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Re: smallest pterosaurs



Dave Peters (davidrpeters@earthlink.net) wrote:

  <... http://www.pterosaurinfo.com/smallest_pteros.html ...>

  I will agree with David, there were some really small pterosaurs,
Tischlinger's *Anurognathus* among them. No one said pterosaurs did not
get very, very small. There has been no argument, however, that argued all
tiny pterosaurs are juveniles, which may be conflated in this issue with
HOW to identify juveniles. In some cases, Dave illustrates skulls as if
they had unfinished edges, to describe the crushed yet reconstructed
nature of the cranial material: at which point are these skull's
questioned for their accuracy? At what resolution of image size are these
done? There are things that personal observation under a 'scope would
resolve better than others, this is no exception. Not that I disagree with
these interpretations, however.

  *Eudimorphodon cromptonellus* is assuredly among the tiny range for an
averaging much larger species, and the incomplete nature of the skull
obscures some needed details. Isolated teeth referred to as eudimorphodont
are rare, and all ways come from larger animals, suggesting small animals
are seldom preserved, or the teeth are overlooked, easy to do when they
are only micrometers long.

  A note on some paedomorphism:

  Small animals will have large eyes on the whole. This should have been
pointed out before, but at the time, we were getting conflated with
juvenile identification. In fact, small animals will have VERY large eyes
(if they use them well) compared to their orbit sizes, than larger
animals. These animals have eyeballs the size of or larger than their
orbits, as in the pipistrelle and other small microbats, and the orbits
are incredibly large compared to their size than in larger bats. Indeed,
portions of small mammal, lizard, and bird skulls tend to be almost
transparent in nature and it is not hard to imagine these filament-thick
bones (yes, they still ossify!) to be rendered invisible during
preservation, if the replacement minerals are larger than the calcite
crystals forming the bone matrix. This would give the look of "incomplete"
preservation, just as much as impressions will likely show up for these
elements (as they do with cartilaginous elements in some amphibian
fossils, in some calcified shark and ray fossils, and in some Recent bird
and mammal fossils/subfossils) -- if the circumstances are right.

  Bear caution in denoting a fossil a juvenile or an adult, with regards
to the sediment it's buried in (I've made this point before): different
sediments preserve in different ways, and it would bear some here good
measure to look into how different sedimentary regimes cause fossils to be
preserved. Say, Bear Gulch versus Mazon Creek for fossil sharks ... or
Chengjiang versus the Burgess Shale ... or Solnhofen versus Sihetun.

  Thanks for the useful comparisons, Dave!

  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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