Moreover, the spongy bone of juvenile skulls is organized in such a way that reflects radial growth of the bone, which indicates rapid growth (Francillon-Vieillot et al., 1990: p. 512). Rather than deflecting concussive

forces from the brain cavity, this radial organization would have more likely directed them into the brain cavity (Goodwin & Horner, 2004). Maryanska et al. (2004) recently renewed the argument for mechanical agonistic RO4929097 behavior, but their analysis had no control for ontogeny or sexual dimorphism, so there is no support for assigning male status to larger and thicker domes as they did. Moreover, the knobs and spikes that ornamented some pachycephalosaur skulls (such

as Stygimoloch) would not have been visible until the heads were lowered, www.selleckchem.com/products/cb-839.html and in any case could not have been involved in combat (Goodwin, Rosner & Johnson, 1998). For these reasons a function in combat for both the domes and ornamentation is implausible. Moreover, there is now evidence that Stygimoloch was a subadult form of Pachycephalosaurus, which has somewhat less extreme spikes than Stygimoloch, thus casting doubt on the functional interpretation (Horner & Goodwin, 2009). Weishampel’s (1981, 1997) study of Parasaurolophus described above was Mannose-binding protein-associated serine protease the first example of an explicit test of a hypothesis that a particular structure functioned in communication.

As noted, this function may apply to this genus, but it has not been proposed and tested for other lambeosaurines until recently, when Evans, Ridgely & Witmer (2009) examined Lambeosaurus, Corythosaurus and Hypacrosaurus. They showed, as Weishampel (1981) had done using Lophorhothon, that the ear region was capable of hearing the low-frequency sounds that Weishampel calculated might have been produced by the resonating crests of these hadrosaurs. However, phylogenetic analysis of lambeosaurines (Horner, Weishampel & Forster, 2004) shows no apparent trends in selection for improvement of the features related to this function (Fig. 4), and Evans et al. (2009) noted that Hypacrosaurus altispinus had a particularly derived and convoluted nasal chamber. Only two kinds of dinosaurian structures have been proposed as thermoregulatory structures. The first is the plates of stegosaurs. Main et al. (2005) showed that the explanation hypothesized for stegosaurs (Buffrenil et al., 1986) could not be completely eliminated for Stegosaurus itself but was unlikely to apply to related taxa, so there was no evidence of the evolution of a functional adaptation in the group.