T Rex's super sense of smell

[sam1]

[sam1]

..That honestly sounds like the single most impressive thing about this animal.
If anyone here can point to some actual scientific data supporting the statement, or is Bob Bakker simply trying to sell some biased subjective guesstimates?

[Infinity Blade]

Clash of the Dinosaurs is something you should really stay away from in terms of obtaining factual information.

Bakker sounds like he’s exaggerating, although I don’t know if anyone quantified how well Tyrannosaurus could smell compared to a bloodhound. But Tyrannosaurus indeed had a superb sense of smell.

For now here’s a news article reporting such findings. I’ll try to provide relevant portions from scientific articles later, assuming no one sees to it before.

www.nature.com/news/2008/081029/full/news.2008.1192.html

Edit:

Olfaction
We would expect there to be significant differences in olfactory capabilities based on the reconstructed olfactory bulbs of T. rex presented by Brochu (2000, 2003; Fig. 6A) and by us (Fig. 6A,B). Had Brochu’s hypothesis been corroborated it would indeed have justified—even demanded—inferences of extraordinary olfactory capabilities (Larson and Donnan, 2002) and perhaps supported the notion of special adaptations for scavenging (Barsbold, 1983; Horner, 1994; Horner and Dobb, 1997). Our new findings (see also Witmer et al., 2008; Zelenitsky et al., 2009) argue for moderation in inferring tyrannosaur olfactory capabilities, but even these findings suggest that tyrannosaurs devoted an unusually large amount of neural tissue to the olfactory apparatus. T. rex and especially CMNH 7541 had relatively large olfactory lobes in comparison to other theropods (our data for Gorgosaurus are inconclusive because the sphenethmoid is not preserved in ROM 1247). Qualitative assessments of olfactory acuity will be quantitatively tested elsewhere using volumetric data, but the recent quantitative study using linear measurements presented by Zelenitsky et al. (2009) fully supports these findings.

Additional information on olfaction can be obtained by consideration of the nasal cavity. Witmer and Ridgely (2008b) recently reconstructed the cephalic air spaces in T. rex, revealing the basic structure and relative sizes of various parts of the nasal cavity. As shown in Fig. 6C here, the nasal cavity of T. rex was very long, extending from the rostroventrally positioned nostril (Witmer, 2001) to the front of the braincase medial to the orbits. The front portion of the nasal cavity is largely devoted to respiration, and the large arrow shows the respiratory airway from nostril to pharynx. The caudal portion, however, corresponds to the olfactory region in modern vertebrates (Witmer, 1995a) and represents the cul-de-sac found in virtually all tetrapods (Negus, 1958) where reduced airflow rates (Fig. 6C, small arrow) allow odorant molecules to diffuse to their receptors on the olfactory epithelium (Simmen et al., 1999; Settles, 2005; Craven et al., 2007). We have no way of knowing how much of this huge olfactory chamber in tyrannosaurs
was actually cloaked in the sensory olfactory epithelium. In extant archosaurs, the vast majority of the equivalent epithelial region is, in fact, histologically olfactory (Witmer, 1995a), and this would be a very large territory in tyrannosaurs. Indeed, some tyrannosaur specimens preserve olfactory turbinates (e.g., CMNH 7541; Fig. 9A; Witmer and Ridgely, in press), suggesting that increasing olfactory epithelial surface area was important. Thus, it is perhaps not unreasonable to suggest that much of the observed olfactory region was indeed sensory. The large size of the olfactory chamber in tyrannosaurs would produce a caudally decreasing gradient in airflow rates. Given that the ability of odorant molecules to adsorb to the epithelial mucosa varies in a complex manner with airflow rate (Dawes, 1952; Sobel et al., 1999; see also Mainland and Sobel, 2006), the large airflow-rate gradient in tyrannosaurs might have provided a refined mechanism for discriminating odors. Moreover, Craven et al. (2007) showed that surface area requirements for olfaction are much greater than for the respiratory function, because odorant receptors tend to have regional specificity requiring adequate surface area to accommodate the numerous receptor types. Thus, again, the large area devoted to the olfactory region in tyrannosaurs may indicate a discriminating sense of smell, particularly given the new findings from genomics (Steiger et al., 2008) and ethology (e.g., Nevitt, 2008; Roth et al., 2008) that extant theropods (birds) may rely much more on olfactory cues than previously thought. The importance of scaling of these phenomena is completely unknown, but such a determination will become tractable as data of the kind presented here and elsewhere (Witmer and Ridgely, 2008b; Zelenitsky et al., 2009) become available for more taxa.

Full PDF here (clickable)