Selaginella altheae differs from S. lechleri Hieron. by the main stem leaves becoming obviously dimorphic above or 1–4 cm (vs. 3–6 cm) below the first branches of the stems, its lateral leaves bases oblique with a seemingly inner [actually it is an acroscopic] (vs. lacking) auricle that is tufted with 3–15 hairs (vs. bases glabrous) and the axillary leaves rounded to cordate or truncate with two, distinct, incurved and ciliate (vs. lacking) auricles at least up to the third or fourth branches along the stems.

BRAZIL. Amazonas: Río Negro, Río Cuaburí, along Río Tucano, vicinity of Base Camp, 20 Nov 1965, B. Maguire, J.A. Steyermark & C.K. Maguire 60249 (holotype: NY).

Plants terrestrial. Stems erect, stramineous, (20)30–65 cm long, 1.4–3.0 mm diam., non-articulate, usually not flagelliform, stoloniferous, 2–4-branched. Rhizophores axillary, ventral and dorsal, borne on lower-most part of the stems and throughout stolons, filiform or stout, 0.2–1.0 mm diam. Leaves seemingly monomorphic and strongly appressed to the stem shortly before or after first branches, then dimorphic throughout, coriaceous, upper surfaces dull to shiny green, slightly corrugate, lower surfaces shiny yellowish green to silvery green, striate, the outer bases short- to long-auricled (these tend to disappear on leaves above first branches), the auricle short- to long-ciliate, cilia 2–10, each 0.2–0.5 mm long. Lateral leaves on main stem after first branches distant to slightly imbricate, strongly ascending to slightly spreading, ovate-deltate to ovate-oblong, 2.0–4.2 × 0.9–2.2 mm; bases truncate, on main stem before first branches with an inner, acroscopic bases strongly overlapping stems, rounded, entire, basiscopic bases free from stems, geniculate, usually ciliate, cilia 1–5, each 0.1 to 0.2 mm long; acroscopic margins on main stem leaves after second branches greenish to narrowly hyaline along proximal ⅔, 1–3 cells wide with the cells elongate, sinuate-walled and glabrous, parallel to margins, otherwise greenish, on branch leaves narrowly hyaline along proximal ¾ and cells as those on main stem, otherwise greenish distally, long-ciliate along proximal ½–¾, otherwise becoming short-ciliate to dentate distally, basiscopic margins greenish, comprising similar cells as in acroscopic margins, entire along proximal ⅔, otherwise sparsely denticulate distally; apices gradually tapering, acute to broadly acute, tipped by 1–3 teeth; upper surfaces comprising irregularly shaped, somewhat rectangular to quadrangular, sinuate-walled cells (often difficult to distinguish because of waxy deposits), with some obscure, idioblast-like, short quadrangular to round or elongate and variously papillate cells, without stomata or with some obscure along basiscopic margins, lower surfaces comprising elongate, sinuate-walled cells, with many of these idioblast-like, elongate and papillate, papillae 5–14 in 1 or 2 rows on each cell lumen, stomata on 1–5 rows along midribs. Median leaves on main stems after first branches distant to slightly imbricate, ascending, ovate, broadly ovate to ovate-elliptic, 1.4–3.0 × 0.8–1.7 mm; bases truncate to truncate-oblique, the outer base tufted with (4)6–20 long hairs, without auricles; margins greenish to narrowly hyaline, 1 or 2 cells wide with the cells elongate, slightly sinuate-walled and mostly glabrous or papillate, parallel to margins, the inner margins short-ciliate along proximal ⅔, denticulate along distal ⅓, the outer margins entire along proximal ⅓, becoming short-ciliate along medial ⅓, otherwise denticulate on distal ⅓; apices acute to slightly acuminate, the acumen ca. 0.1 mm, tipped by 1–3 teeth; upper surfaces comprising irregular (jigsaw puzzle-like), sinuate-walled cells (often difficult to distinguish because of waxy deposits), some of these papillate, papillae 3–14, irregularly arranged, without elongate idioblasts, stomata in 3–7 rows along the midribs and marginal to submarginal along basiscopic ⅓ of outer margins, lower surfaces comprising elongate (jigsaw puzzle-like), sinuate-walled cells, without elongate idioblasts and stomata. Axillary leaves on main stem after first branches ovate-lanceolate, 2.0–3.0 × 0.9–1.5 mm; bases rounded to cordate or truncate, with two small, long-ciliate auricles up to, at least, the fifth branch and then becoming small lobes; margins narrowly hyaline as in median leaves, long-ciliate along proximal ⅘, otherwise short-ciliate to denticulate distally; apices gradually tapering, acute, tipped by 1–3 teeth; both surfaces as lateral leaves. Strobili terminal on main stem and each branch tip, quadrangular, 0.3–1.7 cm. Sporophylls monomorphic, without a laminar flap, each with a slightly developed and seemingly glabrous keel along midribs, ovate to ovate-lanceolate, 0.8–1.0 × 0.4–0.6 mm; bases rounded to truncate; margins narrowly hyaline, 1 or 2 cells wide with the cells elongate, slightly sinuate-walled and glabrous, parallel to margins, short-ciliate along proximal ½, otherwise denticulate to entire distally; apices acute to acuminate, the acumen 0.1 to 0.2 mm, tipped by 3 tooth-like projections; dorsal sporophylls with upper and lower surfaces as in vegetative leaves; ventral sporophylls with both surfaces, silvery green to hyaline, comprising elongate, papillate, sinuate-walled cells. Megasporangia in 2 ventral rows; megaspores white, rugulate-reticulate on proximal faces with a slightly developed equatorial flange and microstructure granulate, perforate and sparsely echinate, mostly open to somewhat closely reticulate on distal faces with the microstructure sparse and minutely echinate and perforate, 180–250 µm diam. Microsporangia in 2 dorsal rows; microspores orange, echinate-rugulate on proximal faces with punctate microstructure, capitate or baculate on distal faces with each caput or bacula and the rest of the surface with echinate microstructure, 20–30 µm diam.

