Affinities of Bennettitales

Affinities of Bennettitales:-

Resemblances of Bennettitales with Ferns:-

• Bennettitalean plants had multicellular ramenta on their entire body, a characteristic also seen in

ferns.

• Some other features suggesting the filicean affinity of Bennettitales include the presence of:

(i) Direct leaf traces,

(ii) Scalariform tracheids, and

(iii) Large pith.

Resemblances of Bennettitales and Cycads:-

• Bennettitales resemble cycads in the:

(i) structure of their fronds,

(ii) presence of short stems covered with an armour of persistent leaf bases,

(iii) presence of barrel-shaped trunk,

(iv) presence of very thick cortex, relatively thin wood and large pith in the stem,

(v) manoxylic wood,

(vi) monocolpate pollen grains,

(vii) orthotropous ovules, and

(viii) dicotyledonous embryo.

Resemblances between Bennettitales with Pteridospermales:-

• Characters common in both Bennettitales and Pteridospermales include:

(i) Presence of ramenta] hairs,

(ii) Syndetocheilic stomata,

(iii) Direct leaf traces,

(iv) Similar anatomical details,

(v) Leafy microsporophyll’s, and

(vi) Presence of cupule.

• The so-called bisporangiate ‘flower’ of Bennettitales could be compared with the bisporangiate fronds of Ptendospermales. 

• Scientists are of the opinion that there exist two lines of evolution from Pteridospermales. Of these, one line gave rise to Bennettitales possessing both uni- and bisporangiate forms, and the other gave rise to mono-sporangiate forms of cycads.