1. Invertebrates: Invertebrates are animals that lack a backbone, and they make up the vast majority of all animal species. Many invertebrates, such as insects, mollusks, and crustaceans, have hard shells or exoskeletons that help protect them from decay. This makes them more likely to be preserved as fossils than soft-bodied animals.
2. Vertebrates with hard structures: Vertebrates are animals that have a backbone, and they include fish, amphibians, reptiles, birds, and mammals. Vertebrates with hard structures, such as bones, teeth, and scales, are more likely to be preserved as fossils than vertebrates with soft bodies.
3. Animals that lived in environments that promote preservation: Certain environments are more conducive to the preservation of fossils than others. For example, animals that lived in marine environments are more likely to be preserved than animals that lived on land. This is because marine environments contain a higher concentration of minerals that can help to preserve organic material.
4. Animals that died in sudden events: Animals that died in sudden events, such as volcanic eruptions or floods, are more likely to be preserved as fossils than animals that died gradually from disease or old age. This is because sudden events can quickly bury animals and prevent them from being scavenged or decomposed.
5. Animals that lived during certain geological time periods: The likelihood of an animal being preserved as a fossil also depends on the geological time period in which it lived. For example, animals that lived during the Carboniferous period (about 300-360 million years ago) are more likely to be preserved as fossils than animals that lived during the Cretaceous period (about 66-100 million years ago). This is because the Carboniferous period was a time of widespread coal formation, which helped to preserve organic material.