You study a group of ammonites (an extinct lineage of cephalopods) that lived during the Mesozoic. You measure the shell diameter of different fossil ammonite species

Question

When you combine your data within each of six different time periods you obtain the following average shell sizes and corresponding standard errors. What rule does this data conform to?

Time interval Mean shell diameter (+/– standard error)
245–214 MYA 15 mm (+/– 5 mm)
215–184 MYA 21 mm (+/– 7 mm)
185–154 MYA 36 mm (+/– 12 mm)
155–124 MYA 63 mm (+/– 21 mm)
125–94 MYA 72 mm (+/– 24 mm)
95–65 MYA 84 mm (+/– 28 mm)

a. Biogenetic rule c. Cope's rule
b. Allen's rule d. Bergmann's rule

Answer 1

C