THE AGE OF SEAWEED
Like animals, plants did not appear in the fossil record as complex organisms
until the late Precambrian or early Cambrian.The distinction between plants
and animals is somewhat blurred in the geologic record of the obscure past,
when they shared many common characteristics. From humble beginnings as
simple algae, single-celled plants probably colonized for similar reasons that
unicellular animals grouped together, such as mutual support, division of labor,
and protection. However, complex marine plants did not appear in the fossil
record until the Cambrian, after which they evolved rapidly.
Although the Cambrian has been referred to as “the age of seaweed,” the
geologic record does not support this contention with strong fossil evidence.
Well-preserved multicellular algae and a variety of fossil spores discovered in
late Precambrian and Cambrian sediments suggest the existence of complex
sea plants. However, no other significant remains have been found. Even as late
Figure 76 Folded
sandstones and shales near
the base of the upper
Silurian near Hancock,
Washington County,
Maryland.
(Photo by C. D.Walcott,
courtesy USGS)SILURIAN PLANTS