From the Guiana Highlands to the Brazilian Atlantic Rain Forest: four new species of Selaginella (Selaginellaceae – Lycopodiophyta: S. agioneuma, S. magnafornensis, S. ventricosa, and S. zartmanii)

Discussion

S. agioneuma is a very distinct species characterized by its decumbent to ascending habit, ventral and dorsal, stout rhizophores, upper surfaces of leaves usually with idioblasts, median leaf apices long-aristate with each arista denticulate and tipped by one to three teeth, and lemon yellow megaspores. In addition, the acroscopic halves of the lateral leaves are twice as wide as the basiscopic halves (i.e., 2.0 × 1.0 mm wide), while the inner halves of the median and axillary leaves are 1∕2 wider than the outer halves (i.e., 1.5 × 1.0 mm wide) and the halves of the dorsal and ventral sporophylls that overlap with each other are 1∕2 smaller than the halves that do not overlap.

Selaginella agioneuma is morphologically similar to S. contigua by having a decumbent to ascending habit, idioblasts on the upper leaf surfaces, median leaf apices which taper into a long arista (which are long-acuminate to short- or long-aristate in S. contigua), and yellow megaspores. In addition, it somewhat resembles S. nanuzae Valdespino, and S. mendocae Hieron., because of its habit, stem width (including lateral leaves), and overall leaf shape. Nevertheless, S. agioneuma differs from S. contigua by the characters listed under the diagnosis, while from S. nanuzae it is easily distinguished by its smooth, green upper and lower leaf surfaces (vs. upper surfaces bumpy and green, and lower surfaces corrugate to striate and silvery green), median leaf inner margins dentate to short-ciliate throughout and the outer margins entire along proximal 1∕2, otherwise dentate to short-ciliate along distal 1∕2 (vs. margins long-ciliate throughout and more obviously so on outer margins, where the cilia are half to one time longer than the inner cilia), the bases subcordate and glabrous (vs. truncate or oblique with outer bases auriculate, the auriculae tufted with 10–18 cilia), the axillary leaves 4.0–5.0 × 1.5–3.0 mm (vs. 1.5–2.6 × 0.8–1.1 mm); the lateral leaf bases denticulate along proximal 1∕2, then becoming entire and again denticulate along distal 1∕4 or denticulate throughout (vs. long-ciliate along proximal 3∕4, otherwise denticulate distally), basiscopic margins entire along proximal 3∕4, otherwise denticulate on distal 1∕4 (vs. long-ciliate along proximal 1∕8, otherwise entire distally or denticulate on distal 1∕8); apices acute to apiculate (vs. falcate and acute or gradually tapering and acute). Selaginella agioneuma differs from S. mendocae (which has obscure idioblasts on the upper and lower surfaces of the leaves and sporophylls, and yellow megaspores) by the upper surfaces of the leaf smooth (vs. strongly corrugate), median leaf outer margins entire along proximal 1∕2, otherwise dentate to short-ciliate along distal 1∕2 (vs. long-ciliate throughout), long-aristate (vs. cuspidate to shortly acuminate) apices, each arista 1∕4–1∕2 the length of the laminae (vs. 1∕20–1∕10), 0.5–1.5 (vs. 0.1 or 0.2) mm long, and oblong or broadly ovate-oblong (vs. oblong) lateral leaves with the basiscopic bases entire (vs. long-ciliate along ca. 1∕10 of the proximal base), and with broad and abruptly tapering apices ending in an acute tip (vs. truncate).

