Embedded Files
New Paleobotany Books!
The radiatopsids (also known as Radiatopses) are a group of plants possessing radiate protoxylem architecture, in which protoxylem strands are found along the ribs of the stele (Beck & Stein, 1993). The protoxylem strands diverge from a central strand and run obliquely upwards through the midplanes of xylem ribs.
The euphyllophytes split during the Early Devonian, giving rise to the radiatopsids, which would lead to robust woody plants such as the "progymnosperms", gymnosperms, and flowering plants. The other lineage is the moniliophytes, which includes the ferns, horsetails, and many ancient fern-like plants
Diversity
Diversity
Stem taxa, included below
Progymnosperms (including Stenokoleales, aneurophytes, archaeopterids)
Seed plants (including all gymnosperms & angiosperms)
Kenrickia bivena †
Kenrickia bivena †
Emsian (late Early Devonian) of Gaspe Bay, Quebec
Plant with main axes bearing four-ranked, decussate, subopposite branches with dichotomous ultimate appendages
Main axes with central, deeply lobed, four-ribbed protostele
Primary xylem maturation mesarch
Protoxylem with radiate architecture: protoxylem strands present at the center of the stele, along the xylem rib midplanes, and at the rib tips
Metaxylem tracheids with Psilophyton-type pitting
Secondary xylem present around primary xylem, tracheids with P-type pitting on radial and tangential walls
Inner cortex with sclereid nests forming a discontinuous layer external to the primary xylem
Outer cortex with alternating longitudinal bands of sclerenchyma and parenchyma
Pairs of Y-shaped bundles diverging tangentially from the tips of primary xylem ribs form traces that supply branches
Protoxylem gaps are present at the two tips of the T bar formed by the primary xylem rib proximal to the trace divergence
Primary branches with bilateral symmetry of vascular tissues arranged in two Y-shaped bundles
Secondary xylem absent in branches
Discontinuous layer of sclereids in the inner cortex, surrounding the two Y-shaped bundles.
Outer cortex is primarily sclerenchymatous
Two terete bundles supply ultimate appendages and have an anatomy similar to primary branches
Above: Five stages in the anatomy of trace divergence of Kenrickia bivena †
Below: The anatomy of Kenrickia bivena †
Gothanophyton zimmermannii †
Gothanophyton zimmermannii †
Remy and Hass, 1986
Late Emsian of West Germany
Winged stem with vascular bundles from the central strand
Possibly aligned with Stenokoleales; possibly aligned with Aneurophytales; Possibly ancestral euphyllophyte to the progymnosperms
Some researchers have placed Gothanophyton at the base of the radiatopsids clade, not in the Stenokoleales or Aneurophytales (Toledo et al. 2021)
Page updated
Google Sites
Report abuse