Cycad or Cycadeoid?

MARTINEZ, LEANDRO CARLOS ALCIDES; STEVENSON, DENNIS

Tucson

Conferencia; Botany Conference 2019; 2019

Botanical Socierty of America

The Cycadales and Cycadeoidales (Bennettitales) are distinguished from each other on the basis reproductive characters, particularly in phylogenetic analyses. This is in part because their vegetative organs appear very similar especially foliar features. Stems can generally be assigned based upon anatomy in that cycads have apomorphic structures not found in Bennies. One caveat here is that one must have sections of the lateral buds of a trunk to show that they are or are not reproductive branches. The assignment of isolated leaves is quite a different situation. For fossils, it is usually characters of the epidermal cell patterns and walls and presumed development of stomata and stomaltal complexes. It appears that some features of internal leaf and leaflet anatomy could be diagnostic if present or at least looked for in fragments. Among these characters are: Articulate and Decurrent Leaflets, Midribs from Dichotomies, Callus Region at Leaflet Base, Anticlinal Wall Pegs, Perforated Epidermal Cells, Anastomosing of Vein Dichotomies, etc.