Additionally, similarities in habit and stem width (including lateral leaves) might cause S. agioneuma to be confused with other Brazilian species of the genus such as S. breynii Spring, S. falcata (P. Beauv.) Spring, and S. flexuosa Spring. Nevertheless, S. falcata has ovate-deltate median leaf with bases cordate, each lobe ciliate, margins ciliate, and acuminate toothed apices that tend to lift up, the acroscopic 1∕4 of the lateral leaf ciliate, and axillary leaves narrowly lanceolate to lanceolate. On the other hand, S. breynii has median leaf outer margins distinctly ciliate throughout, incurved midribs with the long-aristate apices interlocking with the distal portion of the leaf apices above, the outer bases ciliate, the lateral leaf proximal 1∕4 long-ciliate, otherwise distally dentate with the midribs on lower surfaces distinctly marked, the basiscopic margins long-ciliate along proximal 1∕8, the apices mostly gradually tapering into a broad acute tip, and the axillary leaf narrowly lanceolate to lanceolate. Finally, S. flexuosa has leaves upper surfaces distinctly corrugate, median leaf margins denticulate with long toothed aristae abruptly born at the apices, which frequently interlock with the laminae of the leaves above them, the lateral and axillary leaves margins entire to minutely denticulate, and the lower surfaces of the leaves with many, elongate, idioblasts.

Type:–Brazil. Espíritu Santo. Castelo, Parque Estadual Forno Grande, 20°31′51″S, 41°05′56″W, 1,400 m, 28 Jun 2008, A. Salino, G. Heringer, & V.A.O. Dittrich 13704 (holotype: P!; isotypes: BHCB-n.v., fragment PMA!).

LSID:77178085-1.

Diagnosis:–S. magnafornensis differs from slender forms of S. flexuosa by its smooth (vs. corrugate) upper leaf surface, ovate-oblong (vs. oblong) lateral leaves with acroscopic margins shortly ciliate to dentate along proximal 1∕3–1∕2 of each lamina (vs. denticulate along proximal 1∕3, otherwise entire), and ovate, ovate-oblong, ovate-cordate or narrowly ovate (vs. elliptic to oblong-elliptic) axillary leaves, and yellow (vs. white) megaspores.

