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AW: The Karate New Papers



> Padian, K., and Horner, J.R. 2010. The evolution of
> 'bizarre structures' in dinosaurs: biomechanics, sexual
> selection, social selection or species recognition? Journal
> of Zoology. doi: 10.1111/j.1469-7998.2010.00719.x.
> 
> ABSTRACT: 'Bizarre structures' in dinosaurs have four main
> traditional explanations: mechanical function, sexual
> selection, social selection and species recognition. Any of
> these can be plausible for individual species, but they fail
> to be persuasive when other lines of evidence cannot
> adequately test them. The first three also fail as general
> propositions when phylogenetic analyses based on other
> characters do not support scenarios of selective improvement
> of such functions in their clade (or the explanation simply
> does not apply to any other species in the clade). Moreover,
> the hypothesis of sexual selection requires significant
> sexual dimorphism, which has never been conclusively
> established in dinosaurs.
>      We propose instead that species
> recognition may have been a more general force that drove
> the evolution of bizarre structures in dinosaurs. That is,
> the bizarre structures communicate to other individuals a
> variety of possible associational cues, including species
> identification, potential protection and social habits and
> the appropriateness of potential mates. In other words,
> bizarre structures amount to an advertisement for positive
> association. Neither species recognition nor any other
> hypothesis should be a 'default' explanation. Although
> direct observation is impossible, we propose two tests.
> First, contrary to adaptive, social or sexual selection,
> under the species recognition model morphology should be
> expected to evolve without obvious directional trends,
> because the only objective is to differ from one's
> relatives. Hence, patterns of evolution of bizarre
> structures should be relatively proliferative and
> non-directional. Second, several contemporaneous species
> should overlap in geographic range (sympatric, parapatric,
> peripatric). Fossil species often show evidence of this
> pattern in the past by 'ghost ranges' of related taxa. These
> tests together could reinforce or weaken an argument for
> species recognition.

That's pretty interesting. Species recognition via morphology - particularly 
when such extreme anatomical features are involved - indicates against more 
easily achieved means of species recognition, namely those found in extant 
dinos: color and voice. A hollow crest may still be involved in 
species-specific sound production, but spine, sails, massive crests etc for 
which a species-recognition function is the best hypothesis would imply that 
the animal was (perhaps apart from the recognition feature) cryptically 
colored, and not very vocal (perhaps apart from ULF-frequency vocalizations).

Particularly significant for restorations/CGI reconstructions. Dinos (and other 
-sauri) have become quite colorful in the last decade's artwork, and they have 
been walking the Mesozoic landscape hollering and bellowing ever since the 
first stop-motion movies. Always struck me as odd; living animals take care not 
to vocalize needlessly either, and for those that do vocalize much, it is 
usually related to species recognition.


Regards,

Eike