Re: [dinosaur] Latenivenatrix, new troodontid from Dinosaur Park Formation, Alberta (validity of Troodon)

[Tim Williams <tijawi@gmail.com>]

Matt Martyniuk <martyniuk@gmail.com> wrote:

> Well, there was some question over whether or not Troodon was an ornithopod 
> at one point.


Historically speaking, _Troodon_ has had an interesting journey.  It's
been regarded as an ornithopod more than once.  The first time began
when Gilmore synonymized _Stegoceras_ with _Troodon_ in 1924, and
therefore regarded _Troodon_ as a pachycephalosaur (which were
classified as ornithopods back then).  This was reversed by Sternberg
two decades later when he re-classified _Troodon_ as a theropod.

The second time _Troodon_ was regarded as an ornithopod was much
briefer and more obscure, but it did gain some traction in the popular
literature.  In 1983, Galton referred the small ornithopod _Laosaurus
minimus_ to _Troodon_ (citing unpublished evidence).  This spawned the
idea of _Troodon_ as a carnivorous ornithopod, which appeared in David
Lambert's popular dinosaur book _A Field Guide to Dinosaurs_ (which I
knew as _Collins Guide to Dinosaurs_) - there was even an illustration
of this alleged meat-eating ornithopod.  (Although I was very young at
the time, I still remember uttering a 'WTF'.. or something
equivalent.)


> But what we now think of as "troodontids"
> were fairly well known, and known to be theropods. Saurornithoides, 
> Stenonychosaurus, etc. It's just that they were called
> Saurornithoidids back then until Currie synonymized Stenonychosaurus with 
> Troodon.


I'd agree with this in broad terms; but as with most things to do with
_Troodon_, the situation re Troodontidae/Saurornithoididae was
somewhat more complicated.  Barsbold (1974) expressly rejected a close
relationship between _Troodon_ and _Saurornithoides_ when he proposed
the family Saurornithoididae.  In fact, he erected Saurornithoididae
to include _Saurornithoides_ and _Stenonychosaurus_ and to pointedly
exclude _Troodon_: "The teeth of _Saurornithoides_ Osborn differ
strongly from those of _Troodon_ Leidy, forming the basis for removing
_Saurornithoides_ and _Stenonychosaurus_ from the Troodontidae."  I
know this interpretation wasn't the consensus at the time, but it
shows that what we now think of "troodontids" didn't always include
_Troodon_.