re: Tanystropheus egg question

[David Peters <davidrpeters@earthlink.net>]

Earlier I queried:

IF pterosaurs hatched from eggs,
THEN would tanystropheids also hatch from eggs?
and if so,
how would that work out â?? with a _stiff_ neck on the smallest known
specimens already twice the torso in length?
Then apply the same parameters to Quetzalcoatlus.


I'll post pictures early next week at pterosaurinfo.com > taxa >
tanystropheus to show some of the parameters involved with this line of
questioning. Allometry and scale.

Traditionally (based on Wild 1973 for the most part) Tanystropheus has
been considered a giant prolacertiform with juvenile representatives in
the fossil record. The juveniles have a shorter skull and a larger
orbit. The neck on the small one is incredibly long, however. The
cervical series in Exemplar 'a' is allometrically only 0.73 off the
length of a mid-size adult cervical series, as in Exemplar 'k' (the
biggest Tany, 'q' is evidently based on a mandible, etc.). Prior to
posting pics next week, to give a verbal idea of the difference between
the smallest and largest Tany the entire cervical series of the smallest
is about equal to a single cervical in the largest. And 'a' is small
enough to fit inside the torso of the largest, but at half the size it
would have been more comfortably contained.

I actually have two points I wanted to make.

1. Tanystropheus, even at half of a's neck length, is a poor candidate
for an egg, but okay for an amniotic sac.

2, Maybe we're looking at phylogeny here, rather than ontogeny. Consider
the fact that most adult prolacertiforms, including the closest sister
taxon, Tanytrachelos, are more similar in size to the smallest
Tanystropheus.  Maybe the juvie Tanys are really just more primitive
adults? The manus and teeth would appear to be the give-away here. The
"juvenile" proportions of the metacarpus and phalanges don't match the
giant proportions. And everyone knows that multi-cusped teeth appear in
the little ones, not the big ones.  Multi-cusped teeth, big eyes and a
short snout are also found in basal pterosaurs, longisquama,
langobardisaurus, and other prolacertiforms of similar size. The big
Tanys are definitely the oddballs.

There's more, of course, but we'll save those for later.

And yes, it is important for the support of my crazy hypothesis to show
that very few  to no genuine ossified juvenile prolacertiforms are known
in the fossil record. They're all appear to be adults.

Comments?

David Peters
St. Louis