Figure 1. 

Selaginella altheae Valdespino. A Habit, upper surface of stem B Close up of section of the upper surface of the stem C Habit, lower surface of stem D Close up of section of the lower surface of the stem. A–D digitized images of holotype, Maguire et al. 60249 (NY).

Figure 2. 

Selaginella altheae Valdespino. A Habit B Section of main stem above first branch showing median leaves, upper surface C Section of main stem above first branch showing lateral leaves and axillary leaf, lower surface D Close-up of strobilus. A–D line drawings of holotype, Maguire et al. 60249 (NY). Illustration made by Rubén Lozano.

Figure 3. 

Selaginella altheae Valdespino. A Section of upper surface of stem branch B Close-up of lateral leaf from stem branch, upper surface C Section of lower surface of stem branch D Close-up of lateral leaf (from branch), lower surface E Close-up of distal portion and apex of lateral leaf, lower surface (same leaf shown in B); note, elongate and papillate idioblasts (a) and stomata along midrib (b) F Close-up of proximal (basal) portion of lateral leaf, lower surface (same leaf shown in B); note, elongate and papillate idioblasts (a) and stomata along midrib (b). A–F taken from holotype, Maguire et al. 60249 (NY).

Figure 4. 

Selaginella altheae Valdespino. A Section of upper surface of stem branch showing median and lateral leaves B Close-up of median leaves from stem branch, upper surfaces C Close-up of median leaf from stem branch, lower surface D Close-up of median leaf from stem branch, upper surface E Close-up of distal portion and apex of median leaf, upper surface (same leaf shown in D); note, punctate to shortly elongate and papillate idioblasts (a) and stomata (b) along midrib F Close-up of proximal portion and base of median leaf, lower surface (same leaf shown in D); note, punctate to shortly elongate and papillate idioblasts (a), stomata (b) along midrib and submarginal and marginal portion near outer base and long cilia (c) on outer base. A–F taken from holotype, Maguire et al. 60249 (NY).

