Dictyophyllum menendezii, Bodnar & Drovandi & Morel & Ganuza, 2018

Bodnar, Josefina, Drovandi, Juan Martín, Morel, Eduardo Manuel & Ganuza, Daniel Gustavo, 2018, Middle Triassic dipterid ferns from west-central Argentina and their relationship to palaeoclimatic changes, Acta Palaeontologica Polonica 63 (2), pp. 397-416 : 401-403

publication ID	https://doi.org/ 10.4202/app.00459.2018
persistent identifier	https://treatment.plazi.org/id/03F387D6-7810-FF9F-FB02-D499FFCBFB33
treatment provided by	Felipe
scientific name	Dictyophyllum menendezii
status	sp. nov.

Treatment

Dictyophyllum menendezii sp. nov.

Figs. 4 View Fig , 5 View Fig .

Etymology: In honour to Carlos Alberto Menéndez (1921–1976), Argentinean palaeobotanist, for his important studies on Mesozoic floras of Argentina.

Type material: Holotype: PBSJ 832 , half of a fan-shaped once-pinnate frond, with entire pinnae and clear venation . Paratypes: PBSJ 833 , fragment of a fan-shaped once-pinnate frond, with the widest pinnae and clear venation ; PBSJ 836 , two pinnae, with undulate margin towards their apex ; PBSJ 840 , specimen with the maximum number of pinnae per rachial arm ; PBSJ 843 sample with apical part of petiole preserved; all from type locality .

Type locality: Cortaderita Creek , Barreal-Calingasta Depocenter, San Juan Province, Argentina .

Type horizon: EF4, lower member of Cortaderita Formation, Sorocayense Group, early Ladinian (Middle Triassic).

Material.— Type material and additional seven specimens ( PBSJ 834 , 835 , 837–839 , 841 , 842 ) from the type locality .

Diagnosis. —Petiolate fronds bilaterally symmetrical and fan-shaped. Rachis dividing into two opposite arms, each arm bearing 5 or 6 oblanceolate pinnae. The lowest part of the lamina of adjacent pinnae is fused, forming a wide web. Margin of the pinnae entire to undulate. Primary veins catadromous to isodromous, striate and straight. Secondary veins subopposite, smooth and falcate to sinuous. Tertiary veins subopposite to alternate, falcate or with a zig-zag pattern, dichotomizing four times to form a fine reticulate mesh of polygonal irregular areoles.

Description.— Leaf fragments of triangular or fan shape of 6 to 8 cm in length or diameter ( Fig. 4A View Fig 1 View Fig , B). The fronds are once-pinnate, bilaterally symmetrical, and fan-shaped ( Fig. 5A View Fig ). The precise maximum size is unknown but is probably 8–10 cm in diameter. Only the most apical part of the petiole is preserved; its length and width cannot be determined ( Fig. 4E View Fig ).

The rachis dichotomizes into two opposite arms ( Fig. 4C, E View Fig ), each arm bearing 5 or 6 oblanceolate pinnae ( Fig. 4B, C View Fig ). A basal web of lamina unites adjacent pinnae for a length of up to 3 cm ( Fig. 4A View Fig 1 View Fig , B). The free part of pinnae reaches 8 cm in length and 2 cm in width, in the larger specimens. The lamina of the pinnae is glabrous, and their margin is entire in most of its length, but it can be undulate near the apex ( Fig. 4D View Fig ).

Each rachial arm gives rise to a series of 5 or 6 catadromous to isodromous primary veins, each representing the main vein of the pinnae. Primary veins are longitudinally striated and straight ( Fig. 4A View Fig 2 –A View Fig 4 View Fig ), and they extend from the rachial arm to the pinna apex. Their width reaches up to 1 mm near the base and 0.5 mm near the apex. Secondary veins are subopposite, departing at angles of ~70° from the primary veins. They are smooth and falcate to sinuous ( Fig. 4A View Fig 3 View Fig , A 4 View Fig ). In the fused basal portion of the frond lamina, secondary veins acquire a zig-zag pattern and converge between them ( Fig. 4A View Fig 3 View Fig ). Their width varies 0.1–0.3 mm. Tertiary veins are subopposite to alternate, and they depart from secondary veins at 50–90°. They are falcate or have a zig-zag pattern, and dichotomize four times to form a fine reticulate mesh of polygonal irregular areoles ( Figs. 4A View Fig 2 – A View Fig 4 View Fig , 5B View Fig ). First order areoles are elongated (rectangular, pentagonal, or hexagonal), up to 1.5 mm wide and 3.2 mm long. Second order areoles are pentagonal to rhomboidal, up to 0.9 mm wide and 2.3 mm long. In many cases, second order areoles are not present or free veinlets occur inside the first order areoles ( Fig. 5B View Fig ). Sori and sporangia are not observed.

Remarks. —The studied material show the distinctive features of the genus Dictyophyllum , i.e., once-pinnate leaf, pinnae not disposed in a funnel-shape and not spirally arranged, polygonal but not orthogonal areoles ( Ôishi and Yamasita 1936). In comparison with the known species of the genus from the Sorocayense Group, Dictyophyllum menendezi sp. nov. is similar in terms of the general size of the frond but differs in the length of basal lamina that unites adjacent pinna (which is greater in the new species), the entire to undulate pinna margin (lobate-serrate in D. castellanosii and dentate-lobate to pinnatifid in D. tenuifolium ), and the irregular venation areoles ( Table 1, Figs. 3 View Fig , 4A View Fig 2 –A View Fig 4 View Fig , 5B View Fig , 6A, D–F View Fig ). Conversely, Dictyophyllum menendezi sp. nov. shows similitude with D. ellenbergi in its basal web of the pinnae, which are concrescent for comparable lengths, in the number of pinnae per arm, and in the irregular shape of the areoles ( Table 1). However, the South African species differs from the new taxon due to the maximum length and margin of the pinnae. The last character, which is entire to undulate in Dictyophyllum menendezi sp. nov., clearly contrasts with all the previously described species of Dictyophyllum , in which the pinna margin forms distinct lobes. In the few cases where the pinna lobes are not so evident (i.e., D. davidi Walkom, 1917 and D. fuenzalidai Herbst, 2000 ), the margin is dentate, being different from the rounded undulations present in the new species. From the exposed information, we propose a new specific taxon for the specimens from the Cortaderita Formation.