Nannotyrannus

[fossilman7]

hey i want to start by saying that im not trying to start a flame war. but i want the forum's opinion. is nantyrannus its own species? according to "dino" george blasing, rob barker, and peter larsen think that it is its own. but phile currie and dinosaurs uncoded apparently think it is a juvenile t.rex. Many differences are the teeth of nanntyrannus were thin for slicing meat, while t.rex's were for crunching bone. and nanno had 17 teeth in the lower jaw, while t.rex had 13. another is that it seems that nanno's bones were fused, thus representing a 17 ft. full grown dino, while t.rex was 38-45 ft. lastly, its brain was both preportiand differently and was in a different place in the skull than t.rex. thus holding its head in a diff. angle. many see this as undisputible evidence, but the haters gotta hate. they see explainations. they say that they would grow thick teeth when they were hunting live, bulky dinos instead of relaying on mom's scrapes. they alkso found a specimin "tinker", a juvinile t.rex that had 15 teeth in the lower jaw, saying that as they grow, they lost teeth sockets. they also vaguely explained the brain with the dracorex theroy. tdracorex was once its own species, but no0 is just a young packsepholasaurus. they said the skull would change matrix and brain shape. they couldn't explain the lower head placement. as far as i am concered, it is its OWN species. what do u think. Please feel free to vote and leave a comment. Thanks.

Andrew

Edited March 6, 2011 by fossilman7

[tracer]

andrew, i'm not going to vote on it because i don't think i know as much about the subject as you do, but i'll say that i think you're doing well by reading as much as you can about stuff like this that interests you to try to decide what the truth is.

i've said before a number of times on this forum that i worry a bit about people deciding things are a particular species without a lot of bones to study to figure out what the real deal is on something. i wish there were plenty of people and plenty of money and time to go out all over the world looking for fossils to do much more to fill in the gaps in knowledge.

i bought a really big book a while back called The Dinosauria and it has a lot of pretty technical information about dinosaurs in it. I like looking at it and trying to understand and remember the things I want to know about dinosaurs. I wish I lived somewhere nearer to where I could find some dinosaur fossils...

[piranha]

Good work Andrew,

One thing is evident from your research. Paleontology is a work in progress endlessly in pursuit of explanations and answers. The business of discovery is constantly in flux. What was assumed today is often rejected tomorrow as new evidence gathers a fresh vision often requiring a shuffling of taxa and species.

Ironically Phil Currie and Bob Bakker were among the first notable academics to suggest Nanotyrannus back in 1988. Since then however, it appears Currie is now convinced otherwise, Nanotyrannus lancensis must be in actuality a juvenile T.rex. I recall when you previously inquired on this that Bobby (Boesse) had a very detailed explanation to help sort out this long standing debate.

Perhaps he will drift in to refresh us and help broaden our scope of recent consensus on this matter.

[Boesse]

Andrew,

Thus far the evidence is totally insufficient to place Nannotyrannus as its own species. The tooth count difference is totally discountable, as many T. rex specimens of multiple sizes now show a general decrease in the number of tooth positions during growth - Nanotyrannus has many, adult large T. rex have few, and 'subadult' specimens like B. rex have an intermediate number. I can't speak for the inner ear data, but those differences may very well fall within the range of variation of a species, or perhaps the compared specimens are from different time periods (say, a T. rex that is a couple million years older or younger than "Nanotyrannus"). Otherwise, difference in tooth shape is easily overcome during growth - especially since the juvenile teeth are lost, and adult teeth come in later. In fact, if we used that same criteria for mammals, 10-year old Andrew would be classified as a different species than current Andrew because of the differences in your adult and 'baby' teeth! There are many more differences between your two sets of teeth than simply having one set with slightly narrower teeth.

Otherwise, Nanotyrannus does NOT show adult features - claims that the skull of Nanotyrannus is 'fused' are BS, as this doesn't really happen in tyrannosaurids like it does in ceratopsids and mammals. Most skulls of diapsid amniotes don't fuse - this is typical for most dinosaurs, and typically only marginocephalian dinosaurs exhibit much in the way of cranial fusion. The skull of Nanotyrannus is not fused - it just happens to be articulated still, while many other T. rex skulls (B. rex included) are disarticulated. Sue's skull was also articulated when it was discovered. The only way of gauging the age of a tyrannosaurid is by doing histology of leg bones and counting lags - which, unfortunately, Nanotyrannus does not have. 'Jane' is a juvenile T. rex and has an identical skull as Nanotyrannus - and limb bones, the histology of which indicates she was a juvenile (only a year or two old if I recall correctly).

