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



"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minimus_ to _Troodon_ (citing unpublished evidence).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.)"

There is a little more to the 1980s Troodon-as-"hypsilophodont". At Egg Mountain there was a space of years that the distinction between Troodon & its eggs and Orodromeus wasn't clear. The Horner team had the eggs and troodontid teeth as well as postcrania of Orodromeus. There were some SVP talks (and SVP Bulletin news items) following the idea that Troodon was a small hypsilophodont, for which they had the eggs. Horner discusses this in Digging Dinosaurs.

And I think THIS is the actual inspiration for Lambert, although perhaps Galton's was.

On Sun, Aug 13, 2017 at 10:00 PM, Tim Williams <tijawi@gmail.com> wrote:
Thomas Richard Holtz <tholtz@umd.edu> wrote:

> In a related point, if Pisanosaurus does prove to belong in a clade with
> Silesaurus, Asilisaurus, and co., but not dinosaurs, a strict reading of the
> rules means this family should be Pisanosauridae (which has a 30-some year
> priority over Silesauridae).


According to ICZN Article 13.1.1., for a new taxon to be valid, "it
must be accompanied by a description or definition that states in
words characters that are purported to differentiate the taxon".
(This is why Lewisuchidae can be quashed in favor of Silesauridae;
even though Lewisuchidae [as Lewisuchinae] was named 22 years before
Silesauridae, it never received a formal description or diagnosis.)

Even after reading the description of _Pisanosaurus_ (a translated
version, https://urldefense.proofpoint.com/v2/url?u=http-3A__paleoglot.org_files_Casamiquela-5F67.pdf&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=LCpntSTt4htEL66zJOrqN28rCan013zkP6PLjRCfmTk&s=yvc_ZQIoQCudttaaNjrXR5drI-PHteKQYsR5l7K8dV4&e= ) I'm not
certain Pisanosauridae conforms to Article 13.1.1.  _Pisanosaurus_
received a description, and Pisanosauridae is erected as part of this
description... so the unique anatomical characters that distinguished
_Pisanosaurus_ from the remaining ornithischians also distinguished
Pisanosauridae at the same time.. so I guess it's okay.  As you know,
Agnolin and Rozadilla note that their referral of _Pisanosaurus_ to
Silesauridae is not particularly secure (though superior to regarding
it as a basal ornithischian), which is a good reason for retaining
Silesauridae over Pisanosauridae.  (The authors also invoke ICZN
Article 23.9.1.2, but I don't think that applies, given that
Silesauridae was named less than 10 years ago).



David Marjanovic <david.marjanovic@gmx.at> wrote:

> > Tyrannosauridae should certainly have preference over Deinodontidae.
>
> Of course. If you'll write a petition to the Commission, I'll join it.


We shouldn't need to.  ICZN Article 23.9.1.2 should mean
Tyrannosauridae can still be used in preference to Deinodontidae.



--

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu         Phone: 301-405-4084
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