Figure 5. 

Selaginella altheae Valdespino. A Megaspore, proximal face B Close-up of megaspore, proximal face C Megaspore, distal face D Close-up of megaspore, distal face E Microspore, proximal face F Microspore, distal-equatorial-proximal faces G Close-up of microspore, distal-equatorial faces; note, capitate projections and echinulate microstructure. A–G taken from holotype, Maguire et al. 60249 (NY).

Selaginella altheae grows on lowland and montane rainforests at 140–450 m; it is known from the Amazon basin of Colombia, Venezuela and Brazil and found fertile from April through to November.

I am delighted to dedicate this graceful, fern-like species with shiny idioblasts on leaf surfaces to my mother, Althea Quintero (1939–), whose gentle, selfless demeanor, as well as strength and enlightening life-long support has guided and buttressed my life and professional career. She has adorned my path in life in the same manner as her lovely and resilient namesake flower does in nature.

This is a widely distributed species that grows at low elevations in Tropical rainforests of the Amazon basin; therefore, it is considered here of Least Concern (LC), according to IUCN (2012) categories and criteria.

COLOMBIA. Amazonas: Río Amazonas, along a road 8–14 km N of Leticia, 450 m, 3–5 Jul 1974, Breedlove 36331 (CAS).VENEZUELA. Amazonas: Rivers Casiquiare, Vasiva [Pasiba] and Pasimoni, 1853–54, Spruce 3380 (GH, OXF, W); Depto. Río Negro, along river that flows out of the Canyon Grande of Cerro de la Neblina, 2–4 km upriver from base, 10 Feb 1984, Funk & Liesner 6148 (NY, RB [digital image], US), trail leading N-NE, 28 Feb 1984, Funk 6419 (MO, NY, US), Río Mawarinuma, 00°50'N, 66°10'W, 140 m, 27 Nov 1984, Anderson 13372 (CAS, F, UC), Cerro de la Neblina Base Camp on Río Bario (Río Mawarinuma), SE of camp, 00°49'50"N, 66°09'40"W, 140 m, 26 Jan 1985, Beitel & Buck 85042 (NY), 27 Jan 1985, Beitel & Buck 85064 (MO, NY, UC), Beitel & Buck 85068 (NY), 17 Feb 1985, Beitel & Buck 85210 (NY-2 sheets), 4 Dec 1984, Bell 406 (UC), 2–3 Jul 1984, 00°50'N, 66°10'W, 25 Nov 1984, Croat 59312 (MO, NY), 2–3 Jul 1984, Davidse & Miller 26886 (UC), 4–5 Jul 1984, Davidse & Miller 26972 (MO, UC), ca. 160 m, 27 Nov 1984, Kral & Liesner 71851 (UC), ca. 180 m, 4 Dec 1984, Kral 71997 (UC), 0 to 2 km W of Cerro de La Neblina Base Camp, which is on Río Mawarinuma, 140 m, 00°50'N, 66°10'W, 7 Feb 1984, Liesner 15716 (MO), Río Mawarinuma, below Cerro Neblina Camp, 00°50'N, 66°11'W, 140 m, 16 Apr 1984, Gentry & Stein 46677 (MO), ca. 2 km S of Base Camp [Cerro Neblina base camp], along Marawanumi River, 00°50'N, 66°10'W, 140 m, 11 Apr 1984, Thomas & Plowman 3014 (NY), along Río Marawinuma, SE of Base Camp [Cerro Neblina base camp], 00°50'N, 66°09'W, 140 m, 30 Apr 1984, Thomas & Samuels 3291 (NY, PMA).

Selaginella altheae is characterized by its erect, fern-like habit, axillary, lateral and dorsal rhizophores, leaves on main stems becoming obviously dimorphic above or 1–4 cm below the first branches and, below this point, the lateral leaf bases oblique with an acroscopic auricle that is tufted with 3–15 stiff hairs and median leaves above first branches in main stems with oblique, not auricled bases, with the outer bases slightly prominent and tufted with (4)6–20stiff hairs.

