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Ossified tendon lattices in ornithischians

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 --


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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