Re: Preview of new stegosaur plate paper

["Jaime A. Headden" <qilongia@yahoo.com>]

don ohmes (d_ohmes@yahoo.com) wrote:

<Intuitively, it seems to me that the relative size of display structures might
scale negatively with body size. Does anyone have enough data from extant
animals to comment on this?>

  I would only offer that the largest living land mammal (*Loxodonta*)
currently has extremely large display/ventilation structures in its ears and
tusks, and invests more energy in developing and maintaining these than the
other, second largest land mammal (*Elephas*). However, larger mammoths are
noted for having extremely large tusks but with tiny ears (possible tradeoff,
but more likely climactic, in which time in the temperate SW USA region for the
Columbian mammoth may not have allowed persistant size increase. All we can for
positive measurements in ears are steppe mammoths, predecessors of the
Columbian. So I am not sure.

  Large rhinos such as *Coelodonta* has larger nasal bosses for horn growth
than living *Rhinoceros* or *Diceros*, and *Elasmotherium* tipped the rhino
scales in apparent horn size (but it was also very northern and the horn's
function -- display? -- is very debatable).

  The largest cervids have the largest antlers (*Alces*, *Megaloceros*), and
*Rangifer* maintains them (as in *Loxodonta* tusks) in both sexes, but these
again are more northernly climed animals.

  So there may be a positive value for display structure in size, even as many
of these are agonistic in function and thus also correllate with size as use
may require. Size of horns may also increase within a genus positively with
size, as in *Ovis* where the largest sets of horns are most elaborated in the
largest species, example being *Ovis canadensis* and related species group
taxa. Purely display structures (as in peafowl *Pavo*) may still serve an
alternate function, but these also appear in some of the largest of galliforms,
as with turkeys (*Meleagris*, *Agriocharis*, etc.) and forest fowl *Gallus*.

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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