The evolution of anatomical and morphological characters in Cycadales and their relationship with the environment throughout time

MARTINEZ, LEANDRO CARLOS ALCIDES; STEVENSON, DENNIS

Diamante

Simposio; XVII Simposio Argentino de Paleobotánica y Palinología; 2018

The cycads are the antique and basal of living spermatophytes. Actually, the living cycads are just small remnants of a surprisingly diverse lineage of seed plants, with an origin during the Permian. Since their origin, these plants have survived to several extinctions from Palaeozoic to present time. The reason why cycads have survived could be due to acquisition and development of a set of anatomical, chemical and reproductive characters; which were probably transformed across time, depending on the environmental pressure. However, once developed, some characters do not change considerably. In this research, those characters are discussed. Fossils commonly preserve morphological and anatomical characters, such as: girldling traces, medullary bundles, manoxylic wood, primary and secondary rays, polylxylic wood, leaf bases armour, epidermal cells, vein pattern, stomatal type, etc. Other characters (reproductive and chemistry) can be inferred (e.g. multiple cones and toxins). The aim of this research is to evaluate and trace, by a cladistic analysis, the origin and changes through time of some characters present in stems, leaves and reproductive structures of fossil and living cycads. The hypothesis, about the emergence of certain characters in different taxa of cycads and their relationship with the environment conditions, is tested. In both cases, to map and set up the origin of some characters in cycads could explain ecological or environmental events (diversification and extinctions) across Mesozoic and Cenozoic. Moreover, these new evidences will help to verify how cycads survived.