[Taxacom] angiospermy

[John Grehan]

Below is a brief summary statement by Croizat on the temporal origins of
angiosperms. Whatever its merits I am curious to know from any on the list
who either teach on the subject or have participated in university courses,
to know how it compares to what is currently taught.

John Grehan

Croizat 1964 p. 364

Summing up and concluding, the following chronology of angiospermous
origins (the plural is used advisedly) seems to offer grounds for a
concrete basis of discussion, not only, but to agree in the main with what
is currently believed today among aplaeobotanists, and to stand further
corroborated by positive biogeographic and morphogenetic data: 1) A basic
alteration took place in certain relevant poplations of the seed-plants in
ages that are suggested to lie between Mid-Carboniferous and Mid-Permian
(between 250 and 210 million years ago). This basic alteration (see p. 381
for further analysis) laid the ground for eventual development of
angiospermy. Since this alteration was fundamentally embryological, only
starting a tendency of directional (orthogenetic) nature toward eventual
full angiospermy, fossils to document it must be practically inexistent; 2)
between Mid-Permian and Late Triassic (that is, between 210 and 175 million
years ago) these populations did develop prevailingly in the Southern
Hemisphere laying the ground for the proximal ancestors of eventually
modern main angiospermous families; 3) Between Late Triassic and
Mid-Jurassic (that is, between 175 and 165 million years ago) these same
populations did further multiply, gain ground, and begin to yield the
forerunners of subfamiliar groups the world over; 4) Between Mid-Jurassic
and earliest Cretaceous (that is, between 165 and 130 million years ago)
these groups were already world-wide and in very active process of further
differentiation; 5) From earliest Cretaceous onward angiospermous plants
gained ascendancy; 6) It seems probable that the initial tendency toward
angiospermy began with forms none too distantly allied with
Corystospermaceae and similar aggregates.