Geoscience Reference
In-Depth Information
the serrations on a typical steak knife, helping the teeth to saw through flesh. How
this helps ichnologists is that toothmarks can also act as a “fingerprint” for identi-
fying a dinosaur species when examining any bones bearing long, parallel series of
grooves. In such marked bones, each groove corresponds to a denticle. Hence the
spacing and numbers of these traces should match those of known theropod teeth.
Tooth forms even varied within the same dinosaur, a condition called
hetero-
donty
(“different teeth”). Humans, by having incisors, canines, bicuspids, and mol-
ars all in the same mouth, are well acquainted with heterodonty, which is a typical
condition for mammals with varied diets. However, heterodonty can be subtler in
other vertebrates, such as theropods. For instance, if you were to glance at a live
tyrannosaur's open mouth, all you would see at first are a large number of its big
pointy teeth, which understandably might all look alike as you quake in fear. But
if you looked deeper into its mouth, say, while being eaten, you would see that the
teeth in the front curve more toward the rear of the mouth, are more incisor-like on
their ends, and have D-shaped cross sections, with the rounded part of the “D” fa-
cing the front of the mouth. Then, just before you pass down its gullet and become
a bolus, you would note that its rear teeth are rounder and blunter than those in the
front. This will be explained further in just a minute, but in the meantime, just di-
gest the preceding.
Theropod teeth also formed distinctive patterns in how they lined up on both
the upper and lower jaws. This row of teeth is appropriately known as a tooth row.
Certaintheropodshadanexactnumberofteethpertoothrow,butthatnumbercould
also be divided into two parts, a front (anterior) tooth row, and a rear (posterior)
toothrow,whicharedividedbyagapcalleditsinter-toothspacing.Regardless,you
should mind the gap, as the front teeth and rear teeth served different functions in
a theropod mouth. Obviously, the front teeth were what mattered most when it was
love at first bite, whether performed on a living or dead animal.
If a theropod's potential food item, such as a small ornithopod, was still alive
andhavingissueswithaproposalthatitshoulddevoteitslifetofeedingatheropod,