Selaginella altheae, S. lechleri and other members of the S. flabellata group, have microspores distal faces with echinate microstructure. Likewise, S. altheae and S. oaxacana Spring have dorsal rhizophores, as do other members of the S. flabellata group. These two characters, therefore, might represent synapomorphies that define the S. flabellata group. Nevertheless, dorsal rhizophores, which are typical of articulate Selaginella species, are also found in other taxa such as S. psittacorhyncha (Valdespino 2017) and S. philipsonii, suggesting that this character is under-reported and, perhaps, of a wider presence in the genus than hitherto acknowledged. Similarly, different degrees of spore echinate microstructure could occur in other unrelated taxa. Therefore, the occurrence of these characters in morphologically unrelated species warrants further morphological, anatomical and molecular studies throughout the genus to ascertain their evolutionary and phylogenetic implications. Interestingly, a specimen of S. altheae (i.e. Thomas & Samuels 3291, NY) has flagelliform tertiary branch apices that develop strobilus at their tips.

Selaginella altheae is morphologically close to S. flabellata and S. lechleri. Their leaves on the main stems below the first branches are seemingly monomorphic and have similar median leaf above the first branches with the outer bases slightly prominent and tufted with either few or many short- to long cilia, as well as submarginal to marginal stomata along the proximal ⅓ on each outer half of the laminae. Nevertheless, S. altheae is set aside from S. flabellata by its median leaves on main stems ovate, broadly ovate to ovate-elliptic (vs. broadly ovate to ovate-oblong) with the inner and outer halves on the main stems equal in width or the inner halves slightly wider than the outer halves (vs. usually the outer halves distinctly wider) and lateral leaves acroscopic margins long-ciliate along proximal ½–¾ (vs. ¼–½), otherwise distally short-ciliate to dentate (vs. entire or denticulate). It differs further from S. flabellata by its megaspores proximal faces rugulate-reticulate (vs. rugulate) with granulate, perforate and sparsely echinate and perforate (vs. tuberculate, mostly psilate to minutely echinate and perforate) microstructures and distal faces mostly open or somewhat closely reticulate (vs. mostly closely reticulate) with minutely echinate and perforate (vs. prominently tuberculate, psilate and perforate) microstructures. Selaginella altheae differs from S. lechleri, with which it has been confused in the past, by the characters discussed under the diagnosis and by the megaspores proximal faces rugulate-reticulate (vs. reticulate) with granulate, perforate and sparsely echinate (vs. with strongly echinate and perforate) microstructures, while the distal faces are mostly open or somewhat closely reticulate (vs. mostly closely reticulate) with sparse and minutely echinate and perforate (vs. abundantly echinate and perforate) microstructures.

Selaginella altheae may also be confused with the Central and South American S. anceps (C. Presl) C. Presl because of their auriculate leaf bases (i.e. auriculae present on lateral leaves of S. altheae and on seemingly monomorphic leaves of S. anceps) on main stems below the first branches. Selaginella altheae is set aside from the latter by its obviously dimorphic leaves immediately above or 1–4 cm below the first (vs. above fourth) branches of the main stems and median leaf bases on main stems above the first branches without auricles (vs. with inner and outer ciliate auricles or only with an outer ciliate auricle). It is further distinguished from S. anceps by its megaspores proximal faces with a slightly developed (vs. lacking) equatorial flange, rugulate-reticulate (vs. reticulate) ornamentation with granulate, perforate and sparsely echinate (vs. with perforate and strongly echinate) microstructures, while the distal faces ornamentation is mostly open or somewhat (vs. mostly) closely reticulate with sparse and minutely echinate and perforate (vs. shortly echinate, granulose and perforate) microstructures.