Description:–Plants terrestrial. Stems ascending, stramineous, 15–25 cm long, 0.4–0.8 mm diam., non-articulate, not flagelliform or stoloniferous, 2- or 3-branched. Rhizophores ventral, axillar, and dorsal, borne on proximal 1∕8–1∕3 of stems, stout, 0.1–0.5 mm diam. Leaves heteromorphic throughout, chartaceous to slightly coriaceous, strongly distant, upper surfaces smooth and green, lower surfaces smooth and silvery green. Lateral leaves perpendicular to the stems or slightly ascending, ovate to ovate-oblong, 1.7–2.5 × 0.8–1.5 mm; bases rounded to semicordate, glabrous, acroscopic bases strongly overlapping stems, basiscopic bases free from stems; acroscopic margins hyaline in a band one to six cells wide (usually one to three cells wide on basiscopic margins) with the cells elongate, straight-walled and papillate parallel to margins, papillae in one row over each cell lumen, shortly ciliate to dentate along proximal 1∕3–1∕2, otherwise denticulate apically, basiscopic margins narrowly hyaline to greenish hyaline in a band one to three cells wide, the cells as in acroscopic margins, denticulate; apices acute, variously tipped by two to four teeth; upper surfaces comprised of quadrangular or rounded, sinuate-walled cells, many of these along submarginal portion of basiscopic halves and apical 1∕4 of the laminae covered by 2–12 papillae, without idioblasts or stomata, lower surfaces comprised of elongate, sinuate-walled cells and many papillate idioblast on both sides of the midribs, the idioblasts three to six longer than surrounding cells and somewhat interconnecting as to appear veins (i.e., false veins), papillae in one row over each cell lumen, with stomata in one or two rows along proximal 3∕4 of the midribs and at least one or few scattered on proximal, submarginal 1∕2 of acroscopic margins and on distal 1∕3 of the margins. Median leaves ascending, ovate-elliptic, 1.0–1.8(2.0) × 0.8–1.4 mm; bases oblique, glabrous; margins hyaline in a band two to four cells wide, the cells elongate, straight-walled and papillate parallel to margins, papillae in one row over each cell lumen, margins dentate; apices long-aristate, each arista 1∕3–1∕2 the length of the laminae (0.4–0.7 mm long), dentate and variously tipped by one to four teeth; both surfaces without conspicuous idioblasts, upper surfaces comprised of quadrangular, rectangular or rounded, sinuate-walled cells, many of these covered by 6–14 papillae, with stomata in one row along distal 1∕2 of the midribs, sparsely present on submarginal portion along proximal 1∕4 of outer halves of the laminae, lower surfaces comprised of elongate, sinuate-walled cells, without stomata. Axillary leaves similar to lateral leaves or broadly ovate, 1.8–2.4 × 1.0–1.5 mm; bases rounded, glabrous; margins narrowly hyaline, margins dentate to denticulate; apices acute, variously tipped by one to three teeth; both surfaces as in lateral leaves, except for stomata along distal 1∕2 of the laminae and margins. Strobili terminal on main stem and branch tips, quadrangular, 3.0–8.0 cm. Sporophylls monomorphic, without a laminar flap, each with a well developed and seemingly glabrous keel (as observed with SM) along midribs, ovate-lanceolate, 0.9–1.2 × 0.5–0.7 mm; bases rounded; margins slightly hyaline, dentate; apices acuminate to aristate, each acumen or aristae 0.2–0.4 mm long, tipped by one or two teeth; dorsal sporophylls with upper surfaces green and cells as in median leaves, including idioblasts, lower surfaces silvery green and comprised of elongate, sinuate-walled cells; ventral sporophylls with both surfaces greenish-hyaline, comprised of elongate, sinuate-walled cells. Megasporangia in two ventral rows; megaspores yellow to lemon yellow, reticulate-rugulate and with a slightly developed equatorial flange on proximal faces with granulate to slightly echinulate, verrucate and perforate microstructure, reticulate on distal faces with close reticula and verrucate, slightly echinulate, and perforate microstructure (Figs. 8A–8F), 315–340 µm. Microsporangia in 2 dorsal rows; microspores orange, rugulate on proximal faces with slightly verrucate to echinulate and perforate microstructure, capitate or clavate on distal faces with each caput or expanded apex and the rest of the surface with plicate, rugulate, and perforate microstructure (Figs. 8G & 8H), 25–32 µm.

Habitat and distribution:–S. magnafornensis grows as epipetric in dense montane wet forests at 1,400 m in Atlantic forest vegetation. It is known only from the type collection made in Parque Estadual Forno Grande, Espíritu Santo.

Etymology:–The specific epithet is a compound word derived from the Latin “magna”, meaning big (“grande” in Portuguese), and “furnus”, meaning oven (“forno” in Portuguese), and alludes to the name of the park where the species was collected.

Conservation status:–S. magnafornensis is known from a single collection made in a National Park in Brazil, which presumably is well-protected. However, at this point the species is best treated as Data Deficient (DD) according to IUCN categories and criteria (IUCN, 2012).

Discussion

S. magnafornensis is a very distinct species with slender stems with well-spaced branches (1.0–1.5 cm apart) that bear strobili at their tips. It does not seem to have close morphological affinities with other Brazilian Selaginella species but its creeping stems, somewhat stiff and long-aristate median leaves are reminiscent of slender forms of S. flexuosa, however, the characters listed in the diagnosis set them apart.

Type:–BRAZIL. Roraima: [Mpio.] Caracarai, Parque Nacional Serra da Mocidade, 01°71′84.3″N, 61°75′37″W, 1,732 m, 3 Feb 2016, M.H. Terra-Araujo, R. Braga-Neto & A. Vicentini 1320 (holotype: INPA!; isotype: PMA!).

LSID:77178086-1.

