Chiropteris monteagnellii, 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 : 748-750

Chiropteris monteagnellii sp. nov.

Figs. 4E, F, 5A, B.

Etymology: In reference to the geographic location of the fossils at the Monte Agnello.

Type material: Holotype: MGP 194 /8 A, most complete specimen, here designated (Fig. 4 E) . Paratypes: MGP 194 /95 B (reticulate vein structure), MGP 191 /10A (several petioles coming together); both here designated (Figs. 4F, 5A).

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 /74, 63/75 A – B, 171/25, 191/9 A –D, 191/10 A – C, 191/12, 191/17 A – C, 191/19 A – B, 191/29, 191/36, 191/77 A – B, 191/78, 194/8 A – B, 194/17, 194/90, 194/95 A – B, 194/103, all from type locality and horizon .

Diagnosis.— Funnel-shaped leaves with elongate, thick petiole characterized by longitudinal striae. Lamina spathulate, probably only secondarily incised to form several lobes, characterized by anastomosing venation forming very narrow meshes without any “midrib”. Margin entire.

Description.— Thirteen rock samples contain leaf remains belonging to Chiropteris . Several slabs are compound and contain the fragments of more than one frond. The frond fragments are up to 200 mm long and 120 mm wide (MGP 194/8A; Fig. 4E). The frond was originally funnel-shaped, as is clearly shown in one specimen (MGP 194/8A; Fig. 4E); the incisions and division in lobes have been created secondarily by dissection of the lamina caused either by the age of the frond or by the transport and deposition of the specimen. The lamina is characterized by a coarse, loose net venation (MGP 191/9B, MGP 194/95B; Fig. 4F); no “midrib-like” structure can be distinguished as is typical for other species of this genus. In most cases the fragments belong to distal parts of the lamina, in some cases also part of the petiole is preserved (MGP 63/75A; Fig. 5A); the lamina reduces downwards to 30 mm and finally the petiole has a diameter of c. 8–15 mm. The petiole reaches more than 150 mm in length and is characterized by longitudinal striae reflecting probably the veins of the leaves (MGP 63/75A; Fig. 5B). In one specimen at least four different petioles merge together at the base almost as if attached to the same stem or rhizome (MGP 191/10A; Fig. 5B).

This species differs from Chiropteris lacerata (Quenstedt, 1885) Rühle von Lilienstern, 1931 in its larger frond dimensions, the absence of a midrib in our material and a clear division into lobes, apart from secondary incisions. Rühle von Lilienstern (1931a, b) considered the leaves of C. lacerata to be up to 20 cm wide with a narrow petiole up to 15 cm long; some of our fragments are larger than that. Although large frond fragments are preserved, there is no sign of a midrib. The leaves of C. barrealensis Frenguelli, 1942 from the Rhaetian of Barreal ( Argentina), C. tasmanica Walkom, 1925 from the Mesozoic of Tasmania and Chiropteris biloba Bell, Harrington, and McKellar, 1956 from the Late Triassic of New Zealand are all smaller in dimensions (up to 30–40 mm long); the veins branch mostly dichotomously and anastomose only occasionally in the first two species, in the latter the leaves are deeply incised into two distinct segments. In Chiropteris taizihoensis Zhang in Zhang et al. (1980) and Chiropteris yuanii Sze, 1956 from the Late Triassic of China the leaves have even smaller dimensions (15–25 mm), whereas Chiropteris kawasakii Kon’no, 1972 from the Late Triassic of East Malaysia has reniform leaves with a slender petiole and an entire or slightly undulate margin. Chiropteris zeilleri Seward, 1903 from the Rhaetian of South Africa differs because of its orbiculate lamina and the polygonal meshes. Chiropteris waitakiensis Bell, 1956 from the Late Triassic of New Zealand differs because of the lamina’s subdivision into four or more strap-like segments by repeated dichotomy, resembling more a ginkgophyte than a fern frond.

