He likened its physical appearance to Darth Vader and a vacuum cleaner, and compared its tooth shear with a conveyor belt and sharpened piano keys.
As Neil Curtis and colleagues at the University of Hull in England have shown through computer simulations, the tuatara slides its single row of lower teeth across a groove between a double row of upper teeth, shearing the food, said Dr. Curtis, "like a pair of scissors".
No other herbivorous tetrapod has evolved a skull of comparable size with as little bone that is able to withstand sustained impact from tooth-to-tooth shearing.
Two experimental tests over 1/43 reduced samples are first performed and show two collapse mechanisms: dome collapse and tooth-shear collapse.
Information about each donkey that suffered colic was noted including age, gender, farm and the presence or absence of dental disease (at least one of the following features: missing teeth, shear, wave, step, undershot, overshot or diastema).
Bears and procyonids (except the olingo), which tend to be omnivorous, and seals, which eat fish or marine invertebrates, have little or no modification of these teeth for shearing.
Archaeocetes are primitive compared to later cetaceans in retaining cheek teeth with shearing crests, flexible elbow joints, and well-formed hind limbs with feet and toes (Figure 1).
Slow components of the adductor muscle permit sustained adduction, while the interlocking hinge teeth prevent shear.
It is suggested that the in-line HSM with double rows of inclined stator teeth, narrow shear gap width and tip-to-base clearance has the advantage to provide intensified mass transport efficiency in the view of exploring novel chemical reactors.
The shearing teeth (carnassials) are poorly developed, and the molars have broad, flat crowns.
Most carnivores have carnassial, or shearing, teeth that function in slicing meat and cutting tough sinews.
