Is Nanotyrannus A Separate Species Or Is It A Juvenile T Rex?

[Troodon]

Yes but I have teeth identical to those that are 1 1/2". My Rex teeth of similar sizes are very different, fatter with larger serrations. Jane in my opinion is an sub-adult or adult.

[Raptor Lover]

I have mixed feelings on the subject. I have prepared and mounted examples of both dinosaurs. What I took away from my own experience is that they are definitely related. There are some remarkable similarities. There are also some differences in the two as well. These differences can be explained away as simply the differences in development that come with age. Can tooth shape be explained away bast on this theory? It has been proven in other species. T-Rex also has fewer teeth than our little buddy Nano. Less space in the mouth for larger more robust teeth? I don't know. Skull shape is very similar, although Nano is much more gracile. This could be accounted for due to age and maturity. Due to the lack of juvenile skeletons of Rex that are conclusive it may not soon be settled.

I guess this is similar to the debate over Triceratops and Torosaurus.

Seth, in that post, is the first picture a Rex and the second picture a Nano?

[Opisthotriton]

The first image are three juvie Nano teeth, crown 3/8" to 1/2"

IMG_2757.jpg

Thought I would add a couple of Juvie Rex teeth. I'll let you decide which ones they are

IMG_2758.jpg

Keep in mind that the size and shape of the tooth crowns varies with the tooth's position within the jaw. A small tooth is not necessarily from a small dinosaur, be it T. rex or nano.

Look at this T. rex dentary.

http://www.nhm.ac.uk/natureplus/servlet/JiveServlet/showImage/38-3314-60734/t-rex-jaw.jpg

See how there is a very large tooth crown near the front (right) of the dentary, and small short stubby tooth crowns near the back (left ) of the dentary. Your "baby" rex tooth is not a large tooth from a small animal, it is a small tooth from a large animal (I don't know the exact size, since there's no scale bar in your photo).

Slight wear on the very top of the baby Rex tooth see attachment.

Don't have images at the ready on the Nano teeth but will get some.

Trex A1a.jpg

[Troodon]

Your "baby" rex tooth is not a large tooth from a small animal, it is a small tooth from a large animal (I don't know the exact size, since there's no scale bar in your photo).

The crown of that tooth is 5mm long. The tooth was described as from an infant T-rex when it was examined by Robert Bakker and Pete Larsen. I'm sure their expertise in this material gives the ID creditability.

Edit: They also described it as the smallest rooted Rex tooth they had both ever seen. I also have two identical crowns that are a bit smaller.

Edited July 24, 2015 by Troodon

[Troodon]

Here are a couple of pictures of Pete and Robert examining the tooth. Created quite the excitement. Dr Philip Manning was also in group as well as a Paleontologist from the UK whose name I forget. All in agreement.

[Opisthotriton]

The crown of that tooth is 5mm long.

I stand corrected. Sounds adorable!

[Pumpkinhead]

Jack Horner, look what you've done!

[TheClawGuy]

Coming from the Army with credentials to plan higher level and more complex missions, this argument is like planning a mission by using the basic field manual. Example: To plan a sniper mission, you need much more information than distance, terrain and target. Every detail needs to be looked at. Start with the rifle... What caliber, elevation, bullet specs, time of day, and which rifle to use, bolt action or semi auto... Dependent of accuracy needed and potential follow up attack. Now that's the basics of JUST the rifle. Get into the rations, radio frequencies, PACE plan, support fire, time on target allowed, Intel potential, exfil plans, etc... Don't even get me started on an air assault mission or even a demolition based mission. That's just one mission of one day and we ran 3 missions a day on a regular basis. My point argues, rather than simply looking at the teeth, you also take into account the complexity of the entire animal/ mission. There's about 10,000 species of birds, and 22,000 subspecies, 27,000 species of fish, and there's roughly 6,700 species of reptiles. Yet, there's only 700 dinosaur species expanding millions and millions of years longer of evolution. I get we can only study the fossilized remains which is a fraction of the non-fossilized remains, but to assume many more didn't exist would be hubris. Before anyone makes an argument about which researcher says what on those numbers, I'm trying to bring to the table that it's possible another tyrannosaur lived at the same time as the Rex, at the same location with minor variances in features. There's over 150 breeds of dogs that have been created in less than 15,000 years, yet there's only one tyrannosaur found in a certain geological formation spanning over 20 million years? Beyond the teeth, explain the arms, the variances in claw specimens, the brain case, and finally explain how it's NOT possible variances might be less dramatic as the juvenile Rex believers propose? An Akita Inu and a Shiba Inu are very close in genetics, lineage, geological area and time frame YET they are two different animals at much different sizes and that's in a much smaller window of existence. To say a Nanotyrannus couldn't or didn't exist is too dismissive and is just like arguing with a new Lieutenant who is trying to plan a mission based on only the rifle.

