Cladophlebis ladinica, Kustatscher & Dellantonio & Van Konijnenburg-Van Cittert, 2014

Kustatscher, Evelyn, Dellantonio, Elio & Van Konijnenburg-Van Cittert, Johanna H. A., 2014, The ferns of the late Ladinian, Middle Triassic flora from Monte Agnello, Dolomites, Italy, Acta Palaeontologica Polonica 59 (3), pp. 741-755 : 750-752

Cladophlebis ladinica sp. nov.

Figs. 5C–E, 6A.

Etymology: In reference to the stratigraphic position.

Type material: Holotype: MGP 194 /6 B, specimen with clear venation and basiscopic pinnules, here designated (Fig. 5 C) . Paratype: MGP 194 /65 B, the largest specimen showing the pinna arrangement, here designated (Fig. 5D).

Type locality: Monte Agnello, Dolomites, N-Italy.

Type horizon: A tuff layer in the basal part of the “explosion breccia” of the volcanic succession of Predazzo (sensu Calanchi et al. 1977), Ladinian, Middle Triassic .

Material.— MGP 63 /105, 191/10 A – B, 194/3 A – B, 194/4 A – B, 194/5, 194/6 A – B, 194/63 B, 194/64 A – B, 194/65 A – C, 194/66, 194/84 A – B, 194/85, 194/86, 194/102 A – C, 194/109, 194/110, 197/17 A – B, 197/67 A – B, 197/68 A – B, 197/69 A – B, all from type locality and horizon .

Diagnosis.— At least bipinnate fronds with stout, winged rachis. Pinnae arising almost perpendicularly, without imbricating. Basiscopic pinnules enlarged, pinnules decreasing in size apically. Pinnules rhomboidal to falcate in shape; in some cases almost connate. Basal pinnae with fused pinnules. Pinnules without distinct midrib, several veins arising from the rachis, bifurcating up to three times.

Description.— The frond fragments are up to 165 mm long and 92 mm wide. The rachis (2.5–4.5 mm wide) shows a wing (MGP 197/69A; Fig. 5E). The pinnae arise at an angle of 70–90° and are up to 65 mm long and 8 mm wide. Proximally the pinnae reduce in size (22–55 mm long and 6.5–8 mm wide). No apical fragments have been found so far. The pinnae never overlap. The pinna rachis is up to 1 mm wide. The pinnules are rhomboidal to falcate in shape; in some cases they are almost connate (MGP 194/6B, MGP 194/65B; Fig. 5C, D). The pinnules are 3–4.5 mm long and 2.5–3.8 mm wide (MGP 194/6B; Fig. 5C) and inserted at an acute angle. The pinnules are largest at the base, with an enlarged basiscopic pinnule, and decreasing apically (MGP 194/65B; Fig. 5D). Pinnules in the basal pinnae are completely fused demonstrating a sort of fasciculate venation (MGP 194/4B; Fig. 6A ). No midrib is present in the pinnules; several veins arise from the rachis and bifurcate up to three times (almost odontopterid venation).

The Middle and Late Triassic species Todites gaillardotii (Brongniart, 1834) Kustatscher and Van Konijnenburg-van Cittert, 2011 has roundish sterile pinnules with an apex curved slightly upwards, and a venation similar Cladophlebis ladinica . The secondary veins fork 2–3 times, no midrib is present just as in C. ladinica . Todites gaillardotii differs from C. ladinica mainly in the absence of enlarged basiscopic pinnules; moreover, the pinnules in T. gaillardotii are always free up to their constricted bases ( Kustatscher and Van Konijnenburg-van Cittert 2011). Todites roessertii (Presl in Sternberg, 1838) Krystofovich, 1912 from the Rhaeto-Liassic of Europe has larger pinnules with a neuropterid venation, and more importantly lacks specialized basiscopic pinnules.

Assignment of this taxon to an existing fossil genus for fern foliage is problematic because of two characters of this species; the specialized, enlarged first basiscopic pinnules and the radiating and forking venation lacking a clear midrib. We include the specimens in the morphogenus Cladophlebis , as no other genus combines all the characters of our material. Some Cladophlebis species have a more or less radiating venation (see below), some may have a more or less specialized basiscopic pinnule but to our knowledge, no existing species combines both characters. Hence, we establish the new species Cladophlebis ladinica . Three genera of fern foliage are similar in one aspect. Mertensides Fontaine, 1883 (with its type-species Mertensides bullatus [Bunbury, 1864] Fontaine, 1883) is characterized by a specialized basiscopic pinnule with radiating venation, but the other pinnules have a pecopterid gross morphology with a distinct midrib, like almost all species of Cladophlebis see e.g., Bock 1969). Lobifolia Rasskazova and Lebedev, 1968 is a morphogenus for sterile foliage of the type found in e.g., Eboracia , Todites , and Cladophlebis with enlarged basiscopic pinnules. These pinnules, are, however, usually divided into two lobes, and the venation incorporates a midrib in the majority of the species (see e.g., Boureau and Doubinger 1975). Nymborhipteris Holmes, 2003 is characterized by pinnules with a radiating and forked venation as in Cladophlebis ladinica , but it lacks enlarged basal pinnules.

The botanical affinity of Cladophlebis ladinica is not yet clear as no fertile material was found. Species with enlarged, or at least modified basiscopic pinnules are common in the Dicksoniaceae (see e.g., Schweitzer et al. 2009) but they also occur sparsely in other families, such as the Osmundaceae and Schizaeaceae ( Kustatscher and Van Konijnenburg-van Cittert 2011; Van Konijnenburg-van Cittert 2002). Neuropterid venation as seen in C. ladinica occurs mainly in Osmundaceae and Dicksoniaceae , so those two families seem the most likely affiliates of the new taxon.

Figures

Fig. 6. Cladophlebis fronds from the tuff layer in the basal part of “explosion breccia” (late Ladinian, Middle Triassic) of Monte Agnello, Dolomites, N- Italy. A. Cladophlebis ladinica sp. nov., partially fused basal pinnules (MGP 194/6B). B–E. Cladophlebis sp. B. Bipinnate frond fragment (MGP 194/88). C. Pinnae with slightly falcate pinnules (MGP 194/87). D. Detail of the slightly imbricate pinnules (MGP 63/71). E. Possible basal pinnae with broad pinnules (MGP 194/89A). Scale bars 10 mm.