Troodon no longer a valid genus: Latenivenatrix and Stenonychosaurus replace it

[Sim]

I'm wondering now, is the large Alaskan "troodontid" actually known from more than just teeth?  If it's only known from teeth, it seems like a bad idea to name it, considering how unhelpful it's been when dinosaur species have been named for teeth.

Ah, so Troodon may still exist. Just as another mystery dinosaur we know almost nothing about.

Since Troodon-like teeth can't be used to identify a species, it's a case of: Troodon might represent a different species to other named species or it might be the same as another existing species, but we don't have a way to know, so Troodon is no longer considered a valid classification.

That could be another case like Spinosaurus, a very popular name that most people don't know we actually know very little about. Although a bit more on the extreme side, cause there's only a tooth here. I wonder what could happen if future finds would prove that such tooth belonged to a completely different kind of animal, not a troodontid at all. Would the name Troodon remain valid, and would the name Troodontidae remain valid for the family?

I think a difference between Spinosaurus and Troodon is that Spinosaurus is based on diagnostic remains while Troodon isn't.  That's why the former is considered a valid classification while the latter isn't.

Troodon being found to be a different kind of animal to other troodontids has already happened in the past.  The family Troodontidae was originally created to include animals like Pachycephalosaurus and Stegoceras, which at the time were thought to be species of Troodon.  Animals we call "troodontids" today, e.g. Saurornithoides and Stenonychosaurus were called saurornithoidids.  When people became aware that Troodon was a theropod, Troodontidae could no longer be used for the dome-headed dinosaurs, and the family was given the new name Pachycephalosauridae.  When Philip Currie synonymised Stenonychosaurus with Troodon in 1987, he also synonymised Saurornithoididae with Troodontidae, and that's how saurornithoidids became known as troodontids.  If Troodon was found to be a different kind of animal to other animals currently called "troodontids", it would basically be a repeat of what happened with the pachycephalosaurs.  Troodontidae could no longer be the name for the family, and I understand Saurornithoididae would become the family's name again.


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This next part is in response to both of the posts quoted above:

Since Troodon is currently based on a tooth that is not diagnostic, even if diagnostic remains from the same formation are found that could belong to the same species, it doesn't change the fact that the tooth can't show the remains belong to the same species as the tooth.  It seems to me that a neotype would have to be made for Troodon to keep the name valid.   But even if remains from the same formation are found that could be used for a neotype, there's no guarantee a neotype for it will be made.  Leaving a name as a nomen dubium instead of creating a neotype for it when it's possible to has happened before with another classification from the same formation as Troodon: Ceratops.  As Tim Williams said in this DML message that WarrenJB referred to earlier:

A similar situation came up for _Ceratops montanus_, another
time-honored taxon named from non-diagnostic material.  The only hope
of keeping _C. montanus_ alive as a valid genus and species is based
on new/referred material.  The best chance was the diagnostic
chasmosaurine specimen CMN 57081 from the JRF, which matched the _C.
montanus_ type material both osteologically and stratigraphically.
The study that described this material (Mallon et al. 2016
DOI:10.1371/journal.pone.0154218) actually stated "It is possible -
even likely, given their close stratigraphic and geological
association - that '_Ceratops_' and CMN 57081 are the same species".
However, they went on to say "without conclusive evidence for such, it
is preferable to erect a new species for CMN 57081."  So CMN 57081 was
granted its own genus and species _(Spiclypeus shipporum_), rather
than being referred to _Ceratops montanus_.  I reckon the same thing
could happen if a diagnostic JRF troodontid specimen was discovered in
the vicinity of the _T. formosus_ type locality.  Unless a neotype was
nominated (and approved), there would always be doubts over whether it
should be referred to _T. formosus_.

[PaleoMatt]

Thanks, Sim. For clearing up all the information I can only hope Troodon stays valid as a genus as it is my favourite non-avian dinosaur (The Alaskan species to be exact!) but we must wait to see what happens next!

[Dinoguy2]

Thanks, Sim. For clearing up all the information I can only hope Troodon stays valid as a genus as it is my favourite non-avian dinosaur (The Alaskan species to be exact!) but we must wait to see what happens next!

Keep in mind: your favorite dinosaur still exists and is still valid! All we are talking about is it's name.

