Pseudoctenis SEWARD , 1911

Čepičková, Jana & Kvaček, Jiří, 2020, Two Cycads Nilssonia Mirovanae Sp. Nov. And Pseudoctenis Babinensis J. Kvaček From The Cenomanian Of The Bohemian Cretaceous Basin (The Czech Republic) As Indicators Of Water Stress In The Palaeoenvironment, Fossil Imprint 76 (2), pp. 315-324 : 317

Genus Pseudoctenis SEWARD, 1911

T y p e. Zamites eathiensis T. RICHARDS, 1884, p. 117 ≡ Pseudoctenis eathiensis (T.RICHARDS) SEWARD, 1911, p. 692, pl. 6, figs 1–3, pl. 7, figs 1–6.

R e m a r k s. Pseudoctenis and Ctenis LINDL. et HUTTON differ mainly in their venation patterns. Ctenis has anastomosing veins ( Lindley and Hutton 1834). By contrast with Pseudoctenis , Nilssonia typically has lamina attached to the upper side of the rachis, its segmentation is irregular, stomata in some cases surrounded by papillae and the secondary veins never fork ( Harris 1964).

The newly collected material consists of only one pinna fragment. However, its parallel, occasionally forking veins and cuticle with haplocheilic stomata surrounded by numerous subsidiary cells and thick cuticle clearly indicate that the fragment belongs to the genus Pseudoctenis . Pseudoctenis is based on type P. eathiensis (T.RICHARDS) SEWARD, as shown and revised by Van Konijnenburg-van Cittert et al. (1998). P. babinensis was described from the Pecínov locality by Kvaček (2008).

Pseudoctenis babinensis J. KVAČEK, 2008 Pl. 1, Figs 1–8

2008 Pseudoctenis babinensis J. KVAČEK, p. 126, pl. 1, figs 1–7, pl. 2, figs 1–6.

H o l o t y p e. NM-F 2448 (coll. National Museum,

Prague, the Czech Republic).

S t u d i e d m a t e r i a l. NM-F 4597c.

D e s c r i p t i o n. The holotype is a simply pinnate frond showing a robust rachis with typical longitudinal ridges. Pinnae are linear-lanceolate, entire-margined with attenuate apex. Venation of pinna is parallel.

The newly collected and studied specimen is a fragment of an entire-margined pinna (Pl. 1, Fig. 1). The length of the specimen is 45 mm and the width is 7 mm. The fragment has parallel venation with a density of 13 veins per 10 mm. The simple, occasionally forking veins run parallel to the leaf margins. The base and apex are not preserved. The leaf is hypostomatic. Adaxial cuticle bears isodiametric, polygonal ordinary cells (40–70 × 20–40 µm) (Pl. 1, Figs 7, 8). Their anticlinal walls range from straight to curved and their thickness is 6–10 µm. Ordinary epidermal cells of the abaxial cuticle are isodiametric, tetragonal to polygonal (40–90 × 20–50 µm) (Pl. 1, Figs 4, 6). The anticlinal walls are straight to curved and their thickness is 6–10 µm.

Abaxial cuticle consists of isodiametric, polygonal to quadrangular epidermal ordinary cells (40–90 × 20–50 µm), with anticlinal walls, ranging from straight to curved. Thickness of periclinal wall is 8–10 µm. Stomata are irregularly scattered on abaxial cuticle. Their axes are partially randomly oriented, partially oriented parallel to pinna margin (Pl. 1, Figs 4, 6). Stomata are haplocheilic with 7–9 subsidiary cells, 20–50 µm long and 25–60 µm wide. Ledges of guard cells are 45–55 µm long × 7–11 µm wide (Pl. 1, Figs 3–6). Stomata are sunken in stomatal chambers and surrounded by slightly raised cutinized rims (Pl. 1, Fig. 2).

D i s c u s s i o n. The studied material was compared to the type material of P. babinensis ( Kvaček 2008). Based on macromorphology and cuticle micromorphology – similar haplocheilic stomata surrounded by high number of subsidiary cells, it is concluded this material is conspecific with the type . However, due to the small size of the studied specimen, it was not possible to determine and compare distribution of stomata in costal and intercostals zones of the studied material and the type.