Invertebrate paleontology is concerned with the evolution and paleobiology of animals lacking backbones. Many phyla are represented, with Cnidaria (corals), Brachiopoda, Mollusca (clams, snails, squids.), Arthropoda (insects, trilobites, crustaceans, etc.), and Echinodermata (sea-stars, feather-stars, etc.) being among the best known. The state of Michigan covers a large geological basin, the Michigan Basin, which is filled with Paleozoic rock layers rich in invertebrate fossils. Paleontology at Michigan started with exploration and interpretation of the Michigan Basin, and Michigan Basin collections remain a large and important part of the invertebrate collections here.
The invertebrate collections contain over 2,000,000 specimens. There is particular strength in Paleozoic faunas, especially corals, trilobites, ostracods, and echinoderms of the Michigan Basin and surrounding areas. These specimens include material used in the case study that led to Eldredge and Gould's (1972) proposal of "punctuated equilibria." Mesozoic invertebrates are also well represented in collections from Central America, North America, and Europe.
Housed within the invertebrate paleontology collection are the microfossils. Micropaleontology is concerned with the stratigraphic and environmental history of microscopic organisms through the course of geological time. These include various nannoplankton, algal diatoms, protozoan forams and radiolarians, and crustacean ostracodes. Although not invertebrates, the conodonts are also housed within the invertebrate collections.