Phlebopteris fiemmensis, 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 : 744-746

Phlebopteris fiemmensis sp. nov.

Figs. 3B–F, 4A.

Etymology: In reference to the geographic position, the Monte Agnello belongs to the Fiemme Valley.

Type material: Holotype: MGP 191 /11 B, almost entire pinnae with preserved vein structure, here designated (Fig. 3 B) . Paratypes: MGP 181 /57B, fertile specimen; MGP 181-57 A, palmate structure of the frond, here designated (Fig. 3C, D).

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

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

Material.— MGP 63 /70, 181/57 A – C, 191/11 A – B, all from type locality and horizon .

Diagnosis.— Pedate (palmately dissected) frond with at least 14 pinnae. Pinnae lanceolate with longest pinnules in the middle part, proximally pinnules almost fusing. Pinnules lanceolate to falcate, arising at c. 70–80°. Midvein distinct, slightly wavy, secondary veins distant, delicate, arising at an acute angle, bifurcating once or simple. Sporangia arranged in circular sori in two rows along the midrib consisting of a receptaculum surrounded by a ring of sporangia. No indusium present.

Description.— The frond fragments are up to 70 mm long and 60 mm wide (MGP 191/11A, 191/11B; Fig. 3B). Six to fourteen pinna fragments have been counted arising from the main rachis (1–2 mm), from two short arms (MGP 181/57A; Fig. 3D). The pinna fragments are lanceolate, up to 70 mm in length and about 20 mm in width (MGP 191/11A; Fig. 3F). The pinna fragments are inserted closely. The proximal pinnules are almost fused with each other (MGP 63/70; Fig. 3E). The lanceolate to falcate pinnules with a pointed apex arise alternately at an angle of 70–80°. The base is broadly attached to the rachis, connecting the adjacent pinnules.They increase in length throughout the proximal half of the lamina, from about 5 mm long and 2 mm wide at the base, up to 8–11 mm long and 3 mm wide in the middle part of the frond. Apically the pinnules decrease again in size (MGP 191/11B; Fig. 3B 2). The midvein is distinct, slightly wavy in the apical part of the larger pinnules and straight in small pinnules. Secondary veins arise at an acute angle and are widely spaced. They are delicate, simple or bifurcate once near the base (MGP 63/70; Fig. 3E).

So far only a few fertile fragments have been found (MGP 181/57B–C; Fig. 3C). They have sori positioned on two sides of the midrib consisting of a small number of sporangia, probably around six sporangia (MGP 181/57B; Fig. 3C). No indusium is evident.

Comparison.— In Phlebopteris sp. from the late Ladinian of Thale ( Germany), the pinnules are up to 25 mm long and 3–3.5 mm wide with a rounded apex arising perpendicularly from the rachis (2 mm wide). The secondary veins arise at 60 ‒ 70°, forking once or twice and the sori consist of circa eight free sporangia ( Kustatscher and Van Konijnenburg-van Cittert 2011). Phlebopteris smithii (Daugherty, 1941) Arnold, 1947 and its junior synonym P. utensis Arnold, 1956 (see Ash et al. 1982) from the Late Triassic of the USA differ because of the larger pinna dimensions (18 cm long), the more elongate pinnules (10–25 mm long) and its simpler lateral veins. In P. crenulata Weber, 2008 from the Late Triassic of Mexico, the margin of the lamina is crenulate and the venation is reticulate, both characters missing in P. fiemmeae . In P. otongensis Weber, 2008 from the Jurassic of Mexico, the pinnules are linear to triangular, smaller than in our material (5.5 x 1.5 mm), attached almost perpendicularly to the rachis and with crowded and in some cases anastomosing veins ( Weber 2008). Phlebopteris angustiloba (Presl, 1838) Hirmer and Hörhammer, 1936 from the Rhaeto-Liassic of Europe has simple secondary veins arising at an angle of 70 ‒ 90° which define “fields”. Phlebopteris muensteri (Schenk, 1867) Hirmer and Hörhammer, 1936 from the Early

Fig. 3. Osmundaceae and Dipteridaceae from the tuff layer in the basal part of “explosion breccia” (late Ladinian, Middle Triassic) of Monte Agnello, → Dolomites, N-Italy. A. Frond fragment of Neuropteridium elegans (Brongniart, 1828) Schimper, 1879 (MGP 194/83A). B–G. Phlebopteris fiemmensis sp.

nov. B. Holotype ( MGP 191 /11 B), almost complete pinnae with vein structure preserved and attachment area visible ( B 1 ), detail of the vein structure ( B 2 ).

