Caytoniales †

Extinct seed fern with possible affinities to angiosperms

The Caytoniales are an interesting group of highly derived seed ferns that may have important connections to the origins of flowering plants. These plants were thought to be small plants or small trees, growing in periodically, waterlogged habitats. Their leaves are palmately compound, and angiosperm-like. They have fertile branch systems exhibiting cupules containing several seeds. The cupule may have similarities to the angiosperm carpal, but more evidence is needed to assign a link between the angiosperms and the Caytoniales.

Features
  • Geologic RangeLate Triassic - Early Cretaceous
  • Systematics
    Archaeplastida
            Tracheophytes
              Eutracheophytes
                Euphyllophyte
                  Lignophytes
                    Spermatophytes
                        Caytoniales 
  • Stems
    • Stems not commonly found
  • Leaves (Sagenopteris
    • Palmately compound
      • Four to six leaflets 
    • Lanceolate with entire margin
    • Reticulate venation, but lacking orders of venation found in angiosperm leaves
    • Stomata are haplocheilic and abaxial only
  • Reproductive Structures
    • Fertile branch system with seed-bearing cupules (Caytonia
      • Planated, bilaterally symmetrical branch system bearing lateral opposite cupules
        • Interpreted as a megasporophyll by Thomas (1925) 
      • Cupules round and recurved, with lip-like projection near the point of attachment
      • Several, orthrotropous ovules per cupule
        • Ovules possess a single integument (unitegmic); they are flattened and bilateral (=platyspermic)
        • Micropyle faces the cupule opening
    • Pollen organ (Caytonanthus
      • Slender axis bears flattened pinnate lateral branches
        • Each branch bears one to three elongate synangia
      • Pollen is Vitreisporites-type
  • Maybe be the sister group to the angiosperms (Hilton and Bateman 2006)
    • Leaves are very angiosperm-like
    • Cupule would need to represent a modified leaf that encloses ovules
Taxa:
  • Caytonanthus
  • Caytonia
  • Sagenopteris
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