table that allele frequencies will vary idiosyncratically in
particular populations and change throughout selection,
and that selection will exploit some loci but not others at
any given point in a protracted selection response. The
matrix of associations among components of a major cha-
racter, such as any life-history character, is bound to be
complex, with that complexity multiplied by the multiple
interacting characters that define each summative life-
history character.

These findings present a major challenge for the inves-
tigation of life-history evolution, even under the simpli-
fied conditions of laboratory culture. As biologists seeking
to understand the patterns and consequences of natural
selection, we need to acknowledge that our parsing of
the text of evolution may be radically different from the
actual meaning and substructure of that text. The true
story, the devils at work, may be much richer in causally
important details than we have imagined."