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[forelf@internet19.fr: Gorgosaurus, Daspletosaurus and others]

Felix Landry occasionally has difficulty getting mail to the dinosaur
list, so I'm submitting the following on his behalf.  Note that I
didn't write anything below the dashed line, so edit your attributions
and reply addresses accordingly!

-- MPR

To: mrowe@indiana.edu
From: forelf@internet19.fr (Francoise Forel)
Subject: Gorgosaurus, Daspletosaurus and others
Date: Sun, 07 Jun 98 12:19:48 PDT

I just checked my character list on Albertosaurus and the streched-snout

Albertosaurus: Characters 1) (well developped lacrimal "horn"), 2) (well
developped potorbital "horn"), 3) (pointed posterior process on
surangular), 5) (angular with one or two strong dorsal processes), 6)
(jugal with strong pointed ventral process), and 7) (very large surangular
foramen) are OK. Character 4) (jugal-postorbital suture forming a broken
line) isn't present, and the character seems invalid.

Streched-snout daspletosaur: Character 1), 2), 3), 6) and 7) are OK.
Character 4) is not present, and I wasn't able to check character 5).

Now, here's a discussion of each character presented in the original list:

1) This character is probably phylogenetically informative.
Plesiomorphically, there was a small lacrimal "horn" in tyrannosaurids. One
lineage made it much larger; the other one reduced it.

2) I'm not sure this character is valid. Tyrannosaurus could have had a
lerge postorbital "horn", too. If so, this character is diagnostic of the
gorgosaur-daspletosaur+tyrannosaur group.

3) This character is not very strongly developped in Albertosaurus and
Gorgosaurus, it is quite well developped in Daspletosaurus and the unnamed
beast. It is probably informative.

4) This character is obviously variable and uninformative.

5) This character is probably valid. Albertosaurus and Gorgosaurus have one
dorsal process on angular, and Daspletosaurus has two. I don't know the
condition in the unnamed daspletosaur, but I suppose there are two large

6) This character is relatively weakly developped in Gorgosaurus and
Albertosaurus; it is well developped in Daspletosaurus and very strongly
developped in the unnamed daspletosaur.
7) This character is probably informative. I think it is equally developped
in all examined species.

Now, here's my view of tyrannosaurid classification (* means primitive):

          Unnamed group
                    Unnamed group*
                         Gorgosaurus (?*)
                    Unnamed group (?=Daspletosaurus)
                         Unnamed streched-snout daspletosaur
               Tyrannosaurini (?=Tyrannosaurus)
                    "dwarf" forms*
                         T. bataar*
                         T. rex

That's all for now. Any comments/corrections would be appreciated.

Next time I'll post the list of differences between the two Tyrannosaurus
species (and they are many!).

Felix Landry
e-mail: forelf@internet19.fr

Thanks in advance, Mickey!