That being said, if Jane is considered to be "Nanotyrannus" as well - isn't it a little odd that no juvenile T. rex specimens have been discovered? It is especially odd considering that no juveniles in the size range of Jane and Nanotyrannus have been discovered. This alone - and the fact that T. rex is the only other tyrannosaurid in North America at that time - is by no means trivial. If Jane is a juvenile T. rex (which histology indicates) then Nanotyrannus is also a juvenile T. rex.

Lastly, "Dinosaur" George Blasing is not a paleontologist - he's an actor, and does not do research on dinosaur paleontology, and should not by any means be considered an authority. Bob Bakker is a paleontologist, but says a lot of crazy things that may or may not be testable. Pete Larson is a commercial fossil dealer, and whether or not he is a paleontologist is debatable.

[Auspex]

I can't come down hard in either camp, but I do like the argument as presented by the "lumpers". I also like any opportunity to think of a critter as an dynamic package; more fun to consider over the course of its life than as a snapshot of the day it died.

Someday, this may be (largely) settled, but the process of getting there is scholarship at its best.

[bear-dog]

I choose [c] it's still up for dabate.

Actually c was chosen scientifically.My teachers were lazy and always placed the correct answer in the same place [c].The other stupid kids....oops I mean the other students could not figure this out.This knowledge and hookd on fonics got me through skool. :lol:

Edited March 6, 2011 by bear-dog

[RCFossils]

Hopefully the "Tinker" specimen will answer a lot of the outstanding questions.

Personally, I am not yet convinced. There are several features in the skull which would have had to change radically to conform to adult T-Rex skulls.

I was fortunate to be present at the opening of the "Jane" field jacket at the Burpee Museum in Rockford IL. It is an incredible specimen.

I am heading to the Burpee Museum today for Paleofest 2011. I will post some pictures when I get back.

[siteseer]

I think it is an interesting question, "isn't it a little odd that no juvenile T. rex specimens have been discovered?" Tyrannosaurus fossils are rare but a lot more people have been looking for them in the Hell Creek and same-age sediments so there are at least twice as many specimens talked about than there were 15-20 years ago. In that time Nanotyrannus appeared but no T. rex juveniles have. That doesn't seem to bother as many people as it should. Sure, T. rex juveniles would be rare and rarer than adults, but hey, it turns out so is Nanotyrannus. Smaller carnivores should be a lot more common than apex predators.

I met Phil Currie once. He gave a talk in Bakersfield several years ago. He was heading home after a few months of being on the road. I was lucky to be invited along when he had dinner with Bob Ernst. I can understand why others speak so highly of him - his scientific knowledge and experience. On top of that, he was very down-to-earth and uninfluenced by the popular theory-of-the-day when he gave an opinion. I doubt he has ever worn a fedora. If Currie thinks Nanotyrannus is a juvenile T. rex, it isn't because he's hanging his hat on one or two anatomical features. I would side with Currie and Boesse (even if he has worn a fedora) on this one.

[Paleoc]

I think it is an interesting question, "isn't it a little odd that no juvenile T. rex specimens have been discovered?" Tyrannosaurus fossils are rare but a lot more people have been looking for them in the Hell Creek and same-age sediments so there are at least twice as many specimens talked about than there were 15-20 years ago. In that time Nanotyrannus appeared but no T. rex juveniles have. That doesn't seem to bother as many people as it should. Sure, T. rex juveniles would be rare and rarer than adults, but hey, it turns out so is Nanotyrannus. Smaller carnivores should be a lot more common than apex predators.

I would think that juveniles would be more common than adults. Every single adult was once a juvenile and most animals in the wild do not survive to adulthood so you end up with something like this:

Juvenile..Juvenile..Juvenile..Juvenile..Juvenile...Juvenile

...|.............|.............|.............|.............|.............|

Subadult.Subadult.Subadult..DEAD....DEAD....DEAD

...|.............|.............|

Adult.....DEAD.....DEAD

[Boesse]

Paleoc - that's a good point, although that assumes that there's a 1-1 correlation between mortality rate and relative abundance in the rock record. Bones of juveniles have a lower relative preservation potential than adults (in most cases), and in addition, it's easier to find skeletons of adults simply because they're larger and easier to spot.

RCFossils: the difference between the skull shape in Nanotyrannus and T. rex is appreciable to the same changes in skull shape between a juvenile and adult human being - surely, your skull as a baby didn't look like an isometrically scaled down skull of your current self? More extreme transformations in skull shape are already known in other dinosaurs (Pachycephalosaurs, Albertosaurus, Triceratops), and modern mammals (humans, for example).

And Siteseer: I don't wear fancy hats - I have a ratty old 'California Academy of Sciences' baseball hat =)

Bobby

[Auspex]

Here's a question that requires a huge theoretical leap, given the small sample size, but might add another flavor to the stew: was T. rex "R"-adapted or "K"-adapted" (what was their reproductive rate), and what does our narrow sample size suggest from either side of the debate?