Selaginella squamulosa is set aside from similar S. psittacorhyncha and S. vernicosa by its median leaves upper surfaces with 10 (vs. with 25 in S. psittacorhyncha and 35 in S. vernicosa) stomata along the midribs. It differs further from S. psittacorhyncha by its lateral leaf acute (vs. obtuse) apices and hyaline (vs. greenish) margins and median leaf bases oblique (vs. truncate) and from S. vernicosa by the median leaf upper surfaces made up of quadrangular and rectangular (vs. undistinguishable, somewhat appearing quadrangular or elongate) papillate cells and lateral leaf margins on acroscopic side serrate to denticulate (vs. short-ciliate, at least along proximal ⅔) and on basiscopic side sparingly denticulate or entire to slightly denticulate distally (vs. short-ciliate at least along proximal ⅓).

Venezuela – Brazil. Venezuelan, Brazilian frontier, Planicie de Zuluaga, Río Titirico, 2300 m, 10–15 Oct 1970, J.A. Steyermark 103872 (holotype: NY; isotypes: MO, PMA).

Plants terrestrial, epiphytic or epipetric. Stems creeping, stramineous, 10–20 cm long, 0.4–0.8 mm diam., non-articulate, often flagelliform, not stoloniferous, 1–2(3)-branched. Rhizophores axillary along proximal ½ of stem, filiform, 0.1 to 0.2 mm diam. Leaves dimorphic, coriaceous. Lateral leaves distant to imbricate towards stem and branch apices, ascending, broadly deltate-ovate, broadly ovate or ovate-elliptic, (1.0)1.3–1.7 × 0.8–1.7 mm; bases rounded, acroscopic bases overlapping the stem, basiscopic bases free from the stem; margins hyaline, made up of a band 2–4 cells wide, the cells elongate and papillate, parallel to margin, papillae in a single row over cell lumen, acroscopic margins serrate to denticulate, basiscopic margins sparingly denticulate or entire to slightly denticulate distally; apices broadly acute to acute, tipped by 2–4 teeth; both surfaces without idioblasts, upper surfaces mostly glabrous but with short hairs on submarginal and marginal sections of basiscopic half of the lamina, made up of quadrangular to rectangular, irregularly-walled, papillate or not cells, papillae 5–10 over cell lumen arranged in 2 or 3 rows, midribs not prominent, without stomata, lower surfaces glabrous, made up of elongate or asymmetric, straight or slightly sinuate-walled, papillate cells, papillae 8–20 over cell lumen arranged in 2 or 3 rows, midribs raised and prominent at mid-distal section of lamina, stomata concentrated on raised portion of midribs. Median leaves distant to imbricate towards stem and branch tips, ascending and, on branches, they may arise at ca. 45° angle, ovate to ovate-deltate, 1.0–1.5 × 0.6–1.0 mm; bases oblique, inner bases truncate to rounded, outer bases ventricose and often tufted with 2–8 very short hair or teeth; inner margins narrowly hyaline, made up of a band 1 or 2 cells wide, the cells elongate and papillate, parallel to margin, papillae in a single row over cell lumen, serrate to denticulate, outer margins greenish, denticulate at proximal ¼, otherwise sparingly denticulate or entire along middle and denticulate at distal ¼; apices acute, tipped by 2–4 teeth; both surfaces without idioblasts, upper surfaces mostly glabrous but occasionally with short hairs near marginal, submarginal and submedial section of outer half and on submedial section of inner half near distal ¼, made up of quadrangular or with some rectangular, irregularly-walled, papillate cells, papillae 5–10 over cell lumen arranged in 2 or 3 rows, midribs raised and prominent or bevelled specially at mid-distal section of each laminae, stomata concentrated on raised portion of midribs and some marginal on lower ½ of outer margins, lower surfaces glabrous, made up of elongate or asymmetric, straight or slightly sinuate-walled cells, midribs not prominent. Axillary leaves similar to lateral leaves. Strobili terminal and single on branch tips, quadrangular, 0.5–5 mm long. Sporophylls monomorphic, without a laminar flap, ovate to ovate-elliptic, 0.9–1.3 × 0.5–1.3 mm, with a keel along midrib on upper surfaces; base rounded; margins greenish, minutely denticulate to entire; apices acute; both surfaces without conspicuous idioblasts, both surfaces glabrous; dorsal sporophylls with upper surfaces green, except for the half that overlaps the ventral sporophylls where it is hyaline, lower surfaces greenish-hyaline; ventral sporophylls with both surfaces greenish-hyaline. Megasporangia one or two at the base of ventral rows; megaspore yellow, rugulate-reticulate on proximal faces with fissurate microstructure, reticulate-granular on distal faces with granulose and perforate microstructure, 410–445 μm diam. Microsporangia in dorsal rows and distal ¾ of ventral rows; microspores deep orange, proximal and distal faces not studied and not measured.

