ABOUT MESOZOIC PTERIDOPHYLLS

Abstract

Two types of pteridophylls are very common in the Mesozoic era: the Polypodium and the Dipteridaceae. The Polypodium‐type formed by pendulous overtopping is represented in the Mesozoic era by the form‐genus Cladophlebis, in the Paleozoic era by the form‐genus Pecopteris, and today by Dryopteris. Overtopping differs in these three pteridophylls. Nearly all Paleozoic pteridophylls show a catadromic structure. Today pteridophylls with anadromic and combined catadromic/anadromic structures are the dominant ones. The Mesozoic genera demonstrate a transitional structure: catadromic structures are still frequent, but equally frequent are combined catadromic/anadromic structures. Pteridophylls solely with anadromic structures are unknown in the Mesozoic era. The Dipteridaceae‐type is almost exclusively Mesozoic. It is primitive in the dichotomy of the rachis, but advanced in that it is net‐veined. Thus the Mesozoic pteridophylls represent connecting links between Paleozoic and recent leaf‐types. This nature of Mesozoic pteridophylls can be understood only on the basis of the telome theory.