Peltasperms †

Order Peltaspermales

The Peltasperms are a group of seed plants from the late Paleozoic and early Mesozoic. This group gets its name from the umbrella-like (=peltate) reproductive structure on which the ovules are arranged. These plants were probably vines or shrub-like plants with superficially fern-like foliage.

Ecology & form

- Foliage found in the Northern and Southern hemispheres

Stem

- Blister-like sub-epidermal swellings

Leaves

- Numerous late Paleozoic and Mesozoic foliage types associated with the peltasperms
- The main foliage type is a bipinnate frond (Lepidopteris)
  - L. strombergensis exhibits small blisters which may be swellings under the epidermis
  - Pinnules resemble Alethopteris, with stomata on both sides of leaves
  - Inserted subopposite or alternate along the rachis
  - Intercalary pinnules along the rachis between the primary pinnae

Reproduction

- Umbrella-like discs with ovules (Peltaspermum)
  - No cupules
  - Whorled on the underside
  - Discs pinnately-arranged around axis.
  - Curved micropylar beaks
- Microsporophyll (Callipterianthus or Antevsia)
  - Pinnate axis with short branches
  - Clusters of small elongate pollen sacs fused at the base
  - Sterile pinnae in proximal portion of frond; intercalary pinnae on rachis

Classification

└Lignophytes

└Peltaspermales †

Geologic Age

Pennsylvanian (Kerp et al. 2001) – Early Jurassic (Elgorriaga et al. 2019)

Above: Lepidopteris

Diversity

Antevsia †
Arnhardtia †
Auritifolia †
Autunia †
Callipteris †
Comia †
Dichophyllum †
Glenopteris? †
Lepidopteris †
Lodevia †
Madygenia †
Madygenopteris †
Paratatarina †
Peltaspermum †
Permophyllocladus †
Rhachiphyllum †
Scytophyllum †
Sphenocallipteris †
Supaia? †
Tatarina †
Vittaephyllum †

Permophyllocladus polymorphus †

Karasev & Krassilov 2007
Planate branching shoots of variously connate scale leaves, gradationally transformed into imparipinnate phylloclades by extensive leaf cohesion
Leaves typically distinct on lower (abaxial) side, but reduced to coalescent leaf cushions or marked by suture lines alone on the opposite (adaxial) side
Lateral branches opposite or subopposite spreading at open angle, decurrent, forming pinnae or lobed pinnules of pinnate phylloclades
Ultimate units short elliptical or obovate branchlets with transverse sutures of adherent leaf pairs, distally leaflike, rounded or notched at the apex, reduced to phylloclade pinnules.
Phylloclades strongly cutinized, amphistomatic, papillate
Stomata scattered, more numerous abaxially, irregularly oriented, monocyclic. Subsidiary cells, 4–7(6), radial, with proximal papillae.
Florin ring distinct.
Guard cells small, sunken.

Right: Karasev & Krassilov 2007, Permophyllocladus polymorphus: (1) paratype PIN, no. 5139/4, abaxial side of the apical region of a flattened dorsoventral scale-leaved shoot; (2) the same, adaxial side; (3) paratype PIN, no. 5139/3, abaxial side of a shoot with two lateral branchlets; (4) holotype PIN, no. 5139/1, compression of the middle portion of a phylloclade with lateral branchlets; (5) holotype PIN, no. 5139/1, adaxial side of a lateral branchlet; (6) holotype PIN, no. 5139/1, abaxial side; (7) paratype PIN, no. 5139/2, adaxial side of the compression of a lateral branchlet with two rows of scales on the rachis; (8) the same, abaxial side; (1, 2, 6) SEM; (3, 5) LM.

Additional resources

Seed ferns experimented with complex leaf vein networks 201 million years ago, paleontologists find (Phys.org 16Apr 2024)

└Coiro et al. (2024) Parallel evolution of angiosperm-like venation in Peltaspermales: a reinvestigation of Furcula

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