Diagnosis:–S. ventricosa differs from S. microphylla (Kunth) Spring by its leaves with extended (vs. usually with reflexed) margins, broadly acute (vs. acute) median leaves and apices tipped by four to six teeth (vs. by three to five long cilia), with (vs. without) stomata on the upper surfaces, and stomata lacking (vs. present) on the lower surfaces. It also differs from S. microphylla by the median leaf inner hyaline margins along distal 1∕2 and the outer hyaline margins along distal 2∕3 with the papillae of the cells interconnected (vs. papillae distinct) and appearing (vs. not) idioblast-like, and lower surfaces of lateral leaves with many (vs. some) papillate idioblasts, the idioblasts long (vs. short) with papillae mostly in 2 (vs. two to four) rows or in a single interconnected row (vs. always in two or more distinct rows) of papillae.

Description:–Plants epiphytic. Stems creeping, stramineous, 7.0–14.5 cm long, 0.4–0.6 mm diam., non-articulate, not flagelliform or stoloniferous, one- to two-branched. Rhizophores axillary, borne throughout the stem, filiform, 0.1–0.3 mm diam. Leaves heteromorphic throughout, membranaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves spreading, broadly ovate or ovate-oblong, 2.0–2.7 × 1.2–2.2 mm; bases rounded, glabrous, acroscopic bases strongly overlapping the stems, basiscopic bases free from stems; acroscopic margins hyaline along proximal 1∕3 in a band three to seven cells wide with the cells elongate, straight-walled and papillate parallel to margins, papillae in two rows over each cell lumen, long-ciliate along proximal 3∕4, otherwise denticulate distally; basiscopic margins greenish, comprised of quadrangular, sinuate-walled, glabrous and papillate cells, short-ciliate along proximal 1∕8; otherwise entire distally or denticulate on distal 1∕8, apices broadly acute to obtuse, with prickles or tooth-like projections on the upper surface; upper surfaces comprised of quadrangular or rounded, sinuate-walled cells, many of these covered by 7–20 papillae, without idioblasts or stomata, lower surfaces comprised of elongate, sinuate-walled cells, with many of these papillate and with idioblasts on both side of the midribs (more so on basiscopic halves of the laminae), papillae in two to three rows over each cell lumen, with stomata in three to four rows along midribs. Median leaves distant on the main stem, ascending, broadly ovate to ovate-orbicular, 0.8–1.4 × 0.7–1.3 mm; bases truncate to oblique, glabrous, inner margins hyaline in a band two to six cells wide, the cells elongate, straight-walled and papillate parallel to margins, papillae in one row over each cell lumen and often interconnected along distal 1∕2 and appearing as a single line or idioblast, long-ciliate along proximal 4∕5, otherwise dentate to serrate on distal 1∕5, outer margins greenish along proximal 1∕3 and the cells similar to those of the leaf upper surfaces, otherwise hyaline on distal 2∕3 in a band one or two cells wide with the cells similar to those found on distal 1∕2 of inner margins, entire along proximal 1∕3, except for a single long-ciliate at proximal most portion near the base, otherwise short-ciliate on median 1∕3 and dentate to serrate on distal most 1∕3; apices broadly acute, 0.1–0.2 mm long, variously tipped by four to six teeth and with tooth-like or prickle projections along its length on upper surfaces; upper surfaces comprised of quadrangular, rectangular or rounded, sinuate-walled cells, many of these covered by 5–15 papillae, with stomata in one to two rows along distal 1∕2–2∕3 of the midribs ending before distal most apical portion of the lamina and along proximal 1∕3 of outer margins, lower surfaces comprised of elongate, sinuate-walled cells, with papillate idioblasts concentrated on proximal 1∕3 of the outer margins, the papillae in two rows of each cell lumen, without stomata. Axillary leaves narrowly ovate or ovate-oblong, 1.3–1.6 × 1.0–1.3 mm; bases truncate, glabrous; margins hyaline, long-ciliate along proximal 2∕3, especially on inner margins, otherwise denticulate on distal 1∕3; apices acute to broadly acute, variously tipped by one to three teeth; both surfaces as in lateral leaves. Strobili, sporophylls, sporangia and spores not observed because plants where unfertile.