[Boesse]

That's all fine and dandy, but in science you have to adequately demonstrate that a new species isn't something else we've already discovered. When Nanotyrannus was discovered, we didn't know what a juvenile T. rex looked like because nobody had ever found one before. Other fossils that look like "Nanotyrannus" but have been histologically sampled are demonstrably still growing (Jane, a juvenile T. rex). In this particular case, Bakker et al. have not adequately demonstrated that Nanotyrannus is a genuine species. The burden of proof is upon the claimed discoverer/namer.

[siteseer]

I think T. rex lived only over the last few million years of the Cretaceous (depending on how you regard Tarbosaurus and perhaps other remains) with the Hell Creek Formation perhaps spanning less than that. The Hell Creek has been intensely collected by scientists seeking to study the K/T boundary - its pinpoint in geologic time plus what lived a few million years before and after that in an effort to judge the severity of the event(s) separating two eras. It has also been intensely hunted by fossil dealers and collectors looking for T. rex teeth. There's a lot of material out there now with scientists having had a look at some of the commercial stuff and yet no one can say that it has been ruled out that Nanotyrannus could be just a young Tyrannosaurus. Personally, I'm not a "dinosaur guy" but I tend to go conservative whenever there's a question of two different genera being given to teeth and bones of what could be reasonably concluded as the remains of juveniles, young adults, and full-grown adults especially when they're found in the same deposit.

You certainly understand the level of detail that scientists work with but it sounds to me that you are making the "Nanotyrannus-is-a-juvenile-T.rex" argument when you point out how different two breeds of dog can be. All breeds of dog belong to the same species. Homo sapiens changes a lot from newborn to adult with some adults not reaching five feet in height while others surpass seven feet. Some individuals have noticeably thicker teeth than others and others have shorter or longer legs in proportion to the rest of their bodies than others. Imagine how much more the range in body shape would be in our species, or any species, if a height of fifteen or more feet could be reached.

Coming from the Army with credentials to plan higher level and more complex missions, this argument is like planning a mission by using the basic field manual. Example: To plan a sniper mission, you need much more information than distance, terrain and target. Every detail needs to be looked at. Start with the rifle... What caliber, elevation, bullet specs, time of day, and which rifle to use, bolt action or semi auto... Dependent of accuracy needed and potential follow up attack. Now that's the basics of JUST the rifle. Get into the rations, radio frequencies, PACE plan, support fire, time on target allowed, Intel potential, exfil plans, etc... Don't even get me started on an air assault mission or even a demolition based mission. That's just one mission of one day and we ran 3 missions a day on a regular basis. My point argues, rather than simply looking at the teeth, you also take into account the complexity of the entire animal/ mission. There's about 10,000 species of birds, and 22,000 subspecies, 27,000 species of fish, and there's roughly 6,700 species of reptiles. Yet, there's only 700 dinosaur species expanding millions and millions of years longer of evolution. I get we can only study the fossilized remains which is a fraction of the non-fossilized remains, but to assume many more didn't exist would be hubris. Before anyone makes an argument about which researcher says what on those numbers, I'm trying to bring to the table that it's possible another tyrannosaur lived at the same time as the Rex, at the same location with minor variances in features. There's over 150 breeds of dogs that have been created in less than 15,000 years, yet there's only one tyrannosaur found in a certain geological formation spanning over 20 million years? Beyond the teeth, explain the arms, the variances in claw specimens, the brain case, and finally explain how it's NOT possible variances might be less dramatic as the juvenile Rex believers propose? An Akita Inu and a Shiba Inu are very close in genetics, lineage, geological area and time frame YET they are two different animals at much different sizes and that's in a much smaller window of existence. To say a Nanotyrannus couldn't or didn't exist is too dismissive and is just like arguing with a new Lieutenant who is trying to plan a mission based on only the rifle.

