Oncopteris nettwallii 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 : 75

Oncopteris nettwallii DORMITZER in KREJČÍ

Pl. 4, figs 1-7.

Synonymy:

1853 Oncopteris nettwallii DORMITZER in KREJČÍ, p. 28, pl. 2

1872a Oncopteris nettwallii DORMITZER in KREJČÍ, O. Feistmantel, p. 28, pl. 2, figs 3

1872b Oncopteris nettwallii DORMITZER in KREJČÍ, O. Feistmantel, p. 212

1888 Oncopteris nettwallii DORMITZER in KREJČÍ, Velenovský, p. 23, pl. 5, figs 6

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

1872a Alsophilina kauniciana DORMITZER in KREJČÍ, O. Feistmantel, p. 28, pl. 2, figs 4

1872b Alsophilina kauniciana DORMITZER in KREJČÍ, O. Feistmantel, p. 212 (“ Alsophilina vouniciana ”)

1874 Alsophilina kauniciana DORMITZER in KREJČÍ, O. Feistmantel, p. 270

1888 Oncopteris kauniciana (DORMITZER in KREJČÍ) VELENOVSKÝ, p. 22, pl. 5, figs 1

1873 Alsophilina westphalenii STUR , p. 242

H o l o t y p e: NMP F1514, coll. National Museum, Prague (pl. 4, figs 1, 4).

M a t e r i a l s t u d i e d: NMP F1476, F1479, F1483; two unnumbered specimens from Charles University, Faculty of Science (CUFS).

T y p e L o c a l i t y: Kounice.

T y p e h o r i z o n: Peruc-Korycany Formation, Cenomanian, Late Cretaceous.

O c c u r r e n c e: Only the type locality Kounice .

E m e n d e d d i a g n o s i s. Stems covered by leaf cushions arranged in longitudinal rows. Leaf cushions oval to elongate hexagonal. Each leaf cushion bearing an oval leaf scar with vascular bundle divided into two parts accompanied by scars of aerial roots arranged in a semicircle.

D e s c r i p t i o n. The holotype described by Dormitzer ( NMP F1514 ) shows a fragmentary stem cast covered with longitudinal rows of leaf cushions (pl. 4, fig. 1). The stem cast is flattened, 100 mm wide, 250 mm tall. The leaf cushions are pouch like, almost spherical with leaf scars in the upper part. Leaf cushions are 26–36 mm wide and 32–36 mm high. The leaf scars are oval to elliptical, 18–28 mm wide and 12–18 mm high. Height / width ratio for leaf scars is 0.5–0.9 and their density is 8 per 1 dm 2. The vascular bundle scar is divided into two parts which are heart-shaped (pl. 4, fig. 4), the distance between them is 4 mm on average. The external parts of both vascular bundle scars are 15 mm apart and their height is 5 mm. Scars of aerial roots are situated on the upper part of the leaf scars, near to the vascular bundle, forming a semicircle. Aerial roots on the stem were not observed. The specimen (holotype of Alsophilina kauniciana, No. NMP F1515 ) shows part of a stem with longitudinal rows of leaf cushions (pl. 4, fig. 2). This part of the stem is 300 mm tall, flattened – 100× 60 mm. The leaf cushions are in physical contact and they are preserved only on one half of the trunk. In shape they are rounded to elongate hexagonal, narrow at the top and bottom. The leaf cushions are 17–26 mm wide and 21–31 mm high. Leaf scars are elliptical in shape, 18–20 mm wide and 11–18 mm high (pl. 4, fig. 5). The height / width ratio of leaf scars varies from 0.6 to 1.0 and the density is about 18 per 1 dm 2. Leaf scars of vascular bundles are divided into two parts which are U shaped (7× 10 mm). Aerial root scars are situated in the middle part of the leaf scars and create a semicircular formation. Oblong grooves run through the leaf scars, these could be the remains of aerial roots. Aerial roots on the stem were not observed. The specimens ( NMP F1476 , F1479 , and two specimens from CUFS) (pl. 4, figs 3, 7) display leaf cushions clearly arranged in longitudinal rows separated by gaps of about 14 mm. The distance between leaf cushions within a row is 8–10 mm. The leaf cushions are oval elongated (22–31 mm wide, 32–43 mm high) with oval leaf scars in the upper part (21–26 mm wide, 13–16 mm high). The leaf scar height / width ratio is 0.6 – 0.7 and the density on the stem is 7 per 1 dm 2. Vascular bundle scars are the same as those from the holotype .

D i s c u s s i o n. The available specimens of O. nettwallii show a remarkable arrangement of their leaf cushions. The differences among the described specimens are in size, shape and distance between the leaf cushions. These differences can be caused by different ontogenetic stages. The specimen (NMP F1515) originally described as A. kauniciana with elongated hexagonal leaf cushions probably represents physiologically the youngest specimen (pl. 4, fig. 2). The holotype, specimen NMP F1483 and the specimen from Vojice (pl. 4, fig. 7) may represent medium ontogenetic stages. The specimens (NMP F1476, F1479) probably represent the oldest ontogenetic stage (pl. 4, fig. 3).

Oncopteris nettwallii and Alsophilina kauniciana show a number of similarities, including leaf cushions arranged in longitudinal rows, a similar leaf scar shape and the height / width ratio. They differ only in size, shape and distance between leaf cushions. These features support the idea of joining those two taxa into one as suggested already by Velenovský (1888). Alsophilina wesphalenii described by Stur (1873) also shows the same characters. This fact was already confirmed by Feistmantel (1874). Oncopteris nettwallii differs from Protopteris punctata , P. singeri and P. maletinensis in having leaf cushions longitudinally arranged and in having typically divided vascular bundles.