Re: Troodontidae (misfits)

["Mickey Mortimer" <Mickey_Mortimer11@msn.com>]

Ken Kinman wrote-

>       Just how secure is the holophyly of this Family Troodontidae?  What
> else could Sinornithoides be?
>       And what about the unserrated teeth in Byronosaurus?  Could this
> family be a wastebasket of two or more convergent clades of misfits?  Are
> they all really all that bird-like?  [Obviously I haven't given up the
idea
> that at least some of them might be bullatosaurian relatives of
> ornithomimes].

Very secure.  And I can't stress that enough.  It's like saying "how secure
is the holophyly of the Tyrannosauridae?  What else could Gorgosaurus be?"
Troodontids can be diagnosed by the following characters-
- most distal posterior serration forming tip of tooth
- enlarged elongate maxillary fenestra
- dentary foramina inside lateral groove
- calcaneum lost
- tongue-like extension of articular surface on metatarsal III
- metatarsal IV most robust in pes
They also share the following, although some other taxa exhibit them too.
Still, parsimony suggests it was convergence.
- maxilla broadly contacts naris
- nasals narrow caudally
- numerous teeth
- enlarged serrations
- teeth with blood grooves
- interdental plates absent
- inflated parasphenoid
- no basisphenoid recess
- lateral depression in braincase
- fibula reduced to splint
- arctometatarsus
The unserrated teeth of Byronosaurus are of no consequence.  It's actually a
separate OTU in my analysis and always clades with other troodontids,
despite the fact I don't have any of the non-homoplasic characters above
included.  You're looking at the wrong taxa if you want to break something
up.  Segnosaurs and troodontids are quite valid.  Try dromaeosaurids.

Mickey Mortimer