Pogonomyrmex magnacanthus

An open desert species.

Identification
Johnson et al. (2013) - Worker. Pogonomyrmex magnacanthus is a small species (HW = 1.15–1.80 mm) that is identified by: (1) its unusually large eyes (MOD = 0.33–0.49 mm; OI = 27.22–33.61; malar ratio (MOD/OMD) usually < 1.0) (see Figures 1–3). OI is the most reliable character to identify P. magnacanthus given that MOD is positively associated with HW such that it sometimes overlaps with that of other species (see Figure 3). Cole (1968) also listed an unusually large eye and a high ocular index as diagnostic characters for P. magnacanthus. Interestingly, the holotype that Cole selected was somewhat of an outlier for both characters because the eye was relatively small and the OI was lower than that of other paratype workers.

Queen. As in worker diagnosis, but with caste-specific morphology of the mesosoma related to wing-bearing, presence of small ocelli on the head. Mandible with seven teeth; cephalic rugae forming circumocular whorls. Eyes large (OI = 29.35–35.29), MR < 1.00, MOD ranging from 0.30–0.35x HL. All mesosomal surfaces with prominent rugae.

Male. Mandible with four teeth on suboblique cutting margin. Mandibular dorsum with faint rugae/striae, mostly sub-shining. Anterior margin of clypeus moderately concave, lateral lobes distinct, broadly rounded; antennal scapes with faint rugae/striae, sub-shining, or lacking sculpture, smooth and shining. Eye unusually large (MOD > 0.53, OI > 42.5, MR < 0.34)  Pogonomyrmex magnacanthus is most likely to be confused with Pogonomyrmex hoelldobleri, as evidenced by the numerous series of the latter species (including several paratype series) that A.C. Cole misidentified as P. magnacanthus. The significantly larger eye (MOD and OI) separates P. magnacanthus from P. hoelldobleri, but OI is the more diagnostic character because it is consistently higher for P. magnacanthus (OI = 27.22–33.61) than for P. hoelldobleri (OI usually < 27.50)(Figure 3). Additionally, the malar ratio is usually < 1.0 for P. magnacanthus, while this ratio is usually > 1.05 for P. hoelldobleri.

Pogonomyrmex magnacanthus occurs sympatrically with Pogonomyrmex californicus, but it has a low likelihood of co-occurring with Pogonomyrmex maricopa and Pogonomyrmex mohavensis. Two other P. californicus group species (Pogonomyrmex anzensis and Pogonomyrmex snellingi) also occur in the Sonoran Desert, but it is doubtful that P. magnacanthus occurs sympatrically with either species; P. anzensis inhabits unproductive, rocky hillsides that are unlike any sites known to be occupied by P. magnacanthus, while P. snellingi is well removed from the probable geographic distribution of P. magnacanthus. Pogonomyrmex magnacanthus can be distinguished from all of these species using the characters described above.


 * Key to the Pogonomyrmex californicus species group
 * Key to North American Pogonomyrmex

Distribution
Southern Nevada, southeastern California, southwestern Arizona, northern Baja California, and northwestern Sonora.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.



Biology
Cole (1968) - All nests observed by the writer were in unshaded, rather loose, sandy soil of open desert, and each nest was surmounted by a circular, shallow, sand crater of 4 to 6 inches in diameter. Worker populations varied from about 100 to 225 per nest. The workers foraged diurnally at a rather slow and steady gait. They were docile and exhibited none of the usual erratic and rapid movements of Pogonomyrmex maricopa and Pogonomyrmex californicus when disturbed.

Nevada, Wheeler and Wheeler (1986) - Three nests had as superstructures downhill tailings below the entrance. Three had craters of fine sand 6-10 cm in diameter. The workers moved slowly. We have 13 records from 10 localities in Nevada, all from the Hot Desert in the southern portion of the state: 1,200-3,400 ft.

Johnson et al. (2013) - The biology of Pogonomyrmex magnacanthus and Pogonomyrmex hoelldobleri appear to be very similar, and are thus discussed together. In both species, the nests are variable and can range from a nest entrance that lacks a tumulus to a tumulus that ranges from 3–15 cm in diameter; the nest entrance commonly lacks a tumulus in P. hoelldobleri. Nests are typically placed in open exposed sites, but can be difficult to locate because of their small size or absence of an external tumulus. In such cases, nests are most easily located by baiting foragers, then following them back to the nest. Workers of both species forage solitarily during the day, harvesting seeds and related items. Colonies of P. magnacanthus contain relatively few workers; Cole (1968) estimated that colony size ranged from 100–225 workers, which accords with observations of the senior author. Colonies of P. hoelldobleri are also small and appear to contain no more than 300–400 workers (R.A. Johnson, pers. obs.).

