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Re: the opposite of paedomorphosis?



Just out of interest, is there any reason why american
english retains the -ae- in paedomorphosis, but not in
paleontology [palaeontology in ol' proper english] (or
any other paedo- prefix words).

Denver.

-- "Jaime A. Headden" <qilongia@yahoo.com> wrote:

> David Peters (davidrpeters@earthlink.net) wrote:
> 
> <So, if paedomorphosis is the reduction in overall
> size, rostrum length and
> such due to sexual maturity while in the juvenile
> stage, what is the term and
> process for rostrum lengthening, neck elongation and
> overall size increase?>
> 
>   Well, paedomorphosis is actually the process by
> which primitive features are
> retained throughout ontogeny, that is without
> selective change of the features,
> and can result in a "juvenile" appearance of adults.
> Neotenic salamanders, such
> as mudpuppies and hellbenders, are all paedomorphic
> species in that they retain
> ancestral and juvenile features at and adult stage
> of life.
> 
>   The opposite, as Jura/Jason states, is
> peramorphosis, a process by which the
> juvenile condition is modified from the ancestral,
> juvenile condition, and
> juvenile traits are completely or substantially
> modified. Examples include
> Tyrannosauridae and *Panthera*, all of which heavily
> modify the basal or
> juvenile condition through gross reworking of the
> skull anatomy and processes
> and proportions.
> 
>   In the fossil record, the appearance of
> paedomorphic taxa is usually
> identified by the prevalence of "neotenic" appearing
> fossils without
> appropriate "adults" in the same level and with
> smaller age "classes" showing
> the same juvenile conditions as the largest
> preserved. Such is how neotenic
> amphibians are identified. The retention of largely
> juvenile traits in felids
> such as the domestic cat also shows that while
> change occurs, compared to
> *Panthera* and *Neofelis*, this change is much more
> minor, and thus *Felis*
> (and *Leptailurus*) is paedomorphic to some degree,
> less so *Puma*, *Acinonyx*
> or *Lynx*.
> 
>   I hope this helps,
> 
>   Cheers,
> 
> Jaime A. Headden
> 
> "Innocent, unbiased observation is a myth." --- P.B.
> Medawar (1969)
> 
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