The origin and initial radiation of angiosperms In relation to anthophytes

Abstract

Autapomorphics indicate the angiosperms form a monophyletic group. Analysis of Aptian-Cenomanian macrofossils establishes that Chloranthaceae holds a central position in the initial radiation of dicots. While Palmae was basal to monocot initial radiation in the Maastrichtian. By tracing their fossil pollen back in time, two lines probably arose from two different species of Monocrinopollis (Crinopolles Group) in the Norian (Upper Triassic) The Crinopolles Group were extinct angiosperms that evolved directly from Steevesipollenites (Gnetales). The origin and initial radiation of angiosperms occurred in North America under stress habitat conditions. Glossopteridales, Caytoniales and Bennettitales display extreme convergent tendencies to angiosperms, while Gnetales similarities to angiosperms are more numerous and fundamental. Gnetales-angiosperms and Bennettitales-Pentoxylales evolved as two distinct lines of anthophytes. Bennettitales arose from Gangamopteris (Glossopteirdales) in the Lower Permian of South Africa, while Gnetales evolved either from Bennettitales or Glossopteridales at that time, also in South Africa.