Figure 6. 

Selaginella squamulosa Valdespino. Holotype, Steyermark 103872 (NY).

Figure 7. 

Selaginella squamulosa Valdespino. A Habit B Upper surface of stem showing median leaves C Lower surface of stem showing lateral leaves and axillary leaf D Close-up of strobili (apices of branches), upper surface. A–D line drawings of holotype, Steyermark 103872 (NY). Illustration made by Rubén Lozano.

Figure 8. 

Selaginella squamulosa Valdespino. A–B Habit C Upper surface of stem showing median leaves D Lower surface of stem showing lateral leaves and axillary leaf E Close-up of distal portion of stem, upper surface. A–E line drawings of paratype, Boom et al. 6011 (NY). Illustration made by Rubén Lozano.

Figure 9. 

Selaginella squamulosa Valdespino. A Section of upper surface of stem B Close-up of median leaf, upper surface; note, elongate, idioblast-like marginal cells on inner margin and submarginal and marginal stomata (a) along proximal ½ of outer margin and hairs (b) on lamina surface C Close-up of mid-distal portion of median leaf, upper surface (same leaf shown in B); note, elongate, idioblast-like marginal cells on inner margin, papillae on each cell lumen and hairs (b) on lamina surface D Section of lower surface of stem E Close-up of lateral leaf, lower surface F Close-up of section of acroscopic half of lateral leaf; note, papillae on cells lumen and marginal, idioblast-like and papillate cells. A–F taken from paratype, Boom et al. 6011 (NY).

Figure 10. 

Selaginella squamulosa Valdespino. A Megaspore, proximal face B Close-up of megaspore, proximal face C Megaspore, distal face D Close-up of megaspore, distal face. A–D taken from paratype, Boom et al. 6011 (NY).

Selaginella squamulosa grows as a terrestrial, epiphytic or epipetric plant on open slopes to cliff base, in rills and wet depressions of swampy savannas or on scrub dominated forests at 1950–2743 m; it is known from the Guiana Highlands in Cerro de la Neblina, Amazonas State of Venezuela and in Río Cuaburí, Amazonas State of Brazil and found fertile from October through to February.

The specific epithet derives from the Latin “squamulosus”, meaning minutely scaly and refers to the tiny, stiff leaves that resemble small scales.

Conservation status. Selaginella squamulosa is known from two distinct localities at high elevation in isolated tepuis in the Amazon basin of Venezuela and Brazil where human presence is scarce and immediate threats have not been reported. Therefore, it is tentatively considered of Least Concern (LC) according to IUCN (2012) categories and criteria.

VENEZUELA. Amazonas: Depto. Río Negro, Camp VII, Cerro de la Neblina, 5.1 km NE of Pico Phelps (= Neblina), 21.5 km E [of] Neblina Base Camp, ca. 2150 m, 5 Feb 1985, Beitel 85161 (NY–2 sheets, PMA), Neblina Massif, Camp 12, 1950 m, 26–27 Feb 1985, Boom et al. 6011 (NY, PMA, UC). BRAZIL. Amazonas: Río Negro, Río Cuaburí, 8500–9000 ft [2591–2743 m], 2 Dec 1965, Maguire et al. 60466 (NY).