Habitat and distribution:–S. ventricosa grows as an epiphyte in upper montane Amazon forests at 1,732 m in an isolated tepui complex in the southern portion of the Guiana Plateau; it is only known from the type locality in Roraima State, Brazil, where it might be a local endemic. Recently, other plant and insect species were described from the Serra da Mocidade mountain range (see for example Bastos, Sierra & Zartman, 2016; Da Silva-Neto, Aldrete & Rafael, 2016; Dantas & Hamada, 2017) that also has an herpetofauna richness comparable to other Guiana Shield mountains (Moraes et al., 2017), thus highlighting its biodiversity importance within the region.

Etymology:–The species name is derived from the Latin “ventricosus”, meaning swollen, especially on one side, and refers to the median leaf outer halves somewhat ventricose or bulging.

Conservation status:–S. ventricosa was collected in Serra da Mocidade National Park, a poorly explored and isolated tepui complex of the Brazilian Guiana Shield, that is closed to the public and thus this species is considered as Data Deficient (DD), according to IUCN categories and criteria (IUCN, 2012).

Discussion

S. ventricosa is characterized by its broadly ovate to ovate-orbicular median leaves with asymmetric halves, the outer halves 1∕4 or less wider than the inner halves and somewhat appearing ventricose or bulging, truncate to oblique bases. It is further characterized by its median leaf inner margins long-ciliate along proximal 4∕5, the inner margins distal 1∕2 and the outer margins distal 2∕3 hyaline, composed of papillate cells with the papillae interconnected appearing as a single line or idioblast, stomata along proximal 1∕3 of outer margins, broadly acute apices tipped by four to six teeth, and each apex upper surface with prickles or tooth-like projections along its length and with many of the cells lumina covered by 5–15 papillae.

Selaginella ventricosa is a unique species that might be confused with S. microphylla, a taxon within the species group of the same name that is also found in Brazil, by its similar creeping habit and leaves. S. ventricosa is set easily aside from the latter by the characters listed in the diagnosis and by its median leaves with truncate to oblique (vs. distinctly oblique) bases, with the inner margins long-ciliate along proximal 4∕5 and outer margins short-ciliate on median 1∕3 (vs. inner and outer margins usually long-ciliate throughout), and the upper surfaces with 5–15 [vs. 1–4(6)] papillae.

Type:–BRAZIL. Amazonas: [Mpio.] São Gabriel da Cachoeira, Reserva Morro dos Seis Lagos, Lago do Dragão, 0°17′06″N, 66° 40′36″W, 400–450 m, 27 Aug 2011, C.E. Zartman 8586 (holotype: INPA!; isotype: PMA!).

LSID:77178087-1.

Diagnosis:–S. zartmanii is very similar to and easily confused with S. boomii Valdespino from which it is set aside by its glabrous (vs. papillate) upper median leaf surfaces or only with few papillate cells along the midribs (vs. papillae throughout the leaf lamina), lumen of papillate cells each with one papilla (vs. two to four papillae), margins narrowly (vs. broadly) hyaline and composed of one or two (vs. two to four) elongate and papillate cells, short (vs. long) aristate apices which extend 1∕4 (vs. 1∕3 or more) the length of the lamina, lateral leaves basiscopic margins with (vs. without conspicuous) submarginal stomata on upper surfaces, the acroscopic margins on upper surfaces composed of quadrangular to rectangular and glabrous (vs. elongate and papillate) green (vs. hyaline) cells, each assembled in a band of one or two (vs. two to seven) cells, and with (vs. without) conspicuous submarginal stomata along distal 1∕3.