[Ridgehiker]

I think T. rex lived only over the last few million years of the Cretaceous (depending on how you regard Tarbosaurus and perhaps other remains) with the Hell Creek Formation perhaps spanning less than that. The Hell Creek has been intensely collected by scientists seeking to study the K/T boundary - its pinpoint in geologic time plus what lived a few million years before and after that in an effort to judge the severity of the event(s) separating two eras. It has also been intensely hunted by fossil dealers and collectors looking for T. rex teeth. There's a lot of material out there now with scientists having had a look at some of the commercial stuff and yet no one can say that it has been ruled out that Nanotyrannus could be just a young Tyrannosaurus. Personally, I'm not a "dinosaur guy" but I tend to go conservative whenever there's a question of two different genera being given to teeth and bones of what could be reasonably concluded as the remains of juveniles, young adults, and full-grown adults especially when they're found in the same deposit.

You certainly understand the level of detail that scientists work with but it sounds to me that you are making the "Nanotyrannus-is-a-juvenile-T.rex" argument when you point out how different two breeds of dog can be. All breeds of dog belong to the same species. Homo sapiens changes a lot from newborn to adult with some adults not reaching five feet in height while others surpass seven feet. Some individuals have noticeably thicker teeth than others and others have shorter or longer legs in proportion to the rest of their bodies than others. Imagine how much more the range in body shape would be in our species, or any species, if a height of fifteen or more feet could be reached.

The above is an excellent analysis.

I've collected a few hundred large theropod teeth from various formations here in Alberta. I personally can't tell them apart. Take a random 10 teeth from the Scollard Formation and they may be as different from each other as from another random 10 from the Horseshoe Canyon or Oldman Formation.

Also, we need to remember that species do not pop into existence. There wasn't an Albertosaurus one day and then a T. Rex the next. There may have been a dozen or a thousand gradations over a couple million years. Even then, the taxonomy is subjective.

Taxonomy is paleontology is more elusive than in zoology. There often isn't any claim to two species being separate biological taxa because we have no evidence either way on that. Genus and species are based on morphology, etc. At what stage does a change in a tooth, jaw, femur decide a new species? It is arbitrary. There is a 'type' specimen described and a new find is compared to the type specimen. If a paper is reviewed by ones peers and published in a recognized journal, then it is part of the accepted body of legitimate science. New evidence might come along and the two separate species combined again.

Bottom line. Are these theropods separate? There isn't any answer such as yes or no. It's all subjective based on how much weight one gives some anatomical variable.

[PFOOLEY]

I have been intrigued with the late Cretaceous for a while. The term diversity comes up a lot in late Cretaceous literature, documentaries and conversation. Modern day is very diverse. The fact that I can see five different species of bird in my own yard, on any given day, really gives me hope that there was indeed a smaller, faster tyrant.

Team Nano.

[starman]

I think T. rex lived only over the last few million years of the Cretaceous (depending on how you regard Tarbosaurus and perhaps other remains) with the Hell Creek Formation perhaps spanning less than that.

The supposed synonomy of Tarbosaurus and Tyrannosaurus, proposed in GSP's PDW, was challenged by Hurum and Sabath more recently. Tyrannosaurus seems to have predated the Hell Creek deposition, as it appears present in older UT and NM units. The earlier Tyrannosaurs isn't necessarily the same species though. GSP was working on a paper addressing this issue but it may have been shelved.

[TheClawGuy]

You certainly understand the level of detail that scientists work with but it sounds to me that you are making the "Nanotyrannus-is-a-juvenile-T.rex" argument when you point out how different two breeds of dog can be. All breeds of dog belong to the same species. Homo sapiens changes a lot from newborn to adult with some adults not reaching five feet in height while others surpass seven feet. Some individuals have noticeably thicker teeth than others and others have shorter or longer legs in proportion to the rest of their bodies than others. Imagine how much more the range in body shape would be in our species, or any species, if a height of fifteen or more feet could be reached.

I don't see at all how I said "Nanotyrannus-is-a-juvenile-T.rex", I said the exact opposite. A Shiba Inu is quite similar is nearly every aspect of an Akita Inu except for size. So my case states that a Shiba is not a juvenile Akita, hence two different animals all together. I get they are all apart of the Canis Familiaris species but a Shiba is not an Akita just like the Nano and Rex are both a Tyrannosauridae but aren't the same animal. I also get that Homo Sapiens, like all other species, change during growth but what animal's limbs get smaller over age and their brain case shifts? Note that I'm staying away from the tooth argument because that topic has been beaten to death. Edited August 9, 2015 by TheClawGuy

[Boesse]

Siteseer was pointing out that the comparison of dog breeds - being all the same species - is a pretty terrible analogy, and supports a conservative "lumping" interpretation.

