Specifically, I am going to speak on an interesting work of interpretation of the existing bony structures in a group of well-known dinosaurs cone centrosaurinos:
Hieronymus, T.L., Witmer, L.M., Tanke, D.H., Currie, P.J. (2009) The Facial Integument of Centrosaurine Ceratopsids: Morphological and New Histological Correlates of Skin Structures. The Anatomical Record-Advances In Integrative Anatomy And Evolutiona ry Biology, 292: 1370-1396. The first thing, perhaps, would be to tell who the centrosaurinos are... for that we are not dinomaniacos... Since it is a question of a group monofilético of dinosaurs ceratópsidos, that shape the group brother of the Triceratops and similar. The principal characteristic of the centrosaurinos is the presence of a series of nasal bony structures of big development and very varied morphology.
Between the most famous of his members Styracosaurus is, with his ruff surrounded with big thorns (to see above the reconstruction of Sergio Pérez González), Pachyrhinosaurus, with his nasal rugosity of controversial interpretation, or Centrosaurus, with his robust nasal horn.
The big structural similarity between the embellishment "corniformes" of the dinosaurs ceratopsios and it has taken those of the mammals in numerous occasions to the investigators to establish functional relations with similar implications paleobiológicas (competition intraespecífica, sexual selection, recognition of species). But in addition to the horns, some centrosaurinos present a rough surface of bone that has substituted the nasal horn, and these are precisely the most derivative filogenéticamente. For it, the study of the transition between a morphology and other one can throw light on the evolutionary bosses in game in this group. And this is the starting point of this work. 
Two are the principal hypotheses raised to explain the nasal Pachyrhinosaurus rugosity. The first one infers the existence of a big horn of keratin similar to that of the current rhinos, which might serve like visual sign or like "weapon" in the competition for the females. The second one supposes the presence of a corny surface that would serve like "battering-ram" during the struggles between males, of a similar way to as they do nowadays the marine iguanas of the Galapagos Islands. Both interpretations favor the sexual or social selection as essential evolutionary factor in the development of these structures. In this work also other poibilidades appear, since there can be the appearance of hollow horns of type I chat (as those of soak you of the Asian Southeast) or of ossified dermal structures. 
But in any case, since the function of these structures cannot be known straight, since these bugs became extinct his good 65 million years ago (and more), what Hyeronimus and his collaborators have attacked is an analysis of similar bony structures in current vertebrates as regards the function that they redeem (particularly, the struggles between males by means of the heads shock). That way they could have come I hope a real relation exists between the structure and his supposed function, so if it was not then the proposed adaptation would not have been imprecindible so that these structures were generated. The descriptive part of the study is extraordinarily exhaustive and it generates a novel vision on the aspect that the heads of these animals would have, presenting a multitude of different dermal embellishment associated with the different types of bony extructuras that are in his skulls.
The interpretive part on the function of these different structures is based on studies of the relations filogenéticas of different groups of bóvidos and soak you acuales to be able to establish a statistical interrelation between structure and function. The results suggest that, certainly, there is a relation between the males' struggles and the rugosity of the cranial bony surface that receives the impacts of the rival.
Therefore, the nasal Pachyrhinosaurus structures might have a similar morfofuncional in the current musky oxen (Ovibos), which have similar rough surfaces in the frontal bone. In fact, the authors even present an evolutionary stage for the transition between the long and straight horns of the basal centrosaurinos and the flat and rough structures of the most derivative.
This one would do to herself across the curved horns antero-ventralmente of, for example, Einiosaurus, which, due to this curvature they would be more robust and might support the direct shocks of the heads of the male opponents (just as the horns of the current muflones). This behavior would become strong and finally there would favor the development of the rough structures (already without horns) conference in Pachyrhinosaurus. Come this point, it would suit very much to put a reconstruction of two grantes males of some of these species fighting to butts (or narizazos, rather), but I have not found any in the whole web... Very well, to end and if someone has curiosity, only stays to mention that the article that these authors have quoted to me, (for which I am very grateful to them) is:
- Hernández Fernández, M. and Vrba, E.S. (2005) To complete estimate of the phylogenetic relationships in Ruminantia to yourself: to dated species-level supertree of the extant ruminants. Biological Reviews, 80: 269-302. (PDF)
In Research Blogging...
Hieronymus, T., Witmer, L., Tanke, D., and Currie, P. (2009). Facial The Integument of Centrosaurine Ceratopsids: Morphological and New Histological Correlates of Skin Structures Record The Anatomical: Advances in Integrative Anatomy and Evolutionary Biology, 292 (9), 1370-1396 DOI: 10.1002/ar.20985
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