Description:–Plants terrestrial or epipetric. Stems suberect to erect, stramineous or reddish, four to six cm long, 0.2–0.4 mm diam., non-articulate, not flagelliform or stoloniferous, 2 or 3-branched. Rhizophores axillary or ventro-axillary, borne on proximal 1∕3 of stems, filiform, 0.1–0.3 mm diam. Leaves heteromorphic throughout, membranaceous, both surfaces smooth, upper surfaces reddish, greenish or yellowish, lower surfaces reddish, silvery green or yellowish. Lateral leaves ascending, lanceolate-oblong or ovate-oblong, 1.3–1.8 × 0.4–0.9 mm; bases rounded, glabrous, acroscopic bases overlapping stems, basiscopic bases free from stems; acroscopic margins slightly hyaline in a band two or three cells wide with the cells elongate, straight-walled and papillate parallel to margins, papillae in one row over each cell lumen, serrate throughout, basiscopic margins greenish, often revolute, comprised of quadrangular, sinuate-walled cells, serrate throughout; apices acute, variously tipped by three to five teeth; both surfaces glabrous or upper surface sometimes with marginal prickles or tooth-like projections along the distal region of basiscopic margins, upper surfaces comprised of quadrangular or rounded, sinuate-walled cells (often difficult to distinguish because of waxy deposits), many of these covered by one or two papillae, without idioblasts or stomata or sometimes with submarginal to marginal stomata along both margins, lower surfaces comprised of elongate, sinuate-walled cells, with many of these papillate and idioblast-like on both sides of the midribs, papillae in one row over each cell lumen, with stomata in four or five rows along midribs. Median leaves ascending, distant to slightly imbricate in the apical region of stems and branches, ovate-elliptic or ovate, 0.6–1.2 × 0.4–0.7 mm; bases truncate and glabrous; margins slightly hyaline in a band one to three cells wide, the cells elongate, straight-walled and papillate parallel to margins, papillae in one row over each cell lumen, serrate throughout; apices aristate, arista 0.2–0.5 mm long, tipped by five or six teeth and with prickles or tooth-like projections along its length on upper surfaces; both surfaces without conspicuous idioblasts, upper surfaces comprised of quadrangular, rectangular or rounded, sinuate-walled cells (often difficult to distinguish because of waxy deposits), many of these covered by one or two papillae, with stomata in one or two rows along distal 1∕2 of the midribs, sparsely present on submarginal portion along proximal 1∕3 of outer halves of the laminae, lower surfaces comprised of elongate, sinuate-walled cells, without stomata. Axillary leaves lanceolate, 0.8–1.8 × 0.4–1.7 mm; bases rounded to subcordate, glabrous; margins serrate throughout; apices acute, variously tipped by one to three teeth; both surfaces as in lateral leaves. Strobili terminal on branch tips, one per branch, quadrangular, 0.9–5.0 cm long. Sporophylls monomorphic, without a laminar flap, each with a strongly developed and seemingly glabrous keel (as observed with SM) along midribs, ovate, 0.6–0.8 × 0.5–0.7 mm; bases truncate; margins slightly hyaline, dentate; apices acuminate to cuspidate, each acumen (cusp) 0.2–0.3 mm long, tipped by one to three teeth; dorsal sporophylls with upper surfaces green and cells as in median leaves, lower surfaces silvery green and comprised of elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline or greenish hyaline, comprised of elongate, sinuate-walled cells. Megasporangia in two ventral rows; megaspores yellow, rugulate to coarsely rugulate-reticulate on proximal faces with a developed equatorial flange and spheroid or spheroid-perforate to spheroid-foveolate microstructure, coarsely reticulate or rugulate on distal faces with spheroid to spheroid-perforate or rugulate microstructure (Figs. 16A–16D), 200–265 µm. Microsporangia in two dorsal rows; microspores orange, gemmate on proximal faces with psilate microstructure, rugulate-gemmate or gemmate on distal faces with psilate and slightly foveolate microstructure (Figs. 16E & 16F), 22–25 µm.

