[3] He then did an NIH (NRSA) postdoc with evolutionary developmental biologist Rudy Raff at Indiana University from 1989 to 1991.
[5][6] This work led him to propose with Peter Ward that the fossil record of the Mollusca suggested that the extinction at the Cretaceous-Paleogene boundary may have been due in part to marine regression.
[7] It also led to revised estimates of the origination times and fidelity of the fossil record for various lineages, including primates and orchids (with the description of Meliorchis).
[8][9] In 1993, he found empirical evidence for exceptions to Dollo's law of irreversibility with Elizabeth and Rudolf Raff.
[10] His studies on diversity through time included being a Principal Investigator on the grant that led to the creation of the Paleobiology Database with John Alroy.