Reproductive sexuals of P. magnacanthus, P. hoelldobleri, and Pogonomyrmex mohavensis have been collected infrequently (a total of 3 alate queens and 4 males for P. magnacanthus, 8 alate queens and 2 males plus one male pupae for P. hoelldobleri, and 2 alate queens for P. mohavensis); collection dates range from 26 March to 13 June for P. magnacanthus and from 23 April to 5 May for P. hoelldobleri. Mating flights have not been observed for either species, but they are predicted to be similar to those of P. californicus, in which flights are triggered by cues such as photoperiod, temperature, or humidity (but not rain-triggered as in most species of Pogonomyrmex), and they likely take place over several weeks during late spring to early summer (Johnson, 2000). Alate queens of P. mohavensis were collected on 15 September; several nests of P. californicus in the vicinity of this collection also contained alate queens on this date, and these queens were observed outside the nest preparing for their mating flight. Thus, in the central valley area of California, mating flights for P. californicus and P. mohavensis appear to be up to several months later than those in other parts of their geographic ranges.

Both P. magnacanthus and P. hoelldobleri are restricted to hot desert habitats (Wheeler & Wheeler, 1973) in the Mohave and Sonoran Deserts of southeastern California, western Arizona, northwestern Sonora, Mexico, and the San Felipe Desert of Baja California, Mexico; the range of P. hoelldobleri also extends further north into southern Nevada. Current records indicate that the geographic range of P. magnacanthus is more restricted than previously believed (Figure 11), especially given that this study transferred all Nevada records (see Wheeler & Wheeler, 1986) to P. hoelldobleri (see below). Pogonomyrmex magnacanthus inhabits sites at elevations that range from approximately 5–855 m, while P. hoelldobleri is known from elevations that range from 0–1350 m. The two species have broadly overlapping geographic distributions and occur in sympatry at several locales (Figure 11), but preferred microhabitat differs for the two species. Pogonomyrmex magnacanthus is largely restricted to sand dunes, interdune habitats, and other areas with a loose sand substrate (Cole, 1968; Johnson, 2000), whereas P. hoelldobleri sometimes occurs in loose sandy soils, but it is most common in relatively compact sandy or gravelly alluvial soils.

Nomenclature

 *  magnacanthus. Pogonomyrmex (Pogonomyrmex) magnacanthus Cole, 1968: 133, pl. 2, fig. 5; pl. 3, fig. 12; pl. 4, fig. 10; pl. 6, fig. 9; pl. 7, fig. 16; pl. 8, fig. 10; pl. 11, fig. 10 (w.q.m.) U.S.A. Taber, Cokendolpher & Francke, 1988: 51 (k.). See also: Johnson, Overson and Moreau, 2013: 205 (q.m.).

Description
This species was redefined in light of Johnson et al. (2013) evaluating Cole's concept of Pogonomyrmex magnacanthus as a single variable species. Descriptions by both authors are included here.

Worker
Holotype. (Cole Coll. No Cal-378). HL 1.34 mm, HW 1.36 mm, CI 101.5, 5L 1.00 mm, 51 73.5, EL 0.39 mm, EW 0.21 mm, OI 29.1, WL 1.48 mm, PNL 0.34 mm, PNW 0.36 mm, PPL 0.43 mm, PPW 0.54 mm.

Head length and width subequal. Eye very large, its greatest diameter equal to distance from its lower margin to mandibular insertion. Mandible as illustrated in Pl. III, Fig. 12; apical margin faintly and rather evenly convex; basal margin straight; masticatory border with 7 teeth irregular in size, shape, and spacing; apical tooth narrow, sharp, not much longer than subapical tooth which is subequal in size to first and third basals; second basal shorter than any aforementioned teeth; penultimate basal minute; ultimate basal distinctly larger than penultimate. Base of antennal scape as shown in Pl. IV, Fig. 10; shaft moderately, broadly, and evenly curved along basal half, not strongly compressed or flattened along the bend; basal enlargement rather weakly developed; superior lobe acute apically; superior declivity and inferior declivity not steep, meeting the shaft evenly at weak and broadly rounded angles; basal flange weak, very narrow, and thin, extending outward to just beyond apex of superior lobe; lip short, the margin very thin and curved slightly distad; longitudinal peripheral carina and point very weak; outer lateral margin of basal enlargement not impressed. Base of antennal scape similar to that of californicus but the lip shorter, thinner, and not curved so greatly distad.