If my brother changed his name, would I be sad, because now my brother is gone? Uh... no. I would still love my brother. Nothing has changed except now I need to get used to his new name.

If your favorite is the Alaskan species, well A) that's weird because it's a pile of teeth and bone scraps, but people like what they like! and B) It never had a name and has only been called Troodon up until now by convenience

[HD-man]

3 questions:

1) Is there a map showing which specimens were found where like "Torosaurus and Triceratops distribution" ( http://news.bbcimg.co.uk/media/images/58768000/gif/_58768910_dino_464.gif )?

2) What does this mean for the Egg Mountain & Egg Island specimens?

3) What does this mean for Dinosaur Train?

[PaleoMatt]

3 questions:

1) Is there a map showing which specimens were found where like "Torosaurus and Triceratops distribution" ( http://news.bbcimg.co.uk/media/images/58768000/gif/_58768910_dino_464.gif )?

2) What does this mean for the Egg Mountain & Egg Island specimens?

3) What does this mean for Dinosaur Train?

No, not Dinosaur Train!

[Dinoguy2]

3 questions:

1) Is there a map showing which specimens were found where like "Torosaurus and Triceratops distribution" ( http://news.bbcimg.co.uk/media/images/58768000/gif/_58768910_dino_464.gif )?

2) What does this mean for the Egg Mountain & Egg Island specimens?

3) What does this mean for Dinosaur Train?

That Torosaurus distribution map is extremely misleading. It conflates specimens from different time periods and species. The Utah and Texas ones are T. utahensis which lived earlier than the northern T. latus. There are Triceratops-like fossils from that time and area too but they're not included on this chart because they were arbitrarily placed in different genera (like Ojoceratops) while utahensis is only included because it was lumped. T. utahensis might not even be related to Torosaurus proper.

Anyway, a Troodon specimen map would face the problem if what to include. Troodontid teeth from pretty much every time and place in Nirth America have been called Troodon. You may as well ask for a map of Trachodon specimens.

[Sim]

2) What does this mean for the Egg Mountain & Egg Island specimens?

Egg Mountain is in the Two Medicine Formation, and from what I've seen, in the paper that names Latenivenatrix it says: "Similarities between frontals and metatarsals of Stenonychosaurus inequalis from the Dinosaur Park Formation and those of the Two Medicine troodontid suggest that the two taxa may in fact be the same species. Further investigation into the Two Medicine Formation troodontids is required to confirm the assignment of these specimens to Stenonychosaurus inequalis."

I was reading about a Two Medicine Formation troodontid on the Stenonychosaurus Wikipedia page, it seems it provides quite a bit of information, like that it appears to be an adult male that was brooding its eggs.  It's specimen MOR 748.  I've tried to see a photo of it, but I haven't found any.  Hopefully further investigation into the Two Medicine troodontids will be done which will provide a photo of MOR 748 and will classify them in a species.

I don't know about Egg Island specimens, I hadn't heard of them before.

[UtahraptorFan]

This means that the Kaiparowits diorama at the Natural History Museum of Utah now features 2 genera from families that take their names from dubious genera: the troodontid, Talos, eating the ceratopsid, Utahceratops. I've always suspected that the Talos was scavenging the kill of a Teratophoneus.

[Neosodon]

This means that the Kaiparowits diorama at the Natural History Museum of Utah now features 2 genera from families that take their names from dubious genera: the troodontid, Talos, eating the ceratopsid, Utahceratops. I've always suspected that the Talos was scavenging the kill of a Teratophoneus.

You seem quite familiar with the NHMU. I volunteer there sometimes. It would be funny if we met but we wouldn't even know it, lol.

[UtahraptorFan]

This means that the Kaiparowits diorama at the Natural History Museum of Utah now features 2 genera from families that take their names from dubious genera: the troodontid, Talos, eating the ceratopsid, Utahceratops. I've always suspected that the Talos was scavenging the kill of a Teratophoneus.

You seem quite familiar with the NHMU. I volunteer there sometimes. It would be funny if we met but we wouldn't even know it, lol.

I've been there once a year the past 3 years.  In 2015, that and lunch at Red Robin were what my mom said she wanted to do for Mother's Day; last year, I went in April, so before they announced Machairoceratops; and this year, I went up for day two of DinoFest, which was very cool!