Average species life spans and extinction rates for various groups of fossil marine species

group average species life span (millions of years) extinctions per million species per year

all fossil groups 0.5–5 0.2–2

marine animals 4–5 0.2–0.25

all invertebrates 11 0.9

marine invertebrates 5–10 0.1–0.2

diatoms 8 0.12

dinoflagellates 13 0.08

planktonic foraminifera 7 0.13

Cenozoic bivalves 10 0.1

echinoderms 6 0.16

Silurian graptolites 2 0.5

mammals 1 1

Cenozoic mammals 1–2 0.5–1

After data in R.M. May et al., "Assessing Extinction Rates," in J.H. Lawton and R.M. May (eds.), Extinction Rates (1995).