A linear relationship can be used to determine the density of materials (in the density range of bone) from the HU values of a CBCT scan. This relationship is not affected by the object's location within the scanner itself.

The feeding apparatuses of rorqual whales and pelicans exhibit a number of similarities, including long, kinetic jaws that increase gape size, and extensible tissue comprising the floor of the mouth. These specializations enable the engulfment of large volumes of prey-laden water in both taxa. However, the mechanics of engulfment feeding in rorquals and pelicans have never been quantitatively compared. Here, we use ''BendCT,'' a novel analytical program, to investigate the mechanical design of rorqual and pelican mandibles, to understand whether these bones show comparable designs for resisting similar hydrodynamical loads. We also compare the mechanical properties of the extensible tissue used during engulfment in rorquals and pelicans. We demonstrate that the evolutionary convergence in the feeding apparatus of rorquals and pelicans is more pronounced than has been recognized previously; both taxa exhibit mandibular flexural rigidity distributions suited for resisting dorsoventral bending stresses encountered while feeding, and possess similarly extensible tissue on the floor of their mouths. Anat Rec, 294:1273Rec, 294: -1282Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.

Thunniform propulsion is considered a case study in convergent evolution. Independently derived at least four times, it is characterized by uniquely high lift-based thrust and efficient performance. As such, it has been the focus of studies from biologists, engineers, and physicists. Unfortunately, direct physical measurements of this phenomenon are difficult to obtain. Therefore, the majority of research so far has consisted of theoretical modeling or experimental testing with models of low biofidelity. We created a test apparatus that would more accurately mimic thunniform propulsion as seen in the skipjack tuna (Katsuwonus pelamis (L., 1758)). Motion parameters and swimming speeds, as well as caudal fin size, shape, and material properties, were all taken into account and closely matched with in vivo measurements. Instantaneous lateral and in-flow forces were measured in tests over a range of motion regimes. Overall, general motion parameter requirements for thrust generation were determined and quantified. Thrust production, of up to 0.42 N (per whole caudal fin) with a coefficient of thrust of approximately 0.2, were in line with estimates of whole-body drag. Propulsive efficiency estimates were low (≤35%) compared with estimates in the literature of up to 90%. Quasi-static analysis was also conducted and shown to underpredict measured thrust values by up to 50%.

Engulfment‐feeding Bryde's whale (Balaenoptera edeni) off the Pacific coast of Mexico. Rorqual whales and brown pelicans exhibit convergent modes of engulfment feeding. See Figure 1A in Field et al., on page 1274, in this issue.

No abstract