Unlike the end - Cretaceous, the PETM was not a
big extinction event but it generated enough environmental
disruption to cause a high turnover of land animals, the evolution of ever smaller animals (the «Lilliput effect»), and a mass extinction of tiny shell - making creatures that
live on the sea bed (benthic foraminifera).
Demography 27 (1990): 55 - 63; Linda Waite and Lee A. Lillard, «Children and Marital
Disruption» American Journal of Sociology 96 (1991): 930 - 953; Carolyn Pape Cowan and Philip A. Cowan, When Partners Become Parents: The
Big Life Change for Couples (New York: Basic Books, 1992)