C. Paratype, fertile frond fragment with sori on both sides of the midrib (arrow; MGP 181 /57 B). D . Paratype, detail of the palmate structure of the frond MGP 181 /57A). E. Pinnae with detail of the venation ( MGP 63 /70). F . Frond fragment ( MGP 191 /11 A). Scale bars A, B 1 , D, E 10 mm; B 2 , C, F 5 mm.

KUSTATSCHER ET AL.—MIDDLE TRIASSIC FERNS FROM THE DOLOMITES 745

B 2 A B 1 E C G F

Jurassic of Europe and Asia has larger pinnules (at least 60 mm × 4–5 mm), a thick midrib and simple to twice forked lateral veins with a higher vein concentration (30–40 per cm). Phlebopteris muensteri from the Late Triassic of Sweden Pott and McLoughlin 2011) resembles the pinnule shape of Fig. 3E, but the pinnules of P. fiemmensis seem shorter with a denser venation. In Phlebopteris formosa (Givulescu and Popa, 1998) H.-J. Schweitzer, U. Schweitzer, Kirchner, Van Konijnenburg-van Cittert, Van der Burgh, and Ashraf, 2009 from the early Jurassic of Romania, the pinnules are bigger 80–150 mm long and 10–14 mm wide) with lateral veins arising at 2–3 mm interval and bifurcating often to form an almost fasciculate structure. Phlebopteris tracyi Ash, 1991 from the Jurassic of Oregon ( USA) differs because of the reticulate structure of the lateral veins, larger pinnae (up to 50 cm long) and pinnules (40–60 × 3–7 mm). The new species differs from P. polypodioides Brongniart, 1836 and from P. dunkeri (Schenk, 1871) Schenk, 1875 from the Jurassic of Europe and Asia because of the typical anastomosing venation in the latter species (Van Konijnenburg-van Cittert 1993). Phlebopteris fiemmeae shows some resemblance to P. woodwardii Leckenby, 1864 from the Jurassic of Europe with its simple secondary veins; in the latter species the lateral veins arise almost perpendicularly. Anastomoses may also occur in P. woodwardii Leckenby, 1864 ( Harris 1961). Additionally, the lamina of P. woodwardii is very thick and is commonly preserved as fusain.

Discussion.— Only one fragment shows the attachment of the pinnae. It seems that there are two short basal arms on which the pinnae are attached. Unfortunately, the fragment is small and may belong to an unexpanded leaf. The fertile material confirms the attribution to the genus Phlebopteris .

Phlebopteris is typically a Late Triassic–Jurassic genus. So far, the oldest species are known from the Carnian or Norian of North America (Chinle Formation, P. smithii ) or Europe ( P. muensteri ), and it becomes widespread during the Jurassic and has its latest record in the Early Cretaceous Van Konijnenburg-van Cittert 1993). Only a few fragments have been found in the Ladinian so far. Recently, fertile frond fragments were described as Phlebopteris sp. from the late Ladinian of Thale, Germany ( Kustatscher and Van Konijnenburg-van Cittert 2011) because they were too badly preserved to identify them to species level. Thus, Phlebopteris fiemmensis from Monte Agnello is now the oldest formally established species in the genus, although the family seem to appear in the early Middle Triassic of Antarctica ( Millay and Taylor 1990).

Stratigraphic and geographic range.—Late Ladinian of Monte Agnello, Dolomites, Italy.