Phialopteris C.PRESL

Cittert, Johanna H. A. Van Konijnenburg-Van, Pott, Christian, Kustatscher, Evelyn, Schmeissner, Stefan, Dütsch, Günter & Burgh, Johan Van Der, 2018, Phialopteris Heterophylla (Sternberg Ex Göppert, 1836) Comb. Nov., A Rare Schizaeaceous Fern From The Early Jurassic Of Bavaria, Fossil Imprint 74 (1 - 2), pp. 55-64 : 57-58

Genus Phialopteris C.PRESL in STERNBERG, 1838

Phialopteris heterophylla (STERNBERG ex GÖPPERT) VAN KONIJNENBURG- VAN CITTERT, POTT, KUSTATSCHER, SCHMEISSNER, DÜTSCH et VAN DER BURGH, comb. nov. Pls 1–3, Text-fig. 2

B a s i o n y m. Asterocarpus heterophyllus GÖPPERT,

1836, Die fossilen Farnkräuter, p. 382.

1836 Asterocarpus heterophyllus GÖPPERT , p. 382.

1838 Phialopteris tenera C.PRESL in STERNBERG, p. 114, pl. 31, figs 1a–6.

1841 Sphenopteris braunii GÖPPERT , p. 69, pl. 10, figs 1, 2.

1867 Coniopteris braunii (GÖPPERT) SCHENK , p. 36, pl. 6, figs 6–8.

1914 Norimbergia brauni (GÖPPERT) GOTHAN , p. 107, pl. 18, figs 6–8.

1958 Phialopteris tenera C.PRESL in STERNBERG; Kräusel, p. 70, pl. 3, fig. 8.

1968 Phialopteris tenera C.PRESL in STERNBERG; Weber, p. 45, pl. 4, figs 43–45, pl. 5, figs 46–49.

1972 Phialopteris tenera C.PRESL in STERNBERG; Jung and Knobloch, p. 107, text-fig. 1.

1997 Phialopteris tenera C.PRESL in STERNBERG; Kvaček and Straková, pp. 20, 83.

L e c t o t y p e. Designated here. BT 760, Geological Museum of Bayreuth, figured in Sternberg (1838: 114, pl. 31, fig. 1al). Counterpart – Bayerische Staatssammlung für Paläontologie und Geologie, Munich, SNSB-BSPG AS VII 402.

P l a n t F o s s i l N a m e s R e g i s t r y N u m b e r. PFN000109 for new combination; PFN000120 for lectotype designation .

T y p e l o c a l i t y. Reundorf near Bamberg, Bavaria,

Germany.

T y p e h o r i z o n a n d a g e. Hettangian, lower

Jurassic.

M a t e r i a l d e s c r i b e d. UU10015, UU10749, UU10849, UU10960, UU11015 (all from sandpit Lautner, Unternschreez), UU11932, UU11933; 30Kü16, 37Kü16, 38Kü16, G1164-16 (sandpit Küfner, Pechgraben); 23D02, 24D02, E15-91, E215-93 (sandpit Dietz, Pechgraben); UU25755 (Forkendorf).

D e s c r i p t i o n. Phialopteris heterophylla is a delicate fern. Many specimens yield partly or entirely fertile frond portions, only a few sterile portions have been found on some slabs so far. All specimens are incomplete. The fronds are tripinnate, with a thin rachis, up to 500 µm wide, sometimes showing a zig-zag-shape (Pl. 1, Figs 1, 2; Pl. 2, Fig. 5; Pl. 3, Fig. 2). The primary pinnae arise at 30–55° depending on their position in the frond, are alternately or suboppositely arranged, and up to 70 mm long. Secondary pinnae are up to 25 mm long but usually shorter, while ultimate pinnules are up to 10 mm long and 2 mm wide. The branching is commonly katadromic, but the first anadromic ultimate pinnule is often enlarged (Pl. 1, Figs 1, 2; Pl. 2, Fig. 3). A clear midrib is visible in the ultimate pinnules; secondary venation is commonly invisible, which might be due to the delicate nature of the lamina.