Frontal area shining; bearing a strong, median, longitudinal carina. Cephalic rugae delicate, rather widely spaced, subparallel, longitudinal in front but diverging rather strongly and evenly into posterior corners of head and tending to form whorls above the eyes; finer and more closely spaced toward the eyes; those on occiput irregularly and arcuately transverse; interrugal spaces densely and finely punctate, subopaque. Median lobe of clypeus with sparse, delicate, widely and irregularly spaced, longitudinal rugae; interrugal spaces smooth and shining. Mandibles prominently, longitudinally rugose; interrugal spaces smooth and shining. Antennal scares smooth and shining.

Contours of thorax. petiole, and postpetiole as shown in Pl. VI, Fig. 9. Thorax strongly convex, mesoepinotal impression distinct; epinotum armed with a pair of weak angles, the broadly convex base notably longer than the steep, straight declivity. Thoracic rugae strong and rather widely spaced on mesonotum and epinotum, much finer on most of pronotum where they are largely obscured by fine, dense punctures; irregularly and widely spaced on pronotal collar; transverse on dorsum of pronotum, posterior portion of mesonotum, and base of epinotum; longitudinal on anterior portion o[ mesonotal dorsum; absent from declivous face of epinotum; interrugal spaces smooth and shining on pronotal collar, densely and finely punctate and somewhat shining on mesonotum and epinotum, very densely punctate and subopaque on sides of pronotum. Venter of petiolar peduncle and of postpetiole without a prominent process. Contours of petiolar and postpetiolar nodes, viewed from above, as illustrated in Pl. VII, Fig. 16; length and width of petiolar node subequal, the apex rather blunt, the surface finely and densely punctate and subopaque, the posterior portion with sparse, wavy, transverse striate; sculpture of postpetiolar node similar to that of a petiolar node.

Gaster densely and finely shagreened, moderately shining. Body a concolorous, medium, ferrugineous red.

HL 1.25-1.44 mm, HW 1.18-1.44 mm, CI 94.4-97.9, SL 0.95- 1.10 mm, SI 77.4-80.5, EL 0.38-0.46 mm, EW 0.23-0.68 mm, OI 29.8-31.9. WL 1.33-1.52 mm, PNL 0.30-0.42 mm, PNW 0.27-0.38 mm, PPL 0.34-0.46 mm, PPW 0.46-0.53 mm.

In some workers the epinotum is broadly and evenly rounded and devoid of armature, but in most specimens the epinotum is distinctly angulate and bears a pair of distinct tubercles or angles. The interrugal cephalic and thoracic punctures are more dense and prominent in some workers than in others, and hence the interrugal spaces vary in subopacity. I have assigned to this species a small series of workers collected by Dr. Creighton in the Inyo Mountains, California. These specimens differ from the types by having a prominent postpetiolar ventral process, but they agree very well otherwise. In a series of workers taken at a station fifteen miles west of Sentinel, Arizona, the cephalic and thoracic sculpture is everywhere very delicate, and the posterior corners of the head are very smooth and strongly shining.

Johnson et al. (2013) - (mm)—holotype (n = 25 paratypes, all from the type locality at Palm Springs, California [CAL-356, CAL-374, CAL-378, CAL-380, CAL-381, CAL-382], plus 37 non-type workers). HL 1.37 (1.17–1.65); HW 1.38 (1.15–1.80); MOD 0.39 (0.33–0.49); OMD 0.39 (0.31–0.46); SL 1.02 (0.86–1.15); PNW 0.88 (0.73–1.08); HFL 1.38 (1.08–1.74); ML 1.67 (1.28–1.91); PW 0.36 (0.28–0.45); PPW 0.54 (0.40–0.60). Indices: SI 74.45 (63.89–81.67); CI 99.28 (92.54–112.21); OI 28.47 (27.22–33.61); HFI 100.73 (88.00–112.50).

