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T-Rex: facts and fantasies

The scientific approach 09.06.2017 at 14:54

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Too often, when it comes to Tyrannosaurus, and in General any dinosaurs, the main focus falls on one of t-Rex. Among all the dinosaurs he is much more known to the General public, and as a result, virtually every discovery of a new dinosaur (and even many of reginasaurus) as though compared with him. The attractiveness and visibility of the "king tyrant" dinosaur is such that it has become the benchmark for media, regardless of whether any particular story.

of Course, the Tyrannosaurus Rex in his own way was remarkably interesting animals, but excessive attention to it as a kind of benchmark for comparison is often unfounded. It was a typical dinosaur no more than aardvarks, lemurs and kangaroos – a typical mammal. He was an animal with features, polished by the pressure of evolutionary selection down to the shape, very different from most other theropods and, even if we take the extreme forms, from most other tyrannosaurs. Although the closest relatives of Tyrannosaurus Rex in the birth of tarbosaurus and juantorena was very similar to him, he stands out among them is the fact that for decades have explored it disproportionate, and because of this we now know more about him than about any other dinosaur, Tyrannosaurus was the best model for future research. As the fruit fly, Drosophila (Drosophila melanogaster) is the Central object of genetic research, smooth African clawed frog (Xenopus laevis) – neurology, and the small round worm-nematode (Caenorhabditis elegans) – developmental biology, as Tyrannosaurus is a key animal for most studies of dinosaurs. This fact has obviously contributed to its overvaluation in the eyes of the public (and even in some scientific circles), but it also means that it is the most studied of all dinosaurs. We just know more about Tyrannosaurus than any other extinct dinosaur, and as a result, his biology is an excellent subject for discussion (and for me, by happy coincidence, a great topic for writing the book).

the downside of this situation was that I had to refer to the t-Rex more often than I would like, simply because it is often the only representative of the clade for which this specific trait or behavior was confirmed. Other taxa are understudied, and, although in reality some of them are quite new (such as Tyrannus and lotronex), and the other known for a very small amount of material (proceratosaurus, aviations), or both (nanaksar) is required to conduct much more research in the field of anatomy, evolution, and especially of ecology and behavior of many nyiransabimana tyrannosaurs. Probably early forms partly due to their relative especializando in a sense, merge with medium-sized animals like the megalosaurs, are maintaining or allosaurus as regards potential production, feeding methods, etc. However, the t-Rex is particularly interesting is not so much what animal it was, but how he got that way, and also evolutionary ways, the early tyrannosaurs turned in such incredible animals as albertosaurine and tyrannosaurine.

Another problem is that dinosaurs in General and Tyrannosaurus Rex in particular can cause some people have very strange ideas. No area of science has not been spared from occasional bizarre concepts that can come even from talented and respected scholars, not just "marginal" authors. Even if any disputed issues eventually are resolved in academic circles, the information is not necessarily beyond these circles; "scientists agree" – not such exciting news as "the new controversial discussions around the t-Rex". Thus, the public often only hear the beginning of the story, and future work is given much less attention. This primarily was the reason that never-ending topic being discussed "predator or scavenger", while, in the first place, its hardly worth to raise, and second, she was pulled to pieces in the scientific literature more than once (most detail – paleontologist Tom Holz in 2008).

Some of these issues already mentioned by me, while others have been largely omitted for the sake of clarity of presentation of the relevant chapters, but it should come back, because they tend to generate misconceptions or have a significant impact on our understanding of these animals. I should add here that in recent years there has been a situation when the media take seriously such ideas, which can be called intriguing is that out of generosity: for example, that dinosaurs lived in the water or that they have evolved on other planets, parallel worlds and are alive and well today, avoiding the space in your home mass extinction. I won't go into such marginal ideas here (they are more than the details disclosed in the Internet), but in the scientific literature being a serious discussion about some plausible theories, and it is hard not to notice. And the first – and most important of them is the problem of nanotyrannus.

t-Rex-baby?