Chiropteris cuneata (Carruthers, 1872) Seward, 1903 from the Triassic of Queensland and Chiropteris arberi Rühle von Lilienstern, 1931 from the Rhaetian of New-Zealand differ in its delicate secondary veins, which in our specimen are coarse, and in the dentate margin of the latter species. Furthermore, Chiropteris copiapensis Steinmann and Solms-Laubach in Solms-Laubach and Steinmann, 1899 from the Rhaetian of Chile seems to be characterized by an irregularly undulate to laciniate margin and rhomboidal areolae ( Frenguelli 1942). Additionally, these three species have

Fig. 5. Fern remains from the tuff layer in the basal part of “explosion breccia” (late Ladinian, Middle Triassic) of Monte Agnello, Dolomites, N-Italy. →

A, B. Chiropteris monteagnellii sp. nov. A. Frond base with petiole ( MGP 63 /75 A) . B. Paratype , several petioles coming together ( MGP 191 /10 A) .

C, D. Cladophlebis ladinica sp. nov. C. Holotype ( MGP 194 /6 B), frond fragment ( C

2

), detail of basiscopic pinnules with the distinct venation (C

1

).

D. Paratype ( MGP 194 /65 B), one of the largest frond fragments (D 1), detail of the rhomboidal pinnules with the distinct venation (D 2). E. Rachis showing wing ( MGP 197 /69 A). Scale bars 10 mm .

been now assigned to the genus Rochipteris , with a putative gymnosperm affinity, because of the non-petiolate, flabellate shape and slightly anastomosing venation (for more details see Barone-Nugent et al. 2003).

Chiropteris seems to be abundant and diverse globally during the Late Triassic (mostly Rhaetian), even if the type species Chiropteris lacerata (Quenstedt, 1885) Rühle von Lilienstern, 1931 comes from the late Ladinian of the Germanic Basin. The preservation of the new material is special. The veins must have been thick because they are very well preserved, different from most of the other fern taxa. The spathulate lamina of these leaves is locally interrupted by holes” or characterized by undulations because of the presence of lapilli (e.g., MGP 194 /95 B; Fig. 4 F) .

The systematic position of Chiropteris is still unclear. Schimper (1869) evidenced the close resemblance in the net venation between Chiropteris and Sagenopteris ( Caytoniales ). The genera differ, however, in the leaf structure funnel-shaped against two pairs of closely spaced leaflets) and venation (lateral veins are almost parallel to the midrib in Chiropteris against lateral veins arising at an acute angle from the midrib in Sagenopteris ). Other fan-shaped, non-petiolate leaves with a slightly anastomosing venation and an entire to dissected apex belong to the genus Rochipteris Herbst, Troncoso, and Gnaedinger, 2001 . The venation of this Late Triassic genus from Gondwana is, however, only sparsely reticulate, and the leaves are non-petiolate. Additionally they have a gymnosperm, possible ginkgoalean, affinity. Kannaskoppifolia Anderson and Anderson, 2003 , also a putative ginkgophyte leaf, resembles the genus Chiropteris but has a cuneate to flabellate, entire to three times divided lamina and a forking to anastomosing venation; the leaves are irregularly attached on short shoots. Batiopteris Anderson and Anderson, 2003 with its species Batiopteris pulchella Anderson and Anderson, 2003 is characterized by a long, gracile petiole and a fan-shaped to auriculate and bifidly divided lamina with frequently anastomosing veins; this species has also been attributed to the gymnosperms ( Anderson and Anderson 2003). In Cetiglossa Anderson and Anderson, 2003 with its species Cetiglossa balaena Anderson and Anderson, 2003 , a putatively gnetophyte genus of the Carnian of the Karoo Basin, the leaves are elongated with a distinct midrib and a lateral net venation. Gontriglossa Anderson and Anderson, 2003 resembles Sagenopteris with its lanceolate to elliptic leaves and the distinct midrib from which the anastomosing secondary veins arise; the organisation and the shape of the leaves and the distinct midrib distinguish this genus from Chiropteris .

Because of its resemblance with Ophioglossum palmatum Linnaeus, 1753 various authors suggested an attribution to the Ophioglossaceae (e.g., Potonié 1899; Zeiller 1900; Frentzen 1922). Rühle von Lilienstern (1931b) considered some roundish structures on the lower side of the leaves to be sporangia and attributed the genus to the Matoniaceae or Dipteridaceae ; the Dipteridaceae is the only Mesozoic fern family with reticulate venation. Some authors even consider it a ginkgoalean type of leaf ( Taylor et al. 2009). We consider an attribution to the Dipteridaceae the most likely because of the leaf morphology and venation pattern.

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