Ossified tendon lattices in ornithischians

["Nick Gardner" <ratites637@hotmail.com>]

Hello all!  Now, taking a dramatic jump through the cladograms, I now turn 
from coelurosaurs to ornithischians to delve into their anatomy, because I 
think that these are cool, as I do coelurosaurs, but I know jack about 
ornithischians! :-)

Er... now assuming a much, much more serious nature which may be good thing, 
because I doubt anyone will appreciate having wierd jokes mixed all 
throughout this post.

-- The separation between humor and seriousness starts now --

(Cough)

I am overviewing the interrelationships of certain ornithischians and 
preparing a data matrix.  The best of my current resources, IMHO, is Norman 
1990.  This has more data than any of my other ornithischian refs.  I was 
writing out characters from his "Comments upon iguanodontian systematics" 
section and I noticed he uses "rhomboidal lattice of ossified tendons" as a 
unsubstantiated character supporting the unity of *Iguanodon*, 
*Ouranosaurus*, *Probactrosaurus*, and Hadrosauridae.  He also comments that 
the character is size related.

My personal observations from reading the literature, looking over 
photographs, and my photographs from the Carnegie displays seem to provide a 
confusing situation.  Some taxa have these structures over just their 
dorsals and sacrals (ceratopsians, heterodontosaurids), others have them 
across their posterior dorsals, sacrals and anterior caudals (hadrosaurids, 
Iguanodon, Ouranosaurus), and others have their distal tails engulfed in 
them, with smaller structures across their dorsals, sacrals, and anterior 
caudals (Hypsilophodon).

Can anyone spread light on how this character should be considered?




Nick Gardner

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