Why are mammal teeth so much easier to identify than dinosaur teeth?

Photo of a jaw fragment with five teeth.  Each tooht has several tall, pointed cusps arranged in a line.

Many mammal species have very distinctive tooth shapes. Click to zoom.

The discovery of even a single mammal tooth can be exceptionally useful to scientists trying to identify the animals that lived in an ancient ecosystem. Because the shape of the crown (the part of the tooth above the gum) varies a lot between mammal species, it is often possible to know the exact species a fossil mammal tooth came from even if no other teeth or bones are found with it. This level of identification is usually impossible for isolated dinosaur teeth, which do not have such complex shapes.