Invertebrates are the most abundant animal life on earth. Most invertebrate fossils found in Kentucky had hard skeletons and lived in shallow seas. The types (classes) of invertebrate animal fossils commonly found as fossils in Kentucky include:

Arthropods

(trilobites, ostracods, etc.)

Brachiopod sea shells

(common fossil shells)

Bryozoa

(coral-like organisms)

Corals

(rugose and tabulates)

Echinoderms

(crinoids, starfish, etc.)

Mollusks: Bivalve sea shells

(clams, etc.)

Mollusks: Cephalopods

(squids with shells, etc.)

Mollusks: Gastropods

(snails, etc.)

Sponges

(Porifera)

Other invertebrates

Plants are a common form of life on earth, which get their energy from the sun. Fossils of plants are common in Kentucky's coal fields and in parts of far western Kentucky in the Jackson Purchase. Fossil leaves, bark, stems, roots, spores, even standing tree trunks have all been found.

Trace fossils are the tracks, trails, borings, etc. left behind by ancient organisms, rather than parts of the organism's bodies. Trace fossils are common fossils. The study of traces is called ichnology. Most of the trace fossils in Kentucky were made underwater by invertebrate animals.

Fossils of single-celled (protist) life are commonly microscopic, but sometimes colonies of single-celled organisms are macroscopic (e.g., various types of algae, and stromatolites) or large cells secrete calcareous skeletons that are macroscopic (e.g., foraminifera) and can be collected as fossils.