Head subquadrate to quadrate (CI = 92.54–112.21), broadest just posterior to eye; posterior margin flat in full-face view. Longitudinal cephalic rugae prominent, in full-face view median rugae diverging toward posterior corners near posterior margin of head. In side view, rugae converging immediately posterior to eyes to form indistinct to well defined circumocular whorls that often weaken toward vertex, or rugae converging toward vertex, or circumocular whorls and rugae mostly absent posterior to eye and weakly to densely granulate-punctate, dull to sub-shining, especially toward vertex. Vertex rugose, densely granulate, or occasionally smooth to weakly striated, dull to shining. Cephalic interrugal spaces weakly to moderately granulate-punctate on anterior portion of head, often becoming more strongly granulate-punctate on posterior half of head, sub-shining to shining. Anterior margin of clypeus flat to weakly concave. Mandible with seven teeth; mandibular dorsum coarsely striate. In profile, eyes large, MOD ranging from 0.27–0.32x HL, OI = 27.22–33.61, MR usually < 1.0; eye situated near middle of head. Antennal scapes moderately long (SI = 63.89–81.67), failing to reach vertex by length of basal funicular segment. Basal flange of antennal scape flattened and well developed, margin weakly carinate. Psammophore well developed.

Mesosomal profile convex. All mesosomal surfaces with prominent parallel/subparallel rugae. Dorsum of promesonotum with transverse rugae that curve obliquely to posterior, often becoming indistinct on pronotal sides. Mesopleura with subparallel rugae angling posterodorsally. Propodeum lacking spines or teeth, occasionally with minute denticles; in side view, juncture of propodeum and propodeal declivity evenly convex to weakly angulate; rugae on dorsum of propodeum transverse, declivitous face often with one or two discontinuous to continuous transverse rugae, interrugal spaces smooth and shining. Propodeal spiracles narrowly ovate. Interrugal spaces on mesosoma moderately granulate-punctate, sub-shining to smooth and shining; interrugal spaces on pronotal sides moderately to densely granulate, dull. Legs moderately to strongly shining.

Petiolar peduncle long, ventral margin straight. In side view, posterior face of petiole weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface. Apex of node weakly to moderately angulate. In dorsal view, petiolar node longer than broad, sides subparallel or diverging slightly toward the smoothly rounded to weakly angulate anterior margin. Sides and dorsum of petiolar node moderately to strongly granulate-punctate, dull to sub-shining, occasionally with several longitudinal to oblique rugae that are restricted to posterior one-third of petiole. Dorsum of postpetiole convex in profile; in dorsal view, widest at or near posterior margin and tapering to anterior margin, maximal width about equal to length, moderately granulate-punctate, dull to sub-shining. Gaster smooth and strongly shining.

Erect to suberect white pilosity moderately abundant on head, short to medium in length, often with one to few longer hairs, none exceeding MOD. Moderately abundant semidecumbent to decumbent pilosity on scape with occasional suberect hairs, abundant semidecumbent to decumbent hairs on funicular segments. Legs with moderately abundant suberect to semidecumbent white setae. Mesosoma, petiole, and postpetiole with a lower density of mostly long, flexuous hairs mostly concentrated on dorsal surfaces, longest distinctly shorter than MOD; gastric tergites with moderately abundant, medium length suberect hairs. Entire body concolorous light to dark ferruginous orange (Figure 1).

Queen
Paratype. (Cole Coll. No Cal-424). HL 1.79 mm, HW 1.87 mm, CI 104.8, SL 1.22 mm, SI 65.2, EL 0.56 mm, EW 0.39 mm, OI 31.3, WL 2.67 mm, PNL 0.56 mm, PNW 0.60 mm, PPL 0.54 mm, PPW 0.88 mm.

Head, in lateral view, as shown in Pl. II, Fig. 5. Eye very large, its greatest diameter slightly more than distance from lower eye margin to mandibular articulation. Frontal area shining; with a strong, median, longitudinal carina. Caphalice rugae dense, rather fine, longitudinal on anterior part of head, strongly divergent from frons into occipital corners, forming whorls above the eyes, transversely arcuate on vertex and occiput; interrugal spaces smooth and shining; finely and faintly shagreened. Mandibles longitudinally rugose, the rugae broadly spaced, the interrugal spaces shining and finely shagreened.