In the collections of the Cleveland Museum of natural history exhibited modest size, the skull of a theropod. The skull clearly belonged to tyrannosaurine: a broad back, quickly tapers to the front, converging to a long, but still wide muzzle with a rounded end, and in the jaws of a relatively small number of large teeth. In fact, it looks very similar to the skull of a Tyrannosaurus Rex, only less than half the expected size: the length is slightly more than 50 cm Although this skull apparently belonged to an animal of respectable size, full length of the creature was probably closer to 5 m than to the size of a typical adult T. Rex.

originally Described as an instance of a gorgosaurus paleontologist Charles Gilmore in 1946, the skull subsequently for many years remained the subject of many discussions. Partly because he is somewhat younger than the gorgosaurus and actually could be a contemporary of Tyrannosaurus Rex, but also because it's not the skull of a gorgosaurus, and some other animal. The key question is this: it belonged to a young Tyrannosaurus or is it skull miniature tyrannosaurine who lived next to the most famous of the dinosaurs? The second hypothesis was stated officially by Bob Bakker and co-authors in the 1988 article, where they noted that some of the bones of the skull fused look. If so, then we have the skull of an adult individual, and although the animal was able to grow a little more, it obviously was much less than any other North American tyrannosaurs from the late Cretaceous, and deserves recognition as a species. For small dimensions it was called nanotyrannus.

Since then, the debate raging whether it is the animal representative of a separate taxon, as the mere fusion of certain bones of the skull can hardly be considered a decisive indicator of the maturity of the individual. The following is important: if the skull represents a new taxon, then the t-Rex is not the only tyrannosaurine his time in America, and a large gap in size between T. Rex and the various dromaeosaurs and troodontids at least partially filled with nanotyrannus, and that means for predators of this period a completely different environment, than previously estimated. At the same time, if the skull belongs to a juvenile Tyrannosaurus, we will have a great opportunity to explore the growth and development of animals of this kind; besides what is already known very young instance of tarbosaurus, there is a great field to explore how these animals varied with age and possible ecological separation between juvenile and adults.

Those who support the allocation of nanotyrannus in a new view point to some peculiarities in the skull morphology, which are not observed in known specimens of Tyrannosaurus Rex. For example, in the jaws of nanotyrannus for a few more teeth, but always possible individual variation, and it's unclear how the teeth can change the growth of the animal. We already know that he changed the proportions of the limbs and the shape of the skull, so that some other elements could appear and disappear during growth. However, the number of teeth gorgosaurus different age, apparently, was different, and the same may be true for the t-Rex (even if not applicable to tarbosaurus), but the number of teeth of tyrannosaurs in General was probably a highly variable trait. Moreover, additional tests, such as performed by Thomas Carr, suggest that nanotyrannus and Tyrannosaurus Rex have in common, and the first instance is a juvenile and not fully grown.

This problem is further complicated by the presence of Jane (the name, like most others, was given in honor of the achievements of a person, and does not indicate the gender of the individuals) is a largely intact instance tyrannosaurine young, who is also credited or nanotyrannus, or Tyrannosaurus (Fig. 1). Jane was undoubtedly a young specimen, since its skeleton has many dropped out of the bony sutures, and some histological data also indicate that juvenile animal, but it is a young T. Rex or a second nanotyrannus? Instance Jane at the time of death exceeded 6 m in length, and therefore, given the upcoming significant growth, it was hardly "dwarf" animal; moreover, he found more teeth than a typical adult T. Rex, and this supports the idea that the number of teeth in the growth decreased. Several features unique to the Tyrannosaurus, seen in Jane, affirming the idea that it is a young Tyrannosaurus. However, given the similarity of the skull of Jane and the Cleveland findings, we can assume that the second is also "only" a young Tyrannosaurus.

And the last complication of the picture was controversial instance, recently excavated in the USA and are in private hands. Small t-Rex found near ceratopsia, presumably representing the result of a deadly battle (needless to say that the majority of experts are very doubtful), and the hypothesis was expressed that this new instance "solves" the problem of nanotyrannus. However, although this copy is for sale, it has not been available to scholars, so while this theory refers exclusively to the fantasy. A few not very good pictures not fully assembled instance – is not something on which you should base judgments, so currently, this instance is an unfortunate side branch of the overall problem.

there is a Growing amount of evidence that both Jane and the Cleveland skull belong to a real T. Rex, based in part on comparisons with a very young specimens of tarbosaurus from Mongolia and growth trends observed in other dinosaurs. If this assumption is correct, we have a superior scale of growth to harvest even more backed up stored in Los Angeles a small fragment of the muzzle, belonging to a very small specimen, about a year old, judging by the size. In fact, all this suggests the existence of certain differences between tyrannosaurinae. Even shattered, the skull of tarbosaurus looks a little more like an adult, ie it is assumed that the animal has in all ages remained approximately the same shape of the skull, it just got bigger. Meanwhile, Jane skull more skull-like early Tyrannosaurus Rex or alinamin (long and narrow, without a broad back); the growth of the back wall "inflated", forming the classic shape of the skull of a Tyrannosaurus Rex. This indicates significant changes in the functioning of the skull and, perhaps as a consequence, in the ecology of the animal. At the moment, despite some significant counter-arguments, it is better to consider nanotyrannus invalid taxon, not special pygmy t-Rex, no matter how attractive it may seem the idea.