Entirely sterile frond portions in the new material are only preserved on specimens UU11933 and 37Kü16. The first (Pl. 1, Figs 1, 2) is an apical frond fragment (62 mm long and 20 mm wide) with loosely arranged primary pinnae. The secondary pinnae are ca. 10 mm long, the ultimate pinnules up to 2 mm long. The second specimen (Pl. 2, Fig. 5) provides more densely arranged pinnae, of which the secondary pinnae are up to 11 mm long and the ultimate pinnules up to 2.5 mm long.

Frond portions that yield both sterile and fertile pinnules are preserved on 30Kü16 and G1164-16. The proximal ultimate pinnules are commonly sterile and up to 3 mm long and 2.5 mm wide, while the distal and apical ultimate pinnules are partly (30Kü16; Pl. 2, Fig. 3) or entirely (G1164-16; Pl. 3, Fig. 2) fertile. The specimen E215-93 (Pl. 3, Fig. 1) shows sterile frond portions on the left side of the slab, and fertile pinnules on the right side. The two parts are not organically connected but are embedded in one plane, so they may have been part of the same dimorphic frond in which proximal primary pinnae appear to be sterile and distal ones fertile. Other specimens yield (almost) entirely fertile frond portions. A 65-mm-long and 40-mm-wide frond fragment is preserved on UU11015 (Pl. 2, Fig. 1); it has up to six secondary pinnae. The ultimate pinnules (fertile “spikes”) are up to 10 mm long (commonly only 6–7 mm) and have a dentate lamina margin with two rows of alternately arranged sporangia attached to the abaxial surface. The sporangia are circular to slightly oval in shape and have a diameter of ca. 700 µm. The first acroscopic ultimate pinnules appear to be divided into two (or three) lobes (“spikes”). Further details of the sporangia are, unfortunately, obscured by the preservational condition of the specimen. Fertile spikes vary in length from 4 to 6 mm on E215-93. The number of sporangia is clearly visible in this specimen; it varies between 12 to 20 sporangia per fertile spike (pinnule) here.

All completely preserved fertile secondary pinnae end in an apical spike-like ultimate pinnule that is usually larger (longer?) than the other ultimate pinnules (Pl. 2, Fig. 1). The specimens 23D02 and 24D02 yield bipinnate frond fragments and clearly show the arrangement of the fertile spikes mentioned above: In 23D02 (Pl. 2, Fig. 2), some ten fertile secondary pinnae with spikes arise at an angle of ca. 80°; 24D02 (Pl. 2, Fig. 4) provides the densest frond portions with a large number of spikes with preserved sporangia.

Several sporangia were macerated; they yielded large clusters of immature, often slightly folded, spores (Pl. 3, Fig. 5; Text-fig. 2a ). The trilete spores (Pl. 3, Figs 3, 4; Textfig. 2b) are large (55–70 µm in diameter) and roundish – triangular in outline. The exospore is smooth; in a few spores, traces of a faintly granulate perispore were observed ( Text-fig. 2b, c ).

R e m a r k s. Phialopteris heterophylla has a restricted geographical and stratigraphical range as it is known only from a few Hettangian localities in southern Germany. The new material collected from various localities in Bavaria is identical with the specimens described by Presl in Sternberg (1838), Schenk (1864), Gothan (1914), Kräusel (1958) and Weber (1968), and thus can confidently be identified with the species. All published specimens are also only small frond fragments, none of them longer than 60 mm. Most show a bi- or tripinnate frond architecture and all show the typical thin, zig-zag-shaped rachis. The specimen illustrated by Kräusel (1958) yields a sterile frond fragment, but all other published material shows fertile material only, some of which are dimorphic with sterile portions. Gothan (1914: pl. 18, fig. 8) illustrated the arrangement of the sporangia on the dentate lamina of the fertile spikes, also indicating an apical annulus. In the present material, details of an annulus were not observed, but the sporangium is identical in all other aspects. However, we could recover in situ spores of this species for the first time, although they are not completely mature.

Figures

Text-fig. 2. Spores of Phialopteris heterophylla (SEM). a) group of spores from one sporangium,b) trilete spore showing general morphology, and c) detail of (b) showing smooth endospore and faintly granulate perispore remains (arrowheads). Scale bar: a) 50 µm, b) 20 µm, c) 10 µm.