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Analysis of post-mortem buoyancy loss in Nautilus shells suggests that extensive nekroplanktonic drifting occurs infrequently. Most shells do not reach the surface but settle to the sea floor, after a short period of ascent. This occurs because the rate of water influx into the phragmocone due to ambient hydrostatic pressure is sufficiently rapid in most cases to overcome positive buoyancy before the shell reaches the surface. The resulting geographic distribution of Nautilus shells would therefore mirror the distribution of the live animals. Thus, post-mortem drift in Nautilus cannot be used as a basis for questioning the validity of cephalopod paleobiogeography. Estimate of influx rates in ammonoid siphuncles indicates that many, if not most, ammonoid shells also would not become nekroplanktonic. This is especially true for small (<5 cm diameter) shells. Cephalopod paleobiogeographic investigation appears less subject to criticism stemming from the supposed obfuscating effects of post-mortem drift than previously thought.

We investigated the hydrodynamic properties of cephalopod shell sculpture in two ways: 1) flow visualization experiments with sculptured shells; and 2) application of drag coefficient data for simple geometric bodies to cephalopod shells. Results of this work suggest:1) the hydrodynamic effect of shell sculpture depends primarily on the size of the sculptural elements relative to the size of the shell and on the positions of sculpture elements on the shell and relative to each other.2) sculpture is detrimental to swimming (reduces hydrodynamic efficiency) if it exceeds the height of the lower part of the shell's boundary layer.3) sculpture is advantageous to swimming (increases efficiency) if it remains immersed in the boundary layer and induces premature conversion to turbulent boundary layer flow. To be hydrodynamically optimal, small shells (diam ≈ 10 cm) must have rough (sculptured) surfaces, whereas large shells (diam ≈ 100 cm) require smooth surfaces. Thus, in order to maintain maximum efficiency throughout life, the ontogeny of small individuals, or species, should be characterized by progressive roughening of the shell, while large forms should become increasingly smooth. Such allometries are observed among many ammonoids.4) sculpture always has an effect on the flow around a cephalopod shell. In some species this effect was probably negligible, while in others, those with compressed shells especially, it was probably of major importance. In these species, sculpture appears to have functioned primarily to increase swimming ability.

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Measurement of the compressive strength and elastic modulus of the skeletal material of three common Caribbean corals suggests that the mechanical properties of coral skeleton are an important factor in the adaptive repertoire of these animals. The strength (stress at fracture) of the specimens tested is 12–81 meganewtons/meter2, with material from branched colonies being generally stronger than material from massive colonies. These values are lower than the strength of most other carbonate skeletal materials, but higher than that of carbonate engineering materials like concrete and limestone. The comparatively low strength of coral skeleton may be the result of architectural properties produced by the requirements of competing adaptive factors, such as polyp phototropism, or it may reflect the low probability that a colony will be broken, and therefore need to be stronger, before it achieves reproductive parity. The skeleton of the three species tested here is strongest when stress is applied parallel to the growth direction of the polyps. Strength varies inversely with skeletal porosity. Decreasing porosity in highly stressed colonies represents a potentially valuable adaptation for enhancing strength. The adaptive value of porosity modification may explain differences in porosity and strength between highly stressed branched growth forms and more moderately stressed massive growth forms. Boring organisms reduce the strength of coral skeleton by increasing its porosity. Only minor amounts of boring can produce strength reductions of up to 50%. Specialized, stress-minimizing branch arrangements help maximize resistance of coral structures to mechanical degradation in situations where colony size is unusually large or hydraulic energy dangerously high.

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A 71-year-old patient with high-output cardiac failure was found to have an aneurysmal distal aorta with evidence of an arteriocaval fistula on ultrasound scanning. CT demonstrated an aneurysm of the distal aorta and right common iliac artery and an intraarterial digital subtraction angiogram confirmed an arteriocaval fistula. In view of the patient's cardiac failure and general condition an endovascular stent was considered. The right internal iliac artery was occluded with Tungsten coils prior to the insertion of a bifurcated stent-graft. This resulted in total occlusion of the aneurysm and obliteration of the arteriocaval fistula. To our knowledge such a case has not been previously reported.