Final answer:
On hard substrates, common types of ichnofossils include burrows and tracks. Examples of ichnofossils found on hard substrates include Cruziana and Trypanites. These fossils provide information about past organisms and their environments.
Step-by-step explanation:
On hard substrates, the types of ichnofossils that are commonly present include burrows and tracks. Burrows are created by organisms such as worms or mollusks that dig into and move through sediment. Tracks are impressions left by organisms that walk or crawl on the surface of the substrate.
For example, one type of ichnofossil commonly found on hard substrates is the Cruziana trace fossil. This ichnofossil consists of a series of parallel grooves or ridges that were made by arthropods walking along the sediment. Another example is the Trypanites trace fossil, which is a cylindrical burrow made by organisms such as bivalves.
These ichnofossils provide valuable information about the organisms that lived in the past and the environments they inhabited. By studying ichnofossils, scientists can learn about the behavior and ecology of ancient organisms and gain insights into the paleoenvironment.