Oncopteris DORMITZER

Greguš, Josef, Kvaček, Jiří & Halamski, Adam T., 2013, Revision Of Protopteris And Oncopteris Tree Fern Stem Casts From The Late Cretaceous Of Central Europe, Acta Musei Nationalis Pragae Series B 69 (1 - 2), pp. 69-83 : 74-75

Genus Oncopteris DORMITZER in KREJČÍ 1853

Synonymy:

Alsophilina DORMITZER in KREJČÍ 1853, p. 28, pl. 1

T y p e: Oncopteris nettwallii DORMITZER in KREJČÍ 1853, p. 28, pl. 2

E m e n d e d d i a g n o s i s. Stem casts with leaf cushions arranged in longitudinal rows; each leaf cushion bearing one leaf scar of vascular bundle divided into two parts.

D i s c u s s i o n. The genus Oncopteris is defined from fossil stem casts which show leaf cushions in longitudinal rows. The genus Alsophilina was established by Dormitzer in Krejčí (1853) at the same time as Oncopteris . Both genera show the same key diagnostic character – leaf scars in lines. They differ in the shape of the leaf cushions; Alsophilina having hexagonal leaf cushions, while Oncopteris has circular. As already pointed out by Velenovský (1888), the shape of leaf cushions is a secondary character, particularly because the shape of leaf cushions in the genus Oncopteris varies considerably, while the shape of the leaf scars is stable.

Regarding the key character – having leaf scars in lines, the genus Oncopteris differs from the genus Protopteris . The in-line arrangement of leaf scars is typical for Palaeozoic stems of the genus Megaphyton (compare Pfefferkorn 1976). Megaphyton differs from Oncopteris in having much larger leaf scars. They are arranged in two longitudinal rows, one on each side of the stem.