Thoracic rugae longitudinal, fine, and dense on scutum and scutellum; coarser and transversely subparallel on pronotal collar; sparser and more widely spaced elsewhere on pronotum and on sides of mesonotum; rather coarse, widely spaced, and transverse on sides of epinotum; weaker, wavy, and more closely spaced on base of epinotum, absent from declivous face; interrugal spaces smooth, shining, faintly and finely shagreened. Epinotum withour armature, the base meeting the declivity at a well-rounded angle, the margins faintly carinate. Metanotum strongly acute medially. Metsternal angle with a prominent longitudinal carina. Venter of petiolar peduncle without a process. Petiolar node, viewed from above, with the length and width subequal, the apex broadly rounded and bearing small, distinct nipple; dorsum of node with a few, wavy, transverse rugules which are confined mostly to the midportion. Dorsum of postpetiolar node with sparse, wavy, transverse rugules confined to posterior portion, the interrugal spaces and remainder of node densely and finely shagreened and subopaque.

Gaster shining, very finely and densely shagreened. Body a concolorous brownish yellow; mandibles a little darker.

HL 1.71-1.82 mm, HW 1.79-1.90 mm, CI 104.4-104.7, SL 1.22-1.25 mm, SI 65.8-68.2, EL 0.53-0.57 mm, EW 0.34-0.38 mm, OI 31.0-31.3, WL 2.36-2.43 mm, PNL 0.38-0.42 mm, PNW 0.57-0.61 mm, PPL 0.49-0.57 mm, PPW 0.87-0.91 mm.

Johnson et al. (2013) - (mm)—(n = 3). HL 1.79–1.88; HW 1.84–1.95; MOD 0.54–0.66; OMD 0.40–0.58; SL 1.22–1.26; PNW 1.40–1.45; HFL 1.73–1.90; ML 2.61–2.75; PW 0.56–0.62; PPW 0.82–0.93. Indices: SI 64.62–66.30; CI 99.47–107.73; OI 29.35–35.29; HFI 94.02–100.00.

As in worker diagnosis, but with caste-specific structures related to wing-bearing, presence of small ocelli on head, and as illustrated in Figure 4. Small, only slightly larger than conspecific workers. In full-face view, head quadrate to slightly broader than long, posterior margin flat, median rugae diverging toward posterior corners near posterior margin of head. Dorsum and sides of head conspicuously rugose, in side view rugae forming circumocular whorls posterior to eyes, interrugal spaces mostly smooth and shining. Mandible with seven teeth, dorsal surface coarsely rugose, strongly shining. Eyes large (OI = 29.35–35.29), MR < 1.00, MOD ranging from 0.30–0.35x HL. Base of scape not flattened; superior and inferior lobes poorly developed, no wider than width of base of scape.

All mesosomal surfaces with prominent subparallel/parallel rugae, those on mesoscutum and mesoscutellum fine, parallel, and longitudinal; interrugal spaces smooth and shining. In side view, propodeum unarmed, juncture of propodeum and propodeal declivity slightly angulate, sides and dorsal surface transversely or obliquely rugose, declivitous surface smooth and strongly shining. Petiolar peduncle long, ventral margin straight. In side view, petiolar node asymmetrical with anterior surface shorter than posterior surface. Apex of node rounded. In dorsal view, petiole length and width similar to slightly longer than wide; posterior face finely rugose, interrugal spaces weakly coriarious, sub-shining. Postpetiole broader than long; posterior portion finely rugose, interrugal spaces weakly coriarious, sub-shining; anterior portion granulate-punctate. Gastric tergites weakly coriarious and sub-shining to smooth and shining. Most body surfaces with moderately abundant coarse suberect to erect setae. Entire body concolorous light to dark ferruginous orange.

Male
Paratype. (Cole Coll. No. Cal-424). HL 1.25 mm, HW 1.37 mm, CI 109.6, SL 0.61 mm, SI 44.5, EL 0.65 mm, EW 0.38 mm, OI 52.0, WL 2.39 mm, PNL 0.46 mm, PNW 0.65 mm, PPL 0.53 mm, PPW 0.87 mm.

