Metaxya parkeri (Hook. & Grev.) J.Sm.,

Castro-Aguiar, Pedro Henrique, Fernandes, Rozijane Santos & Zappi, Daniela Cristina, 2025, Ferns of the Parque Nacional das Nascentes do Rio Parnaíba Brazilian Cerrado, Rodriguesia (e 00612024) 76, pp. 1-24 : 15-16

11.1. Metaxya parkeri (Hook. & Grev.) J.Sm., London J. Bot. 1: 668 (1842). Fig. 4 h-i

Plants terrestrial. Stem short-creeping, with pale brown hairs. Fronds 75.5–107.7 cm long, monomorphic, 1-pinnate, patent; petiole 35.5–47.5 cm long, paleaceous to brown, sulcate adaxially, with hairs similar to those on the stem at the base; rachis sulcate adaxially, cylindrical abaxially; laminae 40–79 × 22.5–42 cm, oblong to lanceolate; pinnae 13.2–23.5 × 2.2–2.5 cm, 8–14 pairs, linear-lanceolate, chartaceous, glabrous adaxially, with hairs abaxially, more densely arranged close to the costae, margins serrate at the apex, sometimes extending to the middle of the pinnae length, base acute to cuneate, apex acute to acuminate, terminal pinnae conform; veins free. Sori rounded, 1–2(–3) per vein, either concentrated near the costa or irregularly dispersed over most of the pinna, paraphyses present; indusia absent.

Examined material: MARANHÃO: Alto ParnaÍba , PNNRP, Cachoeira do Sussuapara , 10°09’56’’S, 45°55’38’’W, 425 m, 21.IV.2022, P. H. C. Aguiar et al. 19 ( CCAA, UB); P. H. C. Aguiar et al. 40 ( CCAA); 15.XII.2022, P. H. Castro-Aguiar et al. 165 ( CCAA). PIAUÍ: Barreiras do PiauÍ, PNNRP, Cachoeira do Pintado , 10°11’26’’S, 45°51’08’’W, 436 m, 13.XII.2022, P. H. Castro-Aguiar et al. 77 ( CCAA, UB) .

Metaxya parkeri has a Neotropical distribution, occurring in South America and in the Caribbean ( Cárdenas et al. 2016). In Brazil, it is the most widely distributed species of the genus, occurring in the Amazon, Cerrado, and Atlantic Rainforest biomes ( Pietrobom & Santiago 2023). In the study area, it was observed growing in large populations in the vicinity of waterfalls, and on the margins of streams within gallery forest.

Metaxya parkeri resembles M. rostrata (Kunth) C.Presl mainly due to the chartaceous laminae and the arrangement of the sori, with 2–4 per venule, close to the costae or irregularly dispersed over the surface of the pinnae. Nevertheless, M. parkeri differs from M. rostrata by having laminae with more than seven pairs of pinnae (vs. 8–14 pairs in the study area), and with pinnae distally longattenuated to caudate, with serrate margins that can extend up to half of the length of the pinnae or until the base, whilst M. rostrata has up to seven pairs of lateral pinnae, with cuspidate to caudate apex, margins irregularly dentate and almost entire (completely entire excluding the apex) ( Cárdenas et al. 2016).

In Brazil, Metaxya parkeri and M. rostrata occur together in the Amazon biome, in the state of Amazonas. In addition, M. rostrata is also found in Amapá, whilst M. parkeri has a wider distribution, extending to the Eastern coast and occurring in the Cerrado and Atlantic Rainforest biomes ( Cárdenas et al. 2016; Fernandes et al. 2022; Pietrobom & Santiago 2023).

Within the species of the genus, Metaxya parkeri is characterized by a wide variation in the margin of the pinnae and the arrangement of the sori, with the margins generally serrate only apically (up to half the length of the pinnae), but sometimes reaching the base. The sori can be concentrated close to the costae, slightly away from the costae, or irregularly distributed through a large portion of the abaxial pinnae ( Cárdenas et al. 2016). On the specimens of the study area, the sorus can form a row slightly away from the costae, up to 2.5 mm of distance, with the others lightly dispersed on the abaxial pinnae, and the margin can be serrated only apically or up to half of the pinnae.

Figures

Figure 4 – a.Elaphoglossum scalpellum – habit.b-c.Dicranopteris flexuosa – b. habit; c. sori on the abaxial surface.d.Trichomanes pilosum – habit. e. Trichomanes pinnatum – habit. f. Lindsaea divaricata – habit. g. Lindsaea lancea – habit. h-i. Metaxya parkeri – h. babit; i. sori on the abaxial surface. (a. P.H. Castro-Aguiar et al. 172; b-c. P.H. Castro-Aguiar et al. 67; d. P.H. Castro-Aguiar et al. 238; e. P.H. Castro-Aguiar et al. 173; f. P.H.C. Aguiar et al. 8; g. P.H.C. Aguiar et al. 28; h-i. P.H. Castro-Aguiar et al. 165).