Regarding changes in limb size - there's already a trend towards forelimb reduction in tyrannosaurids, likely heterochronic, and as juveniles typically show ancestral morphology that's not quite so surprising. Cats also have proportionally longer limbs as juveniles, relative to adults, for starters. I'm not sure exactly what you mean by "braincase shifting", but the braincase changes significantly in its anatomy from juvenile to adult in practically all tetrapods.

All of these changes that characterize the skeletal growth of vertebrates is collectively termed "allometry".

[cowsharks]

Were the dueling dinosaurs ever sold? The most recent article I can find from 2013 says they didn't sell and went back into storage. One article even quoted a paleontologist as saying he didn't think the dueling dinosaurs had any scientific value because they weren't collected by professionals and none of the normal scientific protocols for documenting and extraction were followed.

Edited August 10, 2015 by cowsharks

[Troodon]

The dinosaurs did not sell at the auction and are currently in storage. I asked your extraction question to a couple of renowned paleontologist who attended the auction and they said it was not a problem. They were extracted in blocks no different than T-rex Sue was.

[-Andy-]

Were the dueling dinosaurs ever sold? The most recent article I can find from 2013 says they didn't sell and went back into storage. One article even quoted a paleontologist as saying he didn't think the dueling dinosaurs had any scientific value because they weren't collected by professionals and none of the normal scientific protocols for documenting and extraction were followed.

Some paleontologists take a hardliner approach, and claim these commercial fossils have no scientific value in order to show their disapproval of auction fossils, as well as to hopefully, send a message to the sellers: "Don't expect any self-respecting museum to spend millions on it!"

[Troodon]

Some paleontologists take a hardliner approach, and claim these commercial fossils have no scientific value in order to show their disapproval of auction fossils, as well as to hopefully, send a message to the sellers: "Don't expect any self-respecting museum to spend millions on it!"

Reminder Sue sold at auction for $8.3M and the Dueling Dino's had a number of museums interested in it for millions but not enough millions.

[TheClawGuy]

Reminder Sue sold at auction for $8.3M and the Dueling Dino's had a number of museums interested in it for millions but not enough millions.

[Cris]

This has been a very informative, thought provoking thread so far. The rarity of juvenile Tyrannosaurus rex specimens when Nanotyrannus is taken out of the picture was mentioned. Do we have a single skull of a juvenile T. rex that is somehow different from what is being called Nanotyrannus? If not, I'd definitely have a problem jumping on the Nanotyrannus band-wagon. We know that there should be something that looks like a small version of T. rex showing up in the same formation eventually since we have adults..and we really have no way of knowing exactly what changes would happen to the skeletal morphology of a T. rex as it matured, do we?

[starman]

I have been intrigued with the late Cretaceous for a while. The term diversity comes up a lot in late Cretaceous literature, documentaries and conversation.

Laramidia appears to have been an exception in that diversity didn't fall elsewhere toward the end although turnover still occurred in western Europe.

[Troodon]

..and we really have no way of knowing exactly what changes would happen to the skeletal morphology of a T. rex as it matured, do we?

Cris, correct we do not know what changes occur as it matures and I believe there are no known juvenile T rex skulls known. This is what we know about the skeletal structure from the Dueling Dinosaurs Tyrannosaur "Nano" its a remarkable skeleton at 99% complete with a phenomenal dark brown bone preservation. Sue the biggest Rex is 85% complete. The arms of this Nano have longer bones and are much more robust than Sue. The finger bones, carpals and arm bones are very different. They appear to be more functional than Sue's. It would see odd that the arms would regress with age but we don't know. It's a shame the seller was greedy because there were lots of museums interested in it because of its preservation and completness. The Cleveland skull had a CT scan done of the brain case and it was different. Everyone does agree that brains do not change with age. Until the Dueling Dino Tyrannosaur or another similar find gets properly studied this debate will continue forever and make for good print and debate. Edited August 11, 2015 by Troodon

[Auspex]

A note on Sue rex; she was correctly and professionally collected, with all data recorded. The fact that she was sold commercially should not impugn her scientific value.

[-Andy-]

One argument for Nanotyrannus and T. rex being distinct species is that Nanotyrannus had more teeth in its upper and lower jaws than adult T. rex. This wouldn't be due to growth stage differences, as Tarbosaurus bataar juveniles and adults had the same tooth count, and paleontologists believe that T. bataar was extremely closely-related to T. rex (so much so some consider them to be both Tyrannosaurus genus).