What Factors Caused the Delay in Angiosperm Radiation?
How important was the mass extinction event at the Triassic-Jurassic boundary in delaying an angiosperm radiation? Tanner et al. (2003) show that disruptions in plant communities were not focussed at the boundary, but occurred through the Norian and into the Early Jurassic (Hettangian), with only three plant families completely disappearing: Glossopteridaceae, Peltaspermaceae, and Corystospermaceae (Ash, 1986; Traverse, 1988). Was there something about Jurassic climates that promoted monotypic floras with very large geographic distributions? Was plant innovation retarded or redirected in the Jurassic by climatic pressures (mutations in angiosperms were restricted in the Jurassic to 18S rather than to rbcL positions: Sanderson and Doyle, 2001), and did it take much of the Jurassic for floral diversity to completely recover? These are questions paleobotanists would not have asked prior to 1994 when one of the first papers on bolide-induced mass extinction at the Triassic-Jurassic boundar
