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Basal Hadrosauroidea

  I notice that *Eolambia* (Albian-Canomanian),
*Telmatosaurus* (u.Campanian?-l.Maastrichtian?),
*Protohadros* (m.Cenomanian), *Secernosaurus* (Upper
Cretaceous: Brett-Surman, 1979), *Gilmoreosaurus*
(u.Cenomanian?-l.Campanian? = Djadokhta
F.-equivalent), *Claosaurus* (u.Campanian?), the
previously-noted La Solana, España, jaw and teeth
(Upper Cretaceous, Company et al., 1998: _Oryctos_
1:121-128), *Orthomerus* (Maastrichtian),
*Ouranosaurus* (l.Aptian), and *Probactrosaurus* (var.
spp. all u.Lower Cretaceous, *Psittacosaurus*
horizons) all demonstrate that relatively rapid
differentiation of hadrosaur-like iguanodntians within
the last 30my of the Cretaceous, but that the actual
origin of these forms stemmed from the Laurasian of
the Early Cretaceous, and spread elsewhere. The
earliest forms are from America and Mongolia, as well
as Africa, and these forms may have spread from one
Laurasian continent to the other, and differentiating
the unique *Ouranosaurus* on the way. It is my thought
that the faunal differentiation went something like
this:


  Mongolia -> Europe --> Africa
                     \_> NAmerica -> SAmerica

  or more linearly:

  Mongolia -> Europe -> Africa -> SAmerica -> NAmerica

  Relatively wide-spread skeletal plesiomorphies are
possibly responsible for the wide array of very
similar forms from most continents. Cranial remains
exhibit the most differentiation, as suggested by the
number of different taxa named from similar skulls
that exhibit slight changes, or from similar forms
with highly distinct cranial changes.

  Anyway, my .02c,

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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