Selaginella squamulosa is distinguished by its centipede-like habit with slender and creeping stems, rhizophores restricted to the lower halves of the stems or often present on flagelliform stems and branches (i.e. Steyermark 103872, NY), coriaceous, scaly-like leaves with raised and prominent midribs on the lower and upper surfaces of the lateral and median leaves, respectively and acute leaf apices. In addition, the midribs on the upper surfaces of the median leaf are straight to strongly arcuate. In the latter case, the inner half of each leaf lamina becomes slightly wider than the outer one. It is further strikingly distinct by having the lateral leaf acroscopic halves on lower surfaces twice as wide as the basiscopic ones. Furthermore, as noted in other Selaginella species, on a duplicate specimen of S. squamulosa (i.e. Steyermark 103872, MO), a rhizophore becomes a leaf-bearing shoot. Remarkably, Boom et al. 6011 (NY, PMA, UC) has a more slender habit with the upper leaf surfaces hispidulous. Apparently, these hairs become caducous since they were not observed in a similar collection (i.e. Beitel 85161, NY, PMA) or in the more coriaceous form represented by the type.

The holotype and an isotype of Selaginella squamulosa at NY and MO, respectively, were originally identified as S. cruegeri Jenman vel aff., which is a synonym of S. minima Spring. The latter species differs most noticeably from S. squamulosa by its ascending (vs. creeping) habit, chartaceous (vs. coriaceous) leaves, median leaf with broadly hyaline margins (vs. inner margins narrowly hyaline and outer margins greenish) and white (vs. yellow) megaspores. A paratype of S. squamulosa (i.e. Boom et al., 6011, NY, PMA, UC) was determined as S. rhodostachya Baker vel aff. Nevertheless, S. squamulosa is easily set aside from S. rhodostachya by its coriaceous (vs. chartaceous) leaves, oblique (vs. rounded to truncate) median leaf bases with the outer bases ventricose (vs. rounded) and ovate (vs. ovate-elliptic) lateral leaf with its acroscopic margins, as well as both margins of the median leaf serrate to denticulate (vs. often long-ciliate). Another of the paratypes of S. squamulosa (i.e. Maguire et al. 60466, NY) was determined as S. brachyclada Baker. However, it differs from the latter by having the inner and outer margins of the median leaf narrowly hyaline and greenish, respectively (vs. both margins widely hyaline) and serrate to denticulate (vs. faintly denticulate), oblique (vs. truncate) bases, ovate or ovate-elliptic (vs. ovate-cordate) lateral leaf, which is distinctly wider at the middle (vs. at the base), ascending (vs. spreading) and deep yellow (vs. white to light-yellow) megaspores that lack (vs. have) a distinct equatorial flange.

Selaginella squamulosa is part of the “Selaginella vernicosa group” and, amongst these, it is morphologically close to S. psittacorhyncha and S. vernicosa. It differs from these two species by the characters discussed under the diagnosis and by its median leaf with the midribs raised at the distal ½ of the laminae but not properly extending into the apices (vs. extending into the apices) with the upper surfaces occasionally puberulent (vs. glabrous). Selaginella squamulosa differs from S. arrecta by its median and lateral leaf apices broadly acute to acute (vs. long-acuminate to aristate), median leaf inner margins narrowly (vs. widely) hyaline, which consists of 1 or 2 (vs. 3–5) elongate cells wide and ca. 10 stomata on raised midribs (vs. up to 85 stomata, widespread on central portion of lamina). In addition, in S. squamulosa, 2–4 teeth tip the acute apices, whereas the acuminate or aristate apices of S. arrecta are made of 6–10, narrowly elongate and papillate cells. Selaginella squamulosa differs from S. roraimensis, S. marahuacae and S. scalariformis by its narrowly ovate-deltate or ovate (vs. ovate-oblong or oblong in S. roraimensis and ovate-elliptic in S. marahuacae and S. scalariformis) lateral leaves with midribs on lower surfaces distinctly raised (vs. plane in profile). Selaginella squamulosa is further separated from S. roraimensis by the lateral leaf basiscopic margins extended (vs. slightly reflexed), from S. marahuacae by its acute (vs. shortly acuminate) median leaf apices and from S. scalariformis by its distant to imbricate and ascending (vs. distant and patent) lateral leaves.