Two Tyrannosaurus Rex?

the Problem of nanotyrannus is just one of a number of taxonomic complexities associated with the question whether the Tyrannosaurus Rex only t-Rex end-Cretaceous in America, as some experts have suggested that there is a second species of Tyrannosaurus. The idea of this so-called t-Rex x first appeared the paleontologist Dale Russell, although the nickname x was given to him Bob Becker. It was based primarily on the fact that some specimens of Tyrannosaurus Rex were at the front of the tooth bone a few small teeth, not one, and that the skulls of some specimens looked much larger than others. Based on these and other proposed differences, the future, the researchers picked up the idea and suggested that the second t-Rex may be hiding among the available instances of Rex.

In a sense, it would be logical: it is noteworthy that the t-Rex, apparently, was the only large predator in its ecosystem, while in modern ecosystems, mammals, and ancient dinosaur usually had two or more species of large predators, i.e. the ecosystem of a Tyrannosaurus Rex looks a bit strange. However, data are scarce, besides the differences between the animals is very small. Of course, between the existing instances there are differences, but you can expect that at least some of them associated with intraspecific variability, and even a few small sustained differences do not necessarily indicate the presence of individual species.

This issue resonates with the idea that the known specimens of Tyrannosaurus Rex there are two identifiable types of the Constitution, designated as "powerful" and "gracile" form: i.e. one is more dense, in proportion to other more fragile. Moreover, it is assumed that the two types of Constitution is not just associated with General differences in appearance, as thick or thin of people, they are allegedly linked with implicit sexual dimorphism, where one form is correlated with males and another with females. As already mentioned, some specimens of dinosaurs (especially t-Rex) get nicknames, but these nicknames are mostly random and not connected with the sex of the animal, so sue is not more female than Bucky or Stan – males. Previous ideas about the distinction between males and females based on the number or shape of the bone chevrons proved ineffective, and the only reliable way to identify the Mature females is the presence of medullary bone. However, even here its absence may indicate either that the animal was a male, or that the death occurred outside the breeding season, in addition, not all instances were studied.

so, are there any of these "morphs", and if so, should be correlated with males and females? And who is who? The majority of researchers remain very skeptical about these ideas. The data are limited, and most of the materials do not overlap in terms of the existing parts of skeletons, in addition, there is variation in time and space. All instances that are separated by thousands of square kilometers and millions of years, attributed to the same species, but theoretically they were supposed to be representatives of very different populations. Thus, even if there is a sign indicating the possibility of separating instances into two groups, how this picture will be distorted by the errors of such data and the fact that animals almost certainly were varied in sizes and shapes in the process of evolution (growth and variability of individuals will also cause difficulties)?

It says not to delete any of the discussed hypotheses, but the inevitable limitations of such an analysis, we should look for much more obvious and persistent differences between two alleged groups. We observe subtle distinctions between various closely related species, but even so usually there are some stable and clear anatomical features that can be used to distinguish between them, and this is the basis of the morphological species concept applied to dinosaurs. We will inevitably have to wait for additional data: new information should lead to an unambiguous interpretation of the results, and if a sufficient number of fossil specimens, it may be possible to analyze the individual populations to eliminate many of the problems discussed above.

Research is ongoing, and although controversies continue to emerge and become the subject of debate, in fact they often lead to additional exploration and refinement of ideas and the development of better diagnostic methods and datasets to support or refute the current point of view. Therefore, controversial ideas can be useful to stimulate new research; the problems start when these assumptions continue to cling long after they are disproved. The concept considered here is at least plausible, defend and discuss serious scientists, but still the idea of "on the verge of madness" also have value. In any case, they show an endless fascination for T. Rex, and directed attention to it.

the Passage from the book of David Hawn "the Chronicles of t-Rex: the Biology and evolution of the most famous predator in the world"

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