This question is certainly well outside my field, and thus I don't have much knowledge of specific evidences or examples. I do, however, have some vague understanding of some of the avenues of research that are used to develop many of the current models. I'll take a stab at this and share with you my views on the matter, but when it comes to details I must defer to others more familiar with this field.
First off, I think that most depictions of dinosaurs are influenced greatly by what we know of modern reptiles. The comparison in many ways is a natural, unavoidable bias of sorts, but one that seems reasonable, given that one could expect that dinosaurs would in fact be similar to modern reptiles in many ways. Analysis of bone structure offers some indication of what a dinosaur looked like in terms of musculature and shape (similar to how forensic scientists today may reconstruct what a person probably looked like based on skull characteristics). Certainly our concept of what dinosaurs looked like in terms of color is almost certainly a matter of speculation based upon the colors of modern reptiles. The colors found in drawings of dinosaurs are probably in large part the result of artistic impression, to add a touch of realism in order to better visualize and appreciate what they might have looked like. In some ways, this is similar to how we use color to illustrate proteins, cells, organs inside the body, etc. in order to provide more comprehensible and interesting visualization models. However, just as no biology textbook would actually describe the nucleus of a cell as being orange despite having drawn it in that color, I would be surprised if specific color characteristics were included in descriptions of a dinosaur. Certainly to draw such conclusions about color would seem somewhat irresponsible, unless very clear evidence pertaining to color was cited. My understanding is that in some rare cases some of the skin pigments are preserved with fossils, in which case such a conclusion is actually possible.
Aspects of dinosaur behavior would seem even more abstract to determine. Again, observation of modern animals would be key in speculating on dinosaur behavior. Vocal capabilities may be inferred to some extent by morphology, as certain structures, head shapes, etc. may be conducive to certain types of vocalizations, as found in modern animals. Fighting in duels may similarly be inferred based on structures (for example, horns or spurs) that are typically used in modern animals for such purposes. Analysis of bone structure may lend insight into the way an animal moved, its strength capabilities, or its eating habits.
The environment in which a dinosaur lived may be indicated by many types of data. For example, oxygen isotope data as derived from ice cores offers information on the temperature of past times. Analysis of sediment layers can also provide information on the environment in which they were deposited, based on isotopic information, type of materials (for example, organic vs. volcanics vs. clays vs. dust), and types of biological organisms or artifacts present within the sediments. Many other avenues of research exist that provide indications of past climate as well. It is important to note, though, that the reconstruction of paleoclimates is incredibly difficult, with many potentially confounding variables influencing each of the different types of information available and oftentimes many unverifiable assumptions being required. Alternative explanations are often possible for a given observation, and most inferences about the processes occurring in the past are based on how things work in the present, which may not be entirely valid under the different environmental conditions of the past. Scientists try to find multiple avenues of evidence that converge to support a similar conclusion, thereby strengthening the strength of the conclusion. Ultimately no model of the past will be 100% correct, given that it is impossible to reproduce what actually occurred in the past (it's hard enough to be 100% sure about things going on in the directly observable present!); the main goal of paleoclimatic research is to develop explanations that are consistent with all of the known data, such that the reconstruction is reasonable if not absolutely definitive.
It would be difficult to assign exact percentages to how much of what you read in a textbook is directly supported by evidence and how much is speculation. Suffice it to say that in some cases a topic may be very well supported and in other cases it may be almost entirely speculation, with most cases falling somewhere in between. A good textbook will take care to indicate levels of confidence for a given piece of information. Again, I reiterate that I must defer to others more knowledgeable in this field-- these are my impressions based upon what I have encountered over the years, but my investigation i
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