Additional specimens examined (paratypes):–BRAZIL. Amazonas: Río Negro, [Mpio. São Gabriel da Cachoeira,] between Manaus and São Gabriel, Serra Curicuriari, 00°20″S, 66°50″W, 10 Jul 1979, Poole 1948 (mixed coll., 1948b at NY), Morro dos Seis Lagos, ca. 80 km N of São Gabriel, 00°20″N, 66°45″W, ca. 100 m, 18 Jul 1979, Poole 2068 (NY-2 sheets), São Gabriel da Cachoeira, Mt. Morro dos Seis Lagos, Lago No. 2, 00°12″N, 66°00″W, 15 Oct 1987, Stevenson et al. 702 (NY, PMA).

Habitat and distribution:–S. zartmanii grows in lowland and mid elevations in tropical wet forests or dense premontane wet forests at 100–450 m in the upper Rio Negro at the Amazon basin. The type collection was made on rocks bordering an isolated lake formed by ancient volcanic plugs in the Morro dos Seis Lagos Biological Reserve, occurring in relative abundance on a geologically unique substrate for the region of an iron-rich reddish lateritic crust formation draining into the Igarapé–Mirim, a tributary of the Cauaburi River of the Rio Negro. This species has only been collected from in or around Mpio. São Gabriel da Cachoeira (including another isolated range in the region, the Serra Curicuriari), State of Amazonas, Brazil, which suggests S. zartmanii may be a local endemic to isolated outcrops of the upper Rio Negro. Further explorations of the Serras do Padre and Neblina complexes might reveal its presence there as well.

Eponymy:–This species honors Professor Dr. Charles Eugene Zartman (1970–), an outstanding American Bryologist who has made significant contributions in taxonomy and ecology of Neotropical mosses and liverworts, as well as in the ecology and botany of the Brazilian Amazon.

Conservation status:–This species grows in zones within the intersection of 3 protected areas: Pico da Neblina National Park, Morro dos Seis Lagos Biological Reserve, and Balaio Indigenous Park (Saraiva & Forzza, 2012) and was reported in the type collection information as consisting of abundant populations there. Therefore, it presently should be classified as a least concern (LC) taxon according to IUCN criteria (IUCN, 2012).

Discussion

Selaginella zartmanii is easily confused with S. boomii because of their overall similar habit and leaves, and often having their lateral leaves basiscopic margins revolute when dry. In fact, Valdespino (2015b), included specimens here cited as paratypes of S. zartmanii under the latter. Nevertheless, a recent study conducted to identify the type collection of S. zartmanii prompted us to reassess the circumscription of S. boomii and to segregate from it those specimens from São Gabriel da Cachoeira, Amazonas State, Brazil, ascribing them to the former species. Selaginella zartmanii differs most noticeably from S. boomii by the characters listed in the diagnosis. In addition, as already advanced by Valdespino (2015b) specimens here assigned to S. zartmanii differ from typical S. boomii in having its megaspores proximal faces coarsely rugulate-reticulate (vs. slightly rugulate-reticulate to rugulate-granulate) with (vs. without) a slightly developed equatorial flange and spheroid to spheroid-perforate (vs. echinulate and perforate) microstructure and coarsely reticulate (vs. slightly rugulate-reticulate to rugulate-granulate) distal faces, the reticula with broad and coarse (vs. fainted or vestigial) muri and spheroid to spheroid-perforate (vs. echinulate and perforate) microstructure [see Figs. 16A–16D depicted here and Fig. 2A–D in Valdespino (2015b), for megaspore sculpturing pattern comparison]. This new species further differs from S. boomii by having the lower surfaces of the lateral leaves with scattered (vs. variously assembled in continuous rows of three to nine) idioblasts mostly along distal 1∕2 or occasionally few proximal (vs. throughout both sides) of each leaf midrib, and glabrous leaf base cells (vs. papillate and idioblasts-like with papillae in one or two rows on each cell lumen).