Eye very large, its greatest diameter about twice the distance from lower eye margin to mandibular articulation or about one-half the head length. Mandible as illustrated in Pl. VIII, Fig. 10; with 4, uneven, broad, sharp teeth arranged on a suboblique masticatory margin; apical tooth large and acute, subapical tooth narrower and notably shorter, the 2 basal teeth subequal in size, basalmost tooth distinctly offset from mandibular margin. Cephalic rugae longitudinal, rather weak, closely spaced, absent from clypeus and frontal area, irregular and broken behind the eyes; interrugal spaces faintly and finely punctured and rather shining. Scapes smooth and shiing, very finely shagreened.

Thorax and appendages mostly smooth and strongly shining, sides of thorax with a few weak striae; Mayrian furrows very weak; epinotum without armature. Petiole, postpetiole, and gaster very smooth and highly polished, not shagreened. Paramere of terminalia as shown in Pl. XI, Fig. 10.

Hairs pale golden yellow, long, flexuous, slender, pointed; abundant on head, scapes, legs, petiole, and postpetiole, somewhat sparser on thorax and gaster. Body a rather uniform, deep, rich brown except the appendages and petiolar peduncle which are lighter and the head which is mostly somewhat darker.

HL 1.14-1.14 mm, HW 1.25-1.25 mm, CI 109.7-109.7, SL 0.53-0.53 mm, SI 42.4-42.4, EL 0.61-0.61 mm, EW 0.38-0.38 mm, OI 53.5-53.5, WL 2.28-2.28 mm, PNL 0.38-0.42 mm, PNW 0.61-0.65 mm, PPL 0.46-0.49 mm, PPW 0.80-0.81 mm.

Johnson et al. (2013) - (mm)—(n = 4). HL 1.09–1.29; HW 1.20–1.36; MOD 0.53–0.59; OMD 0.15–0.19; SL 0.43–0.57; HFL 1.53–1.66; ML 2.29–2.54; PW 0.52–0.61; PPW 0.70–0.82. Indices: SI 32.09–41.91; CI 104.69–111.82; OI 42.54–44.17; HFI 120.59–130.08.

Description. Mandible with four teeth on suboblique cutting margin; basal tooth sometimes weakly bifid; basal tooth not offset; mandibular dorsum as described above. Clypeus lacking sculpture, mostly smooth and shining except for scattered punctures, anterior margin moderately concave, lateral lobes distinct, broadly rounded. Antennal scapes reaching to or near posterior margin of eye, mostly smooth and shining to faintly striate. Parallel/subparallel cephalic rugae fine and close, slightly wavy, interrugae weakly punctate, sub-shining.

In profile, anterior face of mesonotum forming a mostly straight line with pronotum, slightly less than one-half as long as dorsal surface. In side view, juncture between propodeum and propodeal declivity subangulate, without spines or denticles. Sides of pronotal collar smooth and shining; katepisternum mostly smooth and shining with scattered foveae, posterior margin often faintly striate, shining. Mesonotum shiny with piligerous punctures, notauli very weakly impressed. Propodeum smooth and shining. Ventral margin of petiolar peduncle straight. In side view, petiolar node broadly rounded, anterior surface longer than posterior surface, forming a mostly straight continuous to slightly curved profile with dorsal margin of petiolar peduncle. Dorsal surface of petiole smooth and shining with scattered punctures to microrugoreticulate, sub-shining. Postpetiole broader than long, dorsal surface mostly smooth, sub-shining to shining. Head, mesosoma, petiole, and postpetiole with moderately abundant flexuous white hairs, often similar in length to MOD. Gastric tergites smooth and shining, hairs shorter and less dense than on rest of body. Entire body a concolorous ferruginous orange to brownish-orange.

Type Material
Palm Springs, California; holotype and paratype workers, Cole Coll. No. Cal-378, August 8, 1960; paratype workers, same date, Cole Coll. Nos. Cal-375, 376, 377, 379, 382, 383; paratype workers, August 7, 1961, Cole Coll. No. Cal-407, 408, 409, 410; paratype workers, females, and males, June 13, 1963, Cole Coll. Nos. Cal-424, 425, 426, 427, 428, 429.

Etymology
Johnson et al. (2013) - The specific epithet, magnacanthus (from Latin, magna for great or large, and Greek, kanthos, for corner of the eye), likely refers to the greatly enlarged corner of the eye in this species. In describing this species, Cole discussed the unusually large eyes but made no mention in regard to the corners of the eyes.