An evolutionary trend from static, rigid systems to dynamic, flexible ones is one of the most often repeated in TRIZ. Here is a recent biomechanical discovery directly related to this trend.
The discovery explains how bamboo sharks with sharp, small, pointy teeth succeed to crush a well-armored meal like crabs.
"When the bamboo shark's teeth hit soft flesh, the sharp cusps bite in and grasp the prey. A quick shake of the shark's head can then rip the prey in half. But when the shark grabs hard-bodied prey, the sharp points can't make a dent. So instead of letting their edges get dulled on shell, the teeth fold toward the back of the shark's mouth, exposing the front surfaces of the teeth to the prey [see illustration]. The flat tooth face is far better suited to the task of smashing open a crab. Imagine your own teeth tilting backward if you bit a walnut shell, but staying upright on contact with a peach."
From TRIZ perspective, the solution looks like a quite advanced system, not only dynamic, but also approaching ideality.
"The beauty of the system is that no special controls are needed to "decide" whether the prey to be processed is hard or soft. The hardness of the prey itself causes the teeth to change from pointy graspers to lumpy crushers. If the prey is hard, the upright front row folds down onto the next row back, turning the entire dental battery into a crushing plate, similar to the palate of true hard-prey specialists such as the horn shark."
However, here comes a surprise.
"The teeth of the bamboo shark look remarkably similar to those of Elegestolepis, one of the oldest known fossil sharks. Perhaps, then, the shark's all-purpose strategy is quite old. But it's not universal - great white sharks have no trouble cutting through surfboards with a static set of dentures, and tiger sharks rip through sea-turtle carapaces like chainsaws through pine."
In other words, the natural evolution seems to progress in this case from the dynamic, flexible system to static, rigid ones - against the celebrated TRIZ principle. Perhaps, luckily for the modern sharks.
May we suggest that some technical systems might also benefit from their designers NOT following the TRIZ "laws"?