RE: Fwd: juveniles faster than adults.

["John R. Hutchinson" <jrhutch@rvc.ac.uk>]

I generally agree and would broaden the gharial example to almost all crocs
(except some odd small ones like Osteolaemus, maybe), although even adults
are are certainly relatively better at terrestrial locomotion than gharials
(matter of degree). One of these days I'll publish the paper(s)...

There was also some nice work by Glasheen, Hsieh and others on water running
by basilisk lizards, which shows a steep decline in performance with age.
Different principles (hydrodynamics) but same concept of scaling
area:volume.

Finally juvenile animals almost always show a -relative- decline in
performance/athleticism with age (e.g. maximal Froude numbers; peak limb
forces in body weights); that is extremely well established by work on many
tetrapods large and small; e.g. work by Irshick on lizards, Pennycuick 1975
on ungulates, myself and others on elephants, Carrier on hares... just a few
that spring to mind. If interested do a lit search for "ontogenetic scaling"
or "ontogenetic allometry" of locomotion.

Those taxa that decrease -absolute- performance (maximal mph or m/s) just
take that trend to a greater extreme, probably because they cross critical
species-specific size thresholds.

Cheers,
John H


> -----Original Message-----
> From: Jura [mailto:pristichampsus@yahoo.com]
> Sent: 01 December 2010 00:23
> To: dinosaur@usc.edu
> Subject: Re: Fwd: juveniles faster than adults.
> 
> I fail to see why a sprawling gait should invalidate komodo monitors, or
> any other lizards from a question about the speed of juveniles vs adults
> in the tetrapod world.
> 
> We just had an example of this occurrence in wolves, which are
> quadrupedal mammals that get most of their hind limb thrust from the
> pulley-like gluteal muscles (esp gluteus medius). This is very very
> different from how theropods (or any dinosaur) moved.
> 
> We should not be so quick to dismiss comparing dinosaurs to other
> reptiles, especially when the alternative is to compare them to a group
> of animals they haven't shared a common ancestor with in over 235
> million years.
> 
> And since we are on the subject I would also like to submit gharials to
> the list of animals with faster young. Not only are juveniles faster (on
> land at least, making the relevance questionable) but they can also lift
> their bodies off the ground; something adult gharials are incapable of
> doing.
> 
> Jason
> 
> --- On Tue, 11/30/10, Dann Pigdon <dannj@alphalink.com.au> wrote:
> 
> > From: Dann Pigdon <dannj@alphalink.com.au>
> > Subject: Re: Fwd: juveniles faster than adults.
> > To: dinosaur@usc.edu
> > Date: Tuesday, November 30, 2010, 6:54 PM
> > I would also add Komodo monitors to
> > the list. Juveniles need to be faster in order to avoid
> > becoming a meal for an adult. However their sprawling gait
> > probably doesn't make them very good
> > analogues for theropods.
> >
> > --
> > _____________________________________________________________
> >
> > Dann Pigdon
> > Spatial Data Analyst
> >      Australian Dinosaurs
> > Melbourne, Australia
> >      http://home.alphalink.com.au/~dannj
> > _____________________________________________________________
> >
> >
> 
> 
>