Re: The Peters Strikes Back (pterosaurs)

["Jaime Headden" <ja_headden@qilong.8m.com>]

Ron Orenstein (ornstn@rogers.com) wrote:

<What about considering them to be arboreal suspensors?  Longer hind limbs than 
forelimbs are certainly a feature of a number of
arboreal animals, such as sloths, some fossil "slothlike" lemurs, and gibbons 
(though I'm not suggesting pterosaurs were
brachiators!); perhaps colugos are not a bad analogy.>

Of all suspensorial animals, there are usually equally-long limbs (not counting 
the wing finger here, and the forelimb usually
includes the scapula for effective length for suspensorial mammals), very large 
and strongly curved claws on both hands and feet,
generally also of equal size, and elongated penultimate phalanges that bear a 
curved shaft and unusual protuberances on their dorsal
or ventral surface, seen alternately in some scansorial mammals. These features 
are found in suspensorial primates and in extant
sloths, so its likely they should be expected in other fossil suspensorial 
animals, or a likely similar condition. The absence of a
rotary ankle, large pedal phalanges, large pedal claws (except in 
*Jeholopterus,* it seems, who seems to be a likely candidate for
scansorial animal) in pterosaurs makes me suspect there were no suspensorial 
forms known yet. Colugos have disproportionate limbs,
small claws, and I am not familiar with their autopodial morphology.

  A mobile forelimb in mammals may be solved by a fixed shoulder girdle in 
pterosaurs with longer forelimbs. But this does not take
away the pedal adaptations, where the pes must face medially; this also occurs 
in many sciuromorph rodents (scansors) and the highly
scansorial/arboreal procyonids and the viverrid *Cryptoprocta.* These animals 
also have a manus/pes of equal size.

  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)