The trilobite is a common index fossil similar to an ancient horseshoe crab. What three traits must a trilobite have to be an index fossil?
1. Abundance: Trilobites must have been abundant and widespread during a particular time period in order for them to be considered a reliable index fossil. This means that they must have left behind numerous fossilized remains that are easily identifiable.
2. Distinctive characteristics: Trilobites must have distinctive physical characteristics that make them easily recognizable in the fossil record. These characteristics could include their segmented body, multiple pairs of legs, and distinctive shape.
3. Wide temporal range: Trilobites must have existed for a significant period of time and have a wide temporal range in order to be useful as an index fossil. This means that they must have been present in the fossil record for a long time and can be used to help determine the relative age of other fossils found in the same sedimentary layers.