Protopteris maletinensis GREGUŠ et J. KVAČEK, 2013

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

Protopteris maletinensis GREGUŠ et J. KVAČEK sp. nov.

Pl. 3, figs 1-4

H o l o t y p e d e s i g n a t e d h e r e: NHMW 1878B/0006/7141, coll. Naturhistorisches Museum, Wien (pl. 3, fig. 1-3).

T y p e l o c a l i t y: Starý Maletín.

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

E t y m o l o g y: Derived from the name of the type locality – Starý Maletín .

M a t e r i a l s t u d i e d: UGV S17/2, GBA 2013/019/0001, GBA 2013/019/0002, NMP F3717.

O c c u r r e n c e: Starý Maletín, Vyšehořovice.

D i a g n o s i s. Stem cast covered by helically arranged leaf cushions bearing leaf scars. Each leaf scar includes one vascular bundle leaving a horseshoe shaped scar. Leaf scars with enlarged appendages forming pouch-like structure. Height / width ratio of leaf scars 0.4–0.7.

D e s c r i p t i o n. The holotype shows a fragmentary stem cast 80 mm wide, 180 mm, with large bulging leaf cushions arranged helically (pl. 3, fig. 1). They are 18–27 mm wide and 32–43 mm high. Each leaf cushion is topped by a leaf scar. The leaf scars are generally poorly preserved; two of them (8–13 mm high, 18–20 mm wide) showing remains of undivided vascular bundles resembling a horseshoe (pl. 3, fig. 2, 3). Scars of aerial roots are preserved as small pits. Width to height ratio of leaf scars is 0.4–0.7. The density of scars is about 10 per 1 dm 2. Leaf cushions on the holotype show longitudinal grooves below each leaf scar, these structures may be the remains of aerial roots. Other specimens are generally poorly preserved showing helically arranged leaf cushions with leaf scars similar to those in the holotype. Their stems range from 55 mm to 85 mm in diameter. The specimen ( UGV S17 /2) shows large leaf cushions 14–26 mm wide and 23–45 mm high. The height / width ratio of leaf scars reaches 0.4. Remains of aerial roots are preserved in this specimen as small pits (pl. 3, fig. 4). The specimen from Vyšehořovice ( NMP F3717 ) displays leaf cushions 21–25 mm wide and 36–43 mm high. The height / width ratio of leaf scars is up to 0.6. Remains of aerial roots are also preserved in this specimen as small pits .

D i s c u s s i o n. Protopteris maletinensis differs from P. punctata and P. singeri in having pouch like leaf cushions. Protopteris laubei (ENGELHARDT) STENZEL from the Late Eocene of Staré Sedlo ( Engelhardt 1881, Knobloch et al. 1996) is very similar to P. maletinensis , particularly in having pouch-like cushions arranged helically on the stem. The size of leaf cushions in both species is similar even regarding the width of leaf scars. They differ only in the height of the leaf scars which is 8–13 mm for P. maletinensis and 14–19 mm for P. laubei . This height difference affects their average height / width ratio, which is 0.5 for P. maletinensis and 0.8 for P. laubei ( tab. 1). P. laubei differs from P. maletinensis also in having leaf scars protruding from the stem and with wider gaps between them. However, more distant leaf scars may reflect only greater physiological age, so it is not a conclusive feature. The basal parts of each leaf scar in P. laubei show a sharply undulating vascular bundle scar, which is lacking in P. maletinensis . Additionally, they differ remarkably in geological age; P. laubei comes from the Late Eocene whereas P. maletinensis is known from the Cenomanian.

Another similar species is represented by Protopteris witteana SCHENK from the Lower Cretaceous of Germany ( Schenk 1871). It consists of a fragment of a stem cast (50 mm wide, 190 mm tall) also with bulging leaf cushions arranged helically (pl. 3, figs 5, 6). The leaf cushions are much smaller than in P. maletinensis ; their size being 12–15 × 17–24 mm. Between leaf cushions there are 5–7 mm wide gaps. Each leaf cushion is topped by the leaf scar with a relatively well preserved vascular bundle resembling a horseshoe (pl. 3, fig. 6). Leaf scars of P. witteana in comparison to P. maletinensis are higher than they are wide, their mean height / width ratio (1.2) is the same as in P. punctata . The density of scars is about 24 per 1 dm 2. These scars are arranged in the same plane as the surface of the stem cast while P. maletinensis exhibits leaf scars orientated almost perpendicular to the surface of the stem. P. witteana , in comparison to P. maletinensis , does not